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TitleTill mineralogy and geochemistry in the Highland Valley Cu-Mo porphyry district, south-central British Columbia
AuthorPlouffe, AORCID logo; Ferbey, T; Bustard, A L
SourceGeological Association of Canada-Mineralogical Association of Canada, Excursion Guide vol. 39, 2016 p. 73 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20160025
PublisherGeological Association of Canada
MeetingGAC-MAC Margins Through Time; Whitehorse, YT; CA; June 1-3, 2016
File formatpdf
ProvinceBritish Columbia
AreaHighland Valley district
Lat/Long WENS-121.5000 -121.0000 51.0000 50.5000
Subjectsgeochemistry; general geology; ore densities; mineral deposits; till geochemistry; till samples; porphyry copper; porphyry deposits; indicator elements; mineralization; glacial erosion; glacial landforms; Guichon Creek batholith; Highland Valley Copper mine (HVC)
ProgramTargeted Geoscience Initiative (TGI-4) Intrusion/Porphyry Ore Systems
AbstractThe Highland Valley district includes five economic Cu-Mo porphyry deposits hosted in the Guichon Creek batholith of south-central British Columbia. Between 1962 and 2013, 1615 million tonnes of ore grading 0.4%Cu and 0.01% Mo have been processed at the Highland Valley Copper mine (HVC) representing one of the largest Cu deposits in Canada. The HVC region is characterized by an extensive cover of glacial sediments with a predominance of tills from the Late Wisconsinan Fraser Glaciation. Surface landforms include drumlins, flutings and crag-and-tails which indicate ice flow to the south to southeast. A total of 97 subglacial till samples were collected within a 1000 km2 area centered on HVC with the objective of identifying the geochemical and mineralogical footprint of the porphyry mineralization in the surficial sediments. Samples were processed for indicator minerals in the medium to very coarse sand-sized fraction (0.25-2 mm) and for geochemical analyses of the silt plus clay- (<0.063 mm) and clay-sized (<0.002 mm) fractions. Results show that geochemically, the Cu-Mo mineralization is well reflected in till with high Cu and Mo concentrations (e.g. >1500 ppm Cu and >20 ppm Mo in the silt plus clay) close to mineralized zones progressively decreasing to background concentrations (<200 ppm Cu and <1.5 ppm Mo in the silt plus clay) approximately 20 km to the southeast. Similarly, Al2O3 content of till varies from >17% near mineralized zones and drops to background concentrations <16% 10 km to the southeast. The high Al content of till near mineralization is interpreted to be derived from phyllosilicate alteration minerals associated with mineralization. Similar to the Cu concentrations, the number of chalcopyrite grains in till (0.25-0.5 mm; >3.2 specific gravity) is highest (>100 grains/10kg) near mineralized zones and decreases to <10 grains/10kg at about 10 km to the southeast. Scheelite and barite are more abundant in till near mineralization compared to background region and therefore, could be used as porphyry indicator minerals in the Highland Valley district. The regional geochemical and mineralogical footprint measured in till at Highland Valley is interpreted to result from glacial erosion of a cluster of economic and sub-economic mineralized zones and detrital glacial dispersal up to 20 km to the southeast. This project was a collaborative effort between the British Columbia Geological Survey and the Geological Survey of Canada supported by the Targeted Geoscience Initiative-4 (TGI-4) and the Canadian Mining Innovation Council (Cu Footprint Project).
Summary(Plain Language Summary, not published)
In this presentation we will demonstrate that zones in bedrock that are naturally enriched in copper and that are covered by glacial sediments can be detected by analyzing the mineralogy and geochemistry of the glacial sediments. Some of these zones are currently being mine for copper and molybdenum. This mineral exploration method is being transferred to the industry at this conference.

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