some industrial mineral deposit models

7/25/2019 Some Industrial Mineral Deposit Models

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U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Som e Indu s t r i a l Mine ra l Depos i t Mode l s :

Desc r ip t ive Depos i t Mode l s

edited byG.J. Orris1and J.D. Bliss1

Open-File Report 91-11A

1991

This report is preliminary and has not been reviewed for conformity with U.S.Geological Survey editorial standards or with the North American StratigraphicCode. Any use of trade, product, or firm names is for descriptive purposes only

and does not imply endorsement by the U.S. Government.

____________________1 U.S. Geological Survey, Tucson, Arizona


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TABLE OF CONTENTS

Page

INTRODUCTION ................................................................. iii

Descriptive model of diamond bearing kimberlite pipes (Model 12), by T.C. Michalski and P.J. Modreski ................................................................ 1

Descriptive model of wollastonite skarn (Model 18g) by G.J. Orris ................................................................. 7

Descriptive model of amorphous graphite (Model 18k) by D.M. Sutphin ........................................................... 9

Descriptive model of lithium in smectites of closed basins (Model 25lc) by Sigrid Asher-Bolinder ................ 11

Descriptive model of fumarolic sulfur (Model 25m) by K.R. Long .............................................................. 13

Descriptive model of sedimentary zeolites; Deposit subtype: Zeolites in tuffs of open hydrologic systems (Model 25oa) by R.A. Sheppard ................................... 16

Descriptive model of sedimentary zeolites; Deposit subtype: Zeolites in tuffs of saline, alkaline-lake deposits (Model 25ob) by R.A. Sheppard .................................... 19

Descriptive model of epigenetic vein barite (Model 27e) by Sandra Clark and G.J. Orris .................. 22

Descriptive model of exhalative barite (Model 31b) by Sandra Clark and G.J. Orris ..................................... 24

Descriptive model of lacustrine diatomite (Model 31s)

by J.D. Shenk ............................................................... 26

Descriptive model of potash-bearing bedded salt (Model 35ab(T)) by Sherilyn Williams-Stroud ................ 30

Descriptive model of bedded salt; Deposit subtype: Marine evaporite salt (Model 35ac) by O.B. Raup ..................... 33


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Descriptive model of salt domes; Deposit subtype: Diapiric salt structures (Model 35ad) by O.B. Raup ...... 36

Descriptive model of bedded gypsum; Deposit subtype: Marine evaporite gypsum (Model 35ae)

by O.B. Raup ................................................................ 39

Descriptive model of naturally occurring iodine brines (Model 35am) by Sherilyn Williams-Stroud .................. 42

Descriptive model of naturally occurring bromine brines (Model 35an) by Sherilyn Williams-Stroud .................. 44

Descriptive model of sodium carbonate in bedded lacustrine evaporites; Deposit subtype: Green River (Model 35ba) by J.R. Dyni ............................................ 46

Descriptive model of iodine-bearing nitrate (Model 35bl) by Sherilyn Williams-Stroud .................. 51

Descriptive model of lithium-rich playa brine (Model 35bm((T)) by Sigrid Asher-Bolinder ................... 53

Descriptive model of disseminated flake graphite (Model 37f) by D.M. Sutphin .......................................... 55

Descriptive model of graphite veins (Model 37g)

by D.M. Sutphin ............................................................ 58

References .......................................................................... 61

Appendix A: Country Codes................................................ 70

Appendix B: Cox-Singer classification of deposit models .... 71


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INTRODUCTION

This compilation of industrial mineral deposit models is meant as an

extension of U.S. Geological Survey Bulletin 1693, Minera l Deposit Models.

Bulletin 1693 contains very few descriptive or grade-tonnage models forindustrial minerals and yet industrial minerals comprise a large proportion, if

not the majority, of mineral production in the United States and the rest of the

world. This compilation is not exhaustive of the deposit types for industrial

minerals and future publication of additional models is planned. To maintain

compatibility with Bulletin 1693, the models in this compilation follow a similar

format and have been given an alphanumeric model number that fits into the

Cox-Singer litho-tectonic classification presented in that publication. Appendix

B is a complete listing of that classification scheme with the addition of the

industrial mineral models in this compilation (shown in bold-faced type) as well

as others in the development stage.

Many industrial mineral deposits are similar to metal deposits in that

certain geologic criteria are clearly identified as necessary for the presence of a

deposit. However, many types of industrial mineral deposits have been studied

in a geologic sense to a very limited extent, if at all, and this is reflected in the

level of information present in the descriptive models. Many industrial

minerals are known under a variety of trade names or names that reflect their

usages and that do not correspond to a mineral name or deposit type in ageologic sense. The mineral kaolinite which occurs in a variety of deposit types

may be referred to as kaolin, flint clay, ball clay, or china clay; each of these

names indicates different uses and physical properties of a single mineral form.

The reader should know that model identity numbers followed by a "(T)" are

working numbers and may be changed at a later time. Most often this results

because of uncertainty in discriminating between some deposit types. For

example, should lithium in playa brines be a separate model from boron in

playa brines even though Li and B are commonly different components of the

same brine? On the other side of the issue, the Li and B may not have

originated from the same source or been concentrated by the same mechanism.

Additional data and more complete models may help address these issues. The

reader should also know that country(state) codes are listed in Appendix A.

Grade-tonnage and other models are not included in this compilation, but

will be released in future Open-File Reports.


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Model 12

DES CRIP TIVE MODEL OF DIAMOND-BEARING KIMBERLITE1 PIPES

By Thomas C. Michalski and Peter J. Modreski

BRIEF DESCRIPTION

Previous an d (or ) Al tern a t e Vers ion of Model : "Descript ive model of dia mond pipes" (Cox,1986.)

De p o s i t s yn o n y m s : Diatreme, blow, vent, explosion pipe, explosion breccia.

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Diamond.

B y-produc t s : Gem quality pyrope garnet, serpentine.

E n d u s e s : Gemstones, abrasives, semiconductors, scientific instruments, surgical

instruments, machine tools, drill bits.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Diamond bearing kimberlite pipes have been recognized forover 100 years as the most important primary source of economic quantities of gem-qualitydiamonds on the earth's surface. Kimberlite is rare, hybrid, ultrabasic rock that forms in theearth's upper mantle and is rapidly emplaced into the earth's crust along deep seatedfractures developed on or near ancient cratons. As the kimberlite magma approaches theearth's surface, contained volatiles exsolve from the magma and the fracture along which theyare emplaced is enlarged leading to the formation of a pipe-like diatreme near the earth'ssurface. It is generally assumed that most kimberlite pipes erupted on the earth's surface(although surface features are only rarely preserved in most known kimberlite provinces).

Kimberlite diatremes form steeply dipping, downward tapering, conical shaped bodies ofrelatively small surface area. Surface exposures of diamond-bearing pipes generally range

from small bodies less than 30 m in diameter up to pipes slightly larger than 1.5 km indiameter. Most diamond bearing kimberlite pipes occur in ancient cratonic areas as part of akimberlite field or cluster. Pipes within a given field generally have a highly variable size,shape, and diamond content. Only about 5-17 percent of diamond-bearing pipes within agiven field will prove to be economically viable. Generally the larger size pipes within adiamond-bearing kimberlite field tend to be the most diamondiferous (although the verylargest pipe is not necessarily the most diamondiferous).

On a worldwide basis only about 10% of known kimberlites are diamond-bearing and onlyone or two percent of kimberlites contain economic quantities of diamond. The amount ofdiamond contained within diamond bearing pipes is extremely small, with commerciallymineable concentrations ranging from .01 ppm to .20 ppm (.04 to 1.0 carats per ton). Theclarity, size, shape, color, and volume of diamonds within a pipe need to be carefullydetermined before the true economic potential of a diamond-bearing pipe can be determined.

Until relatively recently most researchers believed that diamond crystallized within thekimberlite melt during its formation within the mantle or during its transport to the earth'ssurface. Recent research however indicates that most, if not all, diamond contained withinkimberlites was originally crystallized in eclogite or peridotite layers within the upper mantle.Kimberlite (and lamproite) magma acts as the fluid medium that transport diamond-bearingeclogite or peridotite nodules to the earths surface. Because of the violent and abrasive natureof diatreme formation, most nodules become disaggregated during transport and theircontained diamonds become incorporated into the groundmass of the kimberlite pipe.____


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1Edi tor 's comment : this model current ly inc ludes diam ond-bear ing lamproi te pipes.


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LOCAL GEOLOGIC ATTRIBUTES

Host rock (s): Kimberlite breccia, tuff, hypabyssal kimberlite, lamproite.

Assoc ia te d rock (s): Kimberlite dikes, carbonatite, alkalic rocks.

O re m i ne ra l ogy : Diamond, bort (imperfectly crystallized), carbonado (polycrystallinegenerally dark colored), ballas (spherulitic polycrystalline).

G angue m i ne ra l ogy : Olivine, pyroxene, garnet, ilmenite, serpentine, chromite.

