distribution and geochemistry of the myo rhyolite, flin ... · 2. regional geology the myo rhyolite...

Saskatchewan Geological Survey 1 Summary of Investigations 2005, Volume 2

Distribution and Geochemistry of the Myo Rhyolite, Flin Flon and Creighton, Saskatchewan

K.A. Bailey 1 and H.L. Gibson 1

Bailey, K.A. and Gibson, H.L. (2005): Distribution and geochemistry of the Myo Rhyolite, Flin Flon and Creighton, Saskatchewan; in Summary of Investigations 2005, Volume 2, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep. 2005-4.2, CD-ROM, Paper A-8, 10p.

Abstract The Flin Flon Mining Camp, in the Flin Flon Belt of the Paleoproterozoic Trans-Hudson Orogen, hosts three world-class volcanogenic massive sulphide ore bodies: the Flin Flon, Callinan, and 777 deposits. The deposits are hosted in felsic volcanic rocks of the Millrock Member of the Flin Flon Formation, in the western limb of the Hidden Lake syncline. The Myo Member, of the Flin Flon Formation, is in the west limb of the Beaver Road anticline and is thought to be the time-stratigraphic equivalent of the Millrock Member; thus, the Myo Member is of particular interest for its volcanogenic massive sulphide potential. The purpose of this project is to undertake a stratigraphic and lithogeochemical comparison between the ore-hosting Millrock Member and the Myo Member.

The Myo Member includes three petrographically and geochemically distinct rhyolites, as well as aphyric, amygdaloidal, massive to pillowed basaltic flows, and thinly bedded to laminated mafic tuffs. Preliminary interpretations gleaned from 1:2000 mapping suggest that rhyolites of the Myo Member are approximately 60% intrusive, 5% extrusive, and 35% with an uncertain emplacement history. The large amount of intrusive rhyolite, coupled with the overall high volume of rhyolite and paucity of mafic volcaniclastic rocks in the Myo Member contrasts with what is observed in the Millrock Member, which is made up of a significant volume of mafic volcaniclastic rocks with lesser rhyolitic flows, domes, cryptodomes, and volcaniclastic rocks. These differences suggest that the Myo Member was emplaced outside of the main subsidence structure that hosts the Millrock Member and associated volcanogenic massive sulphide deposits. The Myo Member may have been emplaced in the flanks of a volcano, which is less prospective with respect to volcanogenic massive sulphide deposits.

Keywords: Paleoproterozoic, Trans-Hudson Orogen, Flin Flon Mining Camp, volcanogenic massive sulphide deposit, Myo Member, rhyolite, rhyolite geochemistry.

1. Introduction The Paleoproterozoic Flin Flon Mining Camp hosts three volcanogenic massive sulphide (VMS) deposits (Flin Flon, Callinan, and 777) that collectively total approximately 85.5 million tonnes of massive sulphide, making it one of the largest VMS camps in the world (Gibson et al., 2003). The VMS deposits at Flin Flon are in the Millrock Member of the Flin Flon Formation, a north-northwest–trending, east-dipping unit of heterolithologic breccias and rhyolitic flows, domes, and volcaniclastic rocks (Devine et al., 2002), on the west limb of the Hidden Lake syncline.

The Myo Member is a 6 km long, up to 360 m thick, northwest-trending, predominantly felsic volcanic unit in the west limb of the Beaver Road anticline. Thomas (1989) and MacLachlan et al. (2002) recognized that the rhyolites of the Myo Member (henceforth referred to as the Myo Rhyolites) range in composition from rhyolite to dacite and based on limited study, they tentatively interpreted the Myo Member to be the time-stratigraphic equivalent of the Millrock Member. The objective of this project, which forms the basis for an M.Sc. thesis at Laurentian University, is to determine if the Myo Member is the stratigraphic equivalent of the Millrock Member and, if so, do they share common mechanisms and environment of emplacement. The study included detailed (1:2000 scale) mapping and major, trace, and rare-earth element geochemistry aimed at establishing the litho- and chemo-stratigraphy and physical volcanology of the Myo Member. It is anticipated that the results of this investigation will provide important insights into the exploration potential of the Myo Member.

This paper presents preliminary results from two field seasons of mapping and will focus on the distribution and geochemical characteristics of the Myo Rhyolites. Nomenclature applied to the various rhyolite types is summarized in Table 1. Henceforth, the Myo Rhyolites are subdivided into three types: sparsely quartz porphyritic (SQP) rhyolites, quartz porphyritic (QP) rhyolites, and feldspar porphyritic (FP) rhyodacites (Table 1).

