Geochemistry and genesis of two unconformity-associated gold deposits at the base of the Flinton Group, Grenville Province, southeastern Ontario, Canada

Investigating Mineral Weathering and Metal Transport through Century-Old Ore Chimney Waste Rock

“…Although often measured below the detection limit, PXRD analysis identified the and lower levels of chalcopyrite and pyrite were identified in every fine-and coarsegrained waste-rock sample, which is consistent with the sulfide mineral assemblage identified from underground workings at Ore Chimney from past studies (Dillon, 1985;Moore, 1988, Harnois andMoore, 1989;Archibald, 2012). Solid-phase ICP-AES/MS analyses of Cu, Zn, and Pb all measured higher relative concentrations in the fine-grained fraction.…”

“…Major tectonic stresses exerted on the region over the course of the Grenvillian Orogeny opened fractures in the subsurface carrying fluids with solubilized mineral components from a nearby dyke intrusion that crystallized as a series of quartz veins hosting calcite and dolomite at average volume proportions of 5% that occasionally measured as high as 20% (Harnois and Moore, 1989). Property surveys reveal a network of 14 quartz veins on the Ore Chimney property, five of which display significant sphalerite, galena, pyrite, and chalcopyrite mineralization (Archibald, 2012).…”

“…Extensive drilling through one of the quartz veins yielded gold estimates of 7 g/tonne (Au), silver estimates as high as 193 g/tonne (Ag) and assays of lead and zinc at 3.2 and 1.9 wt.%, respectively (Carter 1984;Archibald, 2012). The quartz veins were the prospected ore deposit and formed 30 m below an unconformable contact between the Tudor Formation and the Bishop Corners Formation (Harnois and Moore, 1989).…”

“…Wheeler (2017) conducted a detailed petrographic study in one 4.0 m deep trench in the waste-rock pile at Ore Chimney and characterized the mineralogy to mainly consist of quartz, biotite, and hornblende with traces of calcite, galena, sphalerite, pyrite, and chalcopyrite. Moore and Thompson (1980) and Harnois and Moore (1989) identified these phases from thin section analyses from fresh in situ samples of the Ore Chimney Formation, Tudor Formation, and neighbouring quartz vein lithologies from bore holes that intersected the underground workings that generated the Ore Chimney waste-rock pile and described in detail the additional presence of plagioclase feldspar, chlorite, and dolomite.…”

“…The entrance of the vertical mineshaft at the Ore Chimney property was confined within the Tudor Formation and underground workings extended laterally at various levels targeting carbonate-rich quartz veins surrounding the Ore Chimney Formation (Dillon, 1985;Harnois and Moore, 1989). The variation in waste-rock mineral abundance with depth along each vertical transect was not considerable enough to distinguish the different lithologies encountered during underground development.…”