Analysis of whole-rock chemical data has identified five distinct geochemical signatures for the FIA volcanic rocks. The F1-M1 rocks occur mostly along the west shore of Reed Lake, in the Reed Mine area and to the north of Fourmile Island. M2-F2 rocks occur mostly near the Fourmile Island area and M3 rocks, a minor component near Fourmile Island, are abundant in the Cowan River area; M3 also often have a strong positive magnetic signature.

Fedikow, M. A. F. 1991: Sediments-hosted Zn-Cu (Bur zone) and Zn-Pb-Ag (Kobar/Ruby) massive sulphide type deposits, Snow Lake area (NTS 63J/13); in Manitoba Energy and Mines, Minerals Division, Report of Activities, 1991, p. 43-46 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. of America Bull., v. 108, no. 5, p. 602–629. Stern, R.A., Syme, E.C., Bailes, A.H. and Lucas, S.B. 1995: Paleoproterozoic (1.90–1.86 Ga) arc volcanism in the Flin Flon Belt, Trans-Hudson Orogen, Canada; Contributions to Mineralogy and Petrology, v. 119, no. 2–3, p. 117–141. Zwanzig, H. V. and Bailes, A. H. 2010: Geology and geochemical evolution of the northern Flin Flon and southern Kisseynew domains, Kississing–File lakes area, Manitoba (parts of NTS 63K, N); Manitoba Innovation, Energy and Mines, Manitoba GeologicalSurvey, Geoscientific Report GR2010-1, 135 p.

Paleoproterozoic rocks in the Reed Lake area are a component of a larger tectonic collage of volcano-plutonic and sedimentary rocks assembled during the closure of an ancient ocean (ca. 1.9–1.8 Ga) and collectively termed the 'Flin Flon belt' (FFB). Previous workers (Stern et al., 1995) recognized that significant stratigraphic, geochemical and isotopic differences exist between arc-volcanic rocks in the Flin Flon (Amisk collage) and Snow Lake areas, suggesting that these two segments of the FFB formed in distinct tectonic settings (Lucas et al., 1996). The Reed Lake area represents a critical bridge between these two segments, as it lies at the boundary between the Amisk collage sensu stricto and the Snow Lake segment.

One of the key geological units of the Reed Lake area, the Fourmile Island assemblage (FIA), is a bimodal succession of volcanic and volcaniclastic rocks of arc or arc-rift affinity that are known to host several VMS deposits. Metavolcanic rocks of the Fourmile Island Assemblage (FIA) are exposed at surface on western Reed Lake where they form a greater than 5.5 km thick sequence of subaqueous bimodal volcanic rocks. The Fourmile Island Assemblage is currently interpreted (Zwanzig and Bailes, 2010) as a back-arc - rift succession formed at about 1.89 Ga during opening of an ocean basin.

Integration of whole-rock chemistry data with published stratigraphic columns and new field data provides new insight on the internal stratigraphy of the FIA in the western Reed Lake area. Bailes (1980) described a simple sequence for the FIA near Dickstone mine (columns A-B below). Syme et al. (1995) encountered a more complex stratigraphy in the western portion of Reed Lake (Columns W, F and S above). Schematic stratigraphic columns from Syme et al. have been modified according to new data.

F1 and M1 rocks display a depleted REE pattern relative to chondrite and they consist mostly of coherent facies volcanic rocks with little volcaniclastic component.

Oppositely, M2 and F2 volcanic rocks show an enriched REE pattern relative to chondrite and present more diversity of volcanic facies, including more volcaniclastics rocks. Minor graphitic/ sulphidic argillite is also often associated with the M2/F2 rocks.

The difference in chemistry and volcanic facies, suggest that M1/F1 and M2/F2 rocks represent different stage of the arc evolution.

The project has been facilitated by the co-operation of Hudbay Minerals Inc., Royal Nickel Corporation (formerly VMS Ventures Inc.) and Rockcliff Metals Corporation that provided access to recent drillcores, permitted sampling and shared some of their own data. This co-operation has significantly expanded the scope of the drillcore examination program and will contribute to our better understanding of the geology of the sub-Phanerozoic basement of Reed Lake.

Acknowledgements

The Flin Flon belt in the Reed Lake area, and its extension to the south under Phanerozoic sedimentary rocks, has significant potential to host additional VMS deposits. Despite the presence of several economic deposits, the geological setting of VMS deposits in the Reed Lake area is not well understood. Discovery of the Reed VMS deposit in 2007 deposit has resulted in renewed interest in the geology of Reed Lake area.