Altera t ion: Serpentinization of diatreme facies kimberlite is very common. Silicification ofinternal and contact zones occurs in some pipes. Fracture filling of secondary calcite, quartz,and zeolites has often been noted. Metasomatism of country rock adjacent to pipe contacts iscommon. Hydrothermal alteration, zeolitization, silicification, calcification, and fenitization ofcountry-rocks can occur near diatremes.

S t r u c t u r a l se t t i n g: The trend of kimberlites often is parallel to prominent joints, dikes, orother linear trends within a district. On occasion diatreme emplacement is fault controlled

and occurs near major faults or at the intersection of major and secondary faults. Contactsbetween pipes and country rock are generally sharp with little or no arching, doming, or radialfractures.

Ore control(s) : Ore grade is generally believed to decrease with depth and is attributed to theresorption of diamond in the less quenched, deep-seated hypabyssal kimberlite zone. Mostpipes also consist of several separate and distinct columns of kimberlite, each of which has adifferent ore grade.

Typi ca l o r e d i men s i ons : Economic pipes generally have an oval or irregular surface outlineand vary in size from 4 to 146 hectares. Most deposits, however, have a surface exposure ofless than 40 hectares and greater than 10 hectares.

T y p ic a l a lt e r a t i o n / o t h e r h a lo d i m e n s i o n s : Alteration is extremely localized (a few cm fromcontact).

Effec t o f w ea t he r i ng : Negative relief and the development of yellow ground (weatheredkimberlite consisting of chlorite, clays, and iron hydroxides) occurs in tropical areas. Effectsof weathering are less pronounced in cooler, less humid areas. In arctic and subarctic areas

yellow ground seldom develops and there is little or no difference in relief between kimberlitesand country rock. Hypabyssal facies kimberlite tends to weather less readily than diatremefacies kimberlite and may on occasion form small areas of positive relief.

E ffe c t o f m e t a m o r p h i s m : Metamorphism at low pressure, high temperature, and moderateto high oxygen fugacity can lead to resorption, graphitization and (or) oxidation of diamonds.

Maxi mum l i mi t a t i on o f ove rburden : Most economic kimberlite pipes discovered to datehave had little or no overburden. Weathering of diamond-bearing pipes often leaves a

weathered surface layer enriched in diamonds. Economic evaluation of pipes not exposed atthe earth's surface would depend on the size of the pipe, the value of gemstones contained

within the pipe, and the amount of overburden above the pipe. Determination of the economicvalue of a deeply buried diamond-bearing pipe would be very difficult and likely involve anextensive core drilling program.


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Geochemical s ignature(s ) : Kimberlites are generally enriched in the following traceelements: Cr, Ni, Co, Re, Os, Nb, Sr, Rb, Ba, U, Th, and rare earth elements. Geochemicalexploration for , and delineation of kimberlites using Ni, Cr, and Nb has proved successful insome areas. Stream sediment sampling for Mg-ilmenite, Cr-pyrope, and Cr-diopside is acommonly used technique for locating kimberlite pipes. The presence of high-Cr/low-Capyrope and chromite is indicative of diamond bearing kimberlite.

Geophys ica l s ignature(s ) : Airborne magnetometer surveys have been used to locate highlocal magnetic anomalies over kimberlite pipes intruded into sedimentary rocks. Negativegravity anomalies can occur over highly brecciated pipes. High resistivity of weatheredkimberlite has been used to delineate buried contacts between kimberlite and country rock.

Other explora t ion guide(s ) : There is often a difference in soil type and vegetation that hasdeveloped on top of weathered kimberlite versus country rock. This difference has beenattributed to higher soil moisture in weathered kimberlite and (or) toxic or fertilizer effects ofcertain elements contained within kimberlites. High levels of soil-hosted Ba cil lus cereus

bacteria over pipes versus country rock has also been noted.

Most r e ad i ly a sce r t a i nab l e r egi ona l a t t r i bu t e : Region of crustal tension on or near ancient

cratons.; alkalic rock provinces with deep seated ultramafic nodules; micro or macrodiamonds, Cr-pyrope, or Mg-ilmenite in stream sediments in the region.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : A high level magnetic anomaly; a change in localvegetation; and micro/macro diamonds, Cr-diopside, high Cr/low-Ca pyrope, Mg-ilmenite, ordeep seated ultramafic nodules in soil and/or stream sediments .

ECONOMIC LIMITATIONS

P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Size, shape, clarity and color are of majorimportance for gemstones. Crystal type and trace element content are of major importance forelectrical applications. Size, shape, and degree of crystallization dictate type of industrial use.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : Serpentinized and weatheredkimberlites are more friable, easy to process, and often have a higher diamond content thandeep-seated, hypabyssal facies kimberlites.

Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : Processing plants are usuallybuilt adjacent to diamond-bearing pipes because large volumes of kimberlite must beprocessed in order to produce a very small volume of diamonds. Transportation is generallynot a problem since the diamond-bearing rock has to only be transported a short distancefrom the mine to the processing plant. Since diamonds occupy a relatively small volume,transportation to end users is generally quite easy. The high value-to-volume ratio ofdiamonds, however, makes security during processing and transport a concern to mostproducers.

REFERENCE:

Atkinson and others, 1984 Gold, 1984.Boyd and Meyer, 1979. Kornprobst, 1984.Clement and others, 1986 Lincoln, 1983.Cox, 1978. McCallum and Mabarak, 1976.Cox, 1986 Meyer, 1976.Dawson, 1980. Milashev, 1988.Glover and Harris, 1985. Mitchell, 1986.


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G angue m i ne ra l ogy : Garnet, diopside, epidote, quartz, calcite.

Altera t ion: Contact metamorphism, metasomatism.

S t r u c t u r a l se t t i n g: Epizonal level.

Ore control(s) : In carbonate or calcareous rocks near igneous contacts.

Typi ca l o r e d i men s i ons : Highly variable-- some bodies are only a few meters in alldimensions, others are over 1000 m long.

E ffe c t o f m e t a m o r p h i s m : N/A.

Maxi mum l i mi t a t i on o f ove rburden : Unknown.

Geochemical s ignature(s ) : None.

Other explora t ion guide(s ) : Commonly, wollastonite mineralization is outboard of thegarnet-diopside zone but closer to the intrusive contact than the calcite(marble)-quartz zone.

Most r e ad i ly a sce r t a i nab l e r egi ona l a t t r i bu t e : Presence of calcareous sediments with acidicintrusions.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : Evidence/presence of any skarn formation.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Chemically inert. For ceramic uses hasgood strength and firing characteristics. Relative whiteness of wollastonite has a reported GE

value of 90 to 93 and a whiteness aspect ratio as much as 20:1. In glass/ceramic use, highiron contents may be a concern especially if the iron content is not lowered adequatelythrough removal of garnet and diopside in processing.

OTHER

Industrial uses for wollastonite were not discovered until the 1950's; prior to that timewollastonite deposits were considered mineralogical curiosities and utilization was limited tolocal use of wollastonite blocks in oven construction and experimental production of mineral

wool (1930's).

REFERENCE

Andrews, 1970. Hyndman, 1972.Elevatorski, 1975. Smith, 1981.Harben and Bates, 1984.


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Model 18k

DESCR IPTIVE MODEL OF AMORPH OUS GR APHITE

by David M. Sutphin

BRIEF DESCRIPTION

De p o s i t s y n o n y m s : Microcrystalline graphite.

Pr i nc i pa l commodi t i e s p roduced : Amorphous graphite.

E n d u s e s : Amorphous graphite is used in brake linings, foundry applications, lubricants,pencils, refractories, and steelmaking.

D esc r ip t i ve / gene t i c synop s i s : Amorphous graphite deposits are formed by the contactmetamorphism of coal beds or other highly carbonaceous sediments by nearby intrusions.Intrusives may be cross-cutting diabasic or granitic dikes or adjacent sills. Host rocks are

usually quartzites, phyllites, metagraywackes, and conglomerates.

Typi ca l depos i t s : Raton, USNMSonora, MXCOKaiserberg, ASTRKureika, USSRdeposits in South Korea.

R e la t i v e im p o r t a n c e o f t h e d e p o s it t y p e : These deposits are an important source ofamorphous graphite. For most applications, synthetic graphite or other materials may besubstituted for amorphous graphite but at increased cost or reduced performance.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Coal beds may be found associated with amorphous

graphite deposits.

RE GIONAL GEOLOGIC ATTRIBUTES

T e c t o n o s t r a t i g ra p h i c s e t t i n g : Continental margin or intercratonic basinal sediments havingcoal seams or other highly carbonaceous sedimentary beds are metamorphosed by nearbyigneous intrusions or by regional metamorphism.

Age range: Mississippian-Cretaceous, but may be younger.


Host rock(s) : Metamorphosed quartzite, phyllite, metagraywacke, and conglomerate.

Associated rock(s) : Diabasic to granitic intrusives.

O re m i ne ra l ogy : Amorphous graphite, anthracite, coke.

G angue m i ne ra l ogy : Quartz, pyrite.

