document - idaho geological survey

STATE OF IDAHO . , ...-:.,; ... : ->' :?;.:

C. C. MOORE, Governor . . ,., . -I- . . ,... ., ,~

. ::, . ,., BUREAU OF MINES AND GEOLOGY b..-.

\;?,

Moscow, Idaho 'G

FRANCIS A. THOMSON, Secretary

IDAHO BUREAU OF MINES AND GEOLOGY BULLETIN ISSUED QUARTERLY-PRICE 50 CENTS

No. 10 November 1 9 2 6

GEOLOGY A N D ORE DEPOSITS OF BOUNDARY COUNTY, IDAHO

BY

VIRGIL R. D. KIRKHAM

AND

ERNEST W. ELLIS

UNIVERSITY O F IDAHO

MOSCOW, IDAHO htered a s second class matter Aug. 11, 1924. a t the post-office a t JIoscom, Idaho.

under the Xct of ;\larch 3. 1Si9.

CONTENTS

ACKNOWLEDGMENTS .

The writers take pleasure in acknowledging indebteclness to the Bonners Fer ry Chamber of Commerce for photographs used hereill and its cooperation and assistance. and to its committee on mining which facilitated the examination of the area especially during the first field season . The courtesy of 31r . R . Rartlett of the Canada Geological Survey in permitting the use of the photographs on Plate VII I . is greatly appreciated . The writers also express gratitutle for the courtesies and favors received from the various mine o\vnera and managers of Bounclary County. including use of maps. reports. and photographs . The writers also wish to acliao\~ledge their appre- ciation of the services of George R . Caustoll ancl ,4 . J . Kent of Bonnerh Fer ry for aicl ancl interest in consummating field arrangements, as well as to thank D r . Francis A . Thornson. dean of the School of 3lincs . University of Idaho . for valuable counsel in preparing the report. am1 for a critical reading of the manuscript . They are also grateful for the care and cooperation giren by G . E . Bjork in the preparatiorl of maps accompanying this report .

Page Acknowledgment .............................................................................................................. 4

................................................................................................................................ preface 8 Introduction ...................................................................................................................... 9

....... ........................................................................ Purpose of the investigation .. 9 Previous geological work in the area .................................................................. 9

........................................................................................................................... Geography 1 1 ........................................................................................................................ Location 1 1

.................................... .......................................................................... Topography : 11 ................................................................................................................ Accessibility 13

.................................................................................... Settlement and occupations 14 .............................................................................................................................. Geology- 1:

............................. ..................................................................... Strat~graphy ........... 1.5 Algonkian system (Belt [Purcell] series) .................................................... 15

........................................................................ Aldridge-Prichard formation 15 ............................................................................ Creston-Ravalli formation 16

.................................................... Kitchener-Nev-land-Wallace formation 1 7 .................................................................................................... Purcell lava 17

...................................................... Quaternary system (Pleistocene series) 18 ........................................................................................ Lake bed sediments 1S

Quaternary system (Recent) ........................................................................... 19 Hill wash and alluvium ............................................................................... 19

Correlation of Pre-Cambrian (Beltian) rocks in southeastern British Columbia and northern Idaho ................................................................................. 20

Correlation table KO . 1 ...................................................................................... 23 Correlation table S o . 2 ........................................................................................ 31

. ....................................................................................... Correlation table KO 3 2.1 Correlation table Xo . 4 ........................................................................................ 26 Correlation table No . 5 ........................................................................................ 27 Correlation table Xo . 6 ........................................................................................ 2;

Structure ...................................................................................................................... 2S General structural features of the area ........................................................ 28 Special structural features of the area ......................................................... 29

................................................................................................ Cabinet range 23 Selkirk range .................................................................................................. 30 Purcell range .................................................................. ............................ 30 Purcell trench .................................................................................................. 31 Kootenai fault .............................................................................................. 32 Round Prairie fault ........................................................................................ 33 3loyie (Lenia) fault ........................................................................................ 34

Upper Priest River unconformit>- .................................................................. 35 Igneous Geology ........................................................................................................ 35

Batholiths .............................................................................................................. 35 Sills ........................................................................................................................ 36

The hloyie sills ............................................................................................. 36 Dikes .................................................................................................................... 38 Lava f l o w .............................................................................................................. 39

The Purcell lava .......................................................................................... 39 Veins .................................................................................................................................. 41

Origin and relationship to rocks ...................................................................... 4 1 Replacement ore-bodies in metamorphic rocks .................................... 42 Shear-zone deposits along bedding planes of quartzite .............................. 43 Joint-plane veins in granite ........................................................................... 43 Fissure veins in or adjacent to basic sills ................................................... 44

6 IDAHO BUREAU OF MIXES AND GEOLOGY

Page Minerals .......................................................................................................................... 46 Ore-deposits .................................................. 47

Lode ore-deposits ........................................................................................................ 48 ...... .................................................... Lead-silrer ores 48

Gold ores ................................................................................................................ 48 Molybdenum ores .................................................................................................. 49

.................................................................................................... Tungsten ores 50 .......................................................... Zinc and copper ores 60

............................................................................................................ Placer deposits 61 Gold ............................... ......... ..................... ... ...................................................... 51

........................................................................................... Mining properties ................ 52 ......................................................................... Idaho Continental Mine -- 52 - -

.................. Cynide Gold Nining Company : ........................................................... 3 1 ................... Damon group ................ 58

International hfolybdenum Company .................................................................. 59 Northern Star claim ................................................................................................. 69

.................................................................................................. American Girl claim 60 Moran property ............................................................................................................ 60

. . ........................................................................................................ M & F property 60 ............................................................................. Boulder Gold Mining Company 61

Idaho-Montana Mining Company .......................................................................... 62 Kate Fry claim ............................................................................................................. 63

.............................................................................................. Keno and Glory claims 63 ................ Arsenopyrite vein : 63

Metals Mining Company 64 Gold Shaft group .................................................................................................. 64

............................................................................................ Golden Hope claims 64 hloyie Gold 31ining and >filling Company, Queen group ................................ 65

............................................................................................ Trust Mining Company 66 ........................................................................................ Eileen Mining Company 67

Lucky Abe 3Iining Company .............................. .l. ................................................. 67 Kent property (Sphalerite claim) ...................................................................... 67

...................................................... Brush Lake JIines Company (Dora tunnel) 68 ................................................................................ Peters and Mitchem property 6s

Leonia Gold 3Iining Nining Company 69 . ......................................................................................... Golden Triplet S o 1 69

Quartz tunnel .................................................................................................. 69 . .......................................................................................... Golden Triplet S o 2 70

Cornmeal tunnel .................................................................................................... 70 Gravel deposits ...................................................................................................... Y O

.......................................................................................................................... Summary 7 2 Conclusion ........................................................................................................................ 74

ILLUSTRATIONS

Flate Facing Page

. ..................................... I Purcell Trench looking north :..............Frontispiece

I1 . Index map of Idaho ....................................................................................... 13

I11 . Reconnaissance Geologic and Structure map of Boundary County. Idaho ...................................................................................... In pocket

........................................................ IV . Types of veins in Boundzry County 41

.......................... V . Moyie Falls, Junction of Kootenai and hloyie rivers 44

VI . Kootenai River . "Sheep-back" rocks . Moyie River . Gorge in hloyie River .................................................................................. 47

VII . Typical Nelson granite . Granite glacial erratic . Lake beds . Lateral moraine .............................................................................................. 50

VIII . Purcell Trench . Purcell Trench and west wall .

........................................................................ Dissected Selkirk peneplain 32

I S . Aplite . veinlets in granite . Joints in granite filled with acidic vein-dikes ..................................... 66

5 . Phoebe's Tip . Cirque or valley-head .................................................................................... 59

XI . Stope in Idaho Continental mine . Smith creek ...................................................................................................... 6 1

XI1 . Typical glacial lake and surrounding terrane in Boundary County . Another one of the "Boche 3Ioutonnes."

........................................................................ Glacial erosion and moraine 68

SI I I . Maps and sketches of ore deposits in Idaho Continental Mine ........................................................................................................ In pocket

PREFACE

This report presents a brief analysis of the mineral possibilities and structural features of the most northerly county of the state of Idaho. Because the area adjoins the international boundary, and because the work of the Geological Survey of Canada has been more extensive and detailed to the northward than has the work of the U. S. Geo- logical Survey to the south~x-ard of the area, the authors have drawn much more freely upon the ~ ~ o r k of Canadian writers than upon that of their American colleagues.

Although there has been a popular tendency to liken Boundary County to the Coeur d'Alenes in its mineral possibilities, the present investigation points to a resemblance rather to southern British Columbia so far as econo~nic possibilities based upon geologic similarity are concerned. The relationship of metalliferous deposits to granitic batholiths is again emphasized and considerable evidence for a zonal arrangement of mineral deposits with respect to igneous mag- mas is adduced. Certain major structural features of rather wide im- plication are also dealt with in this report.

So far as mineral resources are concerned, it is my opinion as the result of several visits to tlie area, both prior to and during the investigation, coupled with a careful study of this report and numerous con- ferences with the writers, that the area is by no means devoid of promise and that more carefuI prospecting of the areas pointed out as geologically favorable is fully justified.

FRANCIS A. THOAISOX, Secretary.

GEOLOGY AND ORE DEPOSITS OF BOUNDARY COUNTY, IDAHO.

By VIRGIL R. D. KIRKHAM A S D ERSEST IV. ELLIS.

INTRODUCTION.

P U R P O S E O F T H E I N V E S T I G A T I O N .

Early reconnaissances of portions of Boundary County by geologists of both the Canada and United States Geological surveys pointed to the presence there of large areas of metamorphosed sediments of great age. Speculations as to age placed them in the Algonkian (pre- Paleozoic) or Cambrian periods. They were thought to be notably faulted and folded, as well as intruded, by various younger igneous rock masses and generally to possess conditions of age and structure similar to those usually ascribed to the famed Coeur d'Alene mining district.

Because of this apparent geologic similarity, a belief that similar results were to be espected in the 71-ay of ore production had naturally arisen.

This assumption, however, ignores the fact that the part of the county west of the Pnrcell trench is practically unexplored, and that the mining developnlent of the county has been, for the most part, based on early reconnaissances which hacl considered only certain limitecl areas.

This situation, coupled with the public-spirited attitude of tlie Bonners Ferry Chamber of Commerce and the Boundary County mine owners, made it possible for the Idaho Bureau of 3lines and Geology to send into this region Messrs. Virgil R. D. Iiirkham and Ernest TIT. Ellis. Their mission was to risit and examine operating or promising properties throughout tlie county, to recommend future dm-elopment, where i t was desirable, and to map the geology of the n-estern part of the county, during August and part of September, 1924.

Examination of mining properties in the eastern part of the county revealed the presence of several unusual and important structural and igneous features which x-ere not shoxvn on earlier reconnaissance maps. Because of their importance and relationship to the mineral deposits, an additional month in 1925 was spent in mapping the

10 IDAHO BUREAU O F XIIXES AND GEOLOGY '

eastern par t of the county ancl in collecting later and more detailed information concerning mining properties. A total of about nine weeks were spent in collecting the field data and several months of office and laboratory work were necessary to prepare the findings for publication.

P R E V I O U S GEOLOGICAL W O R K IN T H E A R E A .

The Tollo~ving brief bibliography represents, as fa r as is known, the -

chief publications on the area as nyell as the most important geological work done therein. References to publications throughout the sue- ceeding pages are made by serial numbers xi-hich refer to the enumera- tions of publications listed.

1. CALKIXS. F. C.. a n d JIXCDOSALD, D. F., A Geological Reconnaissance in Xorthern Idaho a n d Sorthwestern Montana: G. S. Geol. Survey Eull. 384. 1309.

2. CURTIS. W. Jf., The P r ~ e s t Lake Minlng District, Idaho: Englneerlng and Minina Jour. Vol. 52. a. 866. 1906. - , - . -

3. DALY, REGISALD A., Geology of t h e Xorth American Cordillera a t t h e Forty- ninth Parallel: Canada Dept. Interlor. Report of Chlef Astronomer for 1910. Vols. 2 a n d 3, PP. 1-799, nlaD 1913. Also issued a s Memoir 3s. Canada Geol. Survey. Ottalr-a, 1913.

4. , The Differentiation of a Secondary JIaarna Through Gravitative Adjustlncnt. (3Ioyie Sill in t h e Purcell Alountaln Range, Idaho-JIontana.) Festschrift, H a r r y Rosenbusch. pp. 203-233, Stut tgart , 19U(i.

5. KIRKHAJI, \-IRGIL R. D., a n d ELLIS. E R S E S T W.. Press Eulletln on Geology and hllneral Resources of Boundary County. Idaho.: Idaho Bur. of Mines and Geol. Press Eull. 12, Dec. 192:.

6. LAXCASTER. JOSEPH, The Priest Lake District. Idaho: JIining 'FVorld. Vol. 32. p. lU0. 1310.

7. LIVIFGSTOS, D. C., Tungsten, Cinnabar. Manganese, JIoll-bdenum and Tin . Deposits ol Idaho, U n ~ v . of Idaho School of JIines Bull. Z, Vol. I:, pp. 11-13, 40. 1919.

S . JLLCDOSALD D. F . Econon~ic Fea tures of Sor thern Idaho a n d Sorthmastern JIontana: U. S. ~ e b l . ~ u r ' v e y Bull. 285, 1906. 9. &IcCOSSELL, R. G., and BROCK, R. w., Geologic Map of the British Columbia

West Iiootenay sheet . Canada Geol. Surrey, 1901. 10. Xin. P.es. C. S. GeoI. Survey P t . 1, p. 420, 1908. 11. , p. 345, 1909. 12. SCHOI.'IELD, S. J., The Origin of Granite (Xicropegtnatite) in the Purcell

Sills: Canada tieol. Surrey. 3luseunl Bull. 2, pp. 1-31. July 3U, 1314. 13. , Tine Pre-Cambrian (Beltian) Rocks of Southeastern

Eritish Columbia a n d thcir correlat~on. Canada Geol. Sur rcy AIuseun~ Bull. 8. PP. 72-91, July 3U. 1911.

14. . Geology of Cranbrook Map--lrea, British Colulnbia: Canada Geol. Survey 3Iemoir i6, Ortalra, 1915.

15: SI-IASSOS, EARL T-., The Minerals of Idaho: Smithsonian Institution. U. S. N a t ~ o n a l &Iuseum Eull. 131. 1926.

16. SOPER, E . I<.. The Mining Districts of Sor thern Idaho: >lining a n d Sci. Press, Vol. 116, pp. 121-127, 1"s.

17. T-ARLEY, TI-IOJIAS, TTRIGHT.. CLARENCE A.. SOPER., EDGXE I;., and LIVISGSTON. DOUGLAS C.. A Preliminary Report on the h11nlng Districts of Idaho: U. S. Bureau of Alines Bull. 166. 1919.

The above publications probably represent all of the investigations in this district ancl adjacent areas, with the esception of private ill- vestigations ant1 reports unavailable to the public. A fen- of the above listed publications contain recollnaissance maps of small parts of the area, and only a fen- discuss the geology of the area in any detail.

GEOGRAPHY,

L O C A T I O N .

Boundary County is tlie northerrimost county of Idaho, as is shown by the index map. (PI. II., p. 12.) The northern par t is bounded for 45 miles by Canada. On the east, IIontana bounds the county for 34% miles. 71Tashington bounds the county for 10% miles on the west. Bonner County, Idaho, borders the county on the south and west. The county comprises 865,520 acres.

TOPOGRAPHY.

Three types of topography are represented in the area: (1) rugged mountainous provinces, made up of tilted, faulted, metamorphosed sediments, massive basic igneous sills, and a batholithic acid igneous intrusion with its attendant stocks and cupolas, (2) plateau-like areas lower than the mountain masses, planecl off by continental-glacier erosion (PI. I., Frontispiece) and (3 ) stream-valley plains.

Examples of the first type arc abundant tlirongl~out the county. The second type is to be found to the east of Icootenai River and the last type exists in the valleys of Ilootenai, JIoyie, ancl Upper Priest rivers, and Deep Creel:.

T'he relief varies from an elevation of 1797 feet where the Kooteaai River leaves the area a t the Canadian bounclarj-, to 7670 above sea level in the southrrestern par t of the count - along the crest of the Selkirlr Range; thus a relief of nearly 5900 feet occurs in a distance. of less than five ancl oilc-half miles.

Xost of tlic drainage is into the Kootenai River, ~vliich f lo~vs northwest along tlie AIoyie (Lenia) fault and Purcell trench into Canada, where i t joins the Columbia. The rest of the county is drained by Deep Creek and Upper Priest Rivcr, tributaries of the Clark Forli, which also join the Columbia in Canada.

Important tributaries of the Kootenai are Moyie River, Boulder, Grouse, Trail, Tn-enty-mile, JIission, Fall, Ruby, Caribou, Snov-, hIyrtle, Ball, Trout, Parker, Canyon, Smith, and Boundary creeks. Gold, Trapper, Caribou, Lion, T v o IIoutll, Indian, Hunt, and Soldier creeks Contribute to the Upper Priest River drainage.

Numerous small lakes formed by glacial scouring lie within the area, (PI. SII . , p. GS), and until recently morainal damming was re-

IDAHO BUREAU O F J f I S E S AND GEOLOGY BU1,LETIS 10, PLATE 11. GEOLOGY AND ORE DEPOSITS O F BOUNDARY COUSTY 13

I S D E S J IAP O F IDAHO. The a r e a enclosed by the heavy black line is t ha t covered in this report.

sponsible for several permanent lakes of notable size, as well as extensive temporary lakes and swamps in Kootenai Valley, extending from Bonners Ferry to Canada.

The chief drainage lines lie in deep, wide, gIaciated, fault-formed valleys. Structure generally controls the drainage system of the county.

Chief of the mountain ranges is the Selkirk Range, lying in the restern part of the county. I t is serrated and scenic. I t is scarred both by continental and alpine glaciation and many of its peaks rise 7500 feet abo-ie sea level.

Par t of Purcell Range lies in the northeastern part of the county and contains many peaks over 6.500 feet in elevation. Yahk lfountain, approximately 6500 feet above sea le\-el, is its highest point.

The northern part of the Cabinet Range occupies the southeastern part of the county and has Clifty Jfountain, with an elevation of 6700 feet, as its high point. Xany other peaks in this range rise above 6000 feet in elevation.

In nearly all instances the high points of these ranges are deter- m'ined by the resistance of igneous roclis to erosion. A11 of these ranges represent structural bloclis dissected by southrvard-moving continental ice sheets, and subsequent valley glaciation, follo~x-ed by run-off consequent upon glacial melting and high precipitation.

ACCESSIBIL ITY.

Nuch of the area is difficult of access. The transportation lines are confined to the broad, lev-, structural valleys of Deep Creek and Kootenai and Jfoyie r i ~ e r s . These valleys also contain most of the population, all of the toxvns, railways, highn-ays, ancl agricultural land. The Spokane International Rail~vay and the Great Northern main line serve the area adequately, passing through Bonners Ferry, where a branch line of the latter leaves to serve Port I-Ii11 on the Canxdian border. i\lany escellent surfaced highways now traverse the main valleys and much additional mileage is in course of construction.

The larger mining properties are connected with shipping points by auto roads ranging from 4 to 26 miles in length, but the larger number of properties are relatively inaccessible, being approached only by uniinp~.oved wagon roads or trails, open only in the summer months.

14 IDAHO BUREAU O F ;MIXES ASD GEOLOGY

Although the Kootenai River is navigable by small steamers ancl launches, little use is made of this thoroughfare.

S E T T L E M E N T AND OCCUPATION.

The population of the county is less than 5000. Bonners Ferry, the county seat, is the only town of any size in the area. I t s popnlatio~l

of 1350 persons depends chiefly on the agricultural, lumbering ancl mining industries of the tributary region. Other toll-ns and postoffices in the area are Eastport, JIeado~l- Creek, Port Rill, Leonia, Copeland, Saples, bIcArthur, Iloravia, Klockman, BIoyie Springs, Shilol:, ant1 Xcldie.

Of the S6.5,520 acres within the county, 12,300 acres arc in cultiva- tion and are devotecl to fruit, grain, and vegetables. The rainfall of

. the area averages 27 inches, malting irrigation unnecessary. The 35,000 acres of meaclo~vlancl and 166,000 acres of grazing 1a11il provide ample facilities for a successful dairy and l i re stoclr industry.

About 102:000 acres of the county are occupied by timberland and 59:000 acres represent the cutover area.

3Iuch escellellt timber and pulpu-ood give promise of a continuccl logging industry. Drainage pro.jects to reclaim swamps and ovcrflo~v lands by dilies are malting more agricultural land available yearly. The status of the mining industry in the cou11t.y is dcscrihed in the rest of this bulletin.

GEOLOGY.

STRATIGRAPHY.

A.LGOSKIAX SYSTEM (BELT [PURCETALl SERIES.)

Aldridge-Prichard Formation.-This is the olrlest l;non-n fornlation of the Purcell series of the Canadian Geological Survey arlcl of the Belt series of the Uilited States Geological Surrey. The base of this formation is not revealed in the area but tlie upper limit is de- fineil by a fairly distinct transition zone. I t s lithology is notably different from that of the Pricharcl formation in the type section of the Coeur d78lene mining district, ~vhere it collsists chiefly of dad; colored, gray and Blue-banded argillites and slates. This difference is esplailieil by Calkinsl as due to changed conditions of seclimenta- tion a t the time of cleposition, ~vhich altered the type section toward the north and west. IIere the tendency is fo r the formation to become coarser aud more siliceous so that ~vherer-er tlle for~ilatioil is esposecl i11 Bountlary County, it is predominately quartzitic ancl sandy wit!? a minor amount of argillaceous material.

