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Geoscientific Presentation PRES2018-6: Chemostratigraphy and Distribution of Volcanic Rocks of the Fourmile Island Assemblage, F

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Geoscientific Presentation PRES2018-6: Chemostratigraphy and Distribution of Volcanic Rocks of the Fourmile Island Assemblage, F lo eo gic g a a l b s Chemostratigraphy and distribution of volcanic rocks of the o u t r i v n e a MGS y m Fourmile Island assemblage, Flin Flon Belt, West-Central Manitoba 1928 S. Gagné, , E.C. Syme, A.H. Bailes, and S.D. Anderson Introduction Geology of the Reed Lake area Drill holes geochemistry (Hudbay) & Super Zone According to the sequence of rocks M1 observed through the Reed Mine The Flin Flon belt in the Reed Lake area, and its extension to the south under Paleoproterozoic rocks in the Reed Lake area are a component of a larger tectonic geology of the Reed Mine area F1 syncline (bold black line on map to the M3A, B F2 Phanerozoic sedimentary rocks, has significant potential to host additional VMS collage of volcano-plutonic and sedimentary rocks assembled during the closure of an M3 left), which is interpreted to be intact (i.e. deposits. Despite the presence of several economic deposits, the geological setting ancient ocean (ca. 1.9–1.8 Ga) and collectively termed the 'Flin Flon belt' (FFB). During definition and exploration drilling near the Reed deposit, Hudbay not disrupted by faulting), the simplified M3A, B of VMS deposits in the Reed Lake area is not well understood. Discovery of the Recent MGS work has identified several distinct lithotectonic packages of volcanic collected a large quantity (~ 1400 samples) of whole-rock geochemical stratigraphy for the FIA would include Reed VMS deposit in 2007 deposit has resulted in renewed interest in the geology rocks in the Subphanerozoic portion of the FFB south of Reed Lake. New geochemical, M2 (see schematic column to the right) the analyses with trace element data. The dataset was parsed to focus on M2 of the Reed Lake area. In order to gain a better understanding of the geological isotopic and geochronological data has also shown that the North Star assemblage volcanic and volcaniclastic rocks only and the trace element signature of following units, bottom to top: M1, F1, framework and mineral potential of the Reed Lake area and its sub-Phanerozoic represents a distinct package of bimodal volcanic rocks with an arc-signature that individual samples was observed and classified in distinct groupings. The bulk M2, and M3 (A and B; their stratigraphic basement, a multiyear field-mapping and compilation project was initiated in 2013. formed at around the same time than the main VMS-hosting sequence of Snow Lake of Hudbay’s FIA samples also presented the same subsets as the MGS position relative to one another has not and Flin Flon were deposited. For more detail see 2018 Report of activites GS2018-5. dataset. On the map to the right, Hudbay’s samples from the Reed Mine area F1 been resolved). Rhyolitic rocks with an F2 signature have been observed to sit were color-coded based on their subset identity (F1, F2, M1, M2, M3A and F1 within the M3A,B sequence of mafic M3B) and drawn along the drillhole traces. The map to the right outlines a fold M1 Reed Deposit volcanic rocks at Reed Lake and have structure. It is interpred to be a synclinal fold, based on some facing directions VMS observed in drillcore and the asymetric alteration around the deposit (Bailes, been displayed in such manner on the 2010, Hudbay`s internal report) schematic section. The Reed VMS M1 deposit occurs within the M1 mafic volcanic rocks, near its upper contact. orking Group, 1998 W TMAP Geological re-interpretation of SW Reed Lake and the Reed Mine area aided by airborne geophysical and whole-rock geochemical data From NA FIA geological re-interpretation based on geochemical signature Total magnetic intensity map with geological contacts and faults Berry Creek shear zone A compilation of geological data from surface mapping and drillcore was integrated Berry Creek shear zone with Manitoba Geological Survey (MGS) regional geochemistry and industry airborne geophysical surveys to produce two new preliminary maps in 2017 (PMAP2017-01 and PMAP2017-02). A collaboration agreement with Hudbay has provided access to Hudbay`s extensive whole-rock geochemistry database for the Super Reed Lake area. Zone The 2017 new preliminary maps provided a more Reed precise understanding of the mine geology of the Reed Lake area. However the internal unit distribution and Sedimentary Rocks Volcanic rocks, sub-Phanerozoic Juvenile-Arc rocks, exposed basement stratigraphy of the Fourmile Burntwood Group West Reed volcanic package sJ7 Undivided bimodal juvenile-arc volcanic rocks, not exposed Island assemblage (FIA), a Felsic crystal tuff, lapilli tuff and tuff breccia; minor quartz- B1 Greywacke, mudstone J15 volcanogenic massive Volcanic-derived gneisses (juvenile-arc affinity) and plagioclase–phyric dacitic to rhyolitic flows sJ6 metasediments, middle- to upper amphibolite facies Mafic volcaniclastic rocks (tuff breccia, lapilli tuff and tuff); sulphide (VMS)-hosting Greywacke, siltstone, mudstone B1a Volcanic-derived mafic and felsic gneisses, amphibolite, J14 minor basalt; massive flows and pillows sequence of bimodal volcanic sJ6a late granitic intrusions Graphitic, sulfidic mudstone, sulfide facies Fourmile Island assemblage B1b iron formation, minor greywacke Mixed volcanic and sedimentary mafic, intermediate and volcaniclastic rocks was sJ6b gneisses, minor granitic intrusions Geochemistry J8 Porphyritic and aphyric felsic breccia, felsic dikes not completely understood Tectonites Juvenile-arc basalt, andesite, and rhyolite volcanic and sJ5 and further work was Berry Creek Shear Zone volcaniclastic rocks, minor MORB basalt Aphyric and porphyritic pillowed and massive basalt, Legend J4 Outcrops and drill core samples from the FIA collected by MGS show a few distinct signatures that Mafic tectonite: chlorite schist, ± carbonates, Oceanic-arc mafic and intermediate volcaniclastic basaltic andesite, andesite required. sJ5a Economic implications seems to be consistent and may allow to map units using trace element signature. Intrusive rocks T2 brittle/ductile shears Volcanic rocks rocksks, minor mudstone-sandstone sequences The FIA shows 2 dominant distinct signatures for rhyolitic and dacitic rocks, referred to as F1 and Oceanic-arc basaltic andesite, andesite, MORB VMSbasalt, mineralization:Ocean Floor rocks, exposed basement Late granite - granodiorite Basalt, ocean-floorsJ5b signaturefelsic volcanic (MORB) rocks Recent work by the F2 (see below for trace element signature). Mafic volcanic rocks can be subdivided in four subsets Intrusive rocks - New geologicalReed Lake mafic-ultramafic interpretation complex and stratigraphy for the volcanic rocks of the Fourmile that have a distinct, yet consistent trace element geochemical signature and are referred here as Late granodiorite - tonalite Basalt, andesite,MORB calc-alkaline basalt, rhyolite, signature and andesite with weak arc Manitoba Geological Survey P6 Granite to granodiorite sJ4 signature Island assemblageF2 Layered will mafic-ultramafic allow to complex better target exploration for VMS deposits, which are M1, M2, M3A and M3B. has shown that the bimodal Late gabbro - diorite North Star assemblageMORB basalt, and andesite with weak arc signature:stratigraphically controlled. sJ4a massive flows and pillows, subordinate autoclastic Layered gabbro, leucogabbro, anorthosite volcanic rocks of the FIA P5 Granodiorite to tonalite F2a Gants Lake batholith Rhyolite, dacite flows andfacies, volcaniclastic minor sulphidic mudstone facies reflected the presence of a MORB basalt, weak-arc andesite, rhyolite flow and- Large areas of F2bprospectiveLayered melagabbro, rocks gabbro, are pyroxenite virtually unexplored. Fourmile Island intrusion Granodiorite Basalt , andesite flows and volcaniclastic facies few characteristic trace P5a sJ4b felsic volcaniclastic rocks Rock/REEs-Chondrites McDonough & Sun, 1995 Rock/Primitive Mantle Sun & McDonough 1989_V_Sc Rock/REEs-Chondrites McDonough & Sun, 1995 elements signatures, hence Tonalite, granodiorite Granodiorite to tonalite Fourmile IslandCalc-alkali assemblage mafic flows, minor felsic rocks, rare MORB mafic F1 N-type basalts 1000 P5b sJ3 - The Reed mine horizon wraps around the syncline and can be traced through the Super suggesting that a stratigraphy Josland Lake sills Felsic volcanic rocksflows of undetermined geochemistry Zone. VMS deposits often cluster along synvolcanic faults and the area between the F1 100 M1 F1a Northeast Reed pillowed and massive MORB basalt 100 100 M1 Gabbronorite, gabbro P4 Tonalite to quartz diorite of the FIA could be M3A Mafic volcanic rocksMORB basalt,of undetermined andesite, intermediate geochemistry volcaniclastic rocks,Reed Mine and the Super Zone should be considered highly prospective. sJ2 and mudstone-sandstone intervals established. 10 Ferrogabbro P4a Tonalite Rhyolite,sJ1 daciteFourmile with F2 Island trace Assemblage element signature 10 1 10 Gabbronorite, gabbro Gold mineralization: Late sinistral brittle deformation along the Berry Creek shear zone Leucotonalite Basalt, andesite with M3 trace element signature The 2018 research M2 P4c Basaltic andesite, andesite, minor rhyolite and quartz F2 Reed Lake mafic - ultramafic pluton sJ1a (BCSZ) is evidenced by the presence of several smaller faults oriented 15-30° .1 M3B porphyry efforts focused on the Tonalite to quartz diorite Basalt, andesite with M2 trace element signature Layered gabbro, leucogabbro, anorthositeP4d Intermediate to mafic volcaniclastic rock, minor felsiccounterclockwise to the BCSZ and display sinistral displacements similar to Riedel 1 1 Josland sills sJ1b Fourmile Island and Reed .01 Rhyolite, dacite with F1volcaniclastic
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