| Issue ID: | P2012-01-12 |
| Title: | North Coast Project: Tectonics and Metallogeny of the Alexander Terrane, and Cretaceous Sinistral Shearing of the Western Coast Belt |
| Author(s): | Nelson, J.L., Diakow, L.J., Mahoney, J.B., van Staal, C., Pecha, M., Angen, J.J., Gehrels, G., Lau, T. |
| Series Name: | Paper |
| Publication Year: | 2012 |
| Larger Work Citation: | in Geological Fieldwork 2011, B.C. Ministry of Energy and Mines, Paper 2012-01 |
| NTS Map Sheet(s): | 093D,E,L;103A,H,I,J |
| Place Keyword(s): | British Columbia, Coastal, Surf Inlet, Porcher Island |
| Lat/Long (NSWE): | 54.5, 52.5, -131, -127 |
| Theme Keyword(s): | Geological Fieldwork, regional geological mapping, Alexander terrane, Grenville Channel fault, Coast Plutonic Complex |
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Abstract:
| This article presents the results of the final field season of a three year collaborative geological investigation of north coastal British Columbia between the British Columbia Geological Survey, Geological Survey of Canada, and university partners University of Wisconsin at Eau Claire and University of Arizona. The North Coast bedrock mapping and mineral deposit study is part of a cooperative, Natural Resources Canada (NRCan)-led endeavour, the Edges Multiple Metals – NW Canadian Cordillera (B.C. and Yukon) Project. The first two years involved detailed mapping on and near Porcher Island in 2009 and near Klemtu in 2010, and production of open file maps (Nelson et al.). In this final field season the focus was 1) to complete regional-scale geological coverage of the intervening area from Grenville Channel to northern Princess Royal Island in order to update the provincial geological map for all of north coastal British Columbia; and 2) to address problems and questions arising from mapping and U-Pb isotopic results obtained earlier in the program. Highlights from the 2011 field season include:
• Discovered new VMS showings on southern Kennedy Island, hosted by Ordovician rhyolite.
• Visited the Pitt showings on Pitt Island, the only
previously documented VMS occurrence in the southern Alexander terrane of British Columbia, and collected sulphide samples for lead isotopic signatures, for comparison with Neoproterozoic
and Ordovician deposits in southeast Alaska.
• Collected and analysed a suite of samples of meta-igneous rocks east of northern Grenville and Telegraph channels; Permian ages throughout this belt document a previously unknown, late Paleozoic volcanic-sedimentary unit with related dikes in intrusive contact with the Alexander terrane.
• Investigated a large tract of Late Silurian to Early Devonian (ca. 424-411 Ma) orthogneissplutonic complex on Porcher Island, intruded during a Caledonian-age deformational event that probably marked the amalgamation of pericratonic and primitive arc elements within the composite Alexander terrane.
• Traced out Grenville Channel fault for 300 kilometres along strike, collecting key plutonic phases that precisely constrain stages of sinistral motion in Early to mid-Cretaceous time. |