1 Mineral Exploration Research Center, Department of Earth Sciences, Laurentian University, 935 Ramsey Lake Road, Sudbury, ON P3E 2C6.


2. Regional Geology The Myo Rhyolite lies within the Flin Flon Formation in the Flin Flon Belt, part of the 1.9 to 1.8 Ga Trans-Hudson Orogen (Figure 1). This Paleoproterozoic orogen is interpreted to have formed as a result of collisions between older Archean continental blocks, the Superior and Rae-Hearne cratons, and intra-oceanic terranes between them (Lewry and Collerson, 1990). Four tectono-stratigraphic assemblages have been recognized within the Flin Flon Belt: 1) juvenile oceanic arc (1.9 to 1.88 Ga), 2) oceanic floor (1.9 Ga), 3) oceanic plateau/ocean island (undated), and

4) evolved arc (1.92 to 1.9 Ga) (Lucas et al., 1996). These assemblages were formerly known collectively as the Amisk Group (1920 to 1870 Ma; Syme et al., 1999).

Volcanic strata of the Amisk Group, that host the Flin Flon, Callinan, and 777 VMS deposits, are part of the juvenile oceanic arc assemblage and consist of tholeiitic basalts, mafic volcaniclastic rocks, and a volumetrically minor, but economically important, component of rhyolitic volcanic and volcaniclastic rocks (Figure 2). Unconformably overlying the Amisk Group are fluvial and alluvial sandstones and conglomerates of the Missi Group which, based on U-Pb zircon geochronology, have a maximum age of 1832 Ma (Heaman et al., 1992). Late tectonic granitoid to mafic intrusions include the Boundary and Phantom intrusions (e.g., Thomas, 1989) dated at 1842 ±3 Ma (Heaman et al., 1992) and 1820 Ma (MacQuarrie, 1980), respectively.

Rocks in the Flin Flon–Creighton area were affected by multiple deformation events including several phases of faulting and two phases of folding (F1 and F2; Thomas, 1994). Two regional-scale F2 folds, the Beaver Road anticline and Hidden Lake syncline, trend northwest and plunge southeast (Figure 2).

The strata hosting the ore deposits in the Flin Flon Mining Camp are subdivided into three formations (Figure 2). The basal Flin Flon Formation is overlain by the Hidden Formation, whereas the stratigraphic position of the Creighton Formation is uncertain (Devine, 2003). The Flin Flon Formation comprises, from oldest to youngest, the Club, Blue Lagoon, Millrock, and Myo members, with the latter two possibly being correlative (Thomas, 1989; MacLachlan et al., 2002; Devine 2003). The base of the Hidden Formation is marked by the Bomber Member, which is overlain by rocks of the Newcor Member (Figure 2; Thomas, 1989).

Rhyolitic flow and flow breccia, heterolithic breccia, and minor mafic flows make up the lowermost Club Member (Devine et al., 2002). The Blue Lagoon Member on the west limb of the Hidden Lake syncline consists of heterolithic mafic breccia with variable amounts and sizes of feldspar crystals and minor feldspar porphyritic and lesser aphyric basalt flows (Devine et al., 2002). The Blue Lagoon Member on the west limb of the Beaver Road anticline consists predominantly of aphyric and feldspar porphyritic pillowed basalt flows with subordinate interflow volcaniclastic rocks (MacLachlan et al., 2002).

The Flin Flon, Callinan, and 777 VMS deposits occur in the Millrock Member, in the west limb of the Hidden Lake syncline. The Millrock Member consists of: heterolithic and monolithic breccias; mafic and felsic volcaniclastic rocks; aphyric to quartz and feldspar-phyric rhyolitic flows, domes and cryptodomes; and associated autoclastic volcaniclastic rocks (Devine et al., 2002). Correlation of the Millrock Member with the Myo Member on the west limb of the Beaver Road anticline is complicated by faulting that has removed the hinge zone of the F2 anticline. The Myo Member was described by Thomas (1989) and Bailey and Gibson (2004) as consisting of quartz ± feldspar porphyritic rhyolitic to dacitic flows and intrusions, and minor felsic flow breccias and fragmentals. Mapping in 2005 has resulted in redefining the Myo Member to include felsic volcanic rocks and all intercalated basaltic volcanic and volcaniclastic rocks. Thus, the Myo Member now includes aphyric, amygdaloidal, massive to pillowed basaltic flows, and thinly-bedded to laminated mafic tuffs that were previously grouped with the overlying Bomber Member (Thomas, 1989). Consequently, the relationship of the Bomber Member to the Myo Member is currently uncertain.