Altera t ion: Coke may be formed where the intrusion comes into contact with the coal seam.Graphite may grade into coal with increasing distance from the heat source.


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S t r u c t u r a l s e t t i n g: Areas where coal has been thermally metamorphosed. Location may bestructurally simple, as at Raton, New Mexico, or highly faulted and folded, as in deposits atSonora, Mexico.

Ore control(s) : Size, grade, and mineral impurities of the graphite deposit depend on the

characteristics of the original coal seams and sediments. Faulting and folding may control theamount of graphitization and are therefore important ore controls.

Typi ca l o r e d i me ns i on s : There may be several beds each a few meters thick. Deposits maybe several miles in length and width.

Effec t of weat h er ing: Graphite does not chemically weather, but it does not form resistantoutcrops. In Sonora, Mexico, deposits are located by observing blackened graphite-rich soil

where the deposit approaches the surface.

E ffe c t o f m e t a m o r p h i s m : Coal is graphitized producing a dull black, earthy amorphousgraphite that may or may not be recognizable as having previously been coal.

Maxi mu m l i mi t a t i on o f ove rburden : Unknown.

Geochemical s ignature(s ) : Positive vanadium and nickel anomalies and negative boronanomalies.

Geoph ys ica l s ignat ure (s ): Graphite deposits have been located using induced potential,resistivity, electromagnetism, spontaneous potential (SP), and audiomagnetotelluric mapping(AMT). Outcrops may have associated radioactivity because of trace amount of uranium.

Oth er explora t ion guide(s ): Amorphous graphite deposits form only by thermalmetamorphism of coal or other carbonaceous material. Areas to prospect are those in whichsuch beds have been cut by intrusion(s) or subjected to regional metamorphism.


Phys i ca l / ch em i ca l p rope r t i e s a f fec t i ng end use : Major mines currently being minedcommonly contain over 80 percent graphitic carbon. The graphite may contain severalpercent of volatile material (South Korean low-grade amorphous graphite has such volatilecontent that it can be burned as fuel.)

C om p o s it i o n a l / m e c h a n i c a l p r oc e s s i n g r e s t r i c t i on s : Quantity and type of impurities aremajor concerns.

OTHER

REFERENCES

Cameron and Weis, 1960. Weis, 1973.Graffin, 1975. Weis and Salas, 1978.Krauss and others, 1988.


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Model 25l.3(T)

DESCRIPTIVE MODEL OF LITHIUM IN SMECTITES OF CLOSED BASINS

By Sigrid Asher-Bolinder

BRIEF DESCRIPTION

De p o s i t s yn o n y m s : High-lithium clays; hectorite; bentonite.

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Hectorite, potentially Li.

O t h e r p r o d u c t s : Uranium, mercury, boron, magnesium, fluorine, halite, strontium, zeolites,gypsum, sodium sulfate, sodium carbonate.

E n d u s e s : Cosmetics and skin preparations, drilling gels, building materials, ceramics andglass industry, primary aluminum production, manufacture of lubricants and greases.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Three forms of genesis are postulated: Alteration of volcanicglass to lithium-rich smectite; precipitation from lacustrine waters; and incorporation oflithium into existing smectites. In each case, depositional/diagenetic model is characterized

by abundant Mg, silicic volcanics, and an arid environment.

Typica l Depos i t s : Hector Mine, Hector,USCA

McDermitt caldera, USNV and USORLyles Lithium Deposit, USAZ

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : At present only two hectorite and related claydeposits are developed; next most important after currently produced pegmatites and lithium-rich brines.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Associated with sedimentary borate, zeolite, gypsum, andmontmorillonite deposits.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Basin-and-Range or other rift settings characterized bybimodal volcanism, crustal extension, and high rates of sedimentation.

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Closed basins of tectonic or caldera origin in aridenvironments.

Age ran ge: Tertiary to Holocene.


Host rock (s): Volcanic ashes, pre-existing smectites, lacustrine beds rich in calcium andmagnesium.

Assoc ia te d rock (s): Volcanic flows and detritus, alluvial-fan and-flat and lacustrine rocks,spring deposits.


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O re m i ne ra l ogy : Hectorite, saponite, stevensite, montmorillonite.

G angue m i ne ra l ogy : Silica, calcium carbonate, zeolites, gypsum, soluble salts, iron oxides.

Altera t ion: Rocks could be altered to shales or slates; no reported occurrences.

S t r u c t u r a l se t t i n g: Down-dropped closed valleys or unbreached caldera moats.

Ore control(s) : Extent of lacustrine beds; source of lithium.

Typi ca l o r e d i men s i ons : Meter to several meters thick by a few kilometers of area.

T y p ic a l a lt e r a t i o n / o t h e r h a lo d i m e n s i o n s : None.

Effec t o f w ea t he r i ng : Clays may expand with moisture, leading to "popcorn weathering";lithium may be leached by rainwater if it is held as soluble salts; or lithium may be exchangedfor other cations by groundwater if lithium is in exchangeable sites.

E ffe c t o f m e t a m o r p h i s m : Unknown.

Maxi mum l i mi t a t i on o f ove rburden : Unknown.

Geochemical s ignature(s ) : Li >300 ppm; +/-F, U, Be, B enrichment; high Mg.

Geophys ica l s ignature(s ) : Unknown.

Other explora t ion guide(s ) : Presence of white or light pastel swelling clays.

Most r e ad i ly a sce r t a i nab l e r egi ona l a t t r i bu t e : Hydrologically closed basins and presence ofsilicic volcanic rocks.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : Light-colored, ash-rich, lacustrine rocks

containing swelling clays.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Presence of excess gangue minerals,especially iron oxides; presence of fluorine, which prevents its use in cosmetics andmedications.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : Silicification hamperingdisaggregation.

OTHER

At present, only hectorite in a pure white form is suitable as a colloidal clay suitable for use incosmetics and medications.

REFERENCES

Ames and others, 1958. Brenner-Tourtelot and Glanzman, 1978.Asher-Bolinder, 1982. Rytuba and Glanzman, 1979.


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Model 25m

DESCRIPTIVE MODEL OF FUMAROLIC SULFUR

By Keith R. Long

BRIEF DESCRIPTION

De p o s i t s yn o n y m s : Volcanic sulfur.

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Sulfur.

B y-produc t s : None, but potential for recovery of As, Te, and (or) Se.

E n d u s e s : As sulfuric acid: production of phosphate fertilizers, leaching of metal ores,inorganic and organic chemicals, synthetic materials, pulp and paper products, agriculturalchemicals, explosives. As native sulfur: agricultural chemicals, petroleum/coal products,inorganic chemicals, pulp and paper products.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Surficial sublimates, open space fillings and replacements ofnative sulfur in the vent areas of volcanos. Rare precipitates in volcanic lakes fed by thermal

waters, molten sulfur flows and alluvial deposits.

Typi ca l depos i t s : Crater, USCA (Lynton, 1938)Matsuo, JAPN (Vila, 1953)Ollague, CILE and BLVA (Chidester, 1947)

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : Fumarolic sulfur accounts for only 2 percent ofworld supply, but is important locally.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Hot springs Hg, hot springs Mn. the ultimate source of

heat and (or) mineralizing fluids may be intrusions with related epithermal Au-Ag,polymetallic, or porphyry Cu-Mo deposits.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Active or recently active volcanic zones.

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Vent areas of stratovolcanoes.

Age ran ge: Late Miocene to Recent. Older deposits almost certainly have been destroyed byerosion.


Host rock (s): Porous volcanoclastic rocks and lava flows associated with felsic volcaniccenters; less commonly in intruded sediments.

Assoc ia te d rock (s): Less porous, sealing volcanoclastic rocks and lavas.

O re m i ne ra l ogy : Native sulfur.


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G angue m i ne ra l ogy : Iron sulfides and gypsum may be present in variable quantities.Gypsum only found in deposits overlying or within limestone. Cinnabar, stibnite, barite,melanterite and selenium/arsenic sulfates are sometimes found.

Altera t ion: In solfataric zones, rock replaced by quartz, sulfur and minor calcite. Intensealteration reduces host rock to alunite and clay.

ZONING: Sulfur grades gradually diminish with depth.

S t r u c t u r a l se t t i n g: Faults, breccias and other conduits related to vents for lavas andthermal waters.

Ore control(s) : Open space at or near paleosurface or below paleosurface capped by a lessporous, sealing lithology. Proximity to vents for thermal waters which are typically locatedalong steeply-dipping faults or shear zones. Climate determines gangue composition: pyrite(wet climate) or gypsum (dry climate).

Typi ca l o r e d i men s i ons : Range from tabular and chimney-like to highly irregular.Horizontal dimensions exceed vertical dimensions with diameters up to 1000 m and thickness

rarely exceeds 150 m.

T y p ic a l a lt e r a t i o n / o t h e r h a lo d i m e n s i o n s : Deposits typically found in zones of solfataricalteration that may be many tens of square kilometers in extent.

