Publication Type:
Book ChapterSource:
Ni-Cu-PGE magmatic mineralisation, Maney Publishing on behalf of Institute of Materials, Minerals and Mining and the Australasian Institute of Mining and Metallurgy, London, United Kingdom, Volume 116, p.167-187 (2007)ISBN:
0371-7453Keywords:
Abitibi Belt, Australasia, australia, Canada, Canadian Shield, copper ores, cratons, crust, Eastern Goldfields, igneous rocks, KOMATIITE, lithosphere, metal ores, metals, Mineral exploration, mineralization, nickel ores, North America, platinum group, platinum ores, Precambrian, sulfides, superior province, volcanic rocks, Western Australia, yilgarnAbstract:
The Abitibi greenstone belt (AGB) of the Superior Province, Canada, and the extensive greenstone sequences of the Eastern Goldfields superterrane (EGS) both contain komatiite sequences with broadly similar assemblages of volcanic rocks ranging from komatiites to rhyolites and both contain abundant lode gold mineralization. The EGS is greatly endowed with magmatic Ni-Cu-PGE deposits but has only minor occurrences of volcanogenic Cu-Zn sulphides. The situation in the AGB is the reverse. The komatiite assemblages of both belts are compared using a locally-weighted analysis of large whole-rock geochemical data sets. The EGS has a higher relative proportion of olivine-rich cumulate rocks relative to the AGB, and shows more extensive evidence for crustal contamination of komatiite magmas. The most highly mineralized region of the AGB is the most simillar to the EGS in distribution of komatiite rock types and also shows the presence of crustal contamination. Most samples from both data sets show no evidence for extensive PGE depletion attributable to the segregation of sulphide liquid, indicating that in both belts the komatiite suites were undersaturated in sulphide during partial melting, ascent and eruption. The coimbination of abundant thick cumulate-rich komatiite units and widespread crustal contamination in the EGS can be attributed to the predominance of rapid, high-volume eruptions, relative to the generally lower eruption rates in the AGB. Differences in lithospheric structure are likely to be the cause.
Notes:
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