On the west limb of the Hidden Lake syncline, the Bomber Member of the Hidden Formation immediately overlies the Millrock Member and is characterized by abundant synvolcanic basaltic sills and interflow/sill volcanic tuff (Tardif, 2003). The basaltic tuffs are fine-grained (typically <2 mm), plane-bedded, and locally cross-bedded. The Bomber Member is overlain by pillowed basalt flows and flow breccias of the Newcor Member (Thomas, 1989).

Table 1 - Previous subdivisions of the Myo Rhyolites based on field observations (Bailey and Gibson, 2004) and current subdivisions based on both field and geochemical characteristics.

Bailey and Gibson (2004) (field observations only)

This Report (geochemistry and field observations)

Type 1 Feldspar Porphyritic (FP) Type 2 Type 3

Sparsely Quartz Porphyritic (SQP)

Type 4 Quartz Porphyritic (QP)


Figure 1 - Tectonic assemblage map of the Flin Flon Belt (modified from Syme et al., 1996). Location of Figure 2 is indicated by the black outlined box. THO, Trans-Hudson Orogen; MORB, Mid-ocean ridge basalt.

Bear Lake block

Scotty Lake block

apup

s

a

k

ht

o

A

w Lake

Phanerozoic coverSask. Man.

o54 30' N

o102 15' W

10 km

Phanerozoic cover

Flin Flon

Cu

WL

NE Arm shear zone

Cu-Zn MINES

B - Birch Lake

C - Callinan

Ce - Centennial

Co - Coronation

Cu - Cuprus

D - Don Jon

FF - Flin Flon

Fl - Flexar

K - Konuto

M - Mandy

N - North Star

S - Schist Lake

T - Trout Lake

Tr - Triple 7W - Westarm

WL - White Lake

Tholeiitic, mafic-felsic volcanic rocks

Tholeiitic basalt (age unknown)

Calc-alkaline volcanic rocks

Major mafic-felsic tholeiiticintrusive rocks

Missi Groupsandstone, conglomerate

SUCCESSOR ARCINTRUSIVE ROCKS

SUCCESSOR BASINS

JUVENILE ARC

'EVOLVED ARC'

Intermediate-mafic

Felsic plutonic rocks(~1.920 to 1.903 Ga)

Granitic rocks (~2.5 Ga)

Felsic

N-type MORB/E-type MORBLayered mafic-ultramafic complexOCEAN FLOOR

(BACK-ARC)

OCEANIC PLATEAU

PRE-ACCRETION ASSEMBLAGES (1.92 to 1.88 Ga) POST-ACCRETION ROCKS (1.87 to 1.84 Ga)

1.90 to1.88 Ga

ARCHEAN SLICES

Accretion-relatedshear zones (D , >1.87 Ga)1

Younger shear zones and/or faults (D to D )2 5

VMS deposit (see inset key)

Amisk Lake

TrC

FF

S

W

DN

Ce

Co

BK

Fl

M

T

FF

Arc rift basalt

Schist-Wekusko suitegreywacke, mafic sills

1.90 Ga

THO

AtlanticOcean

HudsonBay

NAIN

SUPERIOR

RAE

SLA

VE

HEARNE

WY

OM

ING

<1.8 Ga Orogens

Paleoproterozoic Orogens

ArcheanCratons

130 W

50 N

50 N

60 W


Figure 2 - Simplified geology of the Flin Flon–Creighton area showing location of 1:2000 scale stratigraphic sections of this study and the distribution of the three Myo Member rhyolite types. VMS deposits: C, Callinan; FF, Flin Flon; Tr, Triple 7. Other features: BRA, Beaver Road anticline; CCF, Creighton Creek Fault; CLF, Club Lake Fault; FFLF, Flin Flon Lake Fault; HLS, Hidden Lake syncline; and RLF, Ross Lake Fault (after Stockwell, 1960).

