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TitreOrogenic Ni-Cu-PGE deposits: Cu-PGE mineralization in the DJ/DB Zone of the Turnagain Alaskan-type intrusion, north-central British Columbia, Canada
AuteurJackson-Brown, S; Scoates, J; Nixon, G; Ames, D E
SourceAssociation géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 36, (2013), 2013 p. 118
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140584
ÉditeurThe Geological Association of Canada
ÉditeurAssociation minéralogique du Canada
RéunionGAC-MAC Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Winnipeg; CA; mai 22-24, 2013
Mediapapier; en ligne; numérique
SNRC104I; 104J
Lat/Long OENS-130.0000 -128.0000 59.0000 58.0000
Sujetscomplexe ultramafique Alaskien; roches hôtes; nickel; cobalt; dunites; olivine; clinopyroxénites; hornblende; hornblendites; géochimie du sol; néodigénite; millérite; cobaltite; gersdorffite; ullmannite; antimoine; arsenic; minéraux métalliques
ProgrammeÉtude des gîtes magmatiques de Ni-Cu-EPG, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
The ca. 190 Ma Turnagain intrusion is an Alaskan-type, subduction-related ("orogenic") ultramafic body that is host to a significant nickel-cobalt resource (865 Mt at 0.21% per tonne Ni and 0.013% per tonne Co). The intrusion is approximately 24 km 2 in size and comprises a suite of ultramafic rocks including dunite, wehrlite, olivine clinopyroxenite, hornblende clinopyroxenite, and hornblendite with minor late-stage dioritic intrusions and inclusions of hornfelsed country rocks. A recent geochemical soil survey and subsequent drilling by Hard Creek Nickel Corporation (2004-2007) has revealed an area of copper and platinum group element (PGE) enrichment in a previously under-explored area of the intrusion, the DJ/DB zone, located 2.5 km northwest of the current nickel resource. Within the DJ/DB zone, the Cu and Pt+Pd soil geochemical anomalies are spatially associated, but show a distinct separation between the regions of elevated Cu and Pt+Pd with high Cu values covering a much larger area (2.1 km 2) to the south, east, and northwest of the PGE anomaly (1.2 km 2). From assays on drill core that intersected rocks within the DJ/DB zone, maximum Cu values have been reported in excess of 0.3 wt.% over 7.3 m and combined Pt+Pd of greater than 500 ppb over 19.3 m. The anomalous Cu-PGE values are typically found within magnetite-bearing clinopyroxenite and are associated with areas of increased serpentinization. Sulfur isotope analyses for sulfides from the DJ/DB zone range from\'0534S = -11 to +2.2 (permil), values that are similar to those reported for the rest of the Turnagain intrusion. Inclusions of graphite-bearing pyritiferous phyllitic sedimentary rocks are characterized by values as low as (delta)34 S = -17.8 (permil), indicating a significant role for assimilation of S-bearing crustal rocks during emplacement of the Turnagain intrusion. A reconnaissance SEM investigation has revealed an association between Cu-PGE abundances and the presence of accessory sulfide and arsenide minerals, including digenite (Cu 9 S 5), millerite (NiS), nickeline (NiAs), cobaltite (CoAsS), gersdorffite (NiAsS), and ullmanite (NiSbS). Millerite and digenite, 25-250 um in diameter, are typically intergrown with pentlandite and magnetite surrounding early chromite crystals. The arsenides and antimonides are found as inclusions (10-50 um) within chalcopyrite, although nickeline is typically fully enclosed by gersdorffite or cobaltite. The relationship between areas of high PGE (>300 ppb) and the abundance of arsenides and arsenic-antimony sulfides will be further investigated to determine any potential links between arsenic and PGE in orogenic Ni-Cu-PGE mineralization and its potential use in exploration. (SS9; Wed. 3:40)