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TitleGlacial dispersal of refractory minerals from the Gibraltar porphyry copper deposit, south central British Columbia, Canada
AuthorWolfe, L; Hattori, K; Plouffe, A
SourceGeological Survey of Canada, Scientific Presentation 73, 2017, 1 sheet, (Open Access)
PublisherNatural Resources Canada
Mediaon-line; digital
File formatpdf
ProvinceBritish Columbia
NTS93B/07; 93B/08; 93B/09; 93B/10
AreaTwan Lake; Soda Creek; Alexandria; Narcosli Creek; Fraser River
Lat/Long WENS-122.5833 -122.0833 52.6667 52.4167
Subjectseconomic geology; surficial geology/geomorphology; geochemistry; geochronology; mineral deposits; porphyry deposits; porphyry copper; molybdenum; glacial deposits; tills; till samples; glaciation; ice flow; ice movement directions; mineral occurrences; zircon; epidote; rutile; bedrock geology; lithology; igneous rocks; intrusive rocks; tonalites; diorites; volcanic rocks; metavolcanic rocks; greenschist facies; sedimentary rocks; clastics; geochemical analyses; heavy mineral analyses; trace element analyses; petrography; scanning electron microscope analyses; x-ray emission spectroscopy; mass spectrometer analysis; provenance; zoning; crystallization; temperature; radiometric dating; uranium lead dating; Gibraltar Deposit; Granite Mountain Batholith; Nicola Group; Quesnel Terrane; Cache Creek Terrane; porphyry copper indicator minerals (PCIM); cathodoluminescence analyses; rare earth elements; Phanerozoic; Cenozoic; Quaternary; Tertiary; Mesozoic; Cretaceous; Jurassic; Triassic
Illustrationsgeoscientific sketch maps; photomicrographs; ternary diagrams; geochemical plots
ProgramTargeted Geoscience Initiative (TGI-5), Porphyry systems
Released2017 09 14
Some rutile grains in till at Gibraltar have a trace element composition (Mo and Sb) similar to rutile from the high- and lowgrade ore zones at the El Teniente Cu-Mo porphyry deposit in Chile (Rabbia et al., 2009). Comparison between rutile composition in till and in ore at Gibraltar is in progress.
Zircon grains display sector and oscillatory zoning indicating they are of igneous origin.
Three zircon grains in one till sample located close (<1 km) from the main mineralization show high Ce/Nd ratios suggesting that they are derived from relatively oxidized magmas.
Comparison of zircon grains in till and zircon from the Granite Mountain batholith is on-going.
Epidote shows a compositional variation from Fe-rich epidote to Alrich clinozoisite.
Although Al-rich epidote is similar in composition to that from the mine site, epidote in tills is distinctly different from that in the Granite Mountain batholith because the former shows abundant mineral inclusions and no compositional zoning, whereas epidote in the batholith lacks mineral inclusions and shows distinct compositional zoning with Fe-rich rims (see Kobylinski et al., 2016).
Grains of zircon and rutile with a composition indicative of a porphyry mineralized source have been identified in till samples located close and distal (ca. 12 km) from mineralization. These minerals were dispersed by detrital glacial processes and have survived post-glacial weathering. Our results demonstrate that zircon and rutile recovered from till can be indicative of mineralization but need to be further tested as PCIM.
Summary(Plain Language Summary, not published)
The Gibraltar deposit is a large open-pit copper mine in Canada. There is potential to find more mines like Gibraltar in the Canadian Cordillera but the challenge is that similar potentially economic mineral deposits might be covered by loose sediments left by glaciers which can hinder mineral exploration. On the other hand, the composition of specific minerals in these sediments can provide information on the potential of the underlying rocks to host an economic deposit. In this study, we look at the composition of three minerals (epidote, rutile and zircon) that have some potential to be indicative of mineralization.