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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
Année2013
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
Lang.anglais
Mediapapier; en ligne; numérique
ProvinceColombie-Britannique
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)
LiensOnline - En ligne
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)
GEOSCAN ID296253