I n Boundary County the Xldridge-Pricharcl section is made up of pure cluartzitcs, argillaceous cluartzites, alicl argillires. Tile c1uartzitc.s are generally massive, occurring in beits as thick as eight feet. The argillites a.re thin-bedded, ancl the argillaceous quartzites have a lesser thicline~s tllan the pure cluartzites. Scliofield'%att~.ibutcs to this formation an average stratum thic1;ness of s i s inchcs.

The pure quartzites are light graJ- in color ancl tlie argi l laceo~~s quartzites and argillites arc gray to black. The general ~veatllerccl appearance of the fornlation is a recldisl~, rust)- bron-11. Except for. the subordinate thin-bedding, few evidences of shallo~v-n-ater tlcposi- tion were observed.

Basic igneous sills of great thiekiless and frequency are found ill this formation in the eastezn par t of the county. They will be ile- scribed under the section on igneous geology.

The entire area of eastern dipping sedi~ilents betn-een the Purccll trench on the west ancl the 3Ioyie (Lenia) fault on tile east, ant1 cs - tending the full longituclinal length of the county is believed to be the -4ldridge-Pricharil formation, with the cscept io~l of a small TI-edge a t the Canatlii~ri boundary, one mile northn-est of Robinson Lake, ~vhicll is assignet1 to the Xnvalli group. --I. t r i n ~ g u l a r piltc'll of a l~ou t 1'7

1 6 IDAHO BUREAU OF MINES AND GEOLOGY

square miles in the estreme northeastern par t of the county is also designated as of this formation. The long strip of westward dipping sediments bet~veen the Purcell trench and the igneous area to the west are assigned to the Aldridge-Prichard formation. All other areas are correlated with higher formations.

The 4Qldridge-Pricliard formation, as interpreted by the writers, shows in this county a thickness of more than 10,000 feet, exclusive of the intruded basic sills.

Creston-Raualli Formation.- This formation lies conformably on the Aldridge-Prichard formation. The Creston of the Purcell series conforms with the Ravalli group of the Idaho and Montana Belt series. The Ra~i l l l i is sometimes split into three formations known as the Burke, Revett, and St. Regis-from bottom to top. The lithologic changes from the Coeur d'Alene district to here are not so marked as is the change in the Aldriclge-Prichard formation. 1 1 0 ~ - ever the thiclcness is slightly increased ancl the argillaceous members are felrer. I n this count-, i t is made np chiefly, in the Iomer section, of thin members of siliceous shales, gray, rusty- eatlie lie ring argillaceous quartzites ant1 pure, gray quartzites, which appear to correspond fairly closely to the Burlce member of the Ravalli group. The middle section is chiefly pure n-hite massive quartzite and sericitic quartzite which correlates closely to the Revett of the Ravalli group. The top section is chiefly sandstone and the shale members a re of brown, purple ancl grccii color. These have been correlated to the St. Regis of the Coeur d7Alene section.

TKO basic igneous sills are found intercalated with the probable Burke section ancl one is found in the St . Regis member, being stratigraphically tlic highest sill in the area. Few- evidences of shallow water deposition were observed in this group.

This formation is represented a t three places in the county. The best exposure constitutes the south~vest\vard dipping rocks ~vhicli lie i n a belt whose eastern boundary extends from about two miles east of Eastport southeasterly to the northeast par t of T. 64 N., It. 3 E. These roclis extend to the 31oyie (Lenia) fault on the ri-cst from about three miles south of 31eadolv Creek north~vard to the Canadian line. The thickness exposed here, exclusive of the sills, is approximately 5000 feet. This formation is again exposed west of the Selkirk granite area, in the northx-estern par t of the county, as f a r west as

GEOLOGY A S D ORE DEPOSITS OF BOUXDARY COUXTY 17

the stream valley of Upper Priest River, which appears to flow along a major unconformity. Only the Burke and Revett members could be recognized here. The dips in this area are somewhat divergent, possibly on account of unconformities, faults, or disturbances in the ahallo~v-lying batholith, \\-hose undoubted nearness t o the surface throughout this entire section is attested by the numerous and closely occurring cupolas. The Burke is thought to be exposed in a small wedge between two faults one mile northwest of Robinson Lake.

Kitchener-Newland- Wallace Formation.- The Kitchener of the Purcell series of Canada can be fairly well correlated with the Newland of the Belt series ~vliich is correlated by Calkins1 \I-ith the Wallace formation of the Coeur d'illenes. This formation appears to undergo less lithologic change in passing from the Coeur d'Alene district to Boundary County than any member of the Belt series.

The description of the Se~rlancl in its type locality ancl the Wallace in the Coeur d7Alenc clistrict fi ts very well the rocks of the Iiitchener- Nel~land as esposccl in Bonndarp County. A slight thickening to tLa north apparently occurs. The members are fine-grained and thin- bedded, ancl are notably calcareous. They are chiefly light gray argillaceous and calcareous qualatzites, calcareous banded argillites of blue and white color. There are also a few thin members of sericitie slate and quartzite, and of green impure limestone and dolomite. A11 '

of these grade from one to the other. Evidence of shallon,-water deposition is abundant; ripple marks and sun cracks aid greatly in recognition of this formation.

This formation is thought to occur a t only one locality in the county. I t outcrops as sou thrves t~~ard dipping s t ra ta in a strip about two miles wide just east of the l loyie (Lenia) fault, south of the basic sill and northeast of the Icootenai River and Leonia. It appears to rest conformably on the Creston-Ravalli formation which lies to the northeast, The Iiitcliener-Yexi-land-Wallace formation as exposed here reveals a thickness of about 4500 feet, although i t appears likely that the upper member has been cu t by the Moyie (Lenia) fauIt.

Purcell Lava.-This formation, common in British Columbia Beltian sections, has no counterpart i n the Coeur dYAlene section, having been either omitted or eroded. Stratigraphically the Purcell lava should overlie the Striped Peak formation of the Coeur d7Alene Belt series. The formation is called the Irene conglomerate and

18 IDAHO BURE-4.U O F AIINES Ah-D GEOLOGY GEOLOGY A S D ORE DEPOSITS O F BOUhTDARY COUNTY 19

Irene volcanic formation by Daly3, who assigned to theill an age con- siderably older than the Alclridge-Prichard.

Although the formation bears the name of an igneous rock type, i t will be described under stratigraphy because i t contains large thicltnesses of coarse sandstone and conglomerate and a few dolomite members.

It was deposited unconformahly after a great erosioil interval 011

the underlying Creston-Ravalli formation.

The 1011-er 5000 feet appears to be a local basal conglomerate not typical of the Yurcell lava in other sections and may perhaps be correlated with the Siyeh. I-Ioxvever, the upper par t of the conglomerate is interbedded with the lowermost lava flolr-s, and thus sho-irs its basal relation ancl justification in being eonsiderecl either as a par t of the Purcell lava formation or as the Siyeh formation which has identical relatioris with the lava far ther to the east. Tlie sand and pebbles are chiefly made up of sericitic quartzite and white quartzite very similar to the IZevett of the uiicler1~-ing and nearby Creston-Ravalli group. This was very probably tlie land inass that furiiislicd the material fo r this huge mass of coarse depositional inaterial. Other pebbles are dolomite and slate.

The upper 6000 feet is made up of alterecl basaltic and anclesitie lava flon-s, greenstoile schists, interbecldecl tuffs, conglomerates, breccias, and a 40-foot bcd of dolomite. The formation occurs only in

~ ive r . the nortlirvcsterii par t of the courlty west of Upper Priest P' The lava flon-s are tlionght to be tlie extrnsive phase of the basic

intrusive sheets comiuon in tlie Aldridge-Prichard and overlying formations previously describecl in this section, which a re I<no\vn as tlie Pureell sills. JIoyie sills or St. 3Iarys sills in Canada. These lavas will be more fully describecl under the section on igneous geology. Tlie top of this series. ~ r h i c h the writers believe is the youngest Belt formation in thc county, is approximately 30,500 feet higher stratigraphically, esclusi\-e of sills, than tlie lowest section of the'Aldridge- Prieliard formation observed in the area.

QU.kTERSART S'I-STEJI (PLEISTOCESE SERIES.)

Lake Bed Sediments.-The outline of every dotted and stippled area on the map is also the outline of temporary or semi-permanent lalies which resulted from the glacial inr-asion of the Pleistocene. These lakc deposits )Irere silts, sands, and gri1vt.1~ eroded from the

nearby terrane. Tlie usual phases of sliallo~v water and delta deposition are exhibited in some of these areas. (PI. VII., p. 50.)

Kootenay Lalie, ~vliieli now lacks nearly 14 miles of reaching the northern boundary of the county, extended during Pleistocene time from north to south throughout the county and undoubtedly connected with the basin in which is the p ~ e s e n t Lake Pend OreilIe. Although the lake has varied in depth and altitude a t various times, owing to the resistance of its darn and the fluctuation of its water supply, i t has deposited stratified sediments to a clcpth of more than 200 feet in parts of the area. The highest level of this old lake \\-as con- siderably above the 2200-foot contour, as shown by the terraces. I n its last stages, Iiootenay" Lake \\-as dammed a t JIoravia, and Deep Creek developed a clrainage leacliilg from it. The lake preserved this estent until recent times. Conversion of its southern extremity into a swamp probably has occurrecl only IT-itliin the last fen- hunclretl years.

The lake basin, reachiiig from E a s t p o ~ t into Round Prairie aiitl dotrn below Snyder, Ivas clammed on the south by a res is t i~i~t basic sill which has since been severed by the stream. This lake was a t a higher contour level than old Icootenay LaBe, but n-as smaller ant1 shorter-lived. The deposits in this basin are thin, and only erosional remnants remain. The lalie near l\Ieado~v Creek hael a similar histor- and was dammecl by tlie basic sill which now is responsible for l\Ioyit. Falls. The old lalie on Boulder Creek, formecl 115. a melting alpiircz glacier, is thought to ha\-e been dammed by a basic sill. The old lakes on Grass and Co'iv creeks were dammccl by niol.aina1 obstructions and were uncloubted1~- short-lired.

The olcl lake sediruents in some places provide fertile soil ancl in others gral-el fo r construction purposes and road surfacing. At some places the seclinients are being ~ ~ ~ a s h e d for golcl.

QU-ITERSARY STSTEM (RECEXT.)

Hill Wash and A1lut.ium.-This material, made up of a mixture of eroded materials from the mountains of the region, occupies the larger valleys arid basins and masks rock esposures except in gorge- like channels where i t is cut through. It comprises the chief farming area of tlie region. I n the area dotted or stippled on the map

'The word Kootenay or Kootenai is of course an Indian tribal name. Unfortunately a Variant spelling has been adopted by the two countries through which the river flon-s.

20 IDAHO BUREAU O F MINES AND GEOLOGY

many areas of underlying bed-rock too small to map are esposed. I n some instances they are only a few feet across. Although unmapped, they serve to justify the drawing of sub-surficial contact lines for the older bedrock formations.

CORRELATION O F PRE-CAMBRIAN ( B E L T I A N ) ROCKS I N S O U T H E A S T E R N B R I T I S H COLUMBIA A N D N O R T H E R N IDAHO.

The rocks of the area in British Columbia adjacent to those in Boundary County have been assigned to many different geological ages, by various geologists, and have borne many different designa- tions.

The sediments along the Canadian boundary west of Pureell trench in British Columbia were called the Upper and Lou-er Selkirk series and assigned to the Cambro-Silurian and Cambrian by McConnel19 and Brock on the T e s t Kootenay Sheet in 1904. According to them. the younger Cambro-Silurian rocks lie to the east of the Cambrian group and the youngest roclis lie nearest the main batholithic mass of the Selkirk Range. d

Daly3, a s late as 1915, published a map which shows the same area to be occupied by a group called, by him, the Priest Biver Terrane of pre-Beltian age, containing seven members, and also the Irene volcanic formation ancl Irene conglomerate, which he places a t the base of the Beltian section. According to his column the oldest roclis lie to the east adjacent to the Selkirk batholithic mass. I n 1917, Drys- dale* placed the Irene formations a t the base of the Belt series.

The vr i t e r s place the rocks ne s t to the batliolithie intrusion in the Creston-Rnvalli group and provisiollally assign them to the Burke and Revett formations. The Irene ~ o l c a n i c formation and Ireiie conglomerate are tentati.c-ely assigned to the Purcell lava and Siyeh formation of Upper Beltian age.

Calkinsl, in 1909, believed the narrow strip of highly metamor- phosedsedi~llents lying west of Purcell trench and east of the Selliirk batholithic mass to be older than Beltian, and possibly Arcliean in age. The writers assign this area to the Aldridge-Prichard formation and account for the schists and gneisses as injection gneiss and meta- m s p h i c products - induced by the proximity of this pendant-like strip to the closely unclerlying magma ancl adjacent granite to the east and west.

*Drysdale. Charles Wales. Ymir Jlining Camp. British Colulnbin, Canada Geol. Survey Memoir 94, Ottawa, 1917.

GEOLOGY AND ORE DEPOSITS O F BOUNDARY COUSTY 2 1

The relationships of the schists, gneissic zones, and granite are obvious. A transition occurs to cast and west horizontally, as well as vertically.

The gneissic shell is sometimes only a few hmlclred feet thick. At other places it reaches a thicliness of about 2000 feet.

Traces of basic sills, highly metamorphosed and disturbed, are also found in this strip. They are altered mainly to dark heavy micaceous schists, which could be distinguished from the enclosing schists with such difficulty that sills could iiot be mapped in this area.

That par t of the county lying east of Purcell trench is shown by Calkinsl (1909) to contain Prichard (Beltian) near the trench, Ravalli group (Beltian) east ancl west of the JIoyic fault a t the Canadian boundary, and Prichard in the northeast corner of the county. I-Ie shows Prichard east of Bonners Fer ry and southr-r-est of his Lenia fault, ancl a patch of Xev-land (Beltian) to the east and northeast of his Lenia fault. Less than a tenth of the sedimentary nlass in the county was assigned an age by Calliins in 1909, but those arcas designated were all Beltian roclis.

In 1915 Dal3.3 in his map of the same area shon-s these formatiolis as Creston fornintion (Purcell) of Beltian and L o ~ r e r Cambrian age, IGtchener (Purcell) of JJol-r-cr arid Jlicldle Cambrian age, and Jloyie (Purcell) of JIidtllc Carnbria~i age.

In this same yeilr Scl~ofielcll~uublisl iccl a liiap of the Cranbrook area, British C'0111111bii1. sliowilig Daly's bccls as i\lclridge (Pureell) of Beltian age nncl a narrou- strip of Creston ('Purcell) of Beltian age lying east of tlie JIoyie fault a t the Canadian boundary.

The writers assigii all of tlie area betxveen Purcell trench and 1Ioyic (Lenia) fault to the --\lclridge-Prichard cscept. a small trjnngnlar portion a mile slid a half 1011:. aacl a mile n-iclc a t the Canacliali 1)ounc-lay\- and bounclcd by faults: lying about one mile northwest of Itobiilsoii Lake, x-liich is assigned to the Crcston-Ravalli group, ant1 is probab1~- Burke forination. This correlation agrces largely with those of Calkinsl and of Sc1iofieltl1.', altliough tile latter s1lo~~-s no Creston IT-est of the 310~-ie fault ancl Calltins s h o ~ ~ s Ravalli west of the fanl t and adjacent to it, a t 71-liich place tlie \I-riters find Pricliard.

The writers accept the l'richnrd, Sen-land, and Ravalli in the rest of the eastern par t of the c o u t y as clcsignated by Calliinsl and also the Aldridge and Creston desig~lations of Schofieltl " as slion-11 a t the Canadian 1)ountlary.

22 IDAHO BUREAU O F X I S E S ASD GEOLOGY

The following six correlation tables are designed to conrey to tlic reader the progress macle in attempts to assign to the proper stratigraphic horizon and geologic age the formations within this area and the adjacent area in British Columbia. The first four are excerpts from published correlations. The writers have taken the liberty of including only those districts from each correlation which are thought to be pertinent to solving the stratigraphy of this area. The first table is made up from TT-alcott's'? correlcztioa. The second table is made up from Calkins' correlation.1 The third is excerpted from Dalyz and the fourth from Schofield13, 14. The fifth table is a n endeavor on the par t of the writers to assign stratigraphic and age ~ a l u e s to tho metamorphic sedimellts west of Kootenai Rirer and Purcell trench and to show what names and ages n-ere assigned to the same formations by JIcConnellg and Erock, and by Daly" Table six undertakes to do the same for the metamorphosed rocks east of the river and to show the names and ages assigned to the same formations by Calkins1, and Daly3, and Schofieldl3> 14.

'Valcott, C. D., Bull. Geol. SOC. Am. Vol. li, 1906. 1, 3, 13, 14 See bibliography. -

G E O L O G Y A S D O R E D E P O S I T S O F B O U S D A R T COUNTY 23

CORRELATIOS- TABLE NO. 1 (FROM C. D. WALCOTT.)

1.762 ft. Calcareous a n d

CA)IBRIA~- arenaceous. 1.500 f t . L-SCONFORIIITP .\lARSH, 800 ft. Arenaceous mostl?

reddish color, HELENA. 4 ,491 f t .

calcareous, 2.100 f t

Coeur d'Alene Dis- East Of t r ict , Idaho (Calkins) ~ ~ ~ : ~ ~ a l R1verr

Belt Mountains, hlontana, (Walcott)

SEWLAKD. I from Summit, 3 , S s i l I

Mission Range Montana, ( ~ a i c o t t )

CA?IIRRIAN USCOSFORJIITT CAMP CREEIC SERIES

K.\lPIRE. 6 0 0 i f t . SPOKANE. 1.500+ft. GREYSOX. 3,0004-ft.

arenaceous

/ No superjacent Arcnaceous red Strata. a n d grey colors. IsS i t . of Lime- STRIPED PEAK. stone near 700 f t . 2.000 ft.

grey siliceous CRESTOX, series, 10.000 ft. quartzite, 9.500+ft.

calcareous, 2,2004- ft. BLXCI<I.'OOT, \VALLACE.

calcareous and s~liceous. 5.000+ft.

BURKE, siliceous arenaceous,

ST. REGIS, purple greenish and grey beds. S.OOO ft.

PP.ICHARD. banded dark blue grey. blue, black and

CHAMBERLAIS, siliceous. 1,500 f t .

SEIHART, sandstone. 700 i t .

I'SCONFORXITT. ARCHEAS.

~ ' o t n l 1 7 nnn ft

Base concealed. I Total. ?.i.000 ft.

YXHK. -io!l f:.

JIOYIE, argillite, 3,200 It.

KITCHESER, qtzt.. 7,100 ft.

calcareous and siliceous, 4.803 ft.

- RAVALLI.

siliceous a n d a re - naceous, purple a n d greenish a n d grey colors, S.225 it. -- - -

Rase. concealed. Total. 21.760 ft.

Ease concealed. Total. 20.600 ft.

CORlili'.T.hl'lON 'I'AE1.W NO. 2 (I.'IlOAl 1,'. C!. CAI,I<INS.)

:I ~V,\T.(.'<)'SrL', C. I.)., l ' ~ . c - ( : ; t ~ ~ ~ l > r i ; ~ r ~ f ~ s s i l i f ~ ~ r o i ~ s for111xtio11; 131111. Qeol. SO(:. 1\111. Vol. 10, lS!I'J. I, - - , , \ l g o l ~ k i n ~ ~ for~n: l t io t l s of K o r t l ~ \ v c s t e r n M o n t a n a : I3ull. (;col. Soc:. A m . Vol 17, 1906. c I t : \ N S O ~ T l ~ . 1,'. I,.. :untl C . \ l , l i l K S . 1'. C . , (:cologp a n d o r e d r p o s i t s of the. C o c u r d S ~ \ l c n e d i s t r i c t , I d a l ~ o ; P r o f , paper

I;'? I 1 S i:,a,bl SIBI'VVX. l!lOS -, . . , . , . . . .~. . . . . . .. . . .. , . d T)AI,Y. It. A,. S u r n r n a r y l:cl,l. (:col. S u r v r y C;illatl:~, for 1!lO4. 1905.

Belt M o u n t a i n s , ( W a l c o t t ) a

C 'AhII<I t IAN I J S ~ :I I ~ I < ~ O I < > I I ~ ~ Y A I ; \ I < S I I , SI I , so11 i t .

I1 l~:l,l~:x,\, Is, sI1, Z.Jll0 I!. - . , -

I~:hlPll(l~:, s h . l;I!U f t . SI'U[iz\S1S. XI,. 1,GUI) I t . -- (:I(I.:YSOS, sl1. :.I100 Pl. - S l.:l\rl,..\ XI). Is. s h ,

2.200 f t .

CITA>TBlCRLAIN sl1. ?is, 1,500 f t .

.\ I . : I I I ; \ I~ ' I%, ( l tz t , ~ h , i l l l l i t .

,\l<(!l-T/\1~:,\hr

C O R R E I A A T I O N T A B I Z NO. 3. (I"R0A.I R. A. DALY.)

Mission R a n g e , ( W n l c o t t ) b

C:;\hl l?l{I:\iV I ~ S ( : O S I ~ - ~ I ~ J I I T I ~ (::\.\I I' ( ' I<I~: I ' ; I< , ss,

!.?ti2 i t . sI1, s s , Is, l,!,lil) l 't.

-- - - -- 3s. 4:I!II i t . sll. ss. Is. ::.s1;7 i t . -- --

I:I,>\I:I<I"o( I'I', IS, s h , .I.S05 f l .

I:;\\:;\I.I,I, s s , cltst, 2,560 --- s s , 1,of;Il f t .

ss. ,I,ul;(l f t .

