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TitleDiscovering buried copper porphyry mineralization: geochemistry and indicator minerals in till
AuthorPlouffe, A; Ferbey, T
SourceGeological Survey of Canada, Open File 7680, 2015, 44 pages, (Open Access)
PublisherNatural Resources Canada
Meeting27th annual KEG Conference and Trade Show; Kamloops; CA; April 8-9, 2014
Documentopen file
Mediaon-line; digital
File formatpdf
ProvinceBritish Columbia
NTS92P; 93A
AreaMount Polley; Gibraltar; Woodjam
Lat/Long WENS-122.5833 -120.0000 53.0000 51.0000
Subjectssurficial geology/geomorphology; geochemistry; mineralization; copper; tills; porphyry deposits; gold; 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; tables
ProgramTargeted Geoscience Initiative (TGI-4), Uranium Ore Systems
Released2015 03 12
AbstractTill orientation surveys at Gibraltar Mine (copper-molybdenum porphyry), Mount Polley Mine (copper-gold porphyry) and the Woodjam prospect (copper-gold porphyry) in south central British Columbia have defined geochemical and mineralogical indicators of porphyry mineralization dispersed within till deposits. These indicators are more abundant near mineralization than in surrounding regions which include higher copper values in the clay-sized fraction (<0.002 mm) and elevated chalcopyrite and gold grains counts in the sand-sized fraction of till. The regional distribution of these indicators are dispersed in the direction of former glacial flow. The reconstructed ice-flow history includes two dominant phases of ice movement: a first phase of westerly to southwesterly glacier movement which occurred at the onset of the last glaciation when ice flowed from the Cariboo Mountains and, a second phase of northwesterly glacier movement related to the formation of an ice divide at last glacial maximum, around the 52° north latitude. Using copper and copper-gold porphyry indicator minerals identified as part of the orientation surveys, we test the potential of copper porphyry mineralization in the region of two Late Triassic to Early Jurassic intrusions (Thuya and Takomkane batholiths) that have potential to host porphyry mineralization. A previous regional till sampling survey completed in this region revealed copper enrichment and elevated gold grain counts in till at the northern end of the Thuya batholith and along the western margin of the Takomkane batholith. The region with elevated gold grain counts in till (> 66 gold grains / 10 kg) in the northern sector of the Thuya batholith is aerially extensive (ca. 10 x 20 km or 200 km2) representing one of the largest known gold grain dispersal trains in till in Canada most likely derived from multiple mineralized bedrock sources. A limited number (n=57) of archived heavy mineral (>3.2 s.g.) samples were reprocessed for porphyry copper indicator minerals. Chalcopyrite was identified in nineteen till samples (up to 11 grains per 10 kg) in the same two areas (west of the Takomkane and north of the Thuya batholiths) which suggests that both areas have potential to host copper-gold porphyry mineralization.
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 first part of our study demonstrated that sediments deposited by glaciers contain certain type of minerals and metals that are indicative of metal enrichment in the underlying bedrock. Such enrichment, if significant enough, has the potential to become a mine. Therefore, the presence of those minerals and metals in the glacial sediments can help find mines. We have tested this hypothesis by looking at the composition of glacial sediments in a region where there is no mine. Our results indicate that in two zones, certain minerals enriched in copper and gold found in glacial sediments could be indicative of undiscovered mineralization in rock. This study was completed as part of the Targeted Geoscience Initiative-4 of the Geological Survey of Canada.