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TitreMineralogy of sulphide, arsenide, and platinum group minerals from the DJ/DB Zone of the Turnagain Alaskan-type ultramafi c intrusion, north-central British Columbia
AuteurJackson-Brown, S; Scoates, J S; Nixon, G T; Ames, D E
SourceBritish Columbia Ministry of Energy and Mines, British Columbia Geological Survey Paper 2014-1, 2013 p. 157-168
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140508
ÉditeurGeological Fieldwork
Documentpublication en série
SNRC104I; 104J
Lat/Long OENS-130.0000 -128.0000 59.0000 58.0000
Sujetscomplexe ultramafique Alaskien; platine; roches ignées; roches ultramafiques; arséniures; antimoine; Éléments du groupe de platine; minéralogie
Illustrationslocation maps; photomicrographs; tables
ProgrammeÉtude des gîtes magmatiques de Ni-Cu-EPG, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
The Turnagain intrusion (ca. 190 Ma) is an Alaskan-type, ultramafic body emplaced in an orogenic setting that is host to a significant nickel-cobalt resource (865 Mt at 0.21% per tonne Ni and 0.013% per tonne Co). The 24 km2 intrusion comprises a suite of ultramafic 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), gersdorffite (NiAsS), ullmannite (NiSbS) tucekite (Ni9Sb2S8), and hauchecornite (Ni9Bi(Sb,Bi) S8). Identified 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 ?m grains, within chalcopyrite, pyrrhotite, pentlandite, cobaltite and silicates. Sperrylite and sudburyite also occur as veinlets within and as partial rims (~ 1 - 10 ?m 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.