CLF

RL

F

BR

A

HL

S

Boundary Intrusion

Annabel Lake pluton

Sandstone andconglomerate

Gabbro/diorite

LOUIS FORMATION

HIDDEN FORMATION

Millrock Member

Bomber Member

Newcor Member

Undivided

VMS deposit

Unsubdivided volcanics

Myo Member

Blue Lagoon Member

Fault

Mine shaftN= North MainS= South MainTr= Triple 7

INTRUSIONS

MISSI GROUP

FLIN FLON ASSEMBLAGE

FLIN FLON FORMATION

llTr

Boot Lake-Phantom Lake Intrusive Complex

FP rhyodacite

QP rhyolite

Mafic volcanic flows

SQP rhyolite

Club Member

Detailed 1:2000 stratigraphic sections

2 Myo Lake section (1:2000, Bailey, 2004a)

3 Myo Lake section (1:2000, MacLachlan and Bailey, 2002)

4 West Arm Road section (1:2000, Bailey, 2004b)

5 Phantom Lake section (1:2000, this study)

5

4

2

3

FFLF

1 Hilary Lake section

1

Anticline

Syncline

1

2

3

4

6

7

8

9

1

1

1

1

1

2

2

2

3

3

6

7

89

8

9

5

510

10

11

510

11

11

12

12

4

CREIGHTON FORMATION

Tr

N

S

C

C

Tr

FF

Key Lake

BomberLake

MyoLake

Phantom

Hilary Lake

Flin Flon Lake Ross

Lake

Douglas

Little CliffLake

MacdougalLake

LouisLake

BootlegLake Arthur

LakeDionLake

Club Lake

Hapnot Lake

Hidden Lake

CC

F

Lake

Lake

N

MAN.SASK.

o1015 5’ 54’ 53’ o1015 2’

44’

45’

46’

o544 3’

o544 7’

?

0 kilometres 1

3


3. Myo Rhyolite Overview and Distribution Field mapping in 2004 and 2005 has shown that the Myo Member includes three types of rhyolite. These have been named according to phenocryst type and abundances: 1) sparsely quartz porphyritic (SQP), 2) quartz porphyritic (QP), and 3) aphyric to feldspar porphyritic (FP). Field relationships indicate that the different rhyolites are found at distinct stratigraphic levels: SQP rhyolites are the oldest, followed by QP rhyolites, and FP rhyodacites are the youngest. Four flow facies have been identified in the Myo Rhyolites: massive, flow banded, flow breccia, and volcaniclastic facies. The reader is referred to Bailey and Gibson (2004) for a more detailed description and field photos of the rhyolites of the Myo Member. Part of the 2005 program involved mapping the upper and lower contacts of the rhyolites to determine the distribution of the various types of rhyolite in the Myo Member (Figure 2), as well as the distribution of intrusive and extrusive facies.

a) Sparsely Quartz Porphyritic (SQP) Rhyolite SQP rhyolite, which now includes Types 2 and 3 from Bailey and Gibson (2004) (Table 1), has 2 to 8% quartz phenocrysts that are typically less than 1 mm in diameter. Feldspar phenocrysts range from 5 to 10% and are generally less than 1.5 mm wide (Figure 3). SQP rhyolite exhibits massive, flow banded, flow brecciated and volcaniclastic flow facies with the latter facies restricted to the Myo Lake Section (Figure 2). The lack of volcaniclastic facies beyond the Myo Lake area suggests that the majority of this unit was intrusive and only locally extrusive.

SQP rhyolite forms the base of the Myo Member and is continuous along strike for 6 km between Hilary Lake in the northwest and the east side of Phantom Lake in the southeast (Figure 2). Boundary Intrusions have disrupted the unit along strike. The unit is approximately 240 m thick, but increases to ~360 m at Myo Lake due to dilation by numerous fine- to medium-grained mafic intrusions. SQP rhyolite thins to the northwest and at Hilary Lake it has a thickness of ~120 m.

b) Quartz Porphyritic (QP) Rhyolite QP rhyolite, previously termed ‘Type 4’ (Bailey and Gibson, 2004; Table 1), contains 8 to 12% light blue quartz phenocrysts that range from 1 to 4 mm wide. Feldspar phenocryst concentrations reach 10%; these are less than 1.5 mm long. This unit displays massive, flow banded and flow brecciated facies.

QP rhyolite occurs stratigraphically above the SQP unit and is found to be continuous along strike from west of MacDougall Lake to the west side of Phantom Lake, a distance of 4.2 km (Figure 2). The unit ranges from 100 to 180 m thick. The upper quartz porphyritic unit of the Myo Member is exclusively QP rhyolite. The lower quartz-phyric unit, SQP, however, contains massive lenses of QP rhyolite. The upper contacts of these QP lenses locally cross-cut overlying hanging-wall mafic volcanic rocks as well as SQP rhyolite indicating that this phase of QP rhyolite is an intrusion. The main QP horizon displays flow banded and brecciated facies, however, it lacks flow top breccias which suggests it may also be a large cryptodome. A thin, 420 m long lens of QP rhyolite occurs southeast of Bomber Lake, however, surface and drill data indicate that this rhyolite is not connected to the main QP rhyolite along strike (C. Devine, pers. comm., 2005).

c) Feldspar Porphyritic (FP) Rhyodacite This is an aphyric to feldspar-phyric rhyodacite with feldspar phenocrysts that range from 2 to 7% and are less than 1 mm long. FP rhyodacite weathers grayish orange and is locally amygdaloidal with amygdules from 1 mm to 1 cm wide. This unit occurs almost entirely as massive facies, has sharp and locally discordant contacts with surrounding host rocks, and lacks flow features, which suggests that it is an intrusion. It locally has flow top breccia, however, indicating that it may, in places, be extrusive.