In order to gain a better understanding of the geological framework and mineral potential of the Reed Lake area and its sub-Phanerozoic basement, a multiyear field-mapping and compilation project was initiated in 2013. To complement data acquired through geological mapping, a drillcore examination and sampling component was added to the project in 2015. The drillcores provide essential information in areas that lack surface exposure.

A compilation of geological data from surface mapping and drillcore was integrated with regional geochemistry and airborne geophysical surveys to produce two new preliminary maps, one for the exposed Flin Flon belt in the Reed Lake area – (PMAP2017-01; this poster) and the other for its sub-Phanerozoic extension to the south – (PMAP2017-02; poster T8).

A high magnetic trend (white dashed line on Total Magnetic Intensity map) that parallels the Burntwood group sediments (B1a) in central Reed Lake was investigated. This magnetic anomaly also coincides with a strong conductor. One drillcore (EEL-313) was re-examined and showed Burntwood group rocks with higher proportion of mudstone than usual and a 30 feet long mineralized interval (10-25 % graphite and 1-3% pyrite). No other drillcore drilled through this anomaly has been preserved but historical logs are still available and have been reviewed. Historical logs consistently indicates that the anomaly is caused by graphitic argilite with variable amount of pyrite and lesser pyrrhotite.

Some examples from historical log descriptions:EEL-325: 560 ft of mineralized seds including 138 ft of massive py and 5-20% po19543: 160 ft of slate followed by 240 ft of “mineralized iron formation”19545: mineralized argillite, includes 2 iron formations (20 ft and 100 ft thick)EEL-200: 500 ft of variably mineralized graphitic argillite

A few drill logs describe a progression from a greywacke with minor argillite to a mineralized graphitic argillite. Based on historical logs, this anomaly has been interpreted to represent a graphitic, sulfidic mudstone, with iron formations and minor greywacke (B1b). The progression from greywacke with minor argillite to graphitic, sulphidic argilllite with iron facies formation indicates that this unit represent a previously undocumented facies transition within the Burntwood group.

Recognition that thick graphitic and sulphide-rich argillite with significant lateral continuity occurs within Burntwood rocks has important economic implications. The presence of graphite and sulfur indicate changes of the basin chemical conditions to an anoxic and H S-rich environment. Such 2

sulfur-rich anoxic basin could represent a chemical trap for oxidized hydrothermal fluids released from seafloor vents, possibly focused along a fault, in a similar manner to Sedex deposits.

The Bur deposit, 24 km NE of Snow Lake, is a stratiform Zn-Cu-Pb massive sulphide deposit with an unusual setting compare to other massive sulphide deposits from the area. Fedikow (1991) described the the Bur as stratabound sulphides hosted by amphibolite-facies greywacke and graphitic argillite interpreted to be part of the Burntwood group. The occurrence of stratabound sulfide facies at Reed Lake provides an example for the geological setting of the Bur deposit in Burntwood group rocks.

Based on the presence of laterally extensive stratabound sulfides at Reed Lake and the occurrence of the Bur deposit, it is suggested that the Burntwood group should be considered prospective for additional stratabound massive sulphide mineralization of the Sedex-type.

Introduction

Geological context

Geology of the Exposed Basement in the Reed Lake Area, Flin Flon Belt, West-Central Manitoba (Part of NTS 63K9, 10, 15, 16)

S. Gagné, E. C. Syme, S. D. Anderson, and A. H. Bailes (MGS)

References

Burntwood group: Sedex potential

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!(

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!(

!(

!

Reed

Deep Lake

Woosey

Lake

Halfway

TrampingLake

Sewell

Lake

1894±5 Ma1

390 000

390 000

395 000

395 000

400 000

400 000

405 000

405 000

410 000

410 000

415 000

415 000

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420 000

425 000

425 000

6 0

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UTM projection: Zone 14, NAD83

