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% po 19543: 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 m a n i t o b a g e o l o g i c a l s u r v e y 1 9 2 8 ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! # # # ## # # # # # # # # ####### # # ## # ## # # # # ### # # # # # # # # # # # # # # # # # # # # # ## # # ## # # # # # # # # # # # # # # # # # # ## ## # # # # # # # # # # # # # # # # # # # # # # # #### # # # # # # # # # # # # # # # # # ## ## # # # ### ## ## # # # # # # # # ## # # # ## # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # ## # # # # # # # # # ## ### # # # # # # # # # # # # # # # # # # # ## # # ## ## ## # # # # ## # ## # ## #### ### # # # # # ## ## # # # # # ## # # # # # # # ### ## # # # # # # ## # # # # # # # # # # # ## # # # # # # # # # # # # # # # # ## # # # # # # ## # # # # # ## # # # # # # ## # # # # # # # # # # # # # # # # # # # # # # # # # ## # # # ## # # # ! 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Reed Deep Lake Woosey Lake Halfway Tramping Lake Sewell Lake 1894±5 Ma 1 390 000 395 000 400 000 405 000 410 000 415 000 420 000 425 000 6 055 000 6 055 000 6 060 000 6 060 000 6 065 000 6 065 000 6 070 000 6 070 000 UTM projection: Zone 14, NAD83 complex Wekusko Lake Lake Preliminary Map PMAP2017-1 Jackfish Lake Gabbro Lake Pluton Pluton Snow Lake Assemblage 1836 ±4 Ma 5 Northeast Reed Berry Creek fault zone Fourmile Island assemblage Reed Lake mafic-ultramafic Reed Lake gabbro Josland Lake 1886 ±3 Ma 2 group Maximum age Reed Lake Pluton Batholith 1876 +7/-6 Ma 3 Little Swan Lake Pluton 1826 ±5 Ma 3 West Reed North Star Shear Zone J10a J11 J9 B1b P4f P4a P3a P3b P3c J3 P5a P2a F2c P5a J9 P5a J3 P2a J1 P5f P5c F1c P4e P2f P4a P3a P3b P2b F1c P6a P5a P2f P3c P6a P2f P3b B1a P6a J15 P6a P5c P2 P2 F1c J7 J4 J5a P2 J6b J13b P2b P2b J6a P2b J10c J6c B1a P5 F2a sJ7 J8 J4 J6d J8 B1b J4 J9 J10b P3c P3b B1a F1b P4a P3b J9 P3a F1c J13b P4a P5a J1 T1 P4b P6 P2b F1c P4g J9 P3a P4e J9 P2b P3c J13b P6b J14 P4f P5c P2c P2 F2c F2a B1c F2b J15 P3a J4 M1b P2 P6c B1b J8 F1a B1a J8 J4 J4 B1a J6a F2b F1a B1a P2 F2b P2h T1 J10a P3a P4g J3 P2 P4f T1 P4d B1a P4a P5a P4e P5 P4h B1b J15 P2a,c,P1 J4 J4 F2a F2b F2a 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 P5c J2 B1b sJ4a J4,5a,5b M1a P4g Fourmile Island 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 Star shear zone Precambrian-Paleozoic Boundary 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–phyric dacitic 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 grained sandstone Rhyolite, dacite Coherent flows, massive lobes, autoclastic facies and subordinates felsic volcaniclastic 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 pillow breccia 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, derived tectonite 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 screens and inclusions Intrusion breccia Quartz-porphyritic hornblende-biotite to biotite-hornblende granodiorite Quartz-porphyritic hornblende-biotite granodiorite with abundant small lobate mafic 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 amphibolite xenoliths and late tonalite-granodiorite dikes, moderate to high magnetic signature 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 Kilometres Total magnetic intensity of the Reed Lake area from a 1995 regional Spectrem airborne survey (Assessment File 73859, Manitoba Growth, Enterprise and Trade, Winnipeg) From NATMAP Working Group, 1998 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 east Berry 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.