Implications for Mississippi Valley–Type Deposit
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lo eo gic New Occurrences of Carbonate-Hosted Pb-Zn Mineralization in Manitoba: g a a l b s o u t r i v n e a MGS y m Implications for Mississippi Valley-type Deposit Potential 1 928 K. Lapenskie and M.P.B. Nicolas, Manitoba Geological Survey Introducon Several examples of in situ Pb-Zn mineralizaon have been found in Paleozoic carbonates in the Williston Basin, southwestern Manitoba. The Manitoba Geological Survey (MGS) and several companies have Drillcore RP95-17 There is evidence to suggest potenal for MVT deposits in Manitoba, specifically in the Williston Basin (Gale and undertaken exploratory invesgaons into occurrences of carbonate-hosted sphalerite-galena mineralizaon in the province but have yet to find any deposits. In the 1990s, Cominco Ltd. conducted several In 1995, Cominco Ltd. (Cominco) drilled six holes in the vicinity of Rabbit Point (A.F. 94638) targeng the sub- Conley, 2000; Bamburak and Klyne, 2004). Southwestern Manitoba is blanketed by a thick passage of southwesterly exploraon programs in the Lake Winnipegosis area, looking for base-metal potenal in the sub-Phanerozoic Superior boundary zone (SBZ). A re-examinaon of Paleozoic strata in drillcore from one of these Phanerozoic extension of the SBZ for base-metal potenal in the Winnipegosis komaite belt (Waterton et al., dipping Phanerozoic sedimentary rocks, which were deposited within this basin. Underlying these strata are the programs has idenfied two new occurrences of in situ mineralizaon with a style comparable to that in Mississippi Valley-type (MVT) deposits. 2017). The MGS acquired some of this drillcore from the Rabbit Point programs, including drillcore RP95-17. Precambrian igneous and metamorphic rocks belonging to the Superior Craton and Trans-Hudson orogen (THO), Numerous structural and geological condions in the province indicate that the MVT model may be applicable within Manitoba. Plaormal carbonates, shales, evaporites, karsng and reefal structures, Drillcore RP95-17 provides a nearly complete secon of the lower Paleozoic from the basal Ordovician Winnipeg which are sutured together along the SBZ. oen associated with MVT deposits, are all present in southwestern Manitoba. The SBZ may have acted as source of base-metal bearing fluids and provided conduits for fluid flow. Formaon to the Devonian middle member of the Dawson Bay formaon. The secon is mostly composed of MVT deposits consist of stratabound, carbonate-hosted assemblages of sphalerite, galena and iron sulphides, dolostones and limestones, with subordinate sandstones and argillaceous/shaly units (Fig. 5). A detailed descripon typically occurring within marine plaormal dolostone and limestone near basinal edges (Paradis et al., 2007; Leach of the lithostragraphy of RP95-17 is provided in Lapenskie and Nicolas (Report of Acvies 2017). Drillhole RP95- et al., 2010). It is generally understood that metalliferous, saline basinal waters driven by large-scale tectonic events 101°00'W 17 was drilled to a true vercal depth (TVD) of 633.05 m (total measured depth 731.00 m), including 58.59 m (TVD) Legend STRATIGRAPHY DEPTH (m) LITHOLOGY are the source of ore fluids. MVT deposits oen occur in clusters of tens to hundreds of individual ore bodies that MANITOBA SUBSURFACE MANITOBA OUTCROP LITHOLOGY SBZ DEVONIAN 0 PERIOD of Quaternary sediments and 321.57 m (TVD) of Paleozoic sedimentary rock. make up a broad district. The ore bodies are typically controlled by local lithological and structural features, such as ORR DSR Souris River Formation LEGEND Hatfield Member Hatfield/Minitonas Member Harris Member Sagemace Member DDB Dawson Bay Formation Cyclical shale, limestone and dolostone; soluon collapse breccias, faults/fractures and shale-carbonate shale facies. OSM anhydrite Davidson Member Point Wilkins Member IG 20 Lithology S DW Winnipegosis Formation Mineralizaon in RP95-17 Souris River Fm. Cominco Ltd. conducted an exploraon program in the Lake Winnipegosis area in 1995, targeng Precambrian Souris River Fm. First Red Beds First Red Beds Arenaceous dolostone base-metal mineralizaon. Drillcore RP95-17 (A.F. 94638) was recently examined by the authors, and resulted in the ORR DEP Elm Point Formation Quaternary The Paleozoic secon of RP95-17 contains two occurrences of Pb-Zn mineralizaon. In the lower dolomudstone Arenaneous shale Neely Member DA Ashern Formation 40 upper member (D) of the Red River Formaon, aggregates (<0.65 mm) of galena were idenfied at 344.87 m (TVD) within the skeleton Manitoba Group 54°00'N Limestone and dolostone, porous, discovery of galena in the Ordovician Red River Formaon and sphalerite in the Devonian Winnipegosis Formaon. Argillaceous dolostone Manitoba Group SIG SILURIAN middle member (C) anhydritic; local red