Geology and genesis of the polymetallic Ridge Zone West VHMS deposit, Myra Falls, Vancouver Island, British Columbia, Canada

摘要: The polymetallic Zn-Pb-Cu-Ba-Au-Ag-rich Ridge Zone West volcanic-hosted massive sulphide (VHMS) deposit is one of twelve known deposits in the Myra Falls property located on Vancouver Island, British Columbia, Canada. current pre-mining geological resource estimate for approximately 980,000 tonnes grading 6.8% Zn, 0.8% Pb, 0.9% Cu, 2.0 g/t Au, and 72 Ag. aims this thesis are to (1) derive a genetic model VI-1MS by characterizing the geological setting mineralization, (2) evaluate exploration potential Ridge Zone area. At Falls, other VHMS are near the base Devonian Sicker Group, Wrangellia Terrane, Canadian Cordillera. The Ridge geological comprises from stratigraphic footwall to hangingwall: (1) basement Price Formation basaltic andesite sequence flows, flow breccias, and tuffaceous sediments which conformably overlain Basal Conglomerate, cobble conglomerate deposited prior onset hydrothermal system; Myra Formation H-W Horizon, predominantly felsic, coarse fine-grained volcano-sedimentary rocks intercalated with stacked lenses Zn-rich mineralization; and (3) post-mineralization Hangingwall Mafic flow-sill complex that is overlain or laterally equivalent intermediate mafic Lower Mixed Volcaniclastic Unit consisting graded turbidite deposits, sills, breccias. Rifting formed series restricted basins present Myra Falls property. A high-energy mass Conglomerate into basin during early stages mineralizing event. The subordinate paleo-depression. Intermittent infill the depression volcanic activity inferred fine coarse-grained volcano-sedimentary angular siliceous mudstone clasts, clasts. Following cessation system, Complex (HWMC) was emplaced intrusive possible extrusive events excavating previously deposited, wet unconsolidated volcano-sedimentary sulphides. Lower Mixed Volcaniclastic Unit after HWMC. Three phases deformation interpreted area explained context structural proposed by Jones (2001). are: DI, weak WNW-ESE (mine grid) striking foliation related Paleozoic folding event; Mesozoic D3a strike-slip faults, infrequent D3b shallow dipping thrust faults; (3) D4 normal faults. normal faults most frequently occurring faults study area. The hangingwall in the Horizon hydrothermally altered same mineral assemblage sericitequartz+/-chlorite. Alteration intensity moderate as original textures are preserved. alteration pervasive throughout Conglomerate, generally within top 30 m Formation, observed extend at greater depths two mudstones silicification that occur below, lateral to, above mineralization. The disseminated to massive mineralization associated coarse-grained rocks. The main minerals sphalerite, pyrite, chalcopyrite, galena, tetrahedritetennantite, and barite. Four identified West deposit: lens paleo-seafloor fine-grained sediments period quiescence banded mineralization pyrite framboids; Main economically significant fluids infiltrating replacing permeable, dominantly volcaniclastic shallow sub-seafloor environment. Sulphide textures include anastomosing veins progressing up massive relic lithic clasts; Upper secondary period bands grains soft-sediment deformation textures; (4) late pyritechalcopyrite+/-sphalerite veins crosscutting breccias. Based its overall metal content, classified Zn-Pb-Cu deposit an average Cu ratio [100*Cu / (Cu+Zn)] 11 Zn [100*Zn / (Zn+Pb)] 90. Element associations assay data Zn-Pb-Ag, Au-Ag+/-Ba, and Zn-Cu. Above Au (>4.0 g/t) Ag (> 150 values and Main lens. focused up-flow zone discharge has not been as metal zoning patterns Fe broadly dispersed unfocussed. Exploration includes: eastward towards the Gopher Battle where drill hole intersections Zn-rich mineralization occur; below the footwall Conglomerate; north least 12 hole intersections 7.6 length have contents > 5%; westward at least 200m -250E mine grid, potentially 590 westward to -640E favourable host similar West.