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TitleTill geochemistry and mineralogy near Cu-Au and Cu-Mo porphyry deposits in British Columbia; indicators of buried mineralization
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AuthorPlouffe, A; Ferbey, T; Hashmi, S; Ward, B C
SourceGeological Survey of Canada, Open File 7861, 2015, 1 sheet, https://doi.org/10.4095/296418 (Open Access)
Image
Year2015
PublisherNatural Resources Canada
Documentopen file
Lang.English
Mediaon-line; digital
File formatpdf
ProvinceBritish Columbia
NTS92P; 93A
AreaMount Polley; Gibraltar; Woodjam
Lat/Long WENS-122.5833 -120.0000 53.0000 51.0000
Subjectsgeochemistry; surficial geology/geomorphology; mineralization; copper; tills; porphyry deposits; gold; molybdenum; mineral occurrences; till analyses; till geochemistry; indicator elements; ice flow; ice movement directions; Gibraltar Mine; Mount Polley Mine; Woodjam Prospect; indicator minerals; Cenozoic; Quaternary
Illustrationslocation maps; photographs
ProgramIntrusion/Porphyry Ore Systems, Targeted Geoscience Initiative (TGI-4)
Released2015 05 06
AbstractTill sampling orientation surveys were completed near the Cu-Mo Gibraltar Mine, the Cu-Au Mount Polley Mine, and the Cu-Mo-Au Woodjam prospect with the objective of defining geochemical and mineralogical indicators of buried Cu porphyry mineralization. Mineralization does not outcrop at Woodjam and was in large part covered by glacial sediments at Gibraltar and Mount Polley Mine at pre-mining time. First, we present the distribution of three indicators at each deposit: 1) Cu concentrations in the clay-sized fraction (<0.002 mm), 2) chalcopyrite grain counts and, 3) epidote grain percentages in the 0.25-0.5 mm fraction (specific gravity >3.2). At each site, the indicators occur in greater concentrations (Cu) or in greater amounts (chalcopyrite and epidote grains) near and down-ice of mineralized zones compared to surrounding background regions devoid of known mineralization. In addition to these three indicators of mineralization, gold grains are more abundant near the Cu-Au porphyry deposit at Mount Polley compared to background levels. Therefore, gold grains are interpreted to be indicative of the Au mineralization. Distribution of these indicators in till are related to the presence of mineralization in bedrock and its dispersal by glacial transport, hence the importance of reconstructing ice-flow histories. Secondly, using till compositional data from a previous project (Mountain Pine Beetle), we test the region of two Late Triassic - Early Jurassic intrusions (Takomkane and Thuya batholiths) for their potential to host Cu porphyry mineralization. Two areas with elevated Cu concentrations, and high chalcopyrite and gold grain counts in till suggest potential for porphyry-style Cu-Au mineralization: 1) the Spout Lake pluton, approximately five kilometres west of the Takomkane batholith, and 2) the north end of the Thuya batholith.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. The composition of the sediment directly deposited by glaciers provides information on the composition of the rocks that were crushed and eroded by the same glaciers. For example, a large amount of copper in the glacial sediment indicates that rocks with large amount of copper have been eroded by the glaciers. Near active copper mine, we demonstrate that the glacial sediment contains a lot of copper and the mineral chalcopyrite. Using those indicators (copper, chalcopyrite and gold grains) we postulate that two regions afar from the mines have the potential to host copper and gold deposits.
GEOSCAN ID296418