FP rhyodacite occurs in three different stratigraphic intervals in the Myo Member (Figure 2). FP rhyodacite is most voluminous towards the southeast part of the map area and all three phases pinch out along strike towards the northwest (Figure 2). The unit ranges from 10 m to 140 m thick.

4. Phantom Lake Stratigraphic Section In addition to mapping the distribution of the various phases of rhyolite, a stratigraphic transect through the Myo Member and immediate footwall and hanging-wall strata was mapped at 1:2000 scale. The transect is located west of Phantom Lake and traverses the southeastern extent of the Myo Member (Figure 2). The area is complicated due to faulting, but the section is representative of the stratigraphy of the Myo Member and compliments three sections derived from previous transects [Myo Lake (west) and West Arm Road sections (Bailey, 2004a; Bailey 2004b; Bailey and Gibson, 2004); and Myo Lake (east) section (MacLachlan and Bailey, 2002)].


Figure 3 - Simplified stratigraphic section of the Myo Member and flanking units, Phantom Lake area.

650

600

500

400

300

200

100

0

1100

1000

900

800

700

650

Tu

ff

Bre

ccia

Pill

ow

ed

/Ma

ssiv

e

Fe

lsic

Vo

lca

nic

Intr

usi

on

Ba

sa

lt

SQP

FP Myo

Me

mb

er

QP

FP

FP

Un

su

bd

ivid

ed

Vo

lca

nic

Ro

cks

INTRUSIONS

Boundary

Feldspar-phyric intermediate

Feldspar + pyroxene-phyric mafic

Aphyric mafic

UNSUBDIVIDED

Aphyric amygdaloidal massive to pillowed mafic volcanic flow

Ash to lapilli mafic tuff

PillowsFlow brecciaFlow banding

Quartz phenocryst concentration

Aphric to feldspar (2 to 7%, <1 mm) phyric rhyodacite (FP)

MYO MEMBER

Section Offset

Quartz (8 to 12%, 1 to 4 mm) and feldspar (7 to 10%, 0.5 to 2 mm) phyric rhyolite (QP)

Quartz (2 to 8%, 0.5 to 2 mm) and feldspar (5 to 10%, 0.5 to 1.5 mm) phyric rhyolite (SQP)

Aphyric amygdaloidal mafic

METRES

Tu

ff

Bre

ccia

Pill

ow

ed

/Ma

ssiv

e

Fe

lsic

Vo

lca

nic

Intr

usi

on

Ba

sa

lt

METRES


The Phantom Lake Section is approximately 1200 m thick and includes the SQP and QP rhyolites as well as three FP rhyodacite units. Ten samples from the Myo Member felsic volcanic rocks were analyzed for major, trace, and rare earth elements to complement the lithogeochemical database established in 2004.

The Boundary Intrusion is the lowermost unit of the section and is interpreted to have intruded and removed the footwall (Blue Lagoon Member) stratigraphy below the Myo Member. The Boundary Intrusion ranges from medium-grained pyroxenite, with and without xenoliths, to monzonite, monzodiorite, and heterolithic intrusive breccia. Above the Boundary Intrusion is a thick, medium- to coarse-grained gabbro, which is older than the Boundary Intrusion. The lowermost unit of the Myo Member, SQP rhyolite, is 50 m thick and is cut by the gabbro. A fine-grained, aphyric mafic intrusion separates the SQP rhyolite from the overlying aphanitic, aphyric, amygdaloidal pillowed basalt flows. The flows are in turn overlain by a 150 m thick unit of thinly bedded to laminated mafic tuff intercalated with mafic sills, a basalt flow, and FP rhyodacite. The upper QP rhyolite conformably overlies this succession and is 125 m thick. A discontinuous laminated mafic tuff separates the QP rhyolite from an overlying 25 m thick unit of FP rhyodacite. Conformably overlying the FP rhyodacite is an aphanitic, aphyric, amygdaloidal pillowed flow, which has been intruded by a fine-grained, aphyric gabbro. An overlying unit of FP rhyodacite marks the uppermost unit of the Myo Member and represents the last phase of felsic volcanism. The FP rhyodacite, in turn, is overlain by rocks that are not subdivided into members, but include aphanitic, aphyric, amygdaloidal basaltic flows and associated flow breccias that were increasingly silicified up section towards the Boot Lake–Phantom Lake Intrusive Complex in the southwest (Figure 2; Galley and Franklin, 1987; Thomas, 1990).

