STRATIGRAPHIC AND PALEOTECTONIC STUDIES OF THE MIDDLE PALEOZOIC SICKER GROUP AND CONTAINED VMS OCCURRENCES, VANCOUVER ISLAND, BRITISH COLUMBIA

Wrangellia, a fundamental and economically significant component of the Insular Superterrane, comprises Middle Paleozoic through Late Triassic stratigraphy, and extends over 2500 km in length from southern Vancouver Island through southern Alaska. However, the Paleozoic geology of southern Wrangellia (Vancouver Island) is fundamentally different from that of northern Wrangellia (Alaska and southwest Yukon), leading several authors to question whether or not northern and southern Wrangellia are actually part of the same terrane, or whether they comprise different tectonic entities altogether. The Middle Paleozoic Sicker Group (SG) on Vancouver Island is interpreted to record the evolution of an oceanic island arc that represents the basement of Wrangellia, and hosts many significant volcanogenic massive sulphide (VMS) deposits, including those of the Myra Falls camp, the largest producing VMS deposit in western Canada. Research as part of this study indicates that calc-alkaline felsic volcanism was occurring in southern Wrangellia by 371 Ma (U-Pb zircon), and that Middle Paleozoic, VMS associated calc-alkaline volcanic stratigraphy in southern Wrangellia ranges in age from 365 through 359 Ma (U-Pb zircon). In addition, biostratigraphic and isotopic dating conducted as part of this study indicates that a significant percentage of the volcanic stratigraphy and associated volcanogenic massive sulphide mineralization previously assigned to the SG comprises parts of several newly recognized cycles of magmatism in southern Wrangellia that span Late Devonian through Early Permian time, with significant magmatic pulses occurring at approximately 340, 310 and 295 Ma (U-Pb zircon). Strongly radiogenic Nd isotopic compositions are ubiquitous for Paleozoic rocks studying southern Wrangellia, consistent with an oceanic island arc setting. Newly recognized Late Paleozoic volcanic stratigraphy in southern Wrangellia offers striking similarities to Late Paleozoic stratigraphy in northern Wrangellia, supporting models for Wrangellia as a long lived, multi-episodic and metallogenicically well endowed arc terrane throughout Middle to Late Paleozoic time, and a significant contributor to the crustal growth history of the North American continent.