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TitleFinding deeper porphyry Cu deposits in the Canadian Cordillera using epidote chemistry
AuthorPlouffe, AORCID logo; Kjarsgaard, I; Petts, DORCID logo; Ferbey, T
SourceAME Roundup 2020, technical sessions abstract guide; 2020 p. 26 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 53.0 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20190334
PublisherAssociation for MIneral Exploration
MeetingAME Roundup 2020; Vancouver, BC; CA; January 20-23, 2020
Mediaon-line; digital
ProvinceBritish Columbia
NTS93B/07; 93B/08; 93B/09; 93B/10
Lat/Long WENS-123.0000 -122.0000 52.7500 52.2500
Subjectseconomic geology; geochemistry; surficial geology/geomorphology; Science and Technology; Nature and Environment; mineral deposits; porphyry copper; hydrothermal alteration; alteration; epidote; mineral exploration; exploration methods; glacial deposits; tills; glacial erosion; dispersal patterns; ice transport directions; bedrock geology; lithology; igneous rocks; volcanic rocks; volcaniclastics; Canadian Cordillera; Nicola Group; Phanerozoic; Mesozoic; Triassic
ProgramTargeted Geoscience Initiative (TGI-5) Intrusion/Porphyry ore systems
Released2020 01 27
AbstractThe next generation of porphyry Cu deposits to be discovered in the Canadian Cordillera are likely to be buried by glacial sediments and be located deeper than the known deposits. To overcome this 'poor-exposure and depth' challenge, we are investigating the composition of epidote, a mineral common in alteration zones that surround porphyry systems, as a mean of detecting Cu ore at depth. Epidote is a resistant mineral which can be dispersed from its bedrock source by detrital processes. In previous studies, we demonstrated that epidote is more abundant in till near porphyry mineralization compared to surrounding background regions. The distribution patterns of epidote in till result from glacial erosion and dispersal from the porphyry alteration zones. Consequently, identification of an epidote anomaly in till could become a mean of detecting porphyry Cu mineralization covered by glacial sediments. In the Canadian Cordillera, the challenge is then to discriminate between epidote derived from porphyry hydrothermal alteration versus epidote sourced from barren rocks. In the Cordillera, metamorphic epidote commonly occurs within Upper Triassic Nicola volcanic and volcaniclastic rocks. We analyzed the composition of epidote from porphyry alteration zones and Nicola rocks by LA-ICP-MS. Hafnium, Th, Sc, Cr, and Y occur in higher concentrations in epidote of Nicola rocks compared to epidote from porphyry alteration zones. In addition, the As and Sb content of hydrothermal alteration epidote is higher than in metamorphic epidote. Epidote grains recovered from till in the region of three porphyry deposits have a composition diagnostic of porphyry alteration (i.e. lower Hf, Th, Sc, Cr, and Y and higher As and Sb concentrations relative to Nicola epidote). We conclude that the composition of epidote in detrital sediments within a prospective geological setting can provide an indication of buried porphyry Cu mineralization.
Summary(Plain Language Summary, not published)
The demand for copper at the global scale will increase in the near future for the electrification of transport systems .The presentation will explain how we can explore for deeper copper deposits. By analyzing the composition of a common mineral, epidote, we can detect a large zone that surrounds the copper enrichment in rocks. This zone is a larger target to detect as oppose to the smaller copper enrichment.

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