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TitleMineralogy of sulphide, arsenide, and platinum group minerals from the DJ/DB Zone of the Turnagain Alaskan-type ultramafic intrusion, north-central British Columbia
AuthorJackson-Brown, S; Scoates, J S; Nixon, G T; Ames, D E
SourceGeological Fieldwork 2013; by British Columbia Geological Survey; British Columbia Geological Survey Geological Fieldwork Paper no. 2014-1, 2014 p. 157-168 (Open Access)
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130361
PublisherBritish Columbia Ministry of Energy and Mines, British Columbia Geological Survey
MeetingMineral Exploration Roundup 2014; Vancouver; CA; January 27-30, 2014
File formatpdf
ProvinceBritish Columbia
Lat/Long WENS-129.0000 -128.5000 59.0000 58.7500
Subjectsmineralogy; economic geology; mineralization; mineral occurrences; mineral deposits; platinum; igneous rocks; ultramafic rocks; intrusive rocks; alaskan-type ultramafic complex; arsenides; antimony; Turnagain intrusion; platinum group elements
Illustrationslocation maps; photomicrographs; cross-sections
ProgramTargeted Geoscience Initiative (TGI-4), Mafic-Ultramafic Ore Systems
AbstractThe Turnagain intrusion (ca. 190 Ma) is an Alaskan-type, ultramafi c body emplaced in an orogenic setting that is host to a signifi cant nickelcobalt resource (865 Mt at 0.21% per tonne Ni and 0.013% per tonne Co). The 24 km2 intrusion comprises a suite of ultramafi c rocks including dunite, wehrlite, clinopyroxenite, and hornblendite with minor late-stage dioritic intrusions and inclusions of hornfelsed country rocks. Soil geochemistry and drilling led to the discovery of an area of copper and platinum group element (PGE) enrichment in a previously underexplored area of the intrusion, the DJ/DB zone, 2.5 km northwest of the nickel resource. We conducted a detailed mineralogical investigation to assess the range of compositions and textures of platinum group minerals (PGM) and associated sulphides in the DJ/DB zone. Mineralized clinopyroxenites and hornblendites, typically with less than 5 vol.% sulphide, contain mainly chalcopyrite and pyrrhotite with minor pyrite and pentlandite, and host a variety of arsenides, arsenic-antimony sulphides, and PGM. Arsenic and antimony-bearing phases are typically related to chalcopyrite and include cobaltite (CoAsS), nickeline (NiAs), gersdorffi te (NiAsS), ullmannite (NiSbS) tucekite (Ni9Sb2S8), and hauchecornite (Ni9Bi(Sb,Bi) S8). Identifi ed PGM are predominantly sperrylite (PtAs2) and sudburyite (PdSb), with minor Pd-melonite [(Ni,Pd)Te2], hongshiite (PdCu), testibiopalladite [PdTe(Sb,Te)], and genkinite [(Pt,Pd)4Sb3]. Platinum- and palladium-bearing minerals commonly form equant 1 - 40 µm grains, within chalcopyrite, pyrrhotite, pentlandite, cobaltite and silicates. Sperrylite and sudburyite also occur as veinlets within and as partial rims (~ 1 - 10 µm thick) on the periphery of base metal sulphides. The textural paragenesis and mineral chemistry of PGM and associated minerals in the DJ/DB zone of the Turnagain intrusion are compared to those observed from other Alaskan-type intrusions. These fi ndings highlight the potential for fi nding PGE-mineralized units in other Alaskan-type intrusions in the Canadian Cordillera and older orogenic ultramafic-mafic intrusions elsewhere in Canada.
Summary(Plain Language Summary, not published)
This manuscript published in the BC provincial geological survey reports on the 2013 field season results from the TGI4 Orogenic Ni-Cu-PGE ore systems subproject, Turnagain Cu-PGE activity. For the first time, identification of the platinum group minerals and particularly the elements that they bond with including arsenic, antimony, and tellurium that may be useful as a geochemical vector for buried platinum and palladium mineralization associated with the enormous 865 Million tonne Turnagain Ni-Co resource, in northern British Columbia.