Effec t o f w ea t he r i ng : Deposits are not likely to survive weathering and would be lost withthe erosion of the host volcano.

E ffe c t o f m e t a m o r p h i s m : Any deposits that escape erosion will undergo remobilizationwhen pressure-temperature conditions are such that the native sulfur will be melted. Contactwith metal-bearing solutions may lead to precipitation of metal sulfides.

Maxi mum l i mi t a t i on o f ove rburden : Thin cover of soil, alluvium, travertine, siliceous sinter,

clay or lava.

Geochemical s ignature(s ) : + As + Se + Te + Bi + Sb + Hg.

Other explora t ion guide(s ) : Altered zones appear bleached and are easily recognized byremote sensing.

Most r e ad i ly a sce r t a i nab l e r egi ona l a t t r i bu t e : Broad zones of solfataric alteration instratovolcanoes.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : Areas of current or recent fumarolic activity.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Trace As, Se, and Te must be removedfrom crude sulfur before marketing.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : marketable crude sulfur grades 99.5percent S or better. Thus most fumarolic sulfur ores require considerable and expensiveconcentration.


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Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : Most fumarolic sulfurdeposits are distant from transportation infrastructure and potential markets and are rarely ofsufficient size to justify development under these circumstances.

REFERENCE

Banfield, 1954. Sillitoe, 1975.Colony and Nordlie, 1973.


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Model 25o.1

DESCRIPTIVE MODEL OF SEDIMENTARY ZEOLITES

Depos i t s ub t ype : Zeo l it e s in t u f fs o f open hyd r o log ic s ys t em s

By Richard A. Sheppard

BRIEF DESCRIPTION

De p o s i t s yn o n y m s : Open-system zeolites.

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Chabazite, clinoptilolite, mordenite, phillipsite.

O t h e r p r o d u c t s : Bentonite, pumicite.

E n d u s e s : Zeolites for use in ion-exchange and adsorption applications. for example,

clinoptilolite to remove NH4

+in tertiary sewage treatment; phillipsite to remove Cs and Sr

from radioactive materials.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Microcrystalline zeolites crystallized in relatively thick,generally nonmarine tephra sequences that commonly show a more or less vertical zonation ofzeolites and associated silicate minerals and that reflects the chemical modification ofmeteoric water as it flowed through the vitric sequence. The zeolites crystallized in the post-depositional environment over periods ranging from thousands to millions of years.

Typica l Depos i t s : Oligocene-Miocene John Day Formation, USOR (clinoptilolite)Miocene Paintbrush Tuff, tuffaceous beds of Calico Hills,

and Crater Flat tuff at Yucca Mountain, Nye County,USNV (clinoptilolite and mordenite)

Quaternary Campainian and Neapolitan yellow tuffs near Naples,ITLY (phillipsite and chabazite)Death Valley Junction, USCA (clinoptilolite) (Sheppard, 1985)

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : Very widespread and thick zeolite depositsthroughout the world; especially important sources of clinoptilolite and mordenite.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : The zonation of the open-system type of zeolite depositis similar to the upper zones of burial diagenesis (burial metamorphism) that affected thicksequences of silicic, vitric tuffs. Associated deposits include pumicite and bentonite.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Variety of nonmarine and shallow marine basins in volcanicterrains. Some thick tuffaceous deposits were air-laid onto the land surface and not into

water.

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Most deposits are nonmarine (fluviatile andlacustrine), but some are shallow marine.

Age ran ge: Mesozoic to Holocene, but most are Cenozoic.


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Host rock (s): Tuffs having a broad compositional range, including rhyolite to dacite, trachyteor phonolite, and basalt to basanite. The silicic tuffs commonly were deposited as nonweldedash flows.

Assoc ia te d rock (s): Rhyolite to basalt flows; fluviatile mudstone, sandstone, andconglomerate; diatomite.

O re m i ne ra l ogy : Chabazite, clinoptilolite, mordenite, phillipsite.

G angue m i ne ra l ogy : Authigenic smectite, mixed layer illite/smectite, opal-(cristobalite/tridymite), quartz, and calcite; variety of pyrogenic crystal fragments; variety of

volcanic rock fragments; unreacted vitric material.

Altera t ion: In silicic tuff sequences, the alkali-rich siliceous zeolites (clinoptilolite andmordenite) in the upper part of the deposit are replaced at depth by analcime, potassiumfeldspar, and (or) albite.

S t r u c t u r a l se t t i n g: No apparent correlation with deposit type.

Ore control(s) : Grain size and permeability of host tuff; flow of meteoric water downward inan open hydrologic system; hydrolysis and solution of vitric material by the subsurface waterin the upper part of the system raised the pH, activity of SiO2, and content of dissolved solids

to values where zeolites crystallized; resulted in a vertical or near-vertical zonation of zeolitesand other authigenic minerals; composition of the vitric material may have dictated whichzeolite species precipitated; clinoptilolite and mordenite are common in silicic tuffs, butchabazite and phillipsite are common in mafic or trachytic tuffs.

Typi ca l o r e d i men s i ons : Thickness of the zeolitic tuffs commonly ranges from 100s to 1000s

m. Areal extent is commonly 100s to 1000s km2.

T y p ic a l a lt e r a t i o n / o t h e r h a lo d i m e n s i o n s : N/A

Effec t o f w ea t he r i ng : Zeolitic tuffs resist weathering and are ledge formers. Local yellow tobrown stains by hydrous iron oxides.

E ffe c t o f m e t a m o r p h i s m : Conversion of zeolitic tuff to an assemblage of alkalifeldspar+quartz.

Maxi mum l i mi t a t i on o f ove rburden : Unknown, but probably tens of meters.

Geochemical s ignature(s ) : None recognized.

Geophys ica l s ignature(s ) : Possible use of color-composite imagery from airbornemultispectral scanner data to distinguish zeolitic tuffs.

Other explora t ion guide(s ) : Vertical zonation of zeolites and associated authigenic silicateminerals in thick (100s to 1000s m) tuffaceous sequences, especially siliceous tuffs of Neogeneage that were air-laid on land. The vertical zonation commonly is (from top to bottom)unaltered vitric materialsmectite to clinoptilolitemordeniteopal-(cristobilite-tridymite) toanalcimepotassium feldsparquartz and then to albitequartz. This zonation may cut across

bedding.


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Most r e ad i ly a sce r t a i nab l e r egi ona l a t t r i bu t e : Regional depositional environmentcontaining thick sequence of vitric tuffs of Cenozoic age.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : Vertical zonation of authigenic silicate minerals.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : The Si/Al ratio and exchangeable cationratios of the zeolites affect certain uses. Cation exchange capacity and adsorption capacity for

various gases are important. Color (due to iron staining) and the abundance of non-zeoliticminerals may limit use.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : Hardness and attrition resistance ofzeolitic tuff (commonly affected by abundance of opal-CT or quartz) are important inprocessing and end use. Crystallite size of the zeolite is < 2 m to 30 m and can affect theadsorption of gases and the extent and rapidity of cation exchange.

Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : Unknown at present due to

brief historical production.

REFERENCES

Broxton and others, 1987. Hay and Sheppard, 1981.Gottardi and Obradovic, 1978. Sersale, 1978.Hay, 1963. Sheppard, 1985.


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Model 25o.2

DESCRIPTIVE MODEL OF SEDIMENTARY ZEOLITES

Depos i t subt ype : Zeol i t es in tu ffs of sa l ine , a lka l in e-l ake dep os i t s

By Richard A. Sheppard

BRIEF DESCRIPTION

De p o s i t s yn o n y m s : Closed-basin (closed-system) zeolites.

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Analcime, chabazite, clinoptilolite, erionite, mordenite,phillipsite.

B y-produc t s : Bentonite, fluorite, pumicite, potassium feldspar.

E n d u s e s : Zeolites for use in ion-exchange and adsorption applications. For example,

chabazite to remove CO2and H2S from sour natural gas; clinoptilolite to remove NH4+in

tertiary sewage treatment.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Microcrystalline zeolites that formed during early diagenesisin silicic, vitric tuffs of closed hydrographic basins. The zeolites crystallized in the post-depositional environment over periods ranging from thousands to hundreds-of-thousands of

years by reaction of the vitric material with saline, alkaline pore water trapped duringlacustrine sedimentation. Locally, zeolites also formed from detrital clays, feldspars, andfeldspathoids and from chemically precipitated aluminosilicate gels in the same depositionalenvironment. Unlike zeolites of open hydrologic systems, this subtype is characterized by alateral zonation of zeolites and associated silicate minerals.

Typica l Depos i t s : Late Cenozoic Lake Tecopa, Inyo County, USCAMiocene-Pliocene Big Sandy Formation, Mohave County, USAZBowie Deposit (Late Cenozoic Lake Graham), Graham and Cochise

Counties, USAZ (Sheppard and others, 1987)Quaternary Lake Magadi, KNYA

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : This deposit type contains the largest variety ofzeolite species, and it is the type that accounts for most of the present zeolite production inthe U.S. This deposit type is an especially important source for chabazite, erionite, andphillipsite in the United States.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Continental-basin bedded evaporites; finely crystalline,disseminated fluorite in lacustrine rocks.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Closed hydrographic basins in either block-faulted terrains(such as the Basin and Range province) or trough valleys associated with rifting (such as theEastern Rift Valley of Kenya).

