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TitleTill geochemistry and mineralogy: vectoring towards Cu porphyry deposits in British Columbia, Canada
AuthorPlouffe, AORCID logo; Ferbey, T; Hashmi, S; Ward, B C
SourceGeochemistry: Exploration, Environment, Analysis 2016 p. 1-20,
Alt SeriesEarth Sciences Sector, Contribution Series 20150367
PublisherGeological Society of London
Mediaon-line; digital
File formatpdf; html
ProvinceBritish Columbia
NTS92I; 93A; 92B
AreaWilliams Lake; Fraser River
Lat/Long WENS-122.5833 -122.0833 52.6667 52.4167
Lat/Long WENS-121.2500 -121.2500 52.4167 52.1667
Lat/Long WENS-121.2500 -120.7500 50.5833 50.3333
Lat/Long WENS-121.4167 -121.4167 52.6667 52.4167
Subjectsmineralogy; geochemistry; chalcopyrite; epidote; porphyries; tills; copper; till geochemistry; dispersal patterns; sediment dispersal; gold; mineralization; erosion; porphyry deposits; porphyry copper; ice movement directions; Mount Polley Deposit; Gibraltar Deposit; Woodjam Prospect; Highland Valley deposits; Triassic; Jurassic
ProgramTargeted Geoscience Initiative (TGI-4) Intrusion/Porphyry Ore Systems
Released2016 08 09
AbstractRegional till sampling was completed near four Cu porphyry mineralized zones in south-central British Columbia, Canada: Highland Valley Copper (Cu-Mo), Gibraltar (Cu-Mo), and Mount Polley (Cu-Au-Ag) deposits, and the Woodjam (Cu-Au-Mo) prospect. At all sites, Cu concentrations in the clay-sized fraction and chalcopyrite grains (0.25 -- 0.5 mm; >3.2 specific gravity) are found in greater abundance in till near and down-ice from mineralized zones compared to surrounding background regions. At Mount Polley, the abundance of gold grains in till defines a dispersal train extending at least 3 km down-ice (SW and NW) from mineralization. At three sites out of four, epidote in till heavy mineral concentrates occurs in greater percentage near and down-ice from mineralized zones compared to background regions suggesting that this mineral could be an indicator of propylitic alteration associated with porphyry mineralization. The distribution pattern of Cu concentrations and chalcopyrite grains in till is controlled by the distribution of Cu-porphyry mineral occurrences in bedrock and the direction of ice-flow movements which prevailed during the last glaciation. By comparing study sites, there is a positive relationship between the areal extent of bedrock mineralization that was exposed to glacial erosion and the absolute values of Cu concentrations and chalcopyrite grain counts in till. In the Woodjam region where the till is thick (>10 m), eight samples with background Cu concentrations in the clay-sized fraction of till contain >4 grains of chalcopyrite/10 kg which is indicative of mineralization. This study demonstrates that a combination of till geochemistry and mineralogy is an efficient method for mineral exploration for Cu porphyry deposits covered by variable amounts of glacial sediments.
Summary(Plain Language Summary, not published)
The next generation of copper and gold deposits which will become mines in Canada will likely be buried under glacial sediments because deposits exposed at surface, easier to find, are already being exploited. This paper presents a new mineral exploration method for the detection of copper and gold deposits buried under glacial sediments. This new method is based on the detection of indicators of copper and gold enrichment (copper content and the presence of specific minerals) identified in glacial sediments and traced back to their source by reconstructing past glacier movements that covered the land.

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