complex Wekusko

Lake

Lake

Preliminary Map PMAP2017-1

JackfishLake

Gabbro

LakePluton

Pluton

Snow LakeAssemblage

1836 ±4 Ma5

Northeast Reed

Berry Creek

fault zone

Fourmile Islandassemblage

Reed Lakemafic-ultramafic

Reed Lake

gabbro

Josland Lake

1886 ±3 Ma2

groupMaximum age

Reed Lake

Pluton

Batholith1876 +7/-6 Ma

3

Little Swan Lake Pluton1826 ±5 Ma

3

West

R

eed

No

rth

S

tar

Sh

ear

Zo

ne

J10a

J11

J9

B1b

P4f

P4a P3aP3b

P3c

J3

P5a

P2aF2c

P5a

J9

P5a J3P2a

J1

P5f

P5cF1c

P4eP2fP4a

P3a

P3b

P2b F1c

P6a

P5a P2f

P3cP6a

P2fP3b B1aP6aJ15 P6a

P5cP2P2

F1c

J7

J4J5aP2J6b

J13bP2b

P2b

J6a

P2b

J10c J6cB1aP5

F2a

sJ7

J8J4

J6d J8 B1bJ4

J9

J10b

P3cP3b

B1a

F1b

P4a

P3b J9

P3a

F1c

J13b

P4aP5a

J1

T1

P4b

P6

P2b

F1c

P4g

J9

P3a

P4e

J9

P2b

P3c

J13b

P6b

J14

P4f

P5cP2c

P2

F2cF2a

B1c

F2b

J15

P3a

J4

M1b

P2

P6c

B1b

J8

F1a

B1a

J8 J4

J4

B1a

J6aF2bF1aB1a

P2F2b

P2h

T1

J10a

P3a

P4g

J3

P2

P4f

T1

P4d

B1a

P4a

P5a P4e

P5

P4h

B1b

J15

P2a,c,P1

J4

J4

F2a

F2bF2a

J4

P6b

P5e

P5a

P4h

P4f

P5a

P2c

B1a

P4b

F1a

P5

T2

P4e

P5c

P4h

P4f

F1a

F1a

T3,T4

J10a,b

P5b,c

P5b,c

P5b,c

T3,T4

P4f,e

J13b,a

J10a,b

P2g,h

F2a

J10c

J14

J15

J14

J6a

J4

T2

T2

F1a

F1a F1a

P4f

P5

F1a

P4a

P4f

T4

T2

P4f

P5cJ2

B1bsJ4a

J4,5a,5b

M1a

P4g

FourmileIsland

Bujarsky Lake

Burntwood

of 1859 ±7 Ma

Gants Lake

assemblage

Rail

Pot Lake

Sills

4

Raindrop

Morgan Lake

Jackfish

Wine

Symbols

Geological Boundaries

Contact

Fault

# # # # # Thrust fault

! ! ! !West Reed-North Starshear zone

Precambrian-PaleozoicBoundary

Mineral Deposits

!( Ni-Cu+/-Co+/-PGE

!( Base metals

Geochronology

!( Sample Site

M1

M1a

M1b

B1

B1a

B1b

B1c

T1

T2

T3

T4

J15

J14

J13

J13a

J13b

J12

J11

J10

J10a

J10b

J10c

J9

J8

J7

J6

J6a

J6b

J6c

J6d

J5

J5a

J5b

J4

J3

J2

J1

sJ4a

sJ7

F2

F2a

F2b

F2c

F1

F1a

F1b

F1c

P6

P6a

P6b

P6c

P5

P5a

P5b

P5c

P5d

P5e

P5f

P4

P4a

P4b

P4c

P4d

P4e

P4f

P4g

P4h

P3

P3a

P3b

P3c

P2

P2a

P2b

P2c

P2d

P2e

P2f

P2g

P2h

Sedimentary rocks

Missi group

Conglomerate, pebbly sandstone, sandstone

Polymictic conglomerate, sandstone

Pebbly sandstone, pebble conglomerate, sandstone

Burntwood group

Mudstone, greywacke, derived gneisses and migmatites

Greywacke, siltstone, mudstone

Graphitic, sulfidic mudstone, sulfide facies iron formation, minor greywacke

Garnet-biotite gneiss ±sillimanite or andalusite, local staurolite, biotite gneiss

Tectonites

West Reed - North Star Shear zone

Mafic tectonite, +/- variably mylonitized, felsic intrusive sheets

Berry Creek Shear zone

Mafic tectonite: chlorite schist, ± carbonate, brittle/ductile shears

Felsic tectonite: ± mylonitized flows and dykes of felsic volcanic rocks

Felsic tectonite: strongly foliated to mylonitic felsic plutonic rocks

Juvenile-Arc rocks

West Reed volcanic package

Felsic crystal tuff, lapilli tuff and tuff breccia; minor quartz-plagioclase–phyricdacitic to rhyolitic flows

Mafic volcaniclastic rocks (tuff breccia, lapilli tuff and tuff); minor basalt:massive flows and pillows

Fourmile Island assemblage

Tonalite–granodiorite

Granodiorite

Tonalite, minor quartz diorite

Gabbro, diorite, diabase

Volcanic-derived sediments: laminated mudstone, siltstone and fine grainedsandstone

Rhyolite, dacite

Coherent flows, massive lobes, autoclastic facies and subordinates felsicvolcaniclastic rocks

Dacitic to rhyolitic crystal and lapilli tuffs, subordinate tuff breccia, minor flows

Felsic and mafic flows and dikes, strongly foliated to mylonitic

Basaltic andesite, andesite: massive to pillowed flows, minor amoeboid pillowbreccia