5. Geochemistry As discussed above, three types of Myo Rhyolites are recognized based on phenocryst type and abundance (Table 1). On a Winchester and Floyd (1977) Zr/Ti02-Nb/Y rock type classification diagram (Figure 4), felsic volcanic rocks of the Myo Member plot in two separate groups. Least altered SQP and QP samples plot predominantly in the rhyolite field, whereas least altered FP plots in the rhyodacite/dacite field. FP samples are interpreted to be rhyodacitic in composition as their silica content is higher than that of a dacite (FP SiO2 average 70.6%). Primitive mantle (PM) normalized multi-element diagrams for the three lithofacies illustrate that they are also chemically distinct (Figure 5), consistent with previous geochemical subdivisions proposed by MacLachlan (Saskatchewan Geological Survey unpubl. rep., 2004). A summary of the ratio data discussed below is found in Table 2.

a) SQP Rhyolite The SQP rhyolite has the highest overall light rare earth element (LREE)/heavy rare earth element (HREE) enrichment (LaN/YbN) of the three felsic volcanic types, resulting in a slightly sloped pattern on a multi-element, primitive mantle-normalized plot (Figure 5a). Multi-element primitive mantle-normalized plots show negative Nb, Eu, Ti, V, and Sc, with that for Eu quite pronounced. Comparatively, SQP rhyolites have the highest LREE enrichment as well as the highest overall fractionation (LuN/ScN) values.

b) QP Rhyolite Based on multi-element primitive mantle-normalized plots, QP rhyolite is LREE enriched relative to the middle rare earth elements (MREE) and HREE (Figure 5b). QP rhyolites have negative Nb, Eu, Ti, V and Sc anomalies, with those for Ti and Eu being more pronounced than in FP. As well, unique to this type are very weak, positive Zr anomalies. LuN/ScN ratios indicate that the QP is less fractionated than SQP, but slightly more fractionated than FP.

c) FP Rhyodacite Multi-element primitive mantle normalized spider plots for the

Figure 4 - Plot of Myo Rhyolite samples on a rock type classification diagram of Winchester and Floyd (1977). Samples from 2004 mapping and Hudson Bay Exploration and Development diamond drill hole data.

0.01 0.1 1 100.001

0.01

0.1

1

Zr/TiO2

Nb/Y

SubAlkaline Basalt

Andesite/Basalt

Andesite

Rhyolite

Alkali-Basalt

Trachyandesite

Comendite/Pantellerite

Phonolite

Trachyte

Basanite/Nephelinite

FP rhyodacite

SQP rhyolite

QP rhyolite

Rhyodacite/Dacite


FP rhyodacite have an overall flat pattern (LaN/YbN average 1.22) with negative Nb, Ti, and Sc anomalies as well as weak negative Eu anomalies (Figure 5c). Although data for these units, collected in 2004 does not depict a negative V anomaly (below detection limits), the FP rhyodacite samples from MacLachlan’s dataset do (sample 0264-51). LuN/ScN ratios indicate FP rhyodacites have the lowest overall degree of fractionation, which is consistent with FP plotting in the rhyodacite/dacite field on a Winchester and Floyd (1977) rock type classification diagram (Figure 5).

6. Conclusions and Future Work

Evaluation of geochemical data from samples collected in 2004 and observations from field work in 2004 and 2005 indicate that the felsic units in the Myo Member are divisible into three types. Field relationships tentatively suggest that SQP and QP are stratigraphically and geochemically distinct units of quartz and feldspar porphyritic rhyolite and that their locations in stratigraphy are not the result of fault repetition as previously interpreted (Bailey and Gibson, 2004). The current field work also resulted in redefining the Myo Member to include all mafic volcanic rocks between the lower SQP rhyolite and the upper FP rhyodacite (Figure 2). This includes massive to pillowed flows and laminated to bedded mafic tuffs. Based on the high volume of rhyolite, high proportion of intrusive to extrusive rhyolite, and paucity of mafic volcaniclastic rocks, a preliminary interpretation is that the Myo Member was emplaced in the flanks of a volcano and not in a subsidence structure as was the Millrock Member which hosts the volcanogenic massive sulphides (Devine, 2003).