I - -

49th Para l le l B e t w e e n

River . ( D a l y ) d C r o s s i n g s of K o o t e n a y

Erodcct

-

Y:\ t l K , c11111rtzitc. 51lO

AIOYII-:, : I I . L ~ I ~ ~ ( . :; .Itlo i t ,

l i I 'l 'CFTKXl~~ll,

7.-I00 It. q t z t ,

c~'It1~:STOS. q t z t , ss. :~rgll l i t t . , :1.511n+rt.

Coeur d ' A l e n e D l s t r i c t ( C a l k i n s ) c

l,:lY~(l,~l

_- - STRI l+:rj PIL\I<, - s l l , ss. I.!lOIl+ft. -- \\';\ l A l , ~ \ ~ ~ I G , Is, ss,

~1.(10(1 f t . S'I'. J:l*:OIS, s h , ss.

l,OllO i t . --- l i l~:\'l~:'I:'l', l l t z t ,

1.2110 f t . l< t i l:I<l~:, sI1, s s ,

( ~ t z t . z.n(lo r t . -- l ' l : l ~ ; ~ ~ ~ l ~ t l ~ ,

:lrgiIlitc, s s , ~ , 0 0 0 + - i t .

( C a l k i n s ) &R??P:tral P a r t s

SS, YII, IS. ~ o . o o n + r t .

S'l'lt ll'l*; I ) l'J*C~\li s h , ss. 2,,Oot,-t-r1. ,

N l,:\\'l,~\N I>, Is, SII, 6,000+ f t .

RAVI\T,I;T,

S,flOU+ q t z t . sll. f t . SS,

PRICITAIlI>, a rg i l l i t c , r.ouo f t .

SS, SII, - 1o.0110 i t .

Bel t M o u n t a i n s .

( W a l c o t t l ) I ' ~ . ~ I I ~ I , I . I I I I L ~ tvitll u111)er P.4 r..

I:'\ l,l,,\'l'l s, l* ' l .~\ ' l ' I~NAU,

. \12\l tSli . SOIJ i t , I I l ~ : l , l ~ : s ~ \ , L ' , 1 1 1 1 1 f t . l ~ : ~ l l ' l l : l ~ : , l;llo i t .

S l 'OI i2 \Sl~: , l.5IlO f t .

I ~ I i I ~ ~ Y S O Z J , 3,000-(-it.

1,o'iver 4 ; Ii l~:YSON, I . I I I ) I ) + ~ ~ . . .YI,:\VI'.~SI>, 2,!200 i t . I \ I l - I .,\ IS. l,!il!~l f l . S l*:lH,\ IL'I', 7t10 i t . '1'01ill I l . l ~ u l ~ + f t . . - - I:S(:OS IsYJIiAl- I'I'J', l ! l l l ~ : l ~ l t Y ( * I < l~:I~:l< I%l*:l>s l ~ s ~ ! o , ~ l ~ ~ o l : . \ l - I'I'Y. . - - ",\ l<l:l I,\ la:'\ N"

I. WATACl')'l"l', 2. -- , T ? ~ l l . (.:col. SOc. Aln . Vol. 17, 1906. 3. CAI, I<ISS. 1'. C.. l<1111. 38.1. U. S. (:( .oI. ,Su~.vc:p. 1:lO'J.

Mission R a n g e ,

(Walcot t ' )

?

Coerlr d 'Alene Dis t r ic t ,

(Calk ins3) l ~ : l ~ ~ ~ s l o l l S I I I , ~ ; I ( . ~ ~

C a b i n e t R a n g e (Calk ins ' )

?

--- l ~ ' l ~ ' \ ' l ~ l I l~:'\l.),

<!A\ All' (!I:l~21-:1<, I l.700 I t .

I.ONIC SrSi\R L'.000+ I t .

13l~~1CHIVlf. $ . I I I IO f t . -- l ~ l l ' l ' l , l ~ , I . I ; G I I f t . l l I*~\ \ ' l )Nl<:Y. 2.1100 f t . \Vll I ,I<', uppc*r, I .Ollll-(.Ct.

r ,o \v ic t t w o [.I<*, I .!101)+ft. A I 0 S l i . 5.600 f l . IRISXI*:. volcnnir.. 1;,o011+.ft. I ltl~:sl*;, cg., r,,onu+ i t .

'L'o1:1l - : : ~ , I I ! ~ I I - I . ~ ~ . I ;S(: t . lS l ~ ~ < ) l t ~ l l ' l ' \ ' lJ1,i(~st 1tiv1-r l'lil ICS'I.' It1 \'la:lt

S e l k i r k R a n g e , Surnrn i t S e r i e s ,

( D a l y )

- - S'I'ltI I ,l,:l) J'l<;,\l<, l , l l l l l l .~ i t .

-.- A'IOYII*;, 3,40O+ft.

111'1'1G11 l < I ' C l l ~~,IlOO-~- i t .

I ,( I \\' 1,: It l i l ' l ' < ~ l l l ~ ~ X l ~ : I l , i ,.rno rt. I J I ' I ~ I . : I ~ ~!ltI?.'S'l'ON. .J,llIlO-~-ft.

J.OWT.:R (~lt.l*>S'l'Ox. l~,Giltl+ft. I l ~ l s c c o ~ l c c ~ ~ l c t l

'J'otal ?n.:tno+rt.

- S'l'lil l'l*;L) l ' l* ;~ \ l i , 2.II1III-1-fL,

Ul'k'ER C;\ AIL3ItI,\W C:Ilicfly A1tl)I)rdE ( ! ~ \ A l l < l l l A N

hIlnDT,13 C'iAI 131<1z\W

I.O\Y 1;:R l'.\All3l<l,l~'

-

Purce l l R a n g e , Purce l l s e r i e s ,

( D a l y ) 1';rosion surf;11.,.

I ~I.:\C!Jil~'OO'l', I \ ) a ,uoc~+f t .

T3T,AC!KF'OO'r. .l.sns ~ t . -.

' l ' l*~l: l i . \ lNl~: ____ . _

-- -

lan

S Y S T E M

\Vi \ 1.1 .:\ (!K, 1.l11111 f t . S'l'. It Is:( : I s ,

l , l l l l l l ( 1 . --

--

--

RA \rz\rdT31, Lljll)lbr p:1rt, 4,550 f t .

*

I , O I ~ ~ E I ~ r t A \ r 2 \ l . ~ , ~ , 4,oOO+ft. J i a s e collc~caled

'l'Ot:ll 25,055 f t . -

--

- -

C. I).. I<ull. Gcol. S O ~ . A I I I . VoI. 10, ISg!).

li I.: \ ' 1,:'13'1', I . " I I I I f t . l : l ~ l ~ l i l * : , ~ , l l l l l l I'L, l ' l i l l ' l l .41tl) , ~ I I ) I I V I ' p:ivt, I ,:~llo+it. - . . .

rx)w I.:R l ' l l l l . . \ l : l , G,60O+ft. I::lst. c~ot~(~o:llt.d.

'I'ot:1l l7,2110.] ( I . . . . . -. -

I:<\ \ '~ \ l , l . l , 111)l)cl' l):lr!, Gl~Illl+-It. I:A \'A I . r , ~ . lt,tvt,r ) ) t ~ r t , :J.OOO+ft. -.

I I H A I III.UOO+ft. I ; :~se conr.cnIct1.

-- 'I'Ot2il - 27.oo0+it. -- -

-

. .

~. .

spixley

Text Box

24

spixley

Text Box

25

2 6 IDA110 BURE=\C O F J I I S E S A S D GEOLOGY GEOLOGY AKD O R E DEPOSITS O F BOUNDARY C O U S T P 27

CORRELATIOX TABLE NO. 5.

TENTATIVE CORRELATION O F BOUNDARY COUNTY STRATIGRPPHY W E S T OF PURCELL TREXCH W I T H 3fcCONIUELL8 AXD BROCK, AND P I T H DALT3.

CORRELATIOS TABLE S O . 4. (FRO31 S. J. SCHOFIELD.)

XVILLkCE, 4.000 f t . I " ~ $ , $ , r $ ~ o O ~ . I R ~ T ~ ~ ~ ~ ~ ~ , 4.500 f t . / (Beitian.) \

System

PRE-CAMERIBS

(Beltian.)

- ~ c c o n n e l l and Brock

- LOWER SELKIRI i SERIES,

(Cambrian.)

CPPER SELIiIRK, (Cambro-S~lurlan.)

ST. REGIS, 1,000 f t 'RAvAkLI, RECE'PT. 1,200 ft. 1 X,O~O BURKE, 2,000 f t .

--

SYSTEM 3 and 9 See Bibliography

C Z ~ A l I ~ 1 ~ l ~ l S

CORPLELATIOS TABLE NO. 6

TENTATIVE CORRELATIOb- O F BOUSDARY COUKTY STRATIGRAPHY EAST O F PURCELL T R E S C H W I T H CALKISS' , DALE', a n d SCHOFIELDIJ. 14.

PRE-C-kJIBRI-kS

CRESTOS, 5,000 f t . I

Daly

I R E S E VOLCASIC FORlfATION. I R E S E ,

conglomerate. (Basal Belt.)

UXCONFOR3IITY

Pl l IEST RIVER TERRANE,

(Pre-Eeltian.) - LiITCHESER

Middle Cambnan P ~ ~ ~ l ~ ~ L RANGE'

Modified by Schofield

Erosion Surface. GA'L'EWAY, 1.000 f t .

PURCELL lava

STYEH. 4.000 ft.

COEUR D'ALENE ZABINET RANGE District, I Montana.

(Calkins') I (ca ik insL)

PRICHARD, PRICHXRD, XLDRIDGE , S.OOO ft. I

Kirkham

PURCELL Lava?

S I Y E H ?

UNCOSFORJIITY.

CRESTOX- RAVALLI GROUP - ALDRIDGE- PRICHARD

Erosion Surface. STRIPED PEAK,

1.000 ft.

I I I

1. CALKISS. I?. C., Prof. Paper 6 2 . 72'. S. Geol. Survey, 130s. 2. , Rull. 3s;. U. S. Geol. Survey, 1909. 3. DALT. R. A,. 3Ienioir 3s. Canada Geol. Survey. 1913.

Erosion Surface,

Shales a n d sandstone. 10,000 ft .

STRIPED PEAK, ~ o n o f t .

- -

1, 3. 13, 14. See Bibliography.

System

P E E - CAMBRIAS

(Beltian.)

Daly

KITCHEXER. (Niddle and Lower Cambrian.)

CRESTON. (Lower Cam- brian a n d Beltian.)

MOYIE, (>Iiddle Cam- brian.)

KITCHENER, (Xiddle a n d Lower Cam- brian.)

CRESTON. (Lower Cam- brian a n d Beltian.)

Schofield

CRESTOS

ALDRIDGE

Calkins

XEW-LAND WALLACE BLACKFOOT

RAVALLI. (St. Regis) (Revett) (Burke)

PRICHARD

Kirkham

KITCHENER- NEWLAND- WALLACE

CRESTOS- RAVALLI

ALDRIDGE- PIiICH-4RD

2s IDAHO BUREAU O F NIXES A S D GEOLOGY

S T R U C T U R E .

GEXERALSTRGCTURALFEXTGRES O F T H E AREA.

The structural factor which has most affected the county is faulting. Several large faults, including one overthrust fault of great extent and eriormous throw, traverse thc connty, but only tx-o folds of major importance were noted. The axis of a flat-topped anticlinal fold, with the Aldridge-Prichard formation exposed a t i ts crest, strikes north~vest to southeast through the extreme northeastern par t of the county. The other folcl is an undulation of the tilted beds in the Aldridge-Prichard formation and inclucled sills. I t s attitude is illustrated in structure section A. A. Plate 111 (in pocket.) All areas of sedimentary and metamorphic rocks, excepting Quaternary lake beds and surface deposits, are generally steeply ti l ted as illnstrated by clip signs on the maps and by the structure sections.

Several faults are believed to exist in the area iminecliately bonnd- ing the rnain mass of the batholithic intrusion in the Selliirk Range, but metamorphism is so marked as to prevent recognition of members of the forlnatiol~s in the li~nitccl time available. 11-ithout detailed knowledge of the 1-arious 1nern11er.s of these formations many apparently small displacements could not be proven. I t is believed that Inany sm;lll faults of short length and little vertical or horizontal dis- placelnrnt exist in this area borclering the bi~tllolith. O n l - painstalc- ing dctailccl study, TI-llicli rras impossible in this rapicl reconnaissance\ \vonld revcal enough data for lnapping tllelll.

T x o faults, n-hose location anct es tent are cluestionable, h i~ve bccn jlitlicatcd in the estreme nor t l~~rcs tc rn p;ll*t of tlie county. A11 other 111appcd faults ha\-e been definitc.1~- iclcntii'ic~tl and a good idea. of tht. strntigrnpl~ic rclationsl~ips was obtained ill c>ach case. The rnost iln- portalit f i~u l t s have been given r1xrnc.s and arc sho~vn on tlic map.

Consitleratioll of tllc major structural features of Iclaho in light of the diastropliic ~t-eclgc-theo1.p of R. T. Cllanl1,crlitin" ancl his assoeiatcs, nlaltes i t appeilr possi1)le t11at a compressio~lal origiu for the \vhol(~ Rocky l\louutaill systein ma.>- be assnmcd. Jlucli close folding and 01-ertlirusting is present througliout tlie spstcm, and further detail stndy, n-hich is nulv being prosccutecl, tcllt;ltivcly points to the dc\-el- olxnent of two-sidecl n-edge zorics from connpressional stresses. I t is

*C!inn~l>crlnf~. Rollin T.. The \\-edge Theory of Dinatroghism: Jour. of Geol. PP. "-- , ~ a - ' i 3 2 . Vol. aa. 1925. Flint. Ric!inrd Foster. A Brief Tie\\- of Ilocky JIountnin Structure; Jour. of Geol.

p p 410-431, 1701. 32, 1924.

GEOLOGY AXD ORE DEPOSITS O F BOUNDARY COUNTY 29

not impossible that the block between the Moyie (Lenia) overthrust and the Kootenai fault may prove with detailed study to be one of these wedges.

The down-throw of the north-south faults is on the east side of the larger ones and on the west side of most of the minor ones. Although nearly all the faults appear to be normal in character, the planes seem to be nearly vertical, and may, i n some instances, actually be overthrust. The strikes of the faults appear to follo\v no certain system. although some of the major north-south faults follon- fortnation strikes for par t of their length.

Faul ts have every\\-here espressed themselves i a the topography. Their site is usually marliecl for par t of their lengths, a t least, by wide valleys o r streams. Along the larger faults zones of TI-ealxess and much crushing must have occurred. This resulted in valleys developed both by water ancl ice erosion along these zones. Continental and huge valley glaciers have recently invaded these fault-formed valleys and removed evidence of any escarpments ~ r h i c h may harc

\ existed, ancl a t the present time, because past continental glaciers have overridden all the mountains in the area, the dov-n-tliro\~n side of the block is as liliely as not to be the highest in elevation.

Although the age of faulting can not be definitely placed in this area i t is certainly post-Beltian and pre-Pleistocene. Observations by other geologists in nearby areas place i t definitely as post-carbonifer- ous. All the faults are almost certainly later than the folding and from evidence cited by Schofielcl '"appear to be Jurassic in age, in the area immediately north of the JIoyie and Yahk Ranges. Scl~o- field14 believes the Nelson batholith to be Jurassic in age and thus cites his chief faulting period as Jurassic. Both in this county ancl in British Columbia the major faulting seem to be genetically associated with the batholith and its outlying cupolas. If the batholitliic intrusion is Cretaceous in age, as much evidence seems to indicate, tile faulting would be assigned to the Cretaceous. Schoficld13, in his East Kootenay area, finds only one later fault TI-liich he a ~ s i g n s to early Tertiary.

SPECLAL STRVCTURAL FEATURES O F T H E AREA.

Cabinet Range.-This range, made up of Aldridge-Prieliard sediments containing intercalated basic sills with a generally eastward tilt, has been previously considered as beginning a t Bonners Ferry and

30 IDAHO BUP.EAU O F h l I S E S AXD GEOLOGY GEOLOGY AX'D O R E DEPOSITS O F BOUSDARY COUSTY 3 1

extending sontheastn-ard into 3Iontana and Bonner County, Idaho. To tlic writers, the structural evidence would make necessary the inclu- sion of that area lying \vest of the 3Ioyie (Lenia) fault and east of the Purcell trench as f a r north as Round Prairie fault. This newly included area has formerly been assigned to the Purcell Range. The boundaries of the range in tliis county as 110~1- outlined by the writers arc, Rouncl Prairie Vallcy, caused by faulting, on the north, tlic JIoyie (Lenia) faul t on the east, tlie Kootcnai faul t and the Purcell trelich on the west. and outside of the area the IIope fault on the south.

13csidcs the east~rard-dipping illdriclge-Prichardr ancl included sills this range contains in this county a large batholithic intrusion about 3.3 miles by 7 miles in dimension as Ire11 as four slnall outlying cupolas of the same intrusion.

Selhirk Range.--This range. I\-ithin Boundary County, is chiefly made up of a large batholithic mass which is par t of the Selson batholith. The range is structurally delineated to the east by the Icootenai fault and Purcell trcnch, ancl estcnds out of tlie count - in all other directions. The Alilridgc-Prichard beds on the cast side represent a long, narrow roof pendant about 30 miles by 3 miles in dimension. Tliese bccls are greatly clistnrbed arid metamorphosed but hare a general clip to the west, northwest, o r sout11r~-est, a t varying angles, but with a general strike to the northeast. This is distinctly cliscorclant with the northwest strike of tlic Xlclriclge-Pricharcl formation east of thc I'urcell trench and s ~ ~ p p o s e d Iiootenai fault. The Creston-Rnvalli ( 1 ) beds rvest of tlie main batholithic Inass arc ncarly vertical or dip slightly to thc batliolitli on the east. Their strike is also generally nortlieast. The Siyeh ( a ) ancl Pnrccll lava ( 5) stand almost rertically in the northivest par t of thc county near the bounclary line and also strike northeast.

Tllc batholithic mass in tliis range estencls thc entire longitndinal length of the county and s l io~rs a width in escess of 23 miles. TTI-o outlying cupolas are csposed in tlie extreme nortlirvestern par t of the county. TKO questionable faults are sho~\-n on the map.

Purcell Range.-This range is represented in tliis county by t ~ v o subordinate ranges. Thc Yalll; Range lies in that par t of the county situated cast of tlic JIoyie (Lenia) fault and is made u p of Aldridge- Prichard, Creston-Raralli, Ritchcncr-Sen-land-ll'allace, and their included basic sills. The structure of this range is anticlinal, and par t

of the west limb of the main anticline is shorvn in this par t of : h t 3

range. The beds are flat-lying at the crest and dip steeply soutlirvest- xi-arc1 near the Noyie (Lenia) fault. Other stleuctural boundaries of the range lie outside of the county.

Another minor range of the Purcell is the 171oyie Range, which lie, mainly in Canada but extends into this county as f a r soutll as Round Prairie fault and its ralley. This range, chicfly made up of easttvarcl- dipping Aldridge-Prichard (in this county), is bounded 011 tlic east b~ the JIoyie (Lenia) faul t and on the west by the Iiootenai fault and the Pureell treuch. I t s northern boundary lies i n Canada. I n this county i t contains three (possibly four) minor north-south fault> ~vhicli have disturbed the dldridge-Pricllard and have protecte(1 a small wedge of Creston-Raralli ( ? ) a t one place.

Purcell Trench.-This depression, which separates 3Ioyie Rangc from the Selkirl;~ in the northern par t of the county and the Cabinet Range from the Sellrirli Range for the rest of its lengtli in the county, -estencls without interruption a s f a r south, accorcling to Call;insl. as 'the south end of Lake Coeur d7Alene. This is-aclista~lce along the lint. of tlie trench of more than 100 miles from the poiilt ivhere it.1eares the southein boiniclary of this county. Aceording to Delyq l le Porcell trencli estentls for more than 17.5 miles into Cmada, rrhicll mitli ;I - . -- ~- length of forty miles in Boundary County,gives the treucli a total length of a t lcast 315 miles. ~o the south of the county, the trenc11 reaches a \~-itlth of nine miles and a t one place n-itliia the county i t becomes less tila11 one lnilc across. The average n-icltll f oy i t s entire distancc is bet~vecn 3 and 4 milcs. (Pl. I., ~~ontis;ikcei &d P1. 1'111..

- - . p. .5'7.) The trench is occnpiecl b - Kootenay a ~ l d Coeur cl'3lene 1al;e.i: and par t of Lakc Pend Oreille as well as many s~ua l lc r lakcs an({ swamps. Bootenii, Spokane, and Pack rivers, and sc\-era1 creeks, use this depression for a few miles each.

The present elevations of the lake surfaces in this trerieli range fro111 about 2000 feet above sea level a t the southern end to belo~v 1750 a t its northcrn estremity. The-tre~y!t_!~ottom is probably nearly 500 . .. -. feet de_eper in the larger lakes. The relief afforded b i this depression is

. -- most notable, flanked as i t is a t many pointsbn either side by ranges towering to altitudes of nearlv SO00 feet.

The f la t b<tto'~n . of this depression. a l lere not now occupied by . - . . - .

lakes and - siramps, is corer id with f lur ia l and lachrtriue deposits. All tributaries arc marked either by hanging va l Iq s or deltas.

