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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
MGS
ma
nit
ob
a
geological
su
rv
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1928
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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
420 000
420 000
425 000
425 000
6 0
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6 0
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6 0
60
00
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6 0
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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.
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