Future work will include integrating surface mapping and subsurface drill hole data. This

Figure 5 - Primitive mantle-normalized trace element plots of the three types of Myo Rhyolites: (a) SQP rhyolites, (b) QP rhyolites, and (c) FP rhyodacites. Samples taken from 2004 mapping and Hudson Bay Exploration and Development diamond drill hole data. Elements are normalized to values of Taylor and McLennan (1985).

SQP Rhyolites

0.10

1.00

10.00

100.00

Th Nb La Ce Nd Zr Sm Eu Gd Ti Tb Dy Y Ho Er Tm Yb Lu V Sc

Ro

ck

/PM

0464KB-004 0464KB-024 0464KB-029

0464KB-063 0464KB-064 H71600

QP Rhyolites

0.10

1.00

10.00

100.00


Ro

ck

/PM

0464KB-022 0464KB-071 0464KB-073 H71863

H71869 H71870 72982H

FP Rhyodacites

0.10

1.00

10.00

100.00


Ro

ck

/PM

0464KB-037 0464KB-041 0464KB-042

0464KB-050 0464KB-053 0264-51

a

b

c


Table 2 - Summary of geochemical characteristics of the felsic volcanic groups of the Myo Member. Samples from 2004 mapping and Hudson Bay Exploration and Development diamond drill hole data.

will form the basis for determining the stratigraphic position of the Myo Member relative to the Millrock Member. In addition to the detailed mapping and geochemical characterization, samples of each Myo Member felsic volcanic type have been submitted for neodymium isotope geochemistry. As well, a sample of QP rhyolite has been submitted for U-Pb zircon age dating. This will aid in further comparing and contrasting of the mechanisms, environments, and timing of emplacement of the Myo and Millrock members.

7. Acknowledgments Funding for this project is provided by a NSERC–Laurentian University (LU)–Hudson Bay Exploration and Development Co. Ltd. (HBED)–MIRARCO Collaborative Research and Development (CRD) Grant. Saskatchewan Industry and Resources (SIR) provided additional financial and logistical support throughout the two years of the project. Housing for the summer was supplied by the Manitoba Geological Survey. Kelly Gilmore, Darren Simms, Christine Devine and all the staff of HBED are thanked for their generous support in both the office and field. Kate MacLachlan (SIR) and Steve Piercey (LU) have provided invaluable time, knowledge and supervision on this project and are thanked for their continuous support and advice. We are grateful to Bill Slimmon and Thomas Love (SIR) for their assistance with the map components of this project. Also, Jenna Vanstone is thanked for her excellent field assistance. Revisions of Kate MacLachlan and Steve Piercey helped improve the paper.

8. References Bailey, K.A. (2004a): Bedrock geology, Myo Lake section, Creighton, Saskatchewan (part of NTS 63K-12); 1:2000

scale map with Summary of Investigations 2004, Volume 2, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep. 2004-4.2.

__________ (2004b): Bedrock geology, West Arm Road section, Creighton, Saskatchewan (part of NTS 63K-12); 1:2000 scale map with Summary of Investigations 2004, Volume 2, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep. 2004-4.2.

Bailey, K.A. and Gibson, H.G. (2004): A field description of the Myo Rhyolite, Flin Flon and Creighton, Saskatchewan; in Summary of Investigations 2004, Volume 2, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep. 2004-4.2, CD-ROM, Paper A-1, 11p.

Devine, C.A. (2003): Origin and emplacement of volcanogenic massive sulphide-hosting, Paleoproterozoic volcaniclastic and effusive rocks within the Flin Flon subsidence structure, Manitoba and Saskatchewan, Canada; unpubl. M.Sc. thesis, Laurentian University, Sudbury, 93p.

Devine, C.A., Gibson, H.L., Bailes, A.H., MacLachlan, K., and Galley, A.G. (2002): Stratigraphy of VMS-hosting volcanic and volcaniclastic rocks of the Flin Flon Formation, Flin Flon–Creighton area, Saskatchewan and Manitoba; in Summary of Investigations, 2002, Volume 2, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep. 2002-4.2, CD-ROM, Paper B-4, 11p.

Galley, A.G. and Franklin, J.M. (1987): Geological setting of gold, copper, tungsten and molybdenum occurrences in the Phantom Lake region; in Summary of Investigations 1987, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 87-4, p115-124.

Gibson, H.L., Gilmore, K., Bailes, A., and MacLachlan, K. (2003): The Flin Flon VMS deposits: Challenges for future deep exploration; Open House 2003, Saskatchewan Geological Survey, Sask. Industry Resources, Abstr. Vol., p19.