32 IDAHO BUREAU OF MIXES AND GEOLOGY

The walls of that par t of the trench lying in this county are made up of the Aldriclge-Prichard quartzite with included sills, o r granite batholithic intrusions. The roclis of the Belt series strike in a direction which cuts across the trench i n ~ this area. The sediments also ha~oa:cjoss-cuttiog relation, both north and south o f this area. The origin . of -. the trench is disputed. Schofieldl-' says concerning-its origin: "The region now traversed by the Purcell trench was penc- plained in the Cretaceous, uplifted in the early Tertiary ancl the Pur- cell trench was eroded by one of the rejuvenated Cretaceous rivers during Tertiary times. Xo uplift is recorded in Tertiary or'-re-cent times. The Tertiary valley \\-as glaciated in Pleistocene times, giving rise to the facetted sp~ i r s ancl hanging valleys so prominent in the architecture of the Pnrcell trench." Schofield14 thinlts no fault . is . necessary to explain the presence of this great uninterrupted clepres- sion. Daly3 postulates the formation of the trench by faulting and suggests that i t is a graben" 11-ith faults along . each . . valley ~va l l , and that the trench has been g l a c i a t e d ~ ~ l e i s t o c e n e time. Calkirlsl says that hc and Ransome four~tl some evidence that the trench had -. been detcrminecl by a great fault with the dov-n-throw on the east. They

.-. . . .. thought the beds to the west of t,he trench to be Archean aild separated from the Prichard on the east by the fault. D a l y h l s o believed the roclts to the west of tlic trench to be pre-Beltian and postulated a do\\-nthron- of 30,000 feet in liis fault.

The ~vri ters -- ~ . . . . found . . mncli . - evidence of a major fault, but believe the sediments - . - . on . . . both - sides of the fault are Aldridge-Prichard beds. This fault 1~7ill be discusse~cl in detail as the Icootenai fault. Lobes of the Pleistocene continental glaciers i~i t r i idei l t l l is depressioll ancl left hanging valle\-s, ancl truncatecl the spurs in some places for an estimated distance of two miles, and i t appears evident tliat glaciation is entirely responsible for the wiclth ancl depth of the trench and its present pliysiographic characteristics.

Kootenai Fault.--Evidence of a major fault in this area, extending from the boundary line south as f a r as 1301lners Ferry, IT-as discoveretl by the ~i-rifets. The fault line, as shorvn upon tlie map, follon-%-the trend-df the meandering Kootenai, TI-hose meanders, of course, are very recent and were developecl on the flat-bottomed valley of lon- gradient developed by the last glacial invasion. The fault -- zone prob-

*For the faults from

benefit of adjacent

the layman: areas known

. graben is a section of the crust separated b y horsts which have been relatively eievnted.

GEOLOGY AND ORE DEPOSITS OF BOUNDARY COUNTY 33

sbly extends Tarther to the south but the presence of granite on both _ - - . . .. . sides of i ts projected strike, par t ly covered by lacustrine deposit?, mazes proof difficult.

I n thenorthern of the area the Aldridge-Prichard beds on the west wall of the trench strike several degrees east of north and dip about 20" to the northwest. Evidence of these beds extends out to the river where occasional rock outcrops, of a size too small for mapping on a reconnaissance map of this scale, project out of the alluvium. To the east of the river nearly flat-lying basic sills are exposed in small knobs. These sills are par t of the Blclridge-Pricharcl formation which maltes up the trench wall on the east. The Aldridge-Prichard, and included sills, strikes sevez.al degrees west of north and dips N. 12"-15" E.

The rocks on the \vest \call are highly schistose, but no sills corre- sponding to those observed on the east side were discovered, although the sills shoulcl appear on the west if the trench were cut along the crest of a wide gentle anticline in the Aldridge-Prichard formation. The discordant strikes and dips, the absence of similar sills on the west side, and the abrupt contact of the nearly f la t basic sill east of the river with the western schists, all point to fault relations x i t h he don-n-throw on the cast side. 3Iajor structural considerations, however, point on the other hand to the likelihood of this being an overthrust with an easterly dip.. From Copeland south to Bonners Ferry, the schists ancl quartzites to the westward extend into the valley for a distance similar to those farther north. On the east is found a granitic batholithic intrusive whose continuous straight-line cobtact 1~it11 the metamorpliosecl Xldridge-Prichard suggests a fault. The strike of the TI-estern roclis varies from northrvest to north a t this point and tlie dip to the west ancl nortlirvest steeperls in places to 80". On the eastern valley-\\-all the A-ldridge-Pricharcl formation and the sills continue to strike west of north and dip from 30" to 40" to the northeast. These continued discordant dips and strikes offer further persuasive evidence of faulting. Similar evidence, but not so conclusive, extends sontll~vard to the county line. The fault, if i t exists, has an estimated

- . . -- - . . down-throw of p r o b a b l y - ~ ~ ~ ~ f & t , b r more to the east, and probably has a close genetic relationship with the l o n i batholithic mass east; of the Kootenai River and Deep Creck.

Round Prairie Fault.-This is an east-west fault ~vliicli separates Moyie Rangc from Cabinet Range. I t has formed a depression, since glaciated, ~vhicli is knovn as Round Prairie. The down-thrown side

34 IDAHO BUREAU O F N I X E S A S D GEOLOGY GEOLOGY AXD ORE DEPOSITS O F BOUSDXRY COUSTY 3 3

appears to have been on the south and a horizontal movement of about three miles may have occnrred here. There seems little doubt that the two sills esposed east of Port Hill are the same two exposed on the east valley wall south of SIission Creeli. These latter sills stop abruptly in Ronnd Prairie Valley. The block north of Rouncl Prairie contains three faults shown on the map and possibly another one paralleling the course of Upper SIission Creeli. The -4ldridge-Prichard is probably duplicatecl here but the absence of sills to serve as horizon markers made this fault too doubtful to map. The Ronnd Prairie fault appears to be normal and the vertical throw is probably not less than a thousand feet.

Moyie (Lenia) Fault.-Calkins1 shows his Lenia fault, in this area, extending from the 3Iontana boundary line along the course of the Kootenai River to a point near ~vhere the river changes its course ancl flo~i-s m-est. From there he tentatively projects i t to near the mouth of Xoyie River near 3Ioyie Falls. He also sho~vs a fault about three miles long a t the Canadian boundary striking nearly north and soutll. On both of these faults he places the down-throw on the east side 11-here the younger beds are esposed.

The writers had no difficulty in connecting the two faults of Cal- kins. Beds of discordant dips and ages are o b ~ i o u s for the entire distances. The fault a t the Canadian boundary recognized by Calkinsl \\-as also described and mapped by DalyQncl Schofielcll-'. The latter geologist named i t tlie 3Ioyie fault and traced i t for a distance of 4:3 miles in British Columbia to the valley of the Kootenay River east of Cranbrooli. Although i t dipped steeply, he found i t to be an overthrust fault with tlie overthrust block on tlie west. The total length of the Lenia fault, i n Idaho ancl ?Jontana, as mapped by Calkinsl is about 30 miles. An additional length of 1'7 miles along the llIoyie River in this area is given by the writers. The fault, 11-hich follo~vs the general course of the 3loyie River throughout Boundary County and much of British Columbia, is thought by the writers t o be more properly named the Noyie (Lenia) fault. This steep overthrust fault has a total traced length according to Schofield14, Calliinsl, and the writers, of 90 miles. It describes a wide arc in British Columbia, Idaho and Nontana, and approsimately 26 miles of this length lies in Boundary County. A t the Canadian boundary the Aldridge-Priehard rocks strike west of north and dip from 45 to 50 degrees to the fault on its western side. Creston-Ravalli rocks striking north and north-

east dip 60" or more to the fault on the eastern side. The entire western side of the fault in Idaho is made up of Aldridpe-Prichard beds ancl sills clipping from 50" to 60" to the fault. From the Montana line to a point west of Perkins Lake, the east side of the fault in Iclaho is made up of Ii'itchencr-Se~rlarid-IT-allace beds clipping 50" to 60" to the fault. From this point north to the Canadian Bo~uidary, the Creston- Ravalli lies on i ts eastern side ancl dips from 50" to 60' S. IT. The vertical throw in the southern part , according to Calltinsl, is more than 15,000 feet and aceording to estimates of the writers may be nearly 18,000 feet. The horizontal overthrust is probahly not one- third of this distance. This fault has influenced the course of thc Kootenai River for several miles a1ic1 controlled the conrse of the Moyie River fo r much of i t s length. I t s entire course has been glaciated, thus eliminating an)- notable physiographic features due to faulting.

Upper Priest Rioer Unconforrnity.-Along Upper Priest River the coarse sandy conglomerate ancl overlying lavas tentatively called tile Siyeh and Pnrcell lava, respectively, which are situated west of the stream, appear to lie in angular and erosional unconfor~nity on the rocks east of the stream. These roclis, the writers have tentatively assigned to tlie Creston-Raralli group. A great erosional or depositional hiatus occurred here if these assumecl age relations are correct. Be t~reen ten and tn-elve thousand feet of Creston-Rnvalli and orerly- ing beds are missing. Either these 71-ere not deposited or they have been eroded. I3vidence points to the latter. 31~1th material i n the S iye l~ ( ? ) appears certainly to have been derived from rocks very siliiilar to these missing members. The atti tude of these beds is shown in the structure section D. D. on the map, Plate 111. ( in pocket.) For several miles the course of 'C'pper Priest River has been controlled by the unconformity.

I G N E O U S GEOLOGY.

BATHOLITHS.

Pa&~f._the.\'elsol~ batholithic mass lies in the central-and western par t of the county. Four outlying cupolas have been uncovered in

--A__ _ .

the eastern par t of tlie area and tivo are esposed in the northtvestcrn part. The magmatic intrusion which is believed to have occurred during 3Iesozoie (Cretaceous 1) times is now exposed chiefly as

.- granodiorite, quartz-monzonite and granite. All of these are, of

-. ..- - -. . . .. ~.

36 IDAHO BUREAU O F MINES AND GEOLOGY GEOLOGY AND ORE DEPOSITS O F BOUNDARY COUNTY 37

course, assumed to be differentations from a common magma_possibly ___i__----.--

diorltlc in cqmposition. fi-the field the rock shows a uniform light grey and pink color and

a t every place-observed, excepting the cupola a t Bald Ridge, showed l a v e . phenocrvsts - - w - - - of pink and cream colored orthoclase feldspars. iP1. VII., p. 50.) Phcnocr-sts as long as two inches mere common and Carlsbad twinning appears often. TIie plagioclase feldspar which generally is oligoclase, albite, or both, shows striations, and is n-liite in color. Quartz is generally abundant throughout tlie areas 0 1 ) - served. Biotite anel llornblencle occur in small quantities. 3Lib:i.o- cline and similar orthoclase types were observed as minor mint:-:-::is in some specimens. The most notable field characteristic of r:ib

igneous rock is i t s porphyritic appearance caused by the immi:,,i: orthoclase plienocrysts. Jointing is very comnion throughout m+,t of the masses. These joints are comrnonly occupied by pegrnatltic s n d aplitic dikes. (Pl. IS., p. 56.) Few basic dilres were observed. 1 t - i s believed that this irltrusion, lvllkh is -undoubtedly par t of the Nelson batholith, may serve as a correlation link with the Idaho batholith to the south, ~t~llicll also has a similar porphyritic feldspar phase a t many localities, as \\-ell a s a similar mineralogical conte~i t An aureole of gneissic and scliistose matcrial with an arerage thicliness of about 500 feet is coln~nonly found as a transition phase. A fen- circular expanses of this matcrial, a t a distance from the nlain intrusion, indicate areas underlain a t a sliort clistance by cnpoltis. Contact metamorpliism is apparently ~ r c a t e r a t tlle roof than a t the sides, on account of the presence there of more niagniatic gases and altcrinp agents. The batholitli in this cou~i ty has been erodccl to the fourtli horizon or embatholitllic stage of Enimons-. In this area molybdenum is the only nietal found in conlnlercial cln21ntities in tlie main granite mass.

SILLS.

The Moyie Sills dcscribcrl by Daly 3. -L alld S ~ h o f i e l d ' ~ . l4 and mentioned by Call.;insl are abluiclant1~- I-epreselited in this area. A11 of' the sills observed east of the 1'11rccll trellali are r e p r e s c ~ t e d on tllc geologic map. Tli1~ougliout the t e s t these sills ha re been referred to as basic igneous sills. An attempt will nolv be macle to clcscribc the111 in more detail.

*Ernmons, W. H.. The Relatioils of JIctnlliferous Lode systems to Igneous Intru- s i v e ~ , S o . 1571-1. Trans. A. I. 31. 1.:. June. 1926.

These sills are distributed generally throughout the lower par t of the Belt (Purcell) series ancl are particularly abundant in the Xld- ridge-Prichard formation, in which 14 different sills mere observed. The Cres ton-Ras1 j group of formations showecl three sills. These sills are believed by the writers to extend several miles into Canada, as ~ v e l l a s into JIontann, and Bonner County, Idaho, to the south. Highly metamorpliosed remn;lnts of these sills are believed to have been discovered in the Xlclridge-Prichard lying \vest of Purcell trench. The tlliclrness of these great, in)ectecl, tabular, igneous masses ranges in this area from :I0 to 2000 feet. One sill is csposecl for 3-1: miles witllin the c o u n t y c l is f z l t e d a t the nortli, here its offset extends for 5 1-2 miles more before entering Canada. Because of their supc- rior resistance to erosion they generally are exposed in ridges, peaks or cliffs.

The lithology of these sills is variable but tiieir ~ i l a in nlass is made up of altered gabbro and cliabase clianged in many places bj- uralitiza- tion to a dioritic type.

Gravitational differentiation and magniatic segregation 11a1.e produced, i n a few instances, zones of quartz diorite and granite. The granite zone, where present, is always in the upper par t of the sill ancl the quartz diorite seenis to be a transition zorie betn-een it and the uralitized gabbro. Tlie texture varies from holocrystalline to fine- grained in the thick sills and is sometinies porpllyritic in the thiiiner intrusions.

The original augite of the gabbro is nearly all changed to a greenish-black hornblencle in most places. Lath-shaped labradorite feldspar is second in abundance. Angite and hypersthene'are minor minerals as the roclr is now constituted. JIagnetite, pyrite, pyrrhotite ancl chalcopyrite arc present as accessory minerals in the basic sills. -1 little quartz and apatite are the other minor lililierals in tlie basic. phases. Long pegmatitic segregation zones often occur in the larger sills, but these are orlly strealrs parallel to tlle contact, ~vh ich do not fill craclis, joints, o r fissures. Accorcling to Schofielcl12' the thickness of the granite zollcs in the upper par t of tlie sills does not bear any relation to the tliickness of the entire sill.

The sills were intruclecl into tlie flat-lying Belt (Purcell) series and have consequently taken par t in all the folding, faulting and orogenic movements which built the Cabinet and Purcell ranges.

38 1D;ZHO BUREAU O F MIXES AND GEOLOGY

The stratification of some of the sills, which now stand a t an angle of 60 degrees, makes certain tha t the segregation occurred in a flat- lying position. Columnar jointing perpendicular to the cooling surfaces 11-as observed in thick sills. JIetamorphism on upper as well a s ion-er contact is obvious. Schofield14 finds the stratified sills similar to those of Shonkinsag, and finds in them many characteristics which resemble those of the gabbro sills of Skye.

The contact metamorphic effect is much less than one would expect because the host rock in nearly all cases consists of the quartzitic Ald- ridge-Prichard o r Burke. I n no case did the writers see a contact zone more than five feet wide. I t sometimes is less than one foot in ~viclth. The sills are checker-boarded and crossed by cooling o r strain fissures a t varying angles. These are commonly filled with white massive quartz veins which often contain iron-bearing sulphides. These veins were never observed to extend into the invaded rock.

The sills do not intrude any rock in this area younger than the Crcston-Ravalli group. Daly3 describes them as intruded in the Siyeh formation east of this area n-here they are in close association with the Purcell lava. The sills and Pureell lava are considered by Scho- fieldH- l4 to be of Beltian age. This is the age assigned by the writers.

One of the sills in this area is thought to be 2000 feet thick, two otllers measure 1300 feet, and tn-o more are 1000 feet through. The total thickness of the separate sill injections in this cou11ty is estimated to be not less than 10,000 fcet. The sills a s now exposed take par t in all the structural mo\-emcnt creditccl to the Belt Series under the section on structure.

It appears evident that tu-0 maglnas. differentiated in a single reser- ~ o i r , contributed the material fo r both tlic JIoyie sills and the Purcell lava. The reservoir Tras probably gravitationally stratified and the more acid material producecl the sills in 11-11ich stratiEication now appears and a pure basic magma furnished the sills xi-hich are nevi- en- tirely basic. Both acid and basic flon-s are founcl in the Purcell l a m s with the acid flon-s, of course, subordinate to the andesites aiid bas- alts.

DIKES.

Dikes in the Belt (Purcell) series were observed a t only three places in tlie area. A t all places they were lamprophyres, and of small estent and thickness. I n the tn-o areas where they were associated with ore-bearing veins they were post-mineral and appear to have had no

GEOLOGY AND ORE DEPOSITS O F BOUNDARY COUNTY 39

influence on the mineral deposit. A t the other locality the dike appeared a s a n offshoot from an intruded sill.

Although many aplite and pegmatite dilies were observed in the granite areas, basic dikes appear to be few and small.

LAVA FLOWS.

The Purcell Lava (?) .-In the extreme northwestern par t of the county west of Srlowy Top'Slountain crops out a thick series of basic lava flows. These are called by Daly3 the Irene volcallic formation, of Lower Beltian age. Only a narrou- \\-edge of their outcrop lies within the boundaries of this county. Daly3, who has examined them in greater detail than the XI-riters ancl over a larger area, gives the section as follows :

TOP, Conforma1)le base of Jlonli formation. 50 feet, Greelistonc schist, a crushed basic amygdaloid. 200 feet Angular conglomerate o r breccia with phyllite

cement. 1,710 fect. Cirecnstone schist v i th a fen- thin bands of p h y l l i t ~

ton-ard the top. 40 fcet, Gray to white, fine-grained dolomite.

4,000+feet1 Shearecl and greatly altered basaltic ancl andesitic lavas largely greenstone schist.

DaIj3 states tha t the metamorphism is so great as to nlas!; the fl011- coutacts and to have destroyed all the original magmatic minerals c.x- ccpt plagioclnse and a few iron minerals.

Tlic l a ras a lw co~lt,lin sevcral beds of tuff, and the limestone. according to Dal?" is \ c r y similar to onc in the Sipell. Daly belie\-es that there is no donbt from his esamination of the interbeddect con- gloln~'ratc. that the pebbles are dcrivccl from the rocks lying east of Upper Priest River. The total thickness of this lava series is nearly GOO0 fcet in this area.

Tlie Purcell I a n , described by Daly3, in the ;\IcGillivray Range is 46.5 feet tliiclr and chiefly amygddoidal basalt-andcsite highly metamorphosed and essen t ia l l~ a greenstone. It inclucles 40 feet of tuff and breccia. Sclioficldl~ finds 600 fect of l a r a in this range. I n the Galtou Range the lava is 390 feet thick, with similar characteristics and a band of coarse tuff and breccia 40 feet thick. I n the Clarke Range the thickness of the I'urccll l a r a is described as 260 feet. I n the Iicn-is Rnilge fartllcst to the east it has a total thickness of only

40 IDAHO BUREAU O F MINES -4SD GEOLOGY

58 feet. It thus appears that the Purcell lava thickened to the west. Tlie number of flows also increases to the westwarcl. The Siyeh formation underlying i t has some lithologic similarities to the Irene conglomerate of Daly3 and also has a comfornlable intercalated relation with the lava such as is founcl in the Irene conglomerate.

Lithologically the Purcell lava ancl the Irene volcanic lavas are very similar. The greatest disparity is in thickness. The thickening t oxa rd the west in the four eastern ranges'favors the thiclrness of the Purcell l a u s in the Selliirli Range.

The writers believe the "Priest River Terrane" of Daly to be Ald- ridge-Prichard and Creston-Ravalli of the Eelt-Pnreell series. With Daly" the writers believe that the conglomerate of Daly's Irene vol- can ic~ , as well as the Irene conglomerate. contains pebbles from the "Priest River terrane" becls, ~ ~ h i c h both Daly ancl the writers concede t o be older. I f Daly's Priest River terrane is Beltian then the Irene volcanic formation is the Pnrcell lava. TIie TI-riters wish tentatively to assign this name to the formation.

VEINS.

I O R I G I N A N D R E L A T I O N S H I P T O ROCKS.

Veins of ten different types have been recognized in tlic area, and an attempt to list tliem in the probable order of their economic irn- portance is made here. But because the district has so man?- apparently different typcs. although only one or tv-o examples have n proven value, i t is difficult to be positive in this order of arrangement. On first thought, the relative importance of a vein-type might appear to de- pend on the nnmbcr of prospects slion-ing that particular type. On the other hand, tlie nuinber of prospects of any particular type, coupled with the lacl; of any known commercial ore bodies, luiglit he an argument fo r placing that particular type of vein l o ~ r e r in the scale of importance, on the grouncl that such veins of like type ~roulcl have been attacked a t many elevations and positions, thus increasing the possibilities of encou~itering comrnercial ore-bodies liad any been present. One large procl~zcer, l io~rever, might quite as readily estab- lish the importance of a single vein type. The ten types of vein recognized were :

1. Replacement ore-boclies in metamorphic rocks. 2. Shear-zone deposits along bedding planes of quartzite. 3. Joint-plane reins in granite. 4. Veins cross-cutting basic sills. 5 . Veins within sills and parallel to contact of sills and meta-

n~orphic roclis. 6. Veins along contact of basic sills and quartzite. 7. Veins along contact of granite and quartzite. S. r e i n s cutting contact of quartzite and sills. 9. Veins cutting granite, quartzite, and basic sills.

