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Stratigraphic and paleotectonic studies of Paleozoic Wrangellia and its contained volcanogenic massive sulfide (VMS) occurrences, Vancouver Island, British Columbia, Canada

University of British Columbia

Wrangellia is a fundamental component of the North American Cordillera and contains significant mineral deposits, including Myra Falls (Nyrstar N.V.), which is currently the largest producing volcanogenic massive sulfide (VMS) deposit in western Canada. Understanding the evolution of Wrangellia is therefore important for understanding the crustal growth and metallogenic history of the North American continent, and in doing so, facilitating the discovery of new mineral wealth. Geochronological, lithogeochemical and Nd and Pb isotopic studies of the Paleozoic Wrangellia arc (PWA), Vancouver Island have significantly revised our understanding of the terrane, suggesting that the PWA comprises a progressively rifting Late Devonian through Early Permian oceanic volcanic arc complex developed above an east dipping subduction zone (modern coordinates) with Late Devonian through middle Mississippian, and Pennsylvanian through Early Permian pulses of bimodal volcanism and associated VMS mineralization. The relatively primitive lithogeochemical and Nd isotopic signatures of PWA intrusive and volcanic rocks indicate that the PWA originated in an oceanic arc environment close enough to a continental margin to undergo slight contamination via the subduction of continent derived sediments. Recently recognized, Pennsylvanian-Early Permian aged, VMS associated bimodal volcanic rocks in the PWA have lithogeochemical and Nd isotopic signatures indicative of derivation from more primitive and significantly hotter source melts than their Late Devonian counterparts, suggesting that Late Paleozoic volcanic rocks in the terrane are prospective for VMS mineralization. Lead isotope geochemistry of newly discovered VMS style mineralization in the PWA indicates that host areas for the new mineral occurrences are prospective for Myra Falls-like VMS deposits of Late Devonian-Early Mississippian age. Lead isotope geochemistry for recently recognized Pennsylvanian-Early Permian VMS mineralization in the PWA supports lithogeochemical and Nd isotopic arguments which suggest that Late Paleozoic bimodal volcanic rocks in the PWA were derived from more primitive melts than their Late Devonian-Early Mississippian counterparts, reflective of an origin in a progressively rifting, oceanic island arc environment.

Text

2015-10-23

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/54599

Geological Sciences

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/