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Lacustrine basins that received silicic, vitric materialeither directly by airfall or by reworking. The saline lake water commonly was of the sodium


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carbonate-bicarbonate variety and had a pH of 9 or greater. These lakes are common in aridand semi-arid regions where annual evaporation exceeds rainfall.

Age ran ge: Late Paleozoic to Holocene, but most deposits are Cenozoic.


Host rock (s): Rhyolitic to dacitic, vitric tuff.

Assoc ia te d rock (s): Bedded evaporites (trona, halite, borates), mudstone, diatomite, Magadi-type chert, oil shale.

O re m i ne ra l ogy : Analcime, chabazite, clinoptilolite, erionite, mordenite, phillipsite.

G angue m i ne ra l ogy : Authigenic smectite, mixed layer illite/smectite, opal-(cristobalite/tridymite), quartz, searlesite, potassium feldspar, and calcite; pyrogenic biotite, sanidine, sodicplagioclase, and hornblende; unreacted volcanic glass.

Altera t ion: In certain highly alkaline and saline lacustrine deposits, siliceous and alkalic

zeolites have been replaced during late diagenesis by analcime or potassium feldspar in thecentral part of the basin.

S t r u c t u r a l se t t i n g: Lakes are commonly in block-faulted terranes or rift valleys.

Ore control(s) : Grain size and permeability of the host silicic, alkali-rich, vitric tuff. Salinity,pH, and ratios of alkali and alkaline-earth ions in the pore water are important.

Typi ca l o r e d i men s i ons : Thickness of the zeolitic tuffs commonly ranges from 10 cm to 10m. Areal extent is commonly tens to hundreds of square kilometers.


Effec t o f w ea t he r i ng : Zeolitic tuffs resist weathering and are ledge formers in the lacustrinesequence. Local yellow to brown stains by hydrous iron oxides.

E ffe c t o f m e t a m o r p h i s m : Conversion of zeolitic tuff to an assemblage of alkalifeldspar+quartz.

Maxi mum l i mi t a t i on o f ove rburden : Unknown, but as much as about 30 m can betolerated.

Geochemical s ignature(s ) : Lacustrine environment of sodium carbonate-bicarbonate type,may be enriched in boron.

Geophys ica l s ignature(s ) : Possible use of color-composite imagery from airborne

multispectral scanner data to distinguish zeolitic alteration.

Other explora t ion guide(s ) : Molds of saline minerals, chemical delta of calcite or aragonite,associated dolomitic mudstone, occurrence of bedded or nodular Magadi-type chert.Concentric zonation and lateral gradation in a basinward direction of unaltered volcanic glassto alkali-rich, silicic zeolites to analcime and then to potassium feldspar in the central part ofthe depositional basin.


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Most r e ad i ly a sce r t a i nab l e r egi ona l a t t r i bu t e : Regional depositional environment of silicic,vitric tuffs in an alkaline, saline-lake deposit.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : Host rock of vitric tuff of rhyolitic or daciticcomposition; lateral zonation of zeolites and associated silicate minerals.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : The Si/Al ratio and exchangeable cationratios of the zeolites affect certain uses. Cation exchange capacity and adsorption capacity for

various gases are important. Color (due to iron staining) and the abundance of non-zeoliticminerals may affect use.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : Hardness and attrition resistance ofzeolitic tuff (commonly affected by abundance of opal-CT or quartz) are important inprocessing and end use. Crystallite size of the zeolite is < 2 m to 30 m and can affect theadsorption of gases and the extent and rapidity of cation exchange.

Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : Unknown at present due to

brief historical production.

REFERENCES

Sheppard and Gude, 1968. Surdam and Eugster, 1976.Sheppard and Gude, 1973. Surdam and Sheppard, 1978.Sheppard and others, 1987.


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Model 27e

VEIN BARITE

by Sandra Clark and G. J. Orris

BRIEF DESCRIPTION

De p o s i t s yn o n y m s : Epigenetic vein barite, carbonatite-associated vein deposits.

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Barite.

B y-produc t s : + fluorite + rare earths + base metals + Au + Ag

E n d u s e s : Weighting agent in drilling muds, fillers, chemicals, ceramics, pigments, rubber,plastics, radiation shields, friction materials.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Barite mineralization along faults, fractures, or shear zones.

Barite is fine to coarse grained, crystalline or cataclastic and typically white or light gray.

Typi ca l depos i t s : Del Rio District, USTN (Ferguson and Jewell, 1951)Jebel Ighoud, MRCO (Power, 1986)Darreh, IRAN (Roman'ko and others, 1985)Sangilyn, AFGH (Abdullah and others, 1977)Oraparinna, AUSA (Stevens, 1976)Boguszw, PLND (Paulo, 1982)

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : Probably the major source of world bariteproduction; minor in the United States, but important locally.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Spatial associations known with the following deposit

types: sediment-hosted Au-Ag deposits, polymetallic veins, sedimentary exhalative Zn-Pb,epithermal Au-Ag deposit types, fluorite veins, Kuroko massive sulfide, carbonatites;,southeast Missouri Pb-Zn, evaporites, Appalachian Zn,


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Highly varied.

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Highly varied.

Age ran ge: Precambrian to Tertiary.


Host rock (s): Any type.

O re m i ne ra l ogy : Barite + fluorite + galena + sphalerite + chalcopyrite + rare earth minerals+ Au + Ag.

G angue m i ne ra l ogy : Quartz, pyrite, celestite, rhodochrosite, calcite, siderite, chalcopyrite,galena, sphalerite, clay minerals, fluorite, dolomite, hematite, limonite, rare-earth minerals.


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S t r u c t u r a l se t t i n g: Areas of faults, fractures, shear zones.

Ore control(s) : Faults, fractures, shear zones.

Typi ca l o r e d i men s i ons : Widths of a few centimeters to tens of meters, lengths from tens ofmeters to > 1 km.

Effec t o f w ea t he r i ng : Indistinct, barite is resistant to weathering.

Maxi mum l i mi t a t i on o f ove rburden : Unknown, but not much.

Geochemical s ignature(s ) : Ba + F + Zn + Pb + Au + Ag + Sr

Geophys ica l s ignature(s ) : Relative linear gravity highs for larger deposits.

Other explora t ion guide(s ) : Very heavy sedimentary-looking rock; commonly white to grayin color, but may also be green, orange, other colors.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Barite is resistant to weathering , inert,nonabrasive, dense, and absorbs radiation. Siderite content may be a serious problem fordrilling mud use. The presence of radioactive minerals may limit use

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : Gravity separation may be ineffectivefor some sulfide -rich ores and more expensive flotation techniques are needed when oregrade needs to be improved or sulfides removed for end use.

Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : High density of materialcontributes to relatively high ground transportation costs which may exceed the mined cost ofthe raw material.

OTHER

REFERENCES

Brobst, 1980. Clark and Poole, 1990.Brobst, 1984. Harben and Bates, 1990.Clark and others, 1990.


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Model 31b

SEDIMENTARY EXHALATIVE BARITE

by Sandra Clark and G.J. Orris

BRIEF DESCRIPTION

Previous an d (or ) Al tern a t e Vers ion of Model : "Descript ive mod el of bedd ed ba rite" (Orris,1986.)

De p o s i t s yn o n y m s : Bedded barite; sediment-hosted, stratiform, syngenetic-diageneticbarite; syndepositional barite.

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Barite.

C o-produc t s : + Pb + Zn + Cu + Ag + Au (when intimately associated with exhalative Zn-Pbdeposits).

E n d u s e s : Mainly as a weighting agent in drilling muds. Other uses of high-purity barite arein fillers, ceramics, pigments, rubber, plastics, radiation shields, friction materials, andchemicals.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Fine-grained and finely laminated bedded to massive baritein siliceous, sedimentary basinal sequences and (or) barite clasts incorporated in turbiditesand debris flows. Mineralization results from the migration of deep-circulating heated andreduced fluids along faults or rifts in oceanic crust to sites of precipitation on or just belowthe seafloor. The brines may migrate into seafloor depressions some distance from thedischarge sites. Barite in peripheral parts of deposits may form rosettes. Detritus derivedfrom reworking bedded barite may be transported as debris flows and turbidites. Because oforganic content, color is often dark gray.

Typi ca l depos i t s : Meggen, FederalRepublic of Germany (Krebs, 1981)

Rammelsberg, Federal Republic of Germany (Hannak, 1981)Barita de Cobachi, Mexico (Salas, 1982)Nevada barite belt deposits, USA (Papke, 1984)

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : A major source of world barite production.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Sedimentary exhalative Zn-Pb deposits.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Epicratonic or continental margin marine basins associatedwith oceanic faults or rifts.

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Marine basins.

Age ran ge: Commonly Paleozoic, also Proterozoic.