and green shale of a poorly preserved solitary rugose coral (Fig. 6a,b). The XRF analysis confirmed elevated levels of Pb above 3%. Argillaceous limestone Burr Member The former represents the first known occurrence of in situ carbonate-hosted galena in the Williston Basin. SIG Interlake Group lower member (B) SBZ Argillite Dawson Bay Fm. Second Red Bed Member Second Red Bed Member (A) Sphalerite was idenfied within a calcite-encrusted fracture in calcareous dolomudstone of the lower member Cedar ORDOVICIAN middle member (C) 60 Dawson Bay Fm. Lake F OSW Stonewall Formation Dawson Bay lower member (B) Brecciated mudstone of the Winnipegosis Formaon at a depth of 109.95 to 110.28 m (TVD; Fig. 6c). Several subhedral to euhedral Previous Work Group Formation Second Red Bed Dolostone DEVONIAN White Bear member DW OSM Stony Mountain Formation Manitoba Member (A) P Halite, potash and anhydrite; interbedded crystals occur atop the medium- to coarsely-crystalline calcite lining of the fracture (Fig. 6d). Trace amounts of Exploraon for MVT deposits in Manitoba was prompted by the discovery of a galena pebble near Balmoral (Fig. DDB Easterville Prairie Evaporite transitional beds 80 Limestone Esterhazy Member dolostone Lake ORR Red River Formation chalcopyrite also occur in this secon of core, formed on top of the calcite crystals lining this fracture. ORR upper member 1, Table 1; McCabe, 1969). Geological, geochemical and geophysical exploraon programs to invesgate MVT Winnipegosis OSM Regolith Denbeigh Point OW Winnipeg Formation Winnipegosis Prairie Evaporite Rabbit Point Undifferentiated sediment transitional beds transitional beds potenal in Manitoba began in 1970 and lasted unl the present day. DSR Formation Mafeking PRECAMBRIAN lower member 100 Klyne no. 3 Devonian Sp quarries F Elk Point Group upper member Dolostone, yellow-brown, reefal OSW Igneous and metamorphic rocks Ccp upper member Evidence of MVT Deposits in Manitoba 1969 2000 Accessory Swan lower member Point of interest Ashern Formation Limestone, fossiliferous, high calcium SIG Elk Point Group Minerals lower member Many geological features common to MVT deposits (e.g., Paradis et al., 2007; Leach et al., 2010) are Winnipegosis Fm. Galena pebble discovered in glacially-derived, Sampling program conducted by the MGS; >6300 samples Lake 120 P Winnipegosis Fm. Elm Point Fm. Elk Point Group surficial sediments (McCabe, 1969); exploraon from Paleozoic stragraphic drillcore revealed widespread Kettle Hills RP95-17 Drillhole Ashern Formation Ashern Formation Dolostone and shale, brick red Ccp Chalcopyrite documented in the Williston Basin of Manitoba (Table 2). Modern understanding of MVT deposits suggests that the for MVT in Manitoba begins Cu, Zn, Pb, and Ni anomalies (Gale and Conley, 2000) Minitonas M-01-07 Chert Cedar Lake Formation ores are sourced from high volumes of metal-rich, intrabasinal brines and require a tectonically driven, fluid-flow 140 upper Interlake equivalent 1976 2004 13-10-36-26 WI Cedar Lake Formation East Arm DEP DA K Kaolin v-marker event and fluid conduits to allow for deposion within host carbonates (Paradis et al., 2007; Leach et al., 2010). In Precious and base metal ‘Prairie-type micro- M-02-06 Formation Dolostone, yellow-buff, fossiliferous; Gulf Minerals Canada Ltd. completed drill program DW u-marker OSW P Pyrite 2 several argillaceous markers beds most known MVT districts, orogenic events are thought to be the main driver of saline fluid flow leading to near Minitonas; single occurrence of sphalerite disseminated mineralizaon’ invesgated in late SBZ Atikameg Formation M-05-00 Chemahawin Mb. 160 lower Interlake equivalent Cross Lake Mb. Sp Sphalerite Interlake Group SILURIAN Moose Lake Formation noted in core 13-10-36-26W1 (A.F. 92116) Devonian limestone (Fedikow et al., 2004) F P Interlake Group precipitaon of Pb-Zn sulphides, however, the Manitobe poron of the Williston Basin was far removed from u-marker1 Sul Sulphides Fisher Branch Formation DSR OSM ORR East Arm Formation F P orogenic regions. McRitchie (1991) and Dietrich et al. (1997) presented evidence to suggest that the sub- 1970 1980 1990 2000 2010 2017 upper Stonewall upper Stonewall OW 180 Dolostone, sparsely fossiliferous; t-marker DB Fm. D v-marker bed lower Stonewall Fm. lower Stonewall defines Ordovician-Silurian boundary Phanerozoic extensions of the SBZ in Manitoba underwent movement through crustal flexure during the Paleozoic, F Stonewall 1979-1983 u -marker bed Stonewall Williams Member 2 Williams Member Silurian P Rock Builders which could have provided conduits for fluid flow via reacvaon of basement faults. The SBZ coupled with Canadian Nickel Company Ltd. completed soil, rock, and water Interlake Group Atikameg Formation Brachiopod P Gunton Member Gunton Member Dolostone, yellow-buff sampling, geophysical surveys,