SiO2Myo Rhyolite Range Avg Range AvgTypes (x PM) (x PM) (x PM) (x PM) Range Avg Range Avg Range Avg AvgSQP rhyolite 11.61 to 25.09 16.99 5.42 to 44.65 22.43 24.3 to 48.09 34.17 0.72 to 1.02 0.79 1.98 to 2.64 2.17 76.88QP rhyolite 7.06 to 25.44 12.06 3.21 to 34.66 14.18 12.69 to 28.11 21.70 0.50 to 0.79 0.67 1.85 to 2.86 2.21 74.37FP rhyodacite 8.30 to 23.33 15.31 4.73 to 45.75 15.11 7.26 to 21.71 13.68 0.58 to 0.97 0.74 1.01 to 2.95 1.61 70.60

La/SmHREE Abundance LREE Abundance Lu/Sc Gd/Yb


Heaman, L.M., Kamo, S.L., Ashton, K.E., Reilly, B.A., Slimmon, W.L., and Thomas, D.J. (1992): U-Pb geochronological investigations in the Trans-Hudson Orogen, Saskatchewan; in Summary of Investigations, 1992, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 92-4, p120-123.

Lewry, J.F. and Collerson, K.D. (1990): The Trans-Hudson Orogen: Extent, subdivision and problems; in Lewry, J.F. and Stauffer, M.R. (eds.), The Early Proterozoic Trans-Hudson Orogen of North America, Geol. Assoc. Can., Spec. Pap. 37, p1-14.

Lucas, S.B., Stern, R.A., Syme, E.C., Reilly, B.A., and Thomas, D.J. (1996): Intraoceanic tectonics and the development of continental crust: 1.92-1.84 Ga evolution of the Flin Flon Belt, Canada; Geol. Soc. Amer. Bull., v108, p602-629.

MacLachlan, K. and Bailey, K. (2002): Bedrock geology, Myo Lake section, Creighton, Saskatchewan (part of NTS 63K-12); 1:3000 scale map with Summary of Investigations 2002 Volume 2, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep. 2002-4.2.

MacLachlan, K., Gibson, H.L., and Bailey, K. (2002): Stratigraphic and intrusive relationships in the Myo Lake Section, Flin Flon mine sequence, Creighton, Saskatchewan; in Summary of Investigations, 2002, Volume 2, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep. 2002-4.2, CD-ROM, Paper B-2, 10p.

MacQuarrie, R. (1980): Absolute age of the Flin Flon deposit (abstract); Can. Inst. Min. Bull. v73, no820, p53.

Stockwell, C.H. (1960): Flin Flon–Mandy area, Manitoba and Saskatchewan; Geol. Surv. Can., Map 1078A (with marginal notes), 1:12 000 scale.

Syme, E.C., Bailes, A.H., and Lucas, S.B. (1996): Tectonic assembly of the Paleoproterozoic Flin Flon Belt and setting of VMS deposits; Geol. Assoc. Can./Mineral. Assoc. Can., Jt. Annu. Meet., Winnipeg, May 1996, Field Trip Guidebook B1, 131p.

Syme, E.C., Lucas, S.B., Zwanzig, H.V., Bailes, A.H., Ashton, K.E., and Haidl, F.M. (1998): Geology, NATMAP Shield Margin Project Area Flin Flon Belt, Manitoba/Saskatchewan accompanying notes; Man. Geol. Services Branch/Geol. Surv. Can./Sask. Geol. Surv., 40p.

Tardif, N.P. (2003): Hanging wall alteration above the Paleoproterozoic Callinan and Triple 7 volcanogenic massive sulphide deposits, Flin Flon, Manitoba, Canada; unpubl. M.Sc. thesis, Laurentian University, Sudbury, 100p.

Taylor, S.R. and McLennan, S.M. (1985): The continental crust: its composition and evolution; Blackwell, Oxford, 312p.

Thomas, D.J. (1994): Stratigraphic and structural complexities of the Flin Flon Min sequence; in Summary of Investigations 1994, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 94-4, p3-10.

__________ (1990): New perspective on the Amisk Group and regional metallogeny, Douglas Lake–Phantom Lake area, northern Saskatchewan; in Summary of Investigations 1990, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 90-4, p13-20.

__________ (1989): Geology of the Douglas Lake–Phantom Lake area (part of NTS 63K-12 and -13); in Summary of Investigations 1989, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 89-4, p44-54.

Winchester, J.A. and Floyd, P.A., (1977): Geochemical discrimination of different magma series and their differentiation products using immobile elements; Chem. Geol., v20, p325-343.

distribution and geochemistry of the myo rhyolite, flin ... · 2. regional geology the myo rhyolite...

Documents