10. TTeiiis cutting across bedding of quartzite.

The first three are distinct types within themselves, the latter seven have a similarity in that they are all veins TI-hose walls s1io~1- little or no movement. I t might be well to state here that a detailed study was possible only in tlie replacement and shear-zone type of veins because for the niost par t the other types T\-ere undeveloped. Kone of the typcs shows any evidence of contact metamorphism. 11-ith the possible esception of the replacement deposits and veins containing the mineral scheelite, the tuligsten-bearing mineral.

42 IDAHO BUREAU OF MIKES AND GEOLOGY

REPLACEMEST ORE-BODIES IN JIETAJIORPHIC ROCKS.

The best example of the replacement type of deposit is afforded by the Idaho Continental Nine a t Klockman. The country rock is sericitic quartzite of the Creston-Ravalli group. This deposit lies approximately a mile northwest of the granite batholith which forms the greater par t of the Selkirl; Range in Boundary County. A large granite cupola again outcrops a mile o r less to the northwest and another cupola shows hardly more than half a mile to the northeast. Tlie lat- t e r cupola. however, has a rather limited estent and is entirely snr- rounded by metamorphic sediments. I n other worcls, the qnartzitic area in the vicinity of the property is approximately tn-o miles wide measured across the bedcling and, as may be seen by reference to the map (Plate 111. in poelict). is largely in the nature of a roof-peudant. The formation strikes northeast and extends for several hundred yards.

The ore deposit mas formed by a replacei~ierit ~~r'tiich. follo~ved the bedding of the rock. I n the \-icinity of the "red" vein the countr:- rock is very light colored but farther a1va-c- the rock is a much darker shade of bluish-gray. This n-oulcl suggest hydro-thermal or pneuinato- lytic action oil the count1.y rocl; a t the time of mineralization. Tlie bedcling dips 75" to 90" southeast, thus esposing the edges of the bed5 on tlie surface and affording an eseellcnt opportunity to note the change in the color of the c o u n t y rock as one approaches the "red" cre body. Fielcl e~iclcnce points to coiltact inetarnorplzism of sericitic sl~ales f o l l o ~ ~ e d by prieuuiatolyiic action accompanying ore cleposition. Such action probablj- ~ r o u l d take place along the sliglltly broken-up zone near the center or lon~itucliual as is of the roof-pendant. T11z above discussion does not apply to the "black" ore body.

Specimens of the light-colorecl rock accompanying tlie ore, ancl of the more distant blnisli-gray rock, \\-ere studied under tlie microscope.

The Clark rocli slio~vecl a consiclerable amount of magnetite, some of 11-hieh appearecl to be titaniferous, since a small amount of leneosene was noted. The specimens seemed to be made u p largely of sericite whose crystals sho~vecl a definite f l o~v structure except near the magnetite. Apparently tllc magnetite was so hard that the crystaIs could not conform to the flow structure near it. Tlie dark rock also contained a small amount of quartz and biotite mica.


The magnetite and sericite may be the result of contact metamorphism between the quartzite and the large granite intrusion. I f this be the case, it is not a t all unlikely t ha t all the sedimentary rock in the vicinity of the granite is altered.

The light-colored rock from the vicinity of the ore-body contained a considerable amount of sericite which showed the same flow structure as the dark rock. The light rock also contained a small amount of quartz and no little amount of pyrite in the form of well developed crystals which were distributed throughout the mass. There seemed to be little o r no magnetite o r biotite. From this i t ~vould seem tha t hydrothermal action had accompanied ore deposition o r a t least fol- lowed the same course through the rock.

SHEAR-ZOSE DEPOSITS ALOSG EEDDIIiG PLANES OF QUARTZITE.

The shear-zone type of deposit was found i n three rather widely separated parts of the district. The ~ v i d t h of veins varied from s i s inches to a maximum of five feet. The most important vein and a t the same time the one most developed, namely, tha t a t the Cynicle Golcl JIining property, varied in wiclth f rom 1y2 to 4 feet, with the actual zone of shearing probably a foot o r so wider. Tlie shearing appeared to be due to normal faulting.

This type of vein occurs along the bedding planes of the quartzite, occasionally cutting one or two thin beds cliagonally but in the main holding to the strike and dip of the bedding.

The upper par t of this type of vein s h o ~ s very little quartz. The quartz appears to come in small bunches here and there throughout tlic vein. Accompanying the quartz is generzlly found pyrite. V i t h depth, a small amount of galena appears wit11 no\T and then some splialerite. KO siderite \\-as noted. Gold ancl silver are present but their occurrence is spor1dic.

JOIST-PL-ISE VEISS I S GRASITE.

With but one esception, to be noted later, these appeared to be pegmatite vein-dikes occurring along joint planes in tlie granite. Most of them are a more aciclic pliasc than the enclosing country rock. They vary in thickness from a mere crack to three feet. One prominent series of these veiiis occurred in the large granite batholith compris- ing the Sellrirk Range. They seem quite persistent. TKO sets of these veins had the same strike but dipped some 60" from tlic horizontal in

e

0 u + E C

) 2

L-' t' ?

e 0

u + E C)

2 L-' t' ?

GEOLOGY A S D ORE DEPOSITS OF BOUNDARY COUXTT 45

respect to the strike and dip of the sill. This theory is adranced because the wider the sill the more material there ~ r o u l d be to contract with resultant fissuring in any clirection. Rirthermore, any fissuring that took place parallel to the contact of the sill with the adjacent roclc might actually take place on the contact itself, since tliat 11-ould be a natural plane of weakness.

The veins ~v i th in the sills and parallel to the contact are probably caused in thick sills by rapid cooling on contacts and slov- cooling in the interior.

The actual extent of these veins is not I i n o ~ ~ n , for the total aniouut of development on any one of tllclil is meagre. They vary in wicltli from a fen- inclies up to tu-elve or fourteen feet. The average range is from two to six feet.

With one or two esceptions, there seems to be no evidence of contact metamorphism. I n the case of the exceptions, contact metamorphism has apparently taken place follo~ving thc later granitic intrusion. Tlie filling seems to be largely a hard quartz with little or no movement either in the vein or betu-een the vein and its enclosing u-alls. Small quantities of golcl-bearing sulphides occur. througliout these reins.

Those veins ~vliich cut the contact of quartzite and basic sills seem to he greatly in the minority. T h e - appear to be strongest in the basic hills and to finger out in the clua.rtzite. This is what one ~vonld expect if the fissures n-cre due to shritilcage stresses. The fissuring ~ o u l d progress into the uietanlorpllics onl?- a very short distance, if a t all. Any force sufficiently great to cause fissuring of the quartzite to any cstcntt 11-oulcl probably be irlclepeiitlcrit of the contraction of the adjacent i g a e o ~ ~ s rock but ~ ~ o u l c l be liliely to take place along the snlallcr cracli which n-oulci constitute a plane of weakness.

In o~i ly one or. two instances were these veins explored along their strike for more than a short distance. Lil;c~rise in only one or tv-o instances \I-crc tlicy opened up in depth for more than a fe1-i feet. Devclogment has been conducted only by assessment ~ror lc methoils -a practict: resl~lting probably from failure to strilie any commercial ore-loclics. I\-it11 the consiclcrable number of these veins throughout' the entire field ~vherever the basic sills occur, i t seelns that a ferv eo1nmer.cii11 ore-shoots shoulci liare been discorered even with the compar.ntivcly I i~~i i t ed amor~nt of lvorlc tliat has been done on tlicm. Certniiilj- the liorizun of attack has 11ot been limitccl, for -cr-ithin the

46 IDAHO BUREAU OF JfIXES ASD GEOLOGY

entire field there is several thousand feet of difference between elevil- tions of some of the properties.

MINERALS.

Tlie principal eco~lomic mineral of the district is galena in close association n-ith a silver-Ilearing mineral ~rliicli is probably tetrahedrite. The galena varies in crxstal structure from fine-grained to very coarse.

Gold is fount1 in placer ileposits and scattered along some of tlie streams. Tlle size of the gold particles ranges froin fine to medium coarse. Gold is also found in some of tlie sulphide-bearing veins. These 1-eins s l lo~r pyrite, galena, and minor quantities of chalcoyprite, sl'lialerite, and pyrrhotite. It is believed the gold occurs chiefly ~v i t h the pyrite. Other minerals of possible commercit~l importance are molybclenitc and molybclite: the rnolybclenum sulpliide and oxide respectively. These two minerals are found associated with a brown, glassy quttrtz. Anotlier important inilloral of potential value is scheelite, the tungstate of calcium. Pyrite, pyrrhotite, arsenopyrite, sphalerite, ancl chalcopyrite, are found in minor quantities scattered tl~rongliout the veiils in the basic sills. These minerals are sometimes f o n d together in small bunches throughout the vein and may be acconipanied by sinall quantities of galena. Quartz, calcite, siderite. pyrrliotite, and pyrite, are the chief gangue miacrals. Garnet, actino- litc, enstatite, and hyperbtliene are recognizecl i11 tlic contact meta- morpliic deposits. Sonle of the pyrrhotite found in the district is nickel-beariilg.

O R E DEPOSITS.

Nost of the metalliferous lode ores are genetically related to batholithic intrusions. These are great masses of igneous magma 11-liich invade the country of a region ancl estencl with steeply inclined sides to a n unl<no~vn depth. The magma cools to igneous rock and is later exposed a t the surface in areas ancl patterns which vary with the degree of erosion. Batholiths are generally believeil to be orig- inally intrudecl as inasses which a re either basic or intermediate in composition but which, cluring the s l o ~ v cooling operation, are differentiated by various processes into 11-ell-Linen-n more acidic rock types.

The locle ores are believed to be given off after the differentiation is lvell on i ts \yay ancl the larger number of locles are associatecl with granodiorite, quartz monzoiiite, o r granite phases. I n recent rea rs the association of locle ores x-ith batholiths has received much study and very recently Emmons* has dividecl these ore occurrences into six groups, depending on their vertical ancl horizontal positions with respect to the batholithic intrusive. Each group corresponds to a n erosion horizon in the batholith. In the first one the batholith is as yet unrerealecl, ~vllile i n the s is th stage i t is cut to the core. The Coeur d7Alenc district 11-ould fall in the seconcl o r acrobatholithic group, n-here the ore cleposits oeclir on top of the batholith in or near cupolas o r clomes. 111 contrast with that stage. the Eounclary County area would occur in the fourth or embatholithic group TI-lierein erosion has advanced so f a r as to cut well into the main batholith and reveal subordinate large masses as well as many cupolas, domes. stocl;~, or bosses. The ore deposits in such a state are most likely to occur between the closely spaced igneous outcrops.

I t is also fairly 1-i-ell established tha t the common and well-knon-n metals have a vertical range of occurrence. This means that certain metals appear a111-ays to be deposited far ther away along the vein from the parent intrusive than others. Molybclenum for example is lower than copper, which is in tu rn lev-er than zinc. Tlie la t ter mineral generally underlies and overlaps lead, which is lower than or adjacent to silver, etc. Corroborative evidence fo r this depositional scheme, as I\-ell a s the embatholithic relationship suggested by Em- mons, is found in this county.

'Emmons. W. H.. The Relations of 3Ietalliferous Lode Systems to Igneous In- trusives. Xo. 1571-1. Trans. A. I. JI. E. June, 1326.

48 IDAHO BUREAU O F MIXES AXD GEOLOGY

L O D E O R E DEPOSITS.

LEAD-SILVER ORES.

. In 1923, lead in tile form of galena was being profitably produced in only one par t of tlie countv. Silver occurs v i t h the galena in a direct ratio of 0.35, to 0.40 of a troy ounce of silver per ton to thc per cent o r "unit" of lead. Pyrite and siderite are present in varying quantities. Little quartz is in eridence with the ore, and for tlie most par t the particles of galena are coarse and easily broken along the clearage planes. I n atldition. the ore contains a small amount of sphalerite. The ore occurs in the replacement type of vein and is by fa r the most important deposit of the district yet known. This type of deposit is best seen a t the Idaho Continental 3Iine in the nortlirvest corner of the county. I t is llot unlikely, however, that similar cleposits may be opened up to the west and southwest of the Idaho Continental in similar formation.

A t the Idaho Continental, the ore bodies occur in large kidneys with their axes parallel to the strike of tlie formation and dipping roughly parallel to the bedding. (PI. IT., p. 41.) They also have a very f la t angle of pitch to the northeast. The ore has a tenclency to zigzag back and forth as it fol lo~rs the various cleavage planes and cross-cracking. This "stepping-over" of the ore gives somem-hat the appearance of an ore body cutting the bedding. (Pl. XIII., Figs. -4 ancl C.) The size of tlie kidneys of ore, couplecl wit11 the fact that the formation has a Yery steep dip, renders tlie orebody readily ~vorliec! by open 01-crliancl stoping. The stopc, remain open for a

. long period after the ore lias been extracted. (Pl. XI., p. 61.) Although several other properties throughout the county s h o ~

sltlall quantities of lead-silver ore, none has bee11 snffieiently d e ~ e l - oped to assure comnlereial procluetion.

GOLD ORES.

Gold, together wit11 \i-llate\-er silver may be alloyed with it, is found i11 the shclar-zone type of T-ein in quartzite as ~ r e l l as in the veins of the basic sills.

The best example of tlie sliear-zone type of veiu so fa r devclopcd is founcl.at the Cynicle Golcl 1Ii1ii1ig Compa~iy's propcrty on Buelihorrl 3Iountain. Thc shearing has tnlren pl;~cc along the bedding and onl>- occasioii~illy does i t cross the I~etldiny. ancl t l ic~l a t such a srn:~11 angle a t to give the i~i~prcasion of sllt.;~ring only between tlie bedding. Tile

GEOLOGY AXD ORE DEPOSITS O F BOUKDARY COUNTY 49

gold is free and quite fine and seems to be associated with the iron sulphides which, of course, appear in the upper parts of the vein. There is evidence for believing tha t the gold will decrease with the iron sulphides a t depth and give way to the sulphides of lead and zinc, with accompanying silver. There is comparatively littie quartz in the vein except near the apes where it is honeycombed. There is little evidence of post-mineral movement,

Gold is also found i n a n 18-inch gouge seam between the bedding planes in the quartzite on Queen Mountain. This was in the Queen Group of the JIoyie Golcl >fining and Xilling Co. The seam is 130 feet from and parallel to a vein on the quartzite-diorite contact. As the seam was exposed only by the perimeter of a cross-cut t o the contact vein, sufficient evidence \\-as not obtained to determine its importance.

Free gold was also panned from a massive quartz vein occurring in a basic sill on Boulder Creek. This vein was the property of the Boulder Gold Mining Co. The re in ranged from a f c ~ v inches up to five feet in a comparatively short distance and the gold seemed to be irregularly distributed. KO other minerals %-ere observed. This vein is one of the typical veins in the basic sills approximately paralleling the quartzite contact. The contact \\-as not found but float in- dicated its presence a t no great distance from the vein.

A11 of the veins in o r connected with the basic sills have apparently derived their gold from the sills themselves. The reasons for arriving a t this conclusion a re : First , that the sill rock was found to contain pyrite and pyrrhotite carrying gold in estremely small amounts; second, that the sills are unmistakably of Beltian age and are therefore pre-batholithic. These two facts point to a magmatic segregation of gold-bearing sulphides within the sills themselves, since the veins are not sufficiently continuous in any direction to have obtained their mineralization from an esterior and la ter source.

hIOLYBDENUJ1 ORES.

JIolybdenum occurs in the pegmatitic veins along joint planes in granite. The pegmatite consists chiefly of smoky, glassy, quartz and mica with the metal occnrring a s the sulphide, molybdenite, as well as the yellow oxide, molybdite. There has been too little work clone on these veins either laterally or a t depth t o permit judgment as to the probable extent of mineralization. The largest showing of this

50 IDAHO BUREAU O F NINES AND GEOLOGY

metal is found a t the International BIolybdenum Company's property in the Phoebe Tip country. JIolybdenum was also found in the granite area near Brush Lake a few miles east of Copeland. From the showing, one is justified in saying that the deposits have economic possibilities.

TUXGSTEX ORES.

Tungsten in the form of scheelite occurs a t the JI. & F. property formerly the Tungsten Hill, in the Queen Mountain district, in fissure veins in a large basic sill. A short distance from the property the sill contacts with granite. This granite is par t of the Queen Nountain cnpola. The main vein is from 5 to 6 feet wide. I t strikes nearly east and dips 70' N. This vein comes under the class of veins cross- cutting basic sills. Another vein on an ad.joining claim runs approsimately north and dips some 60" E. It comes under the class of \reins parallel to contact of basic sill and quartzite but lies ~ rho l l y within the sill. This vein has been prospected only to a limited degree.

The face of the drift on the main vein shou-ed massive quartz with scheelite, specks of galena, pyrite, pyrrhotite, and green copper stains. A sample by Professor D. C. Lil-ingston7 taken across a 51,4 foot face s h o ~ ~ e d an average assay of 1.09 per cent \YOj

Scheelite forms under conditions of high temperature and pressure auci is considered a contact metamorphic procluct. This fact, together with the presence of several other typically contact metamorphic minerals, such as garnet, actinolite, enstatite, and hj-persthene, and the prosimity to the granite. suggest a contact metamorphic origin.

ZISC ,LSD COPPER ORES.

Occurrences of both zinc and copper were too limited i n extent to forecast their possibilities as ore. Traces of one or both were found in the majority of reins in or adjacent to the basic sills. I f in in accordance with Spurr's* theory of ore deposition, these two metals underlie the lead-silver horizon, i t is possible that erosion has not yet uncovered thern, or that development has not proceeded to a sufficient depth to reveal them. On the other hand, even by this hypothesis, zinc and copper ~irould not be abundant a t depth, unless lead minerals were abundant nearer the present surface. Seldom is this the case, however, in the vicinity of the basic sills.

*Spurr. Josiah Edward. The Ore >[asmas. JIcGram-Hill. S e w York. 1923.

. ., : < , . , .. . . . .- I-.. , >: A . .. , < :..!..p : .u': ..> >, . L x- i=.. . : . . . . . -.t . : -

GEOLOGY AXD O R E DEPOSITS O F BOUXDARY COUNTY 61

PLACER DEPOSITS.

GOLD.

Placer gold is found on the Moyie River and on Boulder Creek. The aloyie, being rapid, has washed away most of its large banks. The gold is the so-called "oatmeal" gold and is found scattered with the black sand among the large rounded boulders lying on both sides and the bottom of the stream.

The largest probable gold-bearing gravel deposit of the county is on Boulder Creek beginning at a point a little over a mile above its outlet into the Kootenai Rirer. Here the gravel becls are 400 feet deep in places and from .500 feet to 1000 feet wide. The yardage of gravel is enormous. running 17-ell up into the millions. No systematic sampling has been attempted, to learn the clistribution of the gold throughout the gravel, but such sampling is proposed as a metliocl of future procedure. JTueh of the gravel was laic1 do~vn under water. I t was probably brought doxvn by ice and r a t e r during the torrential periods f o l l o ~ ~ i n g the recession of the glacial period. Possibl- the outlet of the stream was damnled by an ice f1o11- fol1011-ing the course of the Kootenai, so that side pressure filled the mouth of Boulder Creek a distance back from its outlet, thus entrapping a lake above. X more probable theory is that a narrowing down of the gulch, due to the slower erosion of a resistant basic sill, may have caused a natural dam during the post-glacial torrential period.

Quartz veins are found in the sills and quartzite of Boulder Crecli. These carry gold in varying amounts. After a general study of all of the placer gold of the area, i t seems probable to the writers that the placer gold originates from the stream erosion of the gold-bearing veins of the basic sills.

/ M I N I N G PROPERTIES.

THE I D A H O C O N T I N E N T A L M I N E .

(No. 8, Plate I l l . )

. (Replacement Deposit Type 1-0. 1.)

The Idaho Continental 3Gne in Sec. 5 , T. 64 N., R. 4 IF*., lies 25 miles south~1-est of Port Hill arid may be reached by a good auto road. After crossing the Rootenai Rix-er a t Port IIill by ferry, the road crosses the International Boundary line twice before i t reaches its destination. The ore is trammed across the river and loaded into cars for shipment on the Great Xorthern Rail~vay. - The property is situated on the crest of the Selliirk Range in tlie northern par t of Boundary County.

The vein, h here first discovered, was a brilliant esposure of un- tarnished and unosic1izecl galena ore on tlie actual drainage di~icle of the range n-here r e l a t i~e ly recent. scalping by continental mountain-riding ice sheets had revealecl it, ~ r i t l i some interruptions, for a length of approximately 3000 feet. The valley, cut by Blue Joe Creel;, runs almost north and consequently the outcrop n-hich strilies in a northeasterly direction, travels dolr-n the side of the glaciated valley allnost to tlie bottom. This makes i t possible to enter the vein by allit tunnels in the valley bottorll a t a dept2i appl-osimately 500 feet belo\\- the original discovery.

The r e l ~ . t i . o n l i p . e r e shoots t.too4he roof-p(~'g~c~g& and cupolas of the nnderlvinc batllolitli is almost an ideal one to illustrate the

psaiclo-rooffpendZt n-hich is flanked on the south by the main gran- .--- --. , -..

it.e mass of the Selliirl; batholith and on the west and northeast bx- -. -- -- - .C

cupolas _.- of - _ . - this batllolith 11-hich are - fii_!nd two mjics,in diameter. The presuniablv I\-edge-shaped pendant i s about-two lnilec

.

a ~ r o s s - ~ its narrower par t and -its long as i s . _ . . _ strilies _. about 40" st of nort11~.~n_c!.,e~t.e1~c1~ for s e v e r a ~ r n i ~ e ~ , X small cupola splits i t into a P-shaped body on the northeast n-here the body of inraclcd rocl; narrows to a mile and one-half on eitlicr limb of tlie T. (See P1. 111.

