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TitleEpidote associated with the porphyry Cu-Mo mineralization at the Gibraltar deposit, south-central British Columbia
AuthorKobylinski, C H; Hattori, K; Plouffe, A; Smith, S W
SourceGeological Survey of Canada, Open File 8279, 2017, 19 pages, (Open Access)
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
RelatedThis publication is related to Kobylinski, C H; Hattori, K; Smith, S; Plouffe, A; (2016). Report on the composition and assemblage of minerals associated with the porphyry Cu-Mo mineralization at the Gibraltar deposit, south central British Columbia, Canada, Geological Survey of Canada, Open File 8025
File formatreadme
File formatpdf (Adobe® Reader®); rtf; xlsx (Microsoft® Excel®)
ProvinceBritish Columbia
NTS93B/07; 93B/08; 93B/09; 93B/10
Lat/Long WENS-122.5833 -122.0833 52.6667 52.4167
Subjectseconomic geology; geochemistry; mineral exploration; mineral deposits; porphyry deposits; copper; molybdenum; mineralization; alteration; hydrothermal systems; mineral zoning; epidote; clinozoisite; allanite; veins; sulphides; iron; sulphur; inclusions; apatite; titanite; scanning electron microscope analyses; electron probe analyses; geochemical analyses; major element analyses; minor element geochemistry; plagioclase; Gibraltar deposit; Granite Mountain Batholith; Canadian Cordillera; Burgess Creek Stock; Nicola Volcanics; Cuisson Lake Unit; Cache Creek Terrane; Quesnel Terrane; Nicola Group; Sheridan Creek Stock; Ashcroft Formation; Cache Creek Complex; ferriepidote; ferriallanite; rare earth elements; epidote group minerals; indicator minerals; Phanerozoic; Mesozoic; Jurassic; Triassic
Illustrationsgeoscientific sketch maps; photographs; tables; photomicrographs; plots
ProgramTargeted Geoscience Initiative (TGI-5), Porphyry systems
Released2017 09 29
AbstractThe Gibraltar porphyry-copper molybdenum deposit in the Canadian Cordillera is hosted by the late Triassic, Granite Mountain Batholith (GMB). The batholith is tonalitic and composed of quartz, plagioclase and minor hornblende and biotite in various modality. The rocks in the batholith show phyllic and propylitic alteration. Propylitic alteration (green rock alteration) is characterised by epidote, chlorite, albite, and is extensive throughout the batholith. The name epidote is used in this paper for epidote group minerals which include clinozoisite, epidote (sensu stricto), allanite, ferriepidote and ferriallanite. Epidote occurs as dissemination, isolated grains, and aggregates, and forms mono-minerallic veins and epidote-bearing veins in the batholith. These veins (>2 cm in width) in the batholith generally strike towards the mineralized centre. Epidote enclosed by chalcopyrite or pyrite is compositionally homogeneous and Fe-poor, suggesting that Fe is preferentially incorporated into sulphides and that epidote crystallized together with sulphide minerals. Individual grains of epidote in epidote-bearing veins show compositional zoning with Fe-poor cores and Fe-rich rims. Epidote grains disseminated in the batholith show similar compositional zoning with Fe-poor cores and Fe-rich rims. Allanite and REE-rich epidote are identified in the GMB less than 2 km from mineralization and within the Burgess Creek Stock (10 km from mineralization). Epidote containing 0.01 -1 wt.% REEs is common in grains forming aggregates throughout GMB. Epidote with high REEs (> 1 wt.% REEs) occurs only in rocks with a bulk composition >70 ppm REEs. Compositional zoning of epidote suggests that the hydrothermal history of the GMB comprised of early S-rich hydrothermal activity, followed by S-poor barren hydrothermal activity. Epidote in the Nicola volcanics and Cuisson Lake Unit near the GMB is homogeneous and Fe-rich and commonly contains inclusions of apatite and titanite. The contents of REEs in epidote in the Nicola volcanics are all below the detection limits of SEM (1000 - 5000 ppm) and EPMA (La, 470 ppm; Ce, 380 ppm; Pr, 640 ppm; Nd, 330 ppm).
Summary(Plain Language Summary, not published)
The Gibraltar deposit is a large open-pit copper mine in Canada. We have studied the composition of epidote which is one mineral that formed during copper mineralisation. However, epidote is also present in country rocks with no mineralisation. The objective of this research is to identify the chemical and physical characteristics of epidote associated with copper mineralisation. Identifying epidote with a copper mineralisation signature in glacial or stream sediments could become a method of mineral exploration for copper deposits.