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Host rock (s): Siliceous , commonly carbonaceous, sedimentary sequences containing chert ,argillite, mudstone, and shale. Locally occurs with limestone, dolostone, siltstone,sandstone, quartzite, greenstone, tuff.

O re m i ne ra l ogy : Barite, + minor witherite.

G angue m i ne ra l ogy : Minor pyrite, limonite, sphalerite, galena; up to several percent organicmatter plus some H2S in fluid inclusions.

Altera t ion: Secondary barite veining; weak to moderate sericitization reported in or nearsome deposits in Nevada.

S t r u c t u r a l se t t i n g: Marine basins adjacent to rifts or deep-seated faults in oceanic crust.

Effec t o f w ea t he r i ng : Indistinct, barite is resistant to weathering. Weathered-out nodulesor rosettes can be found.

E ffe c t o f m e t a m o r p h i s m : Loss of carbonaceous content.

Geochemical s ignature(s ) : Ba + Zn + Pb + Cu + Mn + Sr + organic C

Geophys ica l s ignature(s ) : May be associated with relative gravity highs. When associatedwith base-metal sulfides may have relative magnetic high.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Barite is resistant to weathering , inert,nonabrasive, dense, and absorbs radiation. Density and purity affect end use.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r ic t i o n s :

Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : High density of materialcontributes to relatively high ground transportation costs which may exceed the mined cost ofthe raw material.

OTHER

REFERENCES

Brobst, 1980. Harben and Bates, 1990.Brobst, 1984. Papke, 1984.Clark and others, 1990.


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Model 31s

LACUSTRINE DIATOMITE

by Jonathan D. Shenk*

BRIEF DESCRIPTION

De p o s i t s yn o n y m s : Diatomaceous earth, kieselguhr, bog deposits.

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Diatomaceous earth.

B y-produc t s : Possibly sand and gravel or clays.

E n d u s e s : Filter aid, functional filler, insulation material, absorbent, silica source.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Lacustrine diatomite deposits form in fresh to brackishwater, are invariably associated with volcanism, and are found worldwide both in

paleosediments and in recent lake sediments. It is widely held that the large quantity of silicanecessary for thick accumulations of diatoms is derived from the weathering anddecomposition of silica rich volcanic rocks. The released silica is subsequently transported tothe lake through runoff, groundwater, and hot or cold springs.

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : Lacustrine diatomite deposits, while morenumerous, are of secondary importance to the fewer, but larger, marine diatomite deposits.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Trona, gypsum.

R e p r e s e n t a t i v e d e p o s i t s : Juntura and Otis basins, USOR (Brittain, 1986)Kariandus, KNYA (Barnard, 1950)Lake Myvatn, ICLD (Kadey, 1983)

Riom-les-Montagnes, FRNC (Clarke, 1980)Luneburger-Heide, GRMY (Luttig, 1980)


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Typically found in volcanic terrain. Often associated withcrustal extension (ex: the Basin and Range Province of the western United States, the East

African Rift system, and the Icelandic portion of the mid-Atlantic Rift).

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Depositional conditions necessary for thick diatomaccumulations include: 1) extensive, shallow basins for photosynthesis; 2) an abundantsupply of soluble silica and nutrients; 3) an absence of toxic or growth-inhibiting constituents;4) sustained high rates of diatom reproduction; 5) minimal clastic, chemical, and organic

contamination, and 6) a low energy environment for preservation of the delicate diatomstructure.

Age ran ge: Miocene to Recent. Occurrences noted as early as Late Eocene.



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Host rock (s): Diatomaceous lake sediments are typically hosted in: 1) volcanic rocks(craters, maars) -- example: Riom-les-Montagnes; 2) volcanic and sedimentary rocks(interbedded volcanic flows or tuffs* Consulta nt, Tucson, Arizona


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and fluvial or alluvial sediments) -- example: Juntura and Otis basins; or 3) sedimentaryrocks (fluvial or alluvial sediments) -- example: Luneburger-Heide.

Assoc ia te d rock (s): Diatomite is typically interbedded with: 1) siliciclastic sediments(sandstone, siltstone, mudstone, volcanic ash); 2) chemical sediments (limestone, marl), and3) organic sediments (lignite, peat).

O re m i ne ra l ogy : Diatomaceous silica, opal-cristobalite.

G angue m i ne ra l ogy : Contaminants consist of siliciclastics (various clays, quartz andfeldspar grains, and volcanic glass), calcite, organic matter, + Fe- and Mn-oxides, + gypsum,+ halite.

Altera t ion: N/A.

S t r u c t u r a l se t t i n g: Flat lying to gently dipping, some minor folding and faulting.

Ore control(s) : The formation and localization of ore is controlled by the physical andchemical boundaries of the regional depositional environment.

Typi ca l o r e d i men s i ons : Deposits commonly extend over areas of 1 to 25 square miles and

attain thicknesses of 10 to >200 ft. Deposits covering


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percent, Fe2O3- 0.4 to 2.2 percent, CaO - 0.2 to 3.5 percent, and minor to trace amounts of

TiO2, MgO, Na2O, K2O, and P2O5.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : Processing is kept to a minimum topreserve the diatom structure. Well lithified diatomite generally requires excessive milling.

Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : Distances of 70 to 100 mileshave been reported for transporting crude to the processing plant; higher percentages ofcontained water reduces this distance. While local sources compete for low end use markets,high end use products are shipped worldwide.

OTHER

The International Agency for Research on Cancer (IARC) has classified crystalline silica as aprobable carcinogen. The effect of this classification as it relates to diatomite is still beingdebated. The International Diatomite Producers Association (IDPA) is currently sponsoringresearch into the health and safety issues.

REFERENCES:

Barnard, 1950. Durham, 1973.Breese, 1989. Industrial Minerals, 1987.Brittain, 1986. Kadey, 1983.Clarke, 1980. Luttig, 1980.Coombs, 1990. Williamson, 1966.


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Model 35a.2(T)

POT ASH -BEARING BEDDED SALT

by Sherilyn Williams-Stroud11-89

BRIEF DESCRIPTION

De p o s i t s yn o n y m s : Marine evaporites, altered marine and rift-valley evaporites.

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Potash.

B y-produc t s : None.

E n d u s e s : Fertilizer is 95 percent of U.S. consumption, other uses include soaps anddetergents, glass and ceramics, chemical dyes and drugs, liquid fertilizer, synthetic rubber.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Widespread thick accumulations of chloride evaporitedeposits found in basins where evaporation exceeds inflow rate of waters. Some depositsformed in marine basins which were restricted as a result of sea level fluctuations. Other

basins are altered marine rift-valley grabens with associated hydrothermal inflow.

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : These deposits yield high grade, large tonnage orebodies, many of which are amenable to low cost mining and beneficiation.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Bedded evaporite deposits containing limestone,dolomite, gypsum, anhydrite, and halite.

R e p r e s e n t a t i v e d e p o s i t s : Devonian Elk Point group in Saskatchewan, Manitoba, andAlberta in Canada, Pennsylvanian Hermosa Formation in Colorado and Utah, Permian Castile,

Salado, and Rustler Formations in SE New Mexico and west Texas, Permian ZechsteinFormation in East and West Germany, Netherlands, Denmark, Poland and England, Miocene

Tortorian Formation in Sicily.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Marginal marine basins that underwent subsidence duringdeposition of the evaporites. Pre-existing deep basins into which seawater inflow becamerestricted (for MgSO4-rich potash evaporites). For MgSO4-poor potash deposits, rift-valley

grabens forming incipient seas.

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Arid climate where evaporation exceeds inflow and (or)hydrologic closure of the depositional basin so the outflow is less than inflow, such as localrain shadow deserts formed by rift or strike-slip basins. The supply of sand and mud into the

basin must be less than the supply of solutes.

Age ran ge: MgSO4-poor potash deposits are found throughout the Phanerozoic. MgSO4-rich

potash deposits are found mostly in the Permian, Miocene, and Quaternary.


Host rock (s): Primarily halite, some anhydrite.


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Assoc ia te d rock (s): Halite, anhydrite, carnallite.

O re m i ne ra l ogy : Sylvite interbedded with halite, bedded sylvinite (halite + sylvite), lowergrade ores include carnallite, kainite, langbeinite.

G angue m i ne ra l ogy : Halite, dolomite, anhydrite, bischofite, kieserite, polyhalite, epsomite,tachyhydrite, leonite, bloedite, hexahydrite, vanthoffite, loeweite, glasserite, schonite.

Altera t ion: Groundwater dissolution can destroy potash deposits because of the highsolubility of the ore minerals, or, since sylvite is often considered to be secondary aftercarnallite, incongruent dissolution by groundwater can actually result in conversion of low-grade carnallite to high-grade sylvite.

S t r u c t u r a l se t t i n g: Bedded evaporite deposits. Deformation after burial of salt can lead tointense folding in the very plastic salt.

Ore control(s) : Basin brines of the appropriate composition with salinities high enough toprecipitate potash minerals.