'Emmons. IT. H.. The‘ Relations of >Ietnllifcrous Lode Systelns to Igneous In- t rusires . S o . 1571-1. T r a n ~ . A. I. 11. E., June. 1926.

GEOLOGY AXD O R E DEPOSITS O F BOUXDARY COUNTY 53

in poclret.) The ore body which parallels the long axis of the roof pendant lies about three-fourths of a mile from the surface outcrops of the two cupolas and about one and one-quarter ruiles from tlie main batholith to the south. An idealized sketch of the relationship is presented in figure D on plate S I I I , in pocket. Batholiths are characteristically steep siclecl arici so also are their outlying cupolas. Roof-pendants between cupolas ancl batholiths are generally conceded t o have a depth as great or perliaps tn-0-thirds as great as their width. This gives some idea of the possible clepth to ~vhieh the mineralizecl zone may extend. The beclding planes of the grey schists and of the light colored sericitic schists and quartzites which lie adjacent to or surrounding ore are nearly ~ e r t i c a l in places but they have been sufficiently disturbed either by folding or slipping to cause the dip to vary a t otlicr-points from vertical to 7.5" S. E . The general strike of the beds is S. 40" E., 11-hile that of the ore body is parallel to it o r nearly so. I n a few p1ac.e~ the vein strilces N. 43" E. The mineralizing solutions appear to have follo~vecl the allnost vertical bedding planes. The le~lscs of sdphides, which make up tlie ore body, estencl longi- tudinally parallel to the bedding and also parallel to the dip of tlie ore shoots in their vertical cliluciision. Thcse lenses step over ancl ilre digned in echelon (like shingles 011 a roof) both vertically and 11or- izontr~lly. This causes the actual strike of a line d r a ~ v n tlirough the lcnscs to vary about 5" from the strike of the becis anc1 also causes it

pliuue (1r:ln-LI fro111 an upper lens to a lolver one to have a flatter dip than that of tlict bcds. The horizontal s teppi i~g is illnstratecl in plate SIII . , figure X. Tlic vertical stepping is s h o ~ r n on plate 1111.. figure C.

The zone that contains these lcuses dips to tllc nortli~vest a t arl

aligle \-arying froin 90" to 60" ancl gives a stoping a1.t.a often as xitlt: cis 30 feet.. Tlie zone of lenses also appears to pitch or rake to tl~c, ilortlic;~st a t an unusual1~- f la t angle.

Nany years after the "red" or discovery vein had been b1ocl;ed out, a second or "blacl;" v ~ i n or ore body practically identical in characteristics, attitude, aucl mi~lcralization, mas cliscovereci soutlieast of ;he origiiinl vein and outcropping down the liillside at a l o ~ r c r level. 'I'he llorizontal clistancc bet\\-cell the surface outcrops of the two yeins is about 100 feet. The dip and strike are practically tlie same in both ore bodics. Thcse two ore bodies thus appear in an over-lapping posi- tivii but 112~x-e, otherwise, ahnost identical cliaraeteristics.

64 IDAHO BUREAU O F MINES ASD GEOLOGY

The "black" vein has a much more meager exposure a t the surface and in fact is well esposed only a t i ts southn-esterly extremity and a t its highest point. This is perhaps due to greater glacial erosion a t that extremity. The vein is strong ancl wide a t a short distance underground for most of its esplorecl length but its vertical dimension is very short as the lead ore begins sucldenly a t the top ancl ceases sucldenly a t the bottom of the ore body.

The flat bottom or what has been callecl the nearly horizontal rake of both of these ore shoots has been the object of much puzzlecl specu- lation. The apparent shallon-ness of these veins is hard t.0 reconcile with a stoping width of 30 feet and an exposecl length of 3000 feet along the strike. Seitller vein has as yet shown a vertical stoping length on the shoot of more than 400 feet.

I t appears quite obi-ious that much of the "red" vein has been removed by glacial scalping. This, of course, could explain the apparent shallo~vness of the vein, lvere i t not for the rather abrupt cessation of the ore along a nearly horizontal line. It fails to esplain, 11011-ever, the shallox- depth of the "black" rein ~rhiel l has fairly \veil defined upper and lo~ver limits and XI-hich fails to outcrop a t the surface for much of its length and consequentlp coulcl hardly hare been abbrevi- ated by ice o r other ero;' qlon.

If these veins are unclisturbed and lie nolr in nlneli thc same positions as they were deposited, i t TI-oulcl be unique if more ore of similar iirzture were not found a t greater depth. I n much the same nature as the lenses step-orcr and echelon in thc ore body, so also, perhaps, niaj- the ore bodies step over for relatively greater distances and continue a t greater clepths. These bodies may. perllaps, be connected by thin a d r e l a t i~e ly 11arri.n cross-fracture in ~oe l i s which were not so receptive to ore cleposition and rl-liicli upon exploration by the dril! appear discouraging. Similar bodies might, perhaps, be expected lnt- crally to the northn-cst and southeast of tlicse two yeins a t similar levels ancl also in the strike of the formation to the southn-est.

Another possible esplailation of the unique dimensions of thc "red" a i d "black" veins lies in the Ii~potliesis that the bottom of t1:c "red" ore body is a fanlt plane ~ r h i e h also forms the top of the "blaeli" ore body. The fault plane ~vould have a shnllo~ver dip to tlie northn-est than either the formation or the ore and 11-ould perhaps strike along the formation or. bedcling planes. I t 11-ould be a normal slip fanlt with the clo\v11-t.liron-1~ sicle to tlie northwest? thus bringing

GEOLOGY AXD ORE DEPOSITS O F BOUXDARY COUNTY 55

the "red" segment of the vein in i ts over-lapping position over the truncated "black" segment.

The f la t bottom of the "black" segment would of course be es- plained i n the same manner. This theory explains the similarity of the two veins in nearly all characteristics. Little zinc appears in the "red" vein which ~ r o u l d be the upper portion of the vein under this hypothesis but more zinc, pyrite, and siderite occur in the "black" or supposed lor\-er segment. I f a still lo~b-er segment should lie laterally to the southu-est i t .it-ould perhaps contain proportionately less lead 2nd more zinc than the "black" segment. Carrying on with the same assumption a still higher segment of the "red" vein might conceiv- ably lie to the northrvest and parallel to it.

Evidence against this theory lies first, i n the fact tha t the "black vein lies in a dark grey schist while the "red" vein is surrounded by the light colored sericitic quartzite, second, tha t after the lead has disappeared in the bottom of the "recl" vein some iron continues with depth, and third, that some slight structural difference is said to be apparent after long study. The latter, hon-ever, was not sufficiently marked to be noted by the writers in their brief examination.

Three minor fanlts cut across the ore bodies and effect slight displacements. Two of these are occupied by thin basic lamprophyre dikes. All of these faults and dikes are, of course, later than the ore bodies and had no influence in their genesis or deposition. These faults all strike in a general nort1111-esterly direction ancl friult A is nearly vertical while fanlt B dips to the northv-est a t an agle varying from 40 degrees to 45 degrees. Faul t C clips to the northeast a t a steeper angle averaging 75 degrees. The blocli between faults X and C has been raised in relation to the vein east ancl west of it. The vertical throw appears to be a t least '75 feet as evidencecl by displacement in the ore. This displacement, hou-ever, may have beell much greater sincc the segment of the "red" vein found within this block has a great keel-like irregular bottom which does not tie on to the vein in i ts eastern and western estermities 11-ithout a considerable change in angle. (See Figure C, plate XIII , in pocket.)

d horizontal throw of about 60 feet to the northwest is evidenced on the west edge of the middle block as shown by outcrops. The eastern edge, on thc contrary, is thron-n southn-ard about 40 feet in relation to the eastern block. The bloclr east of fault C is relatively lower than the block west of this fault. The vertical displacement

56 IDAHO BUREAU OF JIINES AND GEOLOGY

appears to be about 40 feet ancl the horizontal displacement results in a small offset ancl a slight change i n direction of the veins. The probable extension of the "blaclr" vein ore body would lie northwest of the B faul t belov7 No. 4 tunnel and on one side o r the other of KO. 5 tunnel probably to the eastrr-ard; and is logically to be explored by cross-cuts from No. 5 tunnel. Any ore body northeast of the B fault i n the "black" vein would of course be downthrown proportionate to the displacenlent on the n-est.

The ore is argentiferous galena in a series of replacement deposits ~vhich are described on page 42, 43, and 45. (Plate IV., p. 41, Vein type No. 1) .

The significance of the area of light colored sericitic quartzite surrounding the "red7 ' veil1 is somervhat lesselled by its failure to appear in connection with the "black" rein further to the sout1:east. Although the eviclence for the alteration is persnasix-e, the difference between the veins is negligible except for the slight difference in mineralization already mentioned.

The company owns twenty claims, fifteen patented and five unpatented. Underground n-or1;ings thus f a r approsimate 10,000 feet. The surface equipment consists of a 1200 cu. f t . I-R Imperial type air compressor; Leyie r drill sharpener; 1600-foot aerial tramri-a\- connecting mine and mill; full mining equipment; and 250-ton con- centrator.

The mill consists of a 10x20 crusher, belt conrc-or, four double four-compartment EI i l r t~ jigs, three rolls 12 in. s 130 in., clrag classifici.. f i re D7ilfley tables, Ilardinge ball mill, four Frue T-anners, flotatiol~ cells and hydroelectric power plant. Tlle concentration of the ore is fairly siniplc, there being .i.ery little zinc accompanying the galena. The mill feed runs from S 76 to 954 lead and is concentrated illto a product varying from 63 % to 70 5 lead. The s i l n r nccornpanies the lead in the ratio of O.:3.3 to 0.40 of a troy ounce to the per cent leacl and maintains this ratio fairly uniformly thronghout the concentration.

This company has produced since 1915, S49:1731 ounces of silver and 43,913,407 pounds of lead. I n 1923 it produced approximately 96,000 orznces of silver and 4,500,000 pounds of lead and in 1924 i t produeed 100,465 ounces of silver and 4,S'i8,9:31 pounds of lead. The property is operated by the Bunker IIiIl & Sullivan 3Iining and Concentrating Company of Iiellogg.

113 . \FIO I?[-I<l.:A{- 0 1 . . lIIh-l.;s * \ X I ) c:KvI.(l(;\- HI-I,I.I.:TIS 111. PLX'L'I. I S .

G E O L O G Y A N D O R E D E P O S I T S O F B O U S D X R Y C O U S T Y 5 7

CYNIDE* GOLD MINING COMPANY.

(No. 15, P la te Ill.)

(Shear Zone, Type No. 2.)

The Cynide Gold S,fining property (See. 27, T. 64 N., R. 3 E.) is in the old 3Ioyie-Yahk district in tlie Purcell Nore specifically, the property lies on the northwest slope of Eiuclrllorn 3Iountain approximately half a mile from the 3Iontana-Idaho line. It is reached from Bonners Fer ry by a good auto road 20 miles long. The road ascends the mountain toward the end of the trip by means of switch- backs.

The formation on Buckhorn Mountain is chiefly BeItian quartzite. It has a general strike of S. 30" to 10" TI-. ancl clips 45" to 55" S. IT.

The shearing is apparently clue to normal faulting. The sheared zone raries from 3 t o 5 feet in thiclmess. The vein ranges from 1v2 to 4 feet. The shearing follo\rs the bedcling very closely. (See vein type KO. 2, Plate IV., p. 41.) Samples are reported t o hare been taken varying from $2.90 to $40.00 across two and a half feet. Gold is the most important metal and is for the most p i ~ r t free. Little silver is alloyed TI-it11 the gold. Construction and development were based on the ore running $10.00 per ton for a n-iclth of four feet. The vcin carries a limited amount of quartz. The sulphides, though slight in quantit>-. appear to be chiefly pyrite with a siilall amount of galena in the lon-est tunnel. The yein can be traced for a mile o r more. To date, there appear to be three ore shoots: the first is about 250 feet Iong, the seconci is approsimately 200 feet, and the third appears to be shorter than the other two, though. a s it occurs near tlie face of the present tunnels it probably has not yet been fully exposed. The shoots arc said to have a northwesterly rake of about 4.7 degrees. This was not verified by the ~vriters, however.

The property consists of six unpatented claims. The rein is rcnchctl by six adit-tunnels ~vhieh either s tar t out as drifts or reach the vein after cross-cutting a short distance. The total length of development is approximately 6,000 feet. The relief i s such as to permit depth dcreloprnent a t minimum expense, should such development prove justified.

The surface equipment consists of a 130 cu. f t . gas-drivcn com- Pressor xvitll s 400 cu. ft . electrically-driven compressor, mining equipment, buildings sufficient to accolnmodate some 30 or 40 men, and

*An unfortunate mis-spelling of "cyanide." Derpetuated by official illiteracy.

58 IDAHO BCREAU O F I I I N E S A N D GEOLOGY

an aerial tramn-ay 4200 feet long connecting mine and mill. There is a 15-ell-equipped cyanide plant, ra ted a t 200 tons capacity and recluir- ing 300 horse power. The equipment consists of a No. 6 Gates gyra- tory crusher, a set of 16x42 Traylor Rolls, four Dorr thickeners, three Dorr agitators, one Dorr clarifier, one 7-foot x 36-inch IIardinge mill, one duplex Dorr classifier, 20 leaf Dorr filter and pump equipment. I n addition the company owns a 673 h. p. hydroelectric po>Irer plant on the 310)-ie River and some 10 miles of transmission line. High water in 1925 ~vashed out one of the abutments of the dam. halting operations a t the mine.

The company has not yet reached the stage oT steady production but is carrying on a development program. Gold was produced by

. the early o ~ ~ n e r s of the property and the present company shipped a small tonnage of gold-bearing sulphide ore to the Bunker Hill smelter a t Kellogg i n 1925.

DAMON GROUP.

(No. 16, Plate Ill.)

(Shear Zone. Type KO. 2.)

The Danlon Group in Sec. 21, T. 64 N., R. 3 E., consists of seven unpntcnted claims a mile or more from the Cgnidc Gold l l ining proper ty and along the strike of the Cynide vein. The vcin on the Damon group strikes S'. 25' t o 30' TI-. and dips 55' to 60' S. V7. The vein appears to b.6 an extension of the Cynide vein. I

Ttie deposit is clearly of the shear zone type, (scc re in type Yo. 2. H a t e I\-.. p. 41); sho \~ ing more o r less quartz, containirlg gold and a small anlount of silx er. Tlie gold occurs free in par t ancl associated in par t \vitii pyritc. The iriilth of the \-?in ranges fro~rl trro feet to n masi-

I rnnm in o ~ i e place of seven feet. I n places the re in consists of broken u p quartzite 11-ith an inch or two of gouge. A t the poitlt wlrere tllc vein measurecl seven feet there r e r c several feet of quartz. Tlie gold assays are erratic, ranging from nothing up to a reported amount of

1 several dollars per ton. 1 About 500 feet of dex-elopment \\-orli had been clotlc on the prop-

I er ty a t thc time of tlie writers' risit, a t 11-hich tinlc the property mas not being n-ot*lied. There was little in the way of equipruerlt other

1 than a building or tn-0. I

PHOEBE'S TIP. . l .y l , i~ ,~ l~ y ~ ~ l v i ~ l ~ ~ y s,.l.zlt,.,{ xi.2::l,t.. 1,..:1k : ~ I I < I c . i r r [ t~g . i!! St:ll<irl<5.

GEOLOGY ASD ORE DEPOSITS OF BOUNDAEY COUNTY 59

I N T E R N A T I O N A L M O L Y B D E N U M COMPANY.

( N o . 9, Plate Ill.) (Joint-Plane Vein in Granite, Type No. 3.)

Probably the most important group of this type of vein is to be found in the Phoebe Tip country in the northwestern par t of the county. Chief among the reins so f a r esplored in that district is that held by the International JIolybdenum Company in Sec. 27. T. 64 S., R. 4 IT. The property is reached by a 25-mile paeli trail frotn Por t 1311. The trail follox~s Smith Creeli.

The property lies in the granite of the Selsoil batholith 11-hich forms the Selkirk Range in Idaho. Joint plane cracks traverse the granite in great numbers running in the four major directions of the con- jugated shrinkage cracks. (See veia type So . 3, Plate IV., p. 41.) These fractures vary from a n inch or so up to three feet in thickness. Their filling also varies from an extremely basic dike rock to a highly acid pegmatite. The International 3Iolybclenum Company's property is located on one of these pegmatite "vein dil<es," though one claim is also located on a basic dike.

1Iolybdcnnm occurs in the pegmatite. The ore is chiefly in the form of molybdenite (molybclenum disulphicle, JIoS,) thongh the yellow oxide (molybdite, 1100,) is foulid occasionally. The ore accompanies a brown glassy quartz.

A t the time the property was visited the ore hacl been esposecl only on the surface by means of an open cut. X short tunnel \\-as being driven 71-hich ~vould cut the rein a fen- feet in depth. The length of this tunnel XI-oulc! be about 75 feet. A Ion-er. tunnel, n-hich ~vould give considerable dcptll or, the rein. had also been started. This tunnel was calculated to intercept the vein in 930 feet horizontally. The company liolcls four unpatentcd claims, one of .rvhich is located along the basic dike. The veil1 strikes S. 35" to 40" TI-. and dips 50" S. TT. The basic dike has practically the same strike as the veil1 ;und dips 60" S. E. There has bee11 no production to date. The equipment consists of txvo cabins, together wit11 hand mining equipment.

N O R T H E R N STAR CLAIM.

(No. 10, Plate Ill.) (Joint Plane Vein in Granite. Type No. 3.)

This elair11 in Sec. 23. T. 64 l\'.: R. 4 I\-., is a mile or so to the north of the Intcrnatioual 3Iolybdenum Company. The vein strikes K. 70" IT. and clips 60" S. It is 18 to 24 inches thicl;. Apparently this rc in

60 IDAHO BUREAU O F MIXES AND GEOLOGY

is the third side of the fracturing scheme shown on the International AIolybdenum property. (See vein type No. 3, Plate IV., p. 41.) Here too the molybdenum occurs as molybdeilite associated with brown glassy quartz. So f a r de,velopment has been in the form of open cuts.

AMERICAN GIRL CLAIM.

(No. 2, P la te Ill.)

.Joint Plane Vein in Granite, Type No. 3.)

This claim is in Sec. 9, T. 6-1 S., R.. 1 E., on the western side of the Queen Mountain batholith. It is in the Brush Lake district some 16 miles north of Bonners Ferry.

Here too, rnolybclen~~m occurs in a pegmatite dike in the granite. The vein had been exposed bj- an open cut or two. As these cuts \\-ere caved, the size, strike, and dip of the rein TI-ere not obtainable.

MORAN PROPERTY.

(No. 2. Pla te Ill.)

(Joint P lane Vein in Grani te , Type Xo. 3.)

This property consists of tliree claims 1y2 miles south~vest of Queen Jlonntain lookout in Sec. 19, T. 64 X., R. 2 E. The veins are also i n the Queen 3Iountain batliolith (PI. 111.: in pocliet.) I t \\-as impossible to visit this property ; ~ t the time when the writers were in the district but several specimens of ore n-ere esamined. The ov-ners of the. property reported that tlie nlaill vein was approsinlately tnro feet n-idc anci shoxrecl silver-bearing galena and gold-bearing pyrite. Thcre is a g~anite-quartzite coxtact in the vicinity of the property. The nature of the vein filling is not l ino~i~n . IIon-ever, it is more than l ikcl- tlie rein is due to ,joint plal~e f ;letui.in?.

M. & F. PROPERTY.

(No. 4, Plate Ill.) (Vein ~ r o s g ~ u t t i n g Basic Sill. Type S o . 4.)

This property is 28 miles from Bonners Ferry in the Queen Noun- tain district, in Sec. 13, T. 6-1 S., R. 1 E. I t is reached, except for the last mile or two, by a good auto road. a considerable par t of whicli is the Idaho Sort11 and South I-Iighrvay.

The veins occur in coarse-grained diorite which contains considerable feldspar. (See vein type So . 4, Plate II'., y. 41.) Tlie veins are but a short ciistance from the granite batholith of Queen Mountai11. These veins sho~v evidence of contact rlletarnorphism due probably to


the intrusion of the granite. I n this respect only do the veins of this property differ from the same type veins found elsewhere in the district.

The ore is chiefly scheelite though accompanying i t in a heavy massive quartz are also specks of galena, pyrite, pyrrhotite, and copper stains. Scheelite, calcium tungstate, was in demand during the World War. A t that time i t could be profitably mined even in small quantities, but a lowering of the price has necessitated development looking toward mining on a larger scale.

The main vein has becn opened up by one long surface cut and is again exposed by a short cross-cut which encounters i t a few feet below the surface cut. A still longer tunnel has been driren I\-hich encounters the vein a t considerable depth but is west of the ore shoot. The face of the Ion-er tunnel sho~vs "sugar7' quartz and calcite. Drifting to the east should open up ore found above. The ~ e i n strikes S. 84' E. and dips '70" X. It is six feet wide where encountered in the upper tunnel. I n all, 500 feet of derelopment worlr has been done.

Open cuts expose another rein on the Elanchc KO. 1 and Xo. 2 claims. These cuts are probably 1500 feet nortliu-est from the 1011-er tunnel on the other rein just described. The Blanche veil1 strilces K. 4" E. and dips 60" E. The esact width of this vein was not determined, but i t is probably about tu-o or three feet xide.

The JI. & I?. property includes 19 claims. The equipment consists of a blackstnith shop, hand mining tools, mine car, and light rail. together with several camp builclings. Actire development operations were discontinuecl in 1922. Since that time assessment r~orlr, including road building and general repair, has been performed. There has been little production to date. The property merits more estensi1-e development work.