Porphyritic and aphyric felsic breccia, felsic dikes

Heterolithic breccia with intermediate-mafic and felsic clasts

Mafic volcaniclastic rocks

Aphyric, amoeboid pillow breccia, subordinate pillowed flows

Heterolithic breccia with rhyolite clasts

Plagioclase-phyric mafic breccia

Plagioclase-phyric amoeboid pillow breccia

Rhyolite, dacite

Quartz-feldspar–phyric rhyolite, autoclastic breccia with rhyolite clasts

Rhyolite dike

Aphyric and porphyritic pillowed and massive basalt, basaltic andesite, andesite

Snow Lake arc assemblage

Volcanic conglomerate, paraconglomerate, minor greywacke, and mudstone.

Heterolithic breccia, dominantly mafic fragments

Pillowed and massive flows

Subphanerozoic units: not exposed

MORB basalt, and andesite with weak arc signature: massive flows and pillows,subordinate autoclastic facies, minor sulphidic mudstone

Undivided bimodal juvenile-arc volcanic rocks, not exposed

Ocean-Floor rocks

Reed Lake mafic-ultramafic complex

Layered mafic-ultramafic complex

Layered gabbro, leucogabbro, anorthosite

Layered melagabbro, gabbro, pyroxenite

Layered pyroxenite, peridotite, subordinate gabbro

N-type basalts

Northeast Reed pillowed and massive basalt

Woosey Lake-File Lake basalt, pillowed and massive basalt, diabase, derivedtectonite

Amphibolite, volcanic derived enclave in Reed Lake Pluton

Plutonic Rocks

Granite to granodiorite

Granite

Granite-granodiorite

Agmatite with P2b,d inclusions

Granodiorite to tonalite

Granodiorite

Granodiorite to tonalite

Foliated to gneissic granodiorite–tonalite, commonly with amphibolite screensand inclusions

Intrusion breccia

Quartz-porphyritic hornblende-biotite to biotite-hornblende granodiorite

Quartz-porphyritic hornblende-biotite granodiorite with abundant small lobatemafic inclusions of P2g and P2h

Tonalite to quartz diorite

Tonalite

Quartz-diorite

Leucotonalite

Tonalite to quartz diorite

Tonalite to quartz diorite with abundant xenoliths

Foliated to gneissic tonalite to quartz diorite, gneissic leucotonalite, migmatite;commonly with amphibolite screens and inclusions

Granodiorite, foliated to weakly gneissic, coarse grained, low magnetic signature

Foliated to gneissic biotite-hornblende tonalite, commonly with amphibolitexenoliths and late tonalite-granodiorite dikes, moderate to high magneticsignature

Josland sills

Compositionally layered gabbro sills and intrusions (Josland sills)

Gabbronorite, gabbro

Ferrogabbro

Quartz ferrodiorite, ferrotonalite, leucotonalite

Gabbro, melagabbro, diorite

Melagabbro

Gabbro

Leucogabbro

Diorite

Diabase

Diorite to quartz diorite

Fine-grained equigranular quartz diorite

Hornblende gabbro

Legend

Total magnetic intensity

Total magnetic intensity (nT)

High : 62804.9

Low : 57800.6

0 1 2 3 4 5 KilometresTotal magnetic intensity of the Reed Lake area from a 1995regional Spectrem airborne survey (Assessment File 73859,Manitoba Growth, Enterprise and Trade, Winnipeg)

Fro

m N

AT

MA

P W

ork

ing

Gro

up

, 1

99

8

EEL-200

EEL-313

EEL-325

19543

19545

EEL-313: greywacke and graphitic argilite with randomly oriented andalusite, likely due to contact metamorphism from gabbro sills less than 1000 m to the east

EEL-313: greywacke and graphitic argilite with randomly oriented andalusite, likely due to contact metamorphism from gabbro sills less than 1000 m to the eastBerry Creek shear zone: mafic

tectonite (T2), likely derived from juvenile mafic volcanic arc rocks.

West Reed volcanic package: heterolithic felsic breccia tuff (J15), a band of moderately flattened rhyolitic fragments define crude bedding perpendicular to flattening direction.

West Reed - North Star shear zone: Mafic tectonites (T1), probably derived from andesitic plagioclase-phyric lapilli tuff, note the intense flattening and stretching of the fragments.

Fourmile Island VMS Deposit: solid sulphide lens of the Fourmile Island deposit (Po>Py>>Cpy) hosted by chlorite-carbonate altered andesite.

1

4

5

3

2

1

2

3

4

5

Pillowed andesite (J4) showing preferential strong pervasive silica replacement.