Typi ca l o r e d i men s i ons : Thickness of potash beds ranges from a few to several tens ofmeters. Volume of a single deposit can be thousands of cubic kilometers, though many high-grade deposits are much smaller, on the order of a few to a few tens of cubic kilometers.


Effec t o f w ea t he r i ng : Surface weathering causes dissolution of potash and deposits do notform outcrops.

E ffe c t o f m e t a m o r p h i s m : Plastic flow of salt and other saline minerals is greatly enhanced.Salt deposits are eventually destroyed by regional metamorphism.

Maxi mum l i mi t a t i on o f ove rburden : Potash is mined by conventional underground miningtechniques, or, in cases where beds are highly deformed, by solution mining. Solution miningtechniques are also used if the ore depth is below 1100 m, where halite creep becomes aproblem.

Geochemical s ignature(s ) : K, Na, Ca, Mg, Br, Cl2, SO4, and H2O.

Geophys ica l s ignature(s ) : High gamma radiation from natural isotope K40provides measureof potassium content of salt in drill hole logs. Relative gravity lows.

Other explora t ion guide(s ) : Potash may be concentrated in areas of deposit containingthickest halite, and is associated with zones of highest insolubles (clay) content of salt deposit.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : Saline well or spring water, thick gypsum oranhydrite outcrops, domal or collapse structures, low gravity geophysical anomalies.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Muriate of potash (KCl), which is thehighest potassium content product, and potassium sulfate (K2SO4) are purer than potassium-

magnesium sulfate and are preferred for chemical industry applications. The low chlorine


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content and lower solubility of potassium sulfate makes it more desirable for certain crops andsoil conditions. All the fertilizer products are sold on the basis of chemical composition andparticle size, with higher potash grades and coarser particles generally more desirable.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : Potash products are concentrated byflotation, selective dissolution ("washing"), or precipitation of the potash mineral from a hot

brine. Insolubles, such as clays and quartz must be removed. The amounts of insolublespresent in the ore and their reactivity increase processing costs.

Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : Transportation represents amajor portion of the delivered price of potash products so costs of mining, processing andtransportation must be balanced to achieve a saleable product.

OTHER

REFERENCES

Adams and Hite, 1983. Hardie, in press.Borchert and Muir, 1964. Searles, 1985.


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Model 35a.3

DESCRIPTIVE MODEL OF BEDDED SALT

Depos i t s ub t yp e : Mar i ne Evapor it e Sa l t

By Omer B. Raup

BRIEF DESCRIPTION

De p o s i t s yn o n y m s : N/A

P r in c i p a l c o m m o d i t ie s p r o d u c e d : Sodium chloride (salt).


E n d u s e s : Chemical and food industry, snow and ice removal, domestic consumption.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Bedded salt deposits of marine origin occur in marginalmarine basins of many sizes. These basins had periodic inflow of sea water which was themajor source of the sodium chloride. Bedded marine salt deposits are frequently of large arealextent and of considerable thickness.

Typica l Depos i t s : Silurian Salina Formation in the Michigan and Appalachian basins withdeposits in northern Ohio, Michigan, and western New York; Permian Hutchinson salt ofcentral Kansas; Mississippian Charles Formation in the Williston basin, North Dakota;Permian Zechstein evaporites of Germany and Poland.

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : This deposit type contains the thickest and mostareally extensive deposits of salt and it accounts for the major production of salt of all of thedeposit types.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Marine evaporites that contain gypsum and potash;sulfur.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Marginal marine basins that were subsiding at a rapid rateduring deposition of the evaporites. Influx of sea water maintained water levels in the basinthat were being lost by evaporation. Some evaporites in this type of setting have somecontribution from inflow from the continent. For most, however this contribution is salt.

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Same as the tectonostratigraphic setting.

Age ran ge: Late Proterozoic to Miocene.


Host rock (s): Primarily anhydrite, with some limestone and dolomite.

Assoc ia te d rock (s): Anhydrite, gypsum, potash.

O re m i ne ra l ogy : Halite with thinly interlaminated anhydrite.


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G angue m i ne ra l ogy : Anhydrite.

Altera t ion: Groundwater dissolution can modify the layering, grain size, or porosity, or it caneven destroy a deposit.

S t r u c t u r a l se t t i n g: Marine evaporites occur in basins near continental margins in ares ofrapid subsidence.

Ore control(s) : Basin brines with salinity high enough to precipitate sodium chloride.

Typi ca l o r e d i men s i ons : Thickness of mineable bedded salt deposits range from 10 to 100m. Areal extent of some deposits covers many square kilometers.

Effec t o f w ea t he r i ng : Surface weathering causes total dissolution of salt in most climaticareas. Salt can be preserved at the surface, however, in areas of extreme aridity.

E ffe c t o f m e t a m o r p h i s m : Regional metamorphism destroys salt deposits and can causealbitization of the surrounding rocks by sodium metasomatism.

Maxi mum l i mi t a t i on o f ove rburden : Specific limit is unknown but bedded salt is mined byconventional methods at depths over 100 m. Much bedded salt is solution-mined at depthsexceeding 500 m.

Geochemical s ignature(s ) : Bedded salt from marine evaporites contains bromine in solidsolution in the range of 60 to 200 ppm. Salt that has been recrystallized or is from acontinental source often contains bromine of lower values.

Geophys ica l s ignature(s ) : Bedded salt gives a very low response on a gamma-ray well logs.

Other explora t ion guide(s ) : Occurrence of basin-edge sediments that contain gypsum oranhydrite which may indicate sediments that are the products of higher salinity (i.e., salt) in

the basin center. High-salinity brines in wells.

Most r e ad i ly a sce r t a i nab l e r egi ona l a t t r i bu t e : High-salinity and high bromine content inwell water; low response on gamma-ray well logs; salt springs.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Impurities must be low.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : Material must be pure enough so thatminimal physical beneficiation is necessary for the intended product.

Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : Transportation is a major

cost of the finished product. Therefore, costs of mining, processing, and transportation mustbe balanced to achieve a saleable product.

REFERENCES

Borchert and Muir, 1964. Morse, 1985.Braitsch, 1971. Raup and Bodine, in press.Kostick, 1985. Smith and others, 1973.


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Lefond, 1969 Symposium on Salt, 1963 through 1985, Numbers One through Six


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Model 35a.4(T)

DESCR IPTIVE MODEL OF S ALT DOMES

Depos i t s ub t ype : Di ap ir i c Sa lt S t r uc t u r es

By Omer B. Raup

BRIEF DESCRIPTION


P r in c i p a l c o m m o d i t ie s p r o d u c e d : Sodium chloride (salt).


E n d u s e s : Chemical and food industry, snow and ice removal, domestic consumption.Mining produces cavities for petroleum storage.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Salt dome deposits occur in marginal marine basins thatoriginally contained thick bedded salt deposits. These basins had periodic inflow of sea water

which was the major source of the sodium chloride. Differential loading by thick overlyingsediments initiated and drove the upward movement of the lower density salt into domes andridges, some of which have risen to the present-day land surface.

Typica l Depos i t s : Jurassic (?) Louann Salt , USTX and USLAPermian Zechstein evaporites , WGER and PLND

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : Salt domes contain large volumes of relativelypure salt, some at depths quite close to the surface. In the United States the Gulf Coast saltdomes are close to the coast which affords inexpensive shipping.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Some salt domes contain potash deposits, notably inGermany and Poland; associated gypsum and sulfur deposits. Various types of Cu, Fe, Pb,Zn, and Ba deposits in the surrounding strata.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Salt domes occur in marginal marine basins that hadreceived thick accumulations of bedded salt. Subsequent clastic sedimentation in the basininitiated and drove the less dense salt into domes and ridges, some of which rose close to thepresent land surface. Salt domes occur in basins near continental margins in areas of rapidsubsidence and sedimentation.


Age ran ge: The age range of the salt in the salt domes is the same as that for bedded saltwhich is Late Proterozoic to Miocene, but most are Paleozoic and Mesozoic. The formation ofthe domes was, of course, later than the deposition of the salt.



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Host rock (s): The host rocks of the salt domes are any of the sedimentary units that thedome penetrated during its rise. this could be any of the normal marine sedimentary rocks.

Assoc ia te d rock (s): Anhydrite, gypsum, potash.

O re m i ne ra l ogy : Halite with thinly interlaminated anhydrite.

G angue m i ne ra l ogy : Anhydrite.

Altera t ion: Groundwater dissolution can modify the original rock textures, or porosity, or itcan even destroy a deposit.

S t r u c t u r a l se t t i n g: Some salt intrusions form as a result of tectonic deformation and followfaults and anticlinal axes.

Ore control(s) : Basin brines with salinity high enough to precipitate sodium chloride plusthe tectonic setting to form the domes.

Typi ca l o r e d i men s i ons : Salt domes can range from one to several square kilometers in

areal extent, and thousands of meters in depth.