B O U L D E R G O L D M I N I N G COMPANY.

(No. 10. Plate I I I.)

(Vein Cross-Cutting Rasic Sill, Type Xo. 4 . )

This property, ~vliich is situated in Sec. 16, T. 60 S., R. 2 E., is reac!led by a good Forest Service road and trail beginning a t Naples. Two miles may be travelecl by auto and then there are some nine miles of trail to the property.

62 IDAHO BUREAU O F MINES AND GEOLOGY

The vein is entirely in a basic sill. Quartzite float indicates a contact with this formation some~vhere between the tunnel and the top of the mountain.

The main vein strikes N. 2.7" W. and dips 50" N. E. I t varies in r ~ i d t h from a fen- inches to five feet. The owners report that the vein has been traced for 3000 feet changing its strike in that distance to N. '70" n-. I t is possible, of course, that the vein showing a changed strike is an entirely different vein.

The vein a t the outcrop is over three feet in width and shox-s "lively" quartz. Samples taken at the outcrop. when crushed and panned shon-ed fine free gold. Indeed very little crushing 11-as re- clnired to liberate the metal. A cross-cut picks up the vein some 13 feet below the out-crop, a t which point the quartz is largely absent and the 7-ein has narro~ved d o ~ m to a few inches. Work had not been done to ascertain whether or not the vein continuecl thus a t depth or whether i t increased in width again. Another tunnel a t a Ion-er elevation, some distance from the first tunnel but along the strike of the vein, picks up the vein again though the gold is absent.

Beside hand mining tools the equipment consisted of a small bunlr house and one other building in which were assembled a few pieces of machinery for milling on a small scale.

I D A H O M O N T A N A M I N I N G C O M P A N Y .

(NO. 17, Plate I l l . ) (Vein Cross-Cuttins Basic Sill, Type So . 4.)

The Two Tail, or lITcstern Bell as it is now called, is in Sew. 34 and 35, T. 62 S., R. 2 E.

The vein is in a basic sill. It strikes S. 30" TV. and dips gently to the S. TT'. a t first and then increases in dip up to 43 degrees or better with depth. I t ranges in ~ r i d t h from four to eight feet. The vein filling consists of brown quartz carrying silver-bearing galena. The quartz has a "lively" appearance with many vugs.

The deposit has been explored for a short distance by an incline from the surface and by unclerhand stoping which also begins a t the surface.

The I\-ork was performed some years ago and the buildings and \\-orkings are in disrepair. The original company held some ten unpatented claims. The present company has restaked two of the most

GEOLOGY AXD ORE DEPOSITS O F BOUNDARY COUNTY 63

important claims and plans development ~5-ork of an exploratory character.

Aside from the 11. & F. property, this vein is probably the most. important shov-ing of the Type 4 group of veins. -4 small amount of ore was produced by the old company.

K A T E F R Y C L A I M .

(No. 25, Plate I l l . ) (Vein Cross-Cutting Basic Sill, Type S o . 4.)

This claim is on Boulder Creek approximately a mile above the mouth of the stream in Sec. 27, T. 61 N., R. 3 E.

The vein strikes S. 60" E. ancl dips 45" to 50" S. TV. The formation strikes N. 25" TIT. and dips northeast. The vein occurs entirely within the basic sill, so fa r as explored, and consists of t ~ ~ o to three feet of quartz. The vein carries small bunches of galena, arsenopyrite, pyrite, and copper stains.

The vein is explored by a tunnel some 350 feet long. There is no equipment on the property and there has been no production to date.

Another claim, known as the Eureka, belonging to the same group. lies across Boulder Creek and to the north of the Kate Fry Claim. I t is Iocated on the same basic sill as the Kate Fry. On the Eureka claim the vein parallels the contact and dips toward it. This vein has been exglored by three short tunnels. It is characteristic of the Gronp 5 type of veins, differing only in dip.

K E N O A N D G L O R Y C L A I M S .


(Veins Cross-Cutting Basic Sill, Type KO. 4.)

These claims mere not visited by the writers. They are in See. 20, T. 61 N., R.. 3 E., near Leonia, Idaho. The owner reports the veins as cutting across a basic sill. A copper-bearing sulphide is apparently

, the chief metalliferous mineral found.

A R S E N O P Y R I T E V E I N .

(No. 1, Plate I l l . ) (Vein Cross-Cutting Easic Sill. T y p e So . 4.)

This vein is near the county road five miles southeast of Bonners Ferry in See. 31, T. 62, N., R.. 2 E.

64 IDAHO BUREAU OF MINES AND GEOLOGY

The vein strikes S. 50" E. and dips 55" to the southwest. It ranges in width from several feet u p to 12 and 14 feet. The vein is chiefly hard quartz carrying a considerable amount of arsenopyrite. A sample taken across the vein shon-ed 0.5% arsenic and no gold o r silver. There is no equipment on the property.

METALS M I N I N G COMPANY.

GOLD SHAFT GROUP.

(No. 6, Plate Ill.) (Vein Cross-Cutting Basic Sill, Type No. 4 . )

This property is on the extreme eastern slope of Clifty i\Iountain in XTTv 1/4 Sec. 1, T. 61 S., R. 2 E. I t is about 10 miles southeast of Bonners Ferry and car1 be reached by road. The last t ~ r o or three miles of the t r ip is made over a wagon road. The group consists of eight unpatented claims.

The vein strilrcs K. 75" to SO" E. and dips 65" N. I t consists of three to five feet of quartz cutting across a basic sill. Galena, probably carrying silver-bearing tetrahedrite, is scattered throughout the quartz in thc upper part of the re in and some copper stains are in evidence.

Tlie vein is esplorctl by a sliaft 4'3 feet deep along the vein and by a 20-foot drift that begins 25 feet clo~rn the shaft.

-In easterly dipping contact betx-een the basic sill and quartzite exists some 40 to 50 feet east of the shaft collar. The writers reconi- m c ~ c l e d that the 20-root drift be extended to this contact and also that a surface cut be made to ascertain XI-Iicther or not tlie vein es- tended into the q~mrtzitc. The vein seemed to har-e little westel-ly estcnsion. Anotlier vein parallel in strilie ancl dip esists some 800 feet to the south. This vein is about tu-o feet ~ ~ i d e . It likewise has been esplored only in the basic sill.

The equipment consists of sinking bucket and hand-mining tools together with living accomniodations fo r two men.

GOLDES H O P E CL4IJIS. (No. 6, Plate Ill.)

(Vein Within Sill and Pnrnllcl to Contnct of Sill and 3Ietamorphic Rock. Type KO. 5 . )

This property consisting of four claims, is in Sections 26 and 35, T. 61 N., R. 2 E. I t lies two and a half o r three miles southeast of Clifty BIountain and is reached by a steep trail ~ ~ h i c h passes over the

GEOLOGY AND ORE DEPOSITS O F BOUSDARY COUNTY 65

ridge to the east of Clifty 3Iountain. Should future development warrant it, a road can be constructed u p Boulder Creek from the property of the Leonia Gold >lining Company.

The vein is in a basic sill. I t strikes N. 10" 7iSr. and dips 45" to 50" E. I t s width ranges from tuTo to three feet. It has been traced for about 2.400 feet and is seemingly cut off a t one end by a cupola of fine- grained granodiorite which is of a later period than the sill in which the vein occurs. (See vein type S o . 5, Plate IV., p. 41.)

The vein sho~vs a. "lively" white and brown quartz with nulnerous vugs. The minerals are galena, pyrite, chalcopyrite, and an unidenti- fied silver mineral. 21 piclred sample showing sulphides, assayed no gold and 3.8 ounces silver to the ton.

There has been comparatively little ~vorlr done on the property as yet. K i t h the exception of one short dr i f t the ~ ~ ~ o r l i done is represented by open cuts along the yein. The equipment consists of a cabin and some hand-mining tools.

This vein is a goocl esaniple of Type KO. 5 veins but because so little ~vorlr has been done i t is not expedient to hazard a guess as to the possibility of finding comniercial ore-bodies.

M O Y I E G O L D M I N I N G A N D M I L L I N G C O M P A N Y , Q U E E N GROUP. (No. 5, Plate Ill.)

(Veln on Contact of Basic Sill and Quartzite. Type KO. 6 . )

This group of claims is on Qneen Jlonntain in Sec. S, T. 64. S., R. 2 E. It is reaclietl by a good Forest Service trail which supplies the Queen JIountai~i iool<out. The trail ascends thc steep eastern slope of Queen 3Iountair1 beginning about three miles south of ;2dclie. T l ~ c di.tance to the property is about three miles. The vein strikes X. 8" TI'. and dips 82" E. I t is four to f i r e feet \ride where cut by the cross-cut. The linnging ~ v a l l is a basic sill and the foot^^-all is quartzite. There was no evidcnce of movement along the vein. (See vein type Yo. 6, Plate IT-., p. 41.)

The re in gatiguc consists of quartz and siderite; the metallic minerals are sphalerite. chalcopyrite, galena, and pyrite. A piclied sample assaved a trace of gold and 6.7 ounces of silvel- to the ton. The totill clevelopment on this property is about 330 feet, but most of this de- veloprilent is reprcsentecl 1,- tlie cross-cut to reach the vein, only a feu- feet of drift ing having been done af ter the vein TI-as cncountercd.

IDAHO BUREAU OF MINES AND GEOLOGY

A small vein of the shear zone type was encountered 110 feet from - the portal of the cross-cut to the contact vein. I t Tas approximately

130 feet from the contact vein and paralleled the larger vein in strike and dip. I t lay between the bedding of the quartzite and consisted chiefly of gouge 16 or 18 inches wide. A channel sample from the vein assayed $12.80 in gold and $,0.90 in silver. I t was exposed only by the perimeter of the cross-cut.

Several small seams occur on the other side of the basic sill from the contact vein. These seaas lie several hunclred feet to the east of the contact vein and evidently lead to the contact between the basic sill and the next succeeding strip of quartzite. The seams have a flat dip. They range from three to five inches in thickness and carry varying amounts of galena. In following these veins 150 feet of tunneling has been done. The proposal now is to drift toward the basic sill and quartzite contact. The equipment consists of a cabin and hand-mining tools.

T R U S T M I N I N G COMPANY.


(Vein on Contact of Basic Sills and Quartzite, Type h-o. 6.)

The Trust Mining Company's property in Sec. 19, T. 65 N., R. 1 E., is half a mile off the North and South Righr~~ay and approximately four miles from Port IIi11.

The vein strikes S. '7" to 15" 11:. and clips 3.3 " to 40" E. Its thicliness ranges from two to six feet. The footwall is quartzite and the hanging wall is for the most part a basic sill. (See vein type No. 6, Plate ITT., p. 41.) The veil1 scenls to be a fissure, showing little or no movement. The filling is mostly a hard v-llite quartz containing iron sulphides. Occasionally stains of copper carbonate were noted. Varying amounts of siderite accompany the quartz as a gangue. A picked samplc assayed 0.06 ounce of gold and 5.4 ounces of silver to the ton.

Tile vein has beell opened up on three different levels. The lowest tunnel is approsimately GO0 feet long, picking up the vein about 480 feet from the portal. The colnp~lul?~ has located s i s claims all told and has done more or less surface I\-ork.

Tlie surface equipment consists of accon~modations for elght men, blacksmith shop, 35 h. p. Tunno Gas Engine, S in. s 6 in. Gardener compressor, mine car, rails, and mining tools.

I GEOLOGY AND ORE DEPOSITS OF BOUSDARY COUNTY 67

E I L E E N M I N I N G COMPANY.

(No. 14, Plate Ill.) (Vein on Contact of Basic Sill and Quartzite, Type No. 6.)

This property is in Section 35, T. 63 N., R. 2 E. I t is approximately half a mile south along the Woyie River and belo~r the power site of the Cynide Gold >lining Company. I t can be reached by a car by way of the porver site or else by the way of Skin Creek.

The 1-eins occur as small quartz seams a fen- inches thick which are found in or adjacent to the contact between the quartzite and basic sill. (See vein type So. 6, Plate IV., p. 41.) These seams sholv some galena and some copper carbonate stains. The bedding strikes N. 10" to 15" E. and dips 55" S. E. A small vein follorvs this strike and dip. d vein in the basic sill strikes X. 55" W. and has a vertical dip. Another small seam in the quartzite strikes N. 60" TT'. and dips 45" s. n-.

The company has located 20 claims in all. Five tunnels with a total length of 600 feet have been driven. The equipment consists of blacksmith shop, hand mining tools, and cabins.

L U C K Y A B E M I N I N G COMPANY.

(No. 21, Plate I l l .) (Vein on Contact of Basic Sill and Quartzite, Type Xo. 6.)

The Lucky Abe in Sec. 4, T. 64 X., R. 5 IT. is said to show lead, silver, and some copper. The writers did not isi it this property. The veil1 is said by the owner to be approximately three feet wide. I t strikes north and has an almost vertical dip. There are apparently t ~ r o veins, one on the contact and one in the diorite paralleling the contact. The contact vein is opened by a drift 1% feet long and the parallel vein is likewise opened by a drift of 175 feet.

K E N T PROPERTY ( S P H A L E R I T E CLAIM. )

(No. 2, Plate I I I.) (Vein on Contact of Granite and Quartzite, Type So. 7.)

This property is in the Brush Lake district in Sec. 9, T. 36 N., R. 1 E. I t is reached by a good auto road approxi~nately tv-o miles in length JL-liich leaves the main Sortli and South IIighn-ay just south of Copeland.

The vein strikes approsimately east and west and dips SO" N. I t is two feet thick arid ~2101~s spllalerite and galena. I t is explored by a

68 IDAHO BUREAU 01' MINES A S D GEOLOGY

shaft 110 feet deep. The shaft as for the most par t inaccessible a t the time'visited. The vein is said to lie between the quartzite and granite, beginning some 50 feet dolt-n from the collar of the shaft.

There was no equipment on the property and, because of the con- dition of the shaft, could not be checlied.

BRUSH L A K E M I N E S COMPANY (DORA TUNNEL. )

(No. 3, Plate Ill.)

(Vein on Contact of Granite and Quartzite, Type No. 7.)

This property is also in the Brush Lake district in Sec. 14, T. 6-1. N., R. 1 E. I t can be reached by a good auto road which leaves the Korth and South Highway a short distance belom Copeland.

The main vein strikes S. 60" E. and dips 60" S. E. It ranges from a few inches to two feet in thickness. The vein begins in granite and continues fo r some 1SO feet until i t reaches a basic sill a t which the main body of the quartz seems to end, leaving smaller seams to enter the sill. (See vein type KO. 7, Plate IV., p. 41.) The company has drifted along this vein for another 350 feet in the diorite without ally apparent ore discovery. (See vein type KO. 9, Plate IV., p. 41.) At a point 200 feet from the portal the drift has been turned to the left, thereby picking np a contact of granite and quartzite. The company a t the tirnc of the vibit, was exploring a gouge seam along this contact ~vhich 7x1s striking S. 75" I\-. ancl dipping 50' to 3.5" S. TIT. Othcr dex-elopment n-orl; consistctcl of a vertical shaft just outside the portal of this worliing aiicl an ntlit 50 feet in length ~vhich lras heacled towarc? the bottom of the shaft. Due to water the sllaft ~ x z s not accessible The work has been cntircly esp1or;ltory to date.

Tutlriel TI-ork has been doue for IS0 feet in opcning up a small quartz vein in the basic sill to the northn-est of the Dora vein. The quartz seems to cease near the face. 'l'llis drift is k n o l ~ n as the Arable Tunnel.

The company holds seven unpatentecl claims. By way of equiprllctlt there are several very substantial buildings, a blaclismitli shop, mine car, rail, nncl hanil-mining tools.

P E T E R S A N D M I T C H E M PROPERTY.

(No. 19, Plate I l l . ) (Vein Cutting Contact of Quartzite and Sill, Type No. 8.)

This property is on the opposite side of the 3Ioyic River from tlle town of Meadov- Creek. I t is in Pee. 23, T. 63 S.. R. 2 E.

IDAHO EUREXU OF 3IISES .\XI) GI::OT,(-)ClT UEI,I,I?TIT 11). PLATE XII.

Tlie vein starts as a rather n-ell-defined quartz vein in the hasic sill ancl fingers out in small seams in the quartzite. (See vein type S o . 8, Plate IV., p. 41.) The vein is some tv-o feet wide rvhere first en- counterect. There are three shafts, whose depths are 50, 91. ancl 21 feet, respcctivelj-. All are vertical. The first two s tar t in the diorite anct follow the vein into the quartzite. The cluartzite here strikes N. 5.5" to 60" Ifr. ancl clips 30" to 35" N. E. Drifts a t different lei-els total- ing altogether about SO feet, are run into it. Tlie longest drift, of about 45 feet, 71-a~ in the 91-foot shaft. ~ l i i c h was filled with t ~ a t e r rvhen 1-isited.

The company liolds 80 acres, which \!-ere procured from the Sor thern Pacific Railroad. Equipnient consists of a small hoist, a sinking 'Jucl;et, and hand-mining tools.

L E O N I A GOLD M I N I N G COMPANY.


This company holcls a eonsiclerable number of quartz and placer claims on Boulder Creek. The holdings are in sections 21, 22, 27, 28, 29, 31, 32, and 33, T. 61 S.. R. 3 E.,; also sectioris 35, and 36, T. 61 N., R. 3 E. ; and sections 5, 6, 7, T. 60 S., R,. 3 E.; also sections 1 and 2, T. 60 S., R. 2 13. The total placer holdings are 296.5 acres. There are also many quartz elainls snperimposed on the placer claims.

The r-eins thus f a r explorecl are represented by Types So . 2, 4, 5 and 10. Sei ther the veins or the gravel banlrs have yet been suf- ficieritly explored to ascertain the value of the deposits.

GOLDES TRIPLET S O . 1.

(Shear-Zone Deposit. Type No. 2.)

A small shear-zone vein was encounterecl on the Golden Triplet So . 1 claim belonging to the Leonia Gold 3Iining Co. in see. 23, T. 61 S . , R. 3 E. The vein confor~ned to the bedding of the quartzite. (See vein type No. 2, Plate IV., p. 41.) I t has a stri1;e of due north and dips 70" TI-. The quartz occurs in small bunches and carries pyrite and galena.

QUARTZ TUSSEL.

(Vein Cross-Cutt ing Basic Sill, Type S o . 4.)

This reill co~lsists of massive quartz from three to 10 feet \vide and strikes north with ari almost vertical dip. The formation strikes N. 1.7" ]I-. X contact of sericitic quartzite and a basic sill occurs a few

70 IDAHO BUREAU O F MIXES AND GEOLOGY

feet to the east of tlle uncovered portion of the rein which has been exposed by stream erosion. Apparently, however, there is no mineralization on the contact. The quartz carries a small amount of pyrite.

An 800-foot tunnel begins as a drift on the vein. The vein, holy- ever, veers some 30" to the southr~-est a short distance in from tlle portal and the tunnel continues on its conrsc, leaving the vein.

GOLDES TRIPLET NO. 2.) (Vein Within Sill a n d Parallel in Str ike to Contact of Sill and JIetamorphic Rock.

Type So. 5. )

This vein appears to be a stained shear-zone paralleling the contact between the basic sill and the quartzite in strike but clipping toward the contact. The vein showed some quartz but little or no golci.

CORNJIEAL TGSSEL. (Vein Cutting Across Bedding of Quartzite, Type So. 10.)

This vein s h o ~ - e d massive quartz some 12 feet wide cntting across the quartzite \\with a strilie of S. 10" to 15" E. (See vein type KO. 10, Plate IV., p. 41), and dipping 63' to 70" S. E. Another vein just over the Cornmeal Tunnel and only a few feet to the southwest also slio~ved massive quartz. The strike and dip were different, hon-erer. the strike being X. 1.5' IT-. and the dip 65" to 70" N. E. The re1 a t ' ion- ship of these veins to each other, if any, has not been solred, and the ~ v o r k done on then1 was too limited to justify a guess as to their con- tinuity or importance as possible ore sources.

GRA'I-EL DEPOSITS.

The grarel bad is hare alreadj- been briefly clescribed on p. 51. I n the absence of systematic sampling, the value of the deposits is unknown. An attempt was made in 1923 to evaluate the grouncl as a placer possibility by hydraulic methods, but thus f a r little has been proven.

Some of the gold recovered from the sluice boses was assayed for i ts fineness. A s there have been many periods of deposition in the various gravel banks, the fincxiess of the gold and silver varies, as the following table sho~vs (figures are basccl on parts per thousand of alloy) :

Sample Gold Silver Base Metal

G E O L O G Y A N D O R E DEPOSITS OFBOUNDARYCOUNTY 71

The exact source of this gold has not been determined. There are three possibilities, namely: from veins in the Boulder Creek drainage, from basic sills, or from material beyond the immediate area brought in by glacial transportation. The probabilities are, however, that the first tu-o are the more important sources. Systematic exploration of the placer ground with the drill i s proposed as an aid to determining the distribution and quantity of the gold.

3Iany fruitless years and upu-ard of two and a half million dollars were spent by the former on-ners, the Idaho Gold and Ruby Nining Company, under the management of J. 171. Schnatterly, in attempting to es t raet gold from unprospected and unsampled gravel banks. Par t of the espencliture is represented by a sis-mile ditch xvith a capacity of 10,000 miner's inches. -4 21-ton Marion shovel was purchased and used for this ditch construction. A grandiose scheme, upon which work was actually begun, proposed t o connect the eamp and the railroad by a til-0-mile tunnel and a 500-foot raise. The present holders of the property, the Leonia Gold Mining Company also took over 2

eamp of 45 d\-iellings and other buildings, a sa~vmill, hydraulic ccluip- ment, machinery, and an elaborate gold and platinum-saving plant of several thousands tons capacity. This plant was erected in Boulder Creek gorge. Boulder Creel; canyon was lined with concrete for several hundred feet above the "mill" but high water destroyed the work soon af ter its complet?on. Such a plant, although representing a large outlap of money, was never used and \\-as wholly unjustifiable. The new company proposes systematic investigation of the placer possibilities as TI-ell as development of the quartz veins.

