Geochemistry of the north Eastern