Effec t o f w ea t he r i ng : Surface weathering causes total dissolution of salt in most climaticareas. Salt can be preserved at the surface, however, in areas of extreme aridity. Dissolutionof salt by groundwater at the top of a salt dome can cause the accumulation of anhydrite that

was disseminated in the salt. This anhydrite usually hydrates to gypsum. Gypsum depositsof this type can be extensive, thick, and very pure.

E ffe c t o f m e t a m o r p h i s m : N/A

Maxi mum l i mi t a t i on o f ove rburden : Specific limit is unknown but salt domes are mined by

conventional methods at depths over 100 m. Much salt dome salt is is solution-mined atdepths exceeding 500 m.

Geochemical s ignature(s ) : N/A

Geophys ica l s ignature(s ) : Salt gives a very low response on a gamma-ray well logs and saltdomes are indicated by ares of low gravity.

Other explora t ion guide(s ) : Salt domes sometimes show up as circular features on arealphotographs or detailed topography. Salt springs are another indicator.

Most r e ad i ly a sce r t a i nab l e r egi ona l a t t r i bu t e : Large marginal marine basins containingthick sediments, with basin-edge sediments of higher-tan-normal salinity.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : High-salinity and high bromine content in wellwater; low response on gamma-ray well logs; salt springs, local topographic features indicatinguplift of domes, circular gravity lows.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Impurities must be low; crystal sizeoptimum for intended use.


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Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : Transportation is a majorcost of the finished product. Therefore, costs of mining, processing, and transportation must

be balanced to achieve a saleable product.

REFERENCES

Borchert and Muir, 1964. Morse, 1985.Kostick, 1985. Raup and Bodine, in press.Lefond, 1969. Smith, and others, 1973.Symposium on Salt, 1963 through 1985.


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Model 35a.5

DESCRIPTIVE MODEL OF BEDDED GYPSUM

Depos i t s ub t ype : Mar i ne evapor it e gyps um

By Omer B. Raup

BRIEF DESCRIPTION


P r in c i p a l c o m m o d i t ie s p r o d u c e d : Gypsum.


E n d u s e s : Wallboard, plaster products, Portland cement, agriculture, fillers.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Gypsum deposits of marine origin occur in marginal marinebasins of many sizes. These basins had periodic inflow of sea water which was the majorsource of the calcium sulfate. Gypsum deposits are frequently of large areal extent and ofconsiderable thickness.

Typica l Depos i t s : Silurian Salina Formation in the Michigan and Appalachian basins withdeposits in New York, Pennsylvania, West Virginia, Ohio, and Michigan; Permian BlaineFormation in Kansas, Oklahoma, and Texas; Tertiary deposits of the Paris basin, France.

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : This deposit type contains the thickest and mostareally extensive deposits of gypsum and it accounts for the major production of gypsum of allof the deposit types.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Marine evaporites that contain limestone and dolomite;bedded celestite.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Marginal marine basins that were subsiding at a moderaterate during deposition of the evaporites. Influx of sea water maintained water levels in the

basins that were being lost by evaporation. Some evaporites in this type of setting have somecontribution from inflow from the continent. For most, however, this contribution is small.


Age ran ge: Late Proterozoic to Miocene, but most are Paleozoic and Mesozoic.


Host rock (s): Primarily dolomite, with some limestone and halite.

Assoc ia te d rock (s): Anhydrite, dolomite and halite.

O re m i ne ra l ogy : Gypsum with thinly interlaminated layers of calcite of dolomite.


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G angue m i ne ra l ogy : Calcite and dolomite.

Altera t ion: Many gypsum deposits are formed by the hydration of anhydrite. Purity andusefulness of the gypsum is dependent of the completeness of the alteration. Groundwaterdissolution can modify the layering, grain size, or porosity of gypsum deposits or it can even

destroy a deposit.

S t r u c t u r a l se t t i n g: Marine evaporites occur in basins near continental margins in areas ofmoderate subsidence.

Ore control(s) : Basin brines with salinity high enough to precipitate calcium sulfate.

Typi ca l o r e d i men s i ons : Thickness of mineable bedded gypsum deposits range from 10 to50 m. Areal extent of some deposits covers many square kilometers.

Effec t o f w ea t he r i ng : Surface weathering causes dissolution of gypsum in most climaticareas. Gypsum is preserved at the surface, however, in areas of aridity.

E ffe c t o f m e t a m o r p h i s m : Metamorphism of rocks containing bedded gypsum can causealteration of the surrounding rocks by calcium and sulfur metasomatism. Skarn minerals andpyrite are some of the products.

Maxi mum l i mi t a t i on o f ove rburden : Most gypsum is mined by strip mining but beddedgypsum is also mined by conventional methods at depths over 50 m.

Geochemical s ignature(s ) : There is no particular geochemical signature for gypsum.

Geophys ica l s ignature(s ) : Bedded gypsum gives a high response on a neutron log because ofthe large amount of water of crystallization.

Other explora t ion guide(s ) : Occurrence of basin-edge sediments that contain thin beds of

gypsum or anhydrite which may indicate thicker deposits toward the basin center. High-sulfate brines in wells.

Most r e ad i ly a sce r t a i nab l e r egi ona l a t t r i bu t e : Large basin containing marine sediments,with basin-edge sediments of higher-than-normal salinity.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : High-sulfate content in well water; highresponse on neutron well logs; saline springs.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Impurities must be low.


Di s t a n c e l im i t a t i o n s t o t r a n s p o r t a t i o n , p r o c e s s in g , e n d u s e : Transportation is a majorcost of the finished product. Therefore, costs of mining, processing, and transportation must

be balanced to achieve a saleable product.

REFERENCES


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Davis, 1986. Raup and Bodine, in press.Pressler, 1985. Smith and others, 1973.


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Model 35a.13

DES CRIP TIVE MODEL OF NATURALLY OCCURRING IODINE BRINES

by Sherilyn Williams-Stroud

BRIEF DESCRIPTION


P r in c i p a l c o m m o d i t ie s p r o d u c e d : Iodine.

C o-produc t s : Bromine, salt, magnesium, calcium salts.

E n d u s e s : Catalysts, animal feed additives, pharmaceuticals, photography, sanitary uses.Minor uses include cloud seeding, herbicides, Geiger counters, airport luggage scanners, andquartz-iodine lights for automobiles, sports stadiums, and television studios.

De s c r ip t i v e / g e n e t i c s y n o p s i s : Brines with high iodine concentrations are theorized to be ofmarine origin. Iodine is fixed in the marine environment by plants and other organisms.Organic material derived from seaweeds and planktonic organisms are deposited in muddysediments and iodine liberated by anaerobic decomposition of the organic matter in sedimentsis transferred to the brine.

Typi ca l depos i t s : Devonian Sylvanian Formation in Michigan; Miocene Monterey Formationand Pliocene Repetto Formation in California; Pennsylvanian Morrowan Formation inOklahoma; Pliocene Kazusa Group in Japan; Pliocene Kalibeng Formation in Indonesia;Permian Inder Salt Dome of Western Kazakhstan in the U.S.S. R.

R e la t i v e im p o r t a n c e o f t h e d e p o s i t t y p e : Economic amounts of iodine occur in brines.Brines represent one of two distinct iodine deposit types.

As s o c ia t e d / r e la t e d d e p o s it t y p e s : Bedded salt, salt domes, potassium, magnesium,nitrates, borates, hydrocarbons, bromine.


T e c t o n o s t r a t i g ra p h i c s e t t i n g : Iodine occurs with hydrocarbons and (or) with salts andbromine in subsurface brines.

R e gi on a l d e p o s i t i o n a l e n v i r o n m e n t : Deposition and accumulation of marine life produceshydrocarbons as an organic residue and iodine is contained in associated brines.

Age ran ge: Devonian to Pliocene for associated brine-bearing host rocks.


Host rock (s): Salt, sandstone, diatomaceous marl, limestone.

O re m i ne ra l ogy : N/A.

G angue m i ne ra l ogy : Evaporite minerals such as halite, potash, gypsum, etc.


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S t r u c t u r a l se t t i n g: Permeable rock reservoirs.

Ore control(s) : Permeable reservoirs in sediments.

Typi ca l o r e d i men s i ons : Resources of iodine-containing brines have not been precisely

measured.

T y p ic a l a lt e r a t i o n / o t h e r h a l o d im e n s i o n s :

Maxi mum l i mi t a t i on o f ove rburden : Unknown, but in Japan, it has been noted that theiodine:chlorine ratio decreases markedly with age. This may be a function of diagenesis.

Most r ead i ly a sce r t a i nab l e loca l a t t r i bu t e : Saline well or spring water.


P h y s i c a l/ c h e m i c a l p r o p e r t i e s a ffe c t i n g e n d u s e : Bromine and chlorine can be substituted

for iodine in some germicidal and antiseptic applications, but for most of its uses, iodine hasno substitute. Iodine is highly toxic and corrosive and must not be allowed to escape into theatmosphere.

C om p o s it i o n a l / m e c h a n i c a l p r o c e s s in g r e s t r i c t i o n s : After iodine is removed from br

some industrial mineral deposit models

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