A small amount of placer gold has been produced from recent hydraulicliing operations.

SUMMARY.

The area examined comprises Boundary County, Idaho, and includes approsiruately 37 townships. I t is ve l l served by railways and highways, with Boriners Ferry as the distributing center.

The topograpliy, outside the stream valleys, is generally rough and mountainous ~l-ith elevations rangiiig from 1800 to '7700 feet above sea level. The area includes the Cabinet, Sclkirl<, 3Ioyie, and Yahk Ranges, and is well drained and heavily forested. The most notable x a t e r bodies arc Kootenai. 3Ioyie, and Upper Priest rivers. Small lakes and streams are numerous.

Almost the entire region lies within the Pend Oreille and Kaniksu Sational Forests. That part of the county lying outside of these re- serves is devoted largelj- to farming, dairying. ancl lumbering.

The stratigraphic column of the area includes several important and much discussed formations included in the pre-Cambrian or Beltian series. Thin Pleistocene sediments also occur. The formation names assigried to this area are Xldridge-Prichard, Creston-Ravalli, Kitchener-Selvland-TI-allace, Siyeh, and Purcell l a ~ a . These occupy an approximate total tliickness of 30,000 feet.

hIuch igneous activity is represented by a batholitliic intrusion ~vitl i its attendant cupolas. thought to be of Cretaceous or possibly ,Jurassic age, also by a notable group of basic igneous sills of great thiclcness and estent ~ ~ h i c h are especially abundant in tlie eastern part of the county. Their total t1iicl;ncss is near 10,000 feet and they are assigned a Beltian age. A few dikes of little importance 15-ere noted. Basic lava flon-s of late Beltian age. totalling GOO0 feet in thickness, occur a t one place.

Structure is dominated by faulting: several large bloclis and normal faults and one major overthrust were observecl. The vertical throw of some of these faults is very large. Structure has controlled drainage; the mountain ranges are chiefly tilted blocks with fen. folds.

The batliolitllic intrnsion has been eroded to the fourth or ernbatho- lithie stage of Euirnons and several cupolas are exposed with the formation of roof-penctnnts. The more significant ore deposits are connected genetically with the cupolas and roof-pendtlnts. Consicler- able mineralizatio~l accompa~lies the basic sills. In all, ten types of veins were recognized. They irlclucie replacements, shear zones, joint- plane fillings, contilct. and gash veins.

GEOLOGY AND ORE DEPOSITS O F BOUNDARY COUSTY 73

The commercial minerals of the district are silver-bearing galena. gold, gold-bearing pyrite, molpbdenite, molgbdite, and scheelite. The mineral which is a t present being produced in the largest quantity is silver-bearing galena.

Txcnty-tx-o properties have been visited and described. Consider- able development 11-ork is in progress a t many of them, but not more than three of them are actually proclucing ore a t the present time. Placer deposits ha r e received considerable attention along with lode prospecting. Xuch money has been invested in some of the ventures in this county and several properties are vrell equipped I ~ i t h surface plants. The largest amount of prospecting has been undertaken on the gash veins in the sill roclrs, rather than on the deposits of greater promise near the outcrops of granodiorite.

CONCLUSION.

I t is now the consensus of opinion among modern students of ore deposition that the most favorable areas for the occurrence of ores of the precious and semi-precious metals are those which lie adjacent or superjacent t o granitic batholiths which have stoped and elbowed their F a y into older and metamorphosed sediments.

I n general the geologic conditions of Boundary County conform to this specification quite closely, and the area must therefore be re- garded, with certain qualifications and reservations, as one justify- ing careful exploration.

The county contains large areas of Beltian rocks similar in age to those of the Coeur d7Xlene district, and which like the Belt series in that district have also been invaded by a Cretaceous ( 8 ) granitic batholith. However, so f a r as revealed by the present rather meagre development, i t appears either that mineralization is less in evidence, o r else that such mineralization if once present has been partly removed by erosion of the topographically higher formations. I n this county a great part of the batholithic roof has been eroded away by mountain-riding continental glaciers and valley-scouring alpine glaciers along with a tremendous amount of erosion attendant upon the run-off of glacial streams. The roof and upper batholithic walls are thought to have received most of the mineralizing solutions and vapors n-hich emanate from such a batholith as is described. I n the Coeur d7-Ilene and similar districts the roof rocks remain uneroded except in a fen- spots. Glaciation" has undo~zbtedly removed from Boundary County great masses of possibly ore-bearing rocks in some places and has dispersed deposits or concealed deposits in other places.

The Beltian roclis of this area, although much disturbed, have not experienced the crushing and tearing that the same or similar formations underwent adjacent to the Osburn fault in the Coeur d'Alene district and this may account in part for the apparent difference in the extent of mineralization. The basic sills of the county have been the scene of most of the prospecting activity. This has to date failed to reveal many important ore bodies. On the other hand the metamorphosed secliments bet~reen and adjacent to the granitic intrusives,

*Kirkham. Virgil R. D.. Somo adverse influences of glaciation on mining. Eng. Min. Jour. Press. Vol. 121, KO. 46, J u n e 96, 1926.

GEOLOGY AXD ORE DEPOSITS O F BOUKDARY COUNTY 76

i n which a t the present time are the only producers, have received little, if any, prospecting.

The writers believe that the sills are more likely to contain small 101~-grade gold deposits, than base metal ore bodies. They further believe tha t the placers in the area have received most of their gold from the sills or their included quartz veins. It is also considered that the Belt series in and near the cupolas and constituting the roof- pendants arc more likely to produce commercial ore deposits of lead. silver, and zinc, than any other localities in the area. Prospecting along the strike of the beds may also reveal some replacement cleposits, similar to the Sullivan ancl other ore bodies of East Kootenay in the same geological horizon. Prospecting for molybdenum and possibly for tin ores shoulcl be confined to the larger granitic lnasscs which are as yet largely uneuplorecl. Tungsten ores are more likely to be found a t the contact of cupolas and the intruded rock.

Although large sums of money have been spent in mining development in the county, much of this expenditure has been ill-advised. Such error undoubtedly has been due to the lack of intelligent en- gineering direction.

INDEX

Pa A

Accessibility .................................................... hddia 14,

.................... Aldridge-Prichard formation Alporlkian sys tem ..................................... ?. Alluvium / . Alpine glaciers 13 , 13 . Xlnerican Girl claini Andesite l ava 18 . . .-\ nticline . 2 31 A])lite d ikes 36 .

................................................ . Arcliean a g e 20 . -4rgiilites . 1 . 16 Arsenopyrite A6, 63, -4rsenol)yrite Vein

n Bald Ilidpe ........................................................ T:all Creek ........................ .- Bartlvtt . R . ..................................................... R a s a l ~ 1:tva 1s . Uxtl~oi i th ...................................................... 3.5, Belt ser ies .................................................... 15, Bibliography Ejork . G . E .

.............................................. lilanche clainis Blue Joe Creek

.................................. . 1:onner County 11 . 30 G<, n n r r s Fe r ry ................................................ Eunners F e r r y Chamber of

Co~imierce .............................................. 4, nossea . Eoulder Creek 11, 61

.......... . Boulder Gold Mining Company 49 Fjoundnry County mine o ~ r n e r s .......... 4 , Iiourtdary Creek IIreccia 1'.

................................ . 1:ritish Col11111bi a. S . 30 ............................................... Crnck . R . \I. 2 0 . ....................................... U r ~ l s h Lake: 3 0 . 61) ,

I:ILISR L a k e J l in ing Company (I>orZ T m ~ n e l )

Guckhurn l l o u n t a i n ................................ -13 . I3unlct.r Hill a n d Sul l i rnn >fining a n d

(:oncentrating Colnpany, Kellogg . Idaho ..........................................................

.............................. . Rurke fornlatiun 16, 17

C . ........................................ Cabinct R a n g e 1 2 Calkins . F . C .

............ 15 . 17 . 20. 21. 22. Z l . 22. 24. 3:. Canadian bound;try .......................... 11 . 20 . Canarla (:eologicnl Survey ...................... 9. Canyon C r r e k .................................................. <;lrI>oniferous sys tem .................................. Caribou Creek ...... Causton . George R ....................................... Calcite Chalcopli~rite ........................................ 3 7 46 . Chambt,rl.iin . R . T . Clark Fork River .......................................... Clark Range .................................................... Cliftv Mountain 13 . ti4 . ~ o e t i r d'Alene mining dis t r ic t ........ S, 3 . Columbia River ............................................. (:onclusions

...................................... . Conrlomerate IS ?.5. Contact n i e t a ~ n o r p l ~ i s t ~ ~ .................. 36, 3S . ( 'ontact veins .............................................. 4 1 . C . n t i n i n t a l glacier .......................... 13. 3% . Cnl!eland c o p p e r ................................................................ l ' , , I n111m1 tunne l ............................................

o ~ e . 1 P a g e . .................................... Correlation tables 30. 22

13 : Coiv Creek ........................................................ I? 65 15 15 13

5 6 33 D 32 Daly . Reginald A . 17 11. 20 . 2 1 I 2 31. i 34. 36. 3 1 39. 64 Datnon a roug 6: , Deep Creek . 1 13 .

1 !) ?? ' .. ti; 9

72 6:;

Cranhrook ........................................................ 3- .................................... Cranl. rook 1nx1) a r e a 21

Creston formation 21 Creston-I?avalli forrnation 16

36 11

39 47 20 10

4 61 52

.......................... . 74 Cretaceous sys tem 2 3. 32 3.5 60 Cupolas 1 47 . 52

...... . 12 I C m i d e Gcild Mining Company 4.3 57. SS

Dikes . basic ................................... -.- ................. Diorite .................................................. 3 , 37 . . ................................................ I>~~lo i i i i t e 1 1s I)rysdale, Chas . Wales ................................

E . ................................................ Eas tpor t 14. 16 E a s t I iootenay a r e a ...................................... E a s t I iootenay dis t r ic t ................................ Eileen 3Iining Company Ellis . E r n e s t W ...............................................

......................... . . Emrnons \I- H 36, 4i, 52,

G GaLbro ....................................... A. 3R

..................................... Caltxna A 6 52. 56 ................................................ (~;alLon Range 39

Ganztte nlinerals .............................. 16. 4S . t;5 (:;LS~I \...ins . 2 7 3 G e n r m l s t ruc tu ra l f ea tu res of t h e a r e a 3S c~:corral)lij- 11

............................................................. (;enlogy 1.5 Glacial erosion ................................ -61, 54 . 74 Glory c l a i n ~ 62

.................................................. . Gneiss 2 0 21 36 ........................................................ (;oirl 46, S i , 711

........................................................ Gold Creek 11 ...................................... l .o ld~. i~ Hvl)e c la ims 66

( ;~ t ld or?r ................................. : ..................... 43 ti<rld Sllaft Croup 64 (.old 8 . n Triplet claims ............................ G9. i0 * . ) .............................................................. Graben -- . c;r;initr . 3 5 47 74, i 5 (.. . ,r, ~ ~ ~ r r d i o r i t e .............................................. 3% 4 i Grass Creek ...................................................... 13 I ;r;tvel deposits ............................................ 70

.................. Great S o r t h e r n Railx~-n~- -13, 52 Greenstone schis ts .................................. 18, 39 Grouse Creek 11

.................................................. I7

9 47 t;!t 61 I

H ........................................ Hanging valleys 3 32

.......................................................... Hill iv:ish I!' ........................................................ 1101)' f;1ult 30

.................................................................. Hors t 32 I Iun t Creek 11 IIydrl~ther l l la l act ion .................................... 42

........................................................ Fa11 Creek 11 . . .............................................. 1. 'aul ts 2 23 54 56 ...... Fissure veins ad jacen t t o basic sills 44

. .................................. Flint Richard Fos te r 25

I Iclnhn Rathnl i th . 36

................ . Id ;~ho Continent:il Mine 42 . 45 .1 2 Idaho Gold a n d Kuby .\ [inill:: Co~np:lrls 71

GEOLOGY A N D ORE DEPOSITS O F BOUSD-4RT C O V S T T

P a g e . 1daho.Montan a. Mining Company .......... 1 9 3 1 Idaho x o r t h a n d Sou th H i a h w a y . ~

6 0 66, 67 Igneous geology .............................................. 35

................................. Index m a p of Idaho .- 12 Indian Creek . 11 Inject ion gne i s s . 20

............................ Internat ional bouneary 8, 52 Internat ional AIoIybdenum Company . ............................................................ 50. 59 60 I rene conglomerate .......................... 17, 20 . 40

.............. . I rene volcanic formation 20 . 39 40

4Ioyie formation 21 hloyie Gold Mining a n d Milling

................. Company ... 4 9 6 5 ........ Moyie (Len ia ) over th rus t f au l t 29, 34 . . hfoyie R a n g e 29 31 33

3Ioyie River 11, 13, 34 . ........................................... 3Ioyie sills 1 . 3 6 38 .. AJoyie Springs 14

Noyie-Tahk d i s t r i c t 57 .................................................... 41yrtle Creek 11

J Joint-plane veins .................................. 41 . 72 ........ Joint-plane veins in granite 43. 59. 60 ~~~~~i~ system 29, 72

K Ranil tsu h-ational Fores t .......................... 72 K a t e F r y claim ......................................... 63

Klockman 1 4 42 Kootenai f au l t 29. 30 . 32 1

N S a p l e s A. 61

................................ Xelson bathol i th 29. 35. 59 .................... ......... S e w l a n d formation -.- 17, 21

.......................... S o r t h e r n Pac i f i c Railn-ay 69 Xorthern S t a r c la im .. 59

A Kellogg ............................................................. 5s Keno claini ........................................................ 63 Kvnt . .% . J ......................................................... 4 K e n t property . 67

. ............................. Kirkham . Virgil R D 9, 74 .............................. . Kitchener forniatioii 1 7 21

Kitcliener-Se~vland-\vallace formation 17

v

"Oatmeal" gold !I Ore deposi ts -42. 47. 33 Ore shoots 5 54, 57 Origin of veins . 41 Osburn fau l t 74

.............................. . Over th rus t f au l t 28, 33 34

Ir .. L a k e beds 1 28,

.................................... L a k e Coeur d'Alene .................................. Lake P e n d Oreillc 13.

.................................................. . Lalces 1 1 13 Lamprophyre dikes .....................................

........................................................ . , Lead 7 49 L e a d - s i l ~ e r o r e s Len ia f au l t 21,

................................................-.. . Leonia 1 4 17 Leonin Gold Mining Company ............ (i3. Lewis P.ange .................................................... Li~ i i e s tone .................................................... 17, Lion Creek ........................................................ Lithology .......................................... 1 16, Livinsston . D . C .............................................

............................................................ Location .......................................... I ~ > d e ore r i e ~ o s i t s

.. ~ ~ ~ : ~ ~ $ i :sf,', ;;~;~;~:.~:I.~::.~~.:~~.~;;:.;;~~~~~~ y.. :: E ; ~ ~ ~ ~ ~ ~ ~ Lake , 31 Iiootenay River 22, 34

Lon-er Selkirk ser ies .................................... .................. Luclcy h b e Mining Colnpany

31 3Iable tunne l ..................................................

.......................................... . 3Ia rne t i t e 3 7 42 31 . Fc I.'. property 50, 60, JIc;\rthur 3IcConnel I. R . G .................................... -20, 1\IcGillivray R a n g e ........................................

.................................... . Meadow Creek 1.1, IF 3Iesozoic period ..............................................

............................ 3Ietals .\lining Colnpany 3Ietarnorphosed sediments ........... 20 , 33 . 1\Iinemls ........................................................ 46, JI ining propert ics AIissiun Creek 11, .\ Ioly1)denite ........................................ 4 49, .\ Iolybdenum 47, 59,

............................................ Jtolybditc 4 49, 3tonli formation ............................................ . ................................................ J I o ~ ~ t a n a 1 30 I lnn tana- Idnho boundary .............. 34, 35 . AIoran property

........................................................ . I I o r a \.ia 14

.. Pack River 1 31 .................................................. P a r k e r Creek 11 . P e g m a t i t e d ikes 36, 43 59

................ P e n d Orrille S a t i o n a l Fores t 72 Perk ins L a k e Pe te r s a n d 3I i tchem property ................

............................................ :: Phoebe 's T i p 50, . Placer deposi ts 46, 51 . 31; Pleistocene se r i e s ........................... IS, 19 35 Pneumatolyt ic act ion . i j P o r t Hill 13 4s Previous geological x o r k in t h e a r e a .. . Pr ichard formation 15, 21 :$ P r ~ r s t Ei\-er t e r r a n e 211 ,

........................ . . Purcel l lax-a 17, 20, 39 40 . . !: Purcell Range 13 . . & Purcel l ser ies 15 16 Purcel l sills !, $ purcei1 t r ench 9, 11,

50 Purpuse of invest igat ion 11 PI-r i te 4s I F'yrrhotite 20 67 Q

Q ttartz ................................................................ cluar tz dior i te ........................

6s Quarzi te 1.5, 43 Quar tz n;onzonirc 3 .5 , 63 Quar tz tunne l 1 4 Qua te rna ry s y s t e m -1S. 13 . 22 33 . . Queen Ciueen JIountain croup -49. 49 60, .

licplacenient formation de r 16, I r . . L a k c -15, 17

59 Rocky Jrouritain sys tem . .................................. . 39 Roof pendan t -.?0 42 . .................................... . 34 Round Prair ie I!) 33

57 Round Prair ie f au l t 30 . 31 . 60 Round Pra i r i e \-alley .................... 30, 31 . 19 1 Ruby Creek

IDAHO BUKEAU O F XIIXES ASD GEXLOGY

S ............................................ St . Jfaries sills 18 .................................... St . Regis formation 1 6 . Scheellte ........................................ . 4 46 50

Schists . . . 20. 33, 53 Schnatterly . J . 31 . 71 Schofielrl, S . J .

................ lL.21, 22. 29, 32, 34, 36, 38, 39 Selkirk batholith - ............................ i' i';"i .. : 35; Selkirk Range .................................... Sericite 4 43 Sericitic quartzite ............................ 16, 18, 55 Sericitic schists 17, .5 3

$ ~ ~ ~ I " , ~ ~ ~ ~ ~ & d d " , ~ S ~ ~ ~ , " ~ ~ . . . i: Shear-zone 41, , 69 Shil-~h 14 Siderite .............................................................. 46 Sills . basic . 1 . 1 5 . 36 Silver .............................................................. 4 . 56 Siyeh formation ................................ 18, 20. 39 Skin Creek 67 ........................................................ slate 15, 18 Smith Creek 1 , 59 ................................................

Creek ...................................................... 11 snowy-top >fountain .................................. 39 Snyder 19 Soldier Creek 11 .................................................. Special structural features of the a r ea 29 Sphalerite ............................................ 4 56, 6 5 Sphalerite claim 67 ............................................ S p ~ k a n e International Railway .............. 13 z",,"," n ~ o ~ i ~ ~ r E ; i i c . a r ; i ; i ; i . . ~ . . . Stocks .......................................................... 1 47 Stratigraphy .................................................... 15 Striped Peak formation .............................. li Structure .................................................... 28 Sullivan Mine 75 .................................................. ~ u n i m a r y .......................................................... i Z Swamps 13, 19, 31

T ........................................ 2 9 32

Tetrahedrite . . , 74 Th,lmson. Francis A ............................... 4. Tin ore 75 Topivgraphy 11 ...................................................... .I.r.iil Creek . .............. 11 Trails . 13

.... Tri~pper Creek 11 Trout Creek 11 Trust JIining Company 66 ' ruff ................................................................ 1 , 39 Tungsten Hill 50

. Tungsten ores 5 . 7 5 ...................................... Twenty-mile Creek 11

Two-mouth Creek ....................................... 11 .......... Two-tail mine 62

U United States Geological Survey ..... S. 9 . 15 Upper Priest River 17, 35 39 .......................... . Epper priest unconformity 17. 35

pper Selkirk series 20 '[jralization 37

V Valley glaciers 23

...................................................... Veins 41. 45. 52 Veins along contact of basic sills and

............ quartzite 44 Veins along contact of basic sills and

granite ........................................................ 44 'Ieins cross-cutting basic ................ 44 Veins cutting across bedding of

quartzite 4 4 68 C-eins cutting contact of quartzite and

sills ............................. -. ........................ 4 . 7 0 cutting granite, quartzite and

basic .................................................. 44 1-ein-dikes -.- 43 .............................. ....................... Veins On 'Ontact of basic and

quartzite 6 5 66' 67 Veins on contact with granite and

r e i ~ ~ ~ , " ~ ~~e111t6'6'c6ntactto~~asi'd'd'siiis 68 and quartzites ........................................ 50

types ..................................................lv 72 and in strike

to contact .................................... 44. G4, 70

W . ....... n-a'c0tt3 C. 22

~ ~ ~ ~ ~ , " n " { , " ~ " f a ~ ~ ~ ~ n ~ ~ ~ . . . . . . . . . . . . .................................................. Wedge-theory 28

.................................................... Wedge-zones 28 Western Bell mine 62 \Vest Kootenas sheet .................................. 20

Y Yahk 31ountain ............................................ 13

........................................ yi'hk Range 2 9 30' 72

z Zinc ..................................................... 47. 49. 5 5

. Zinc ores - 50 ........................................ Zonal arrangement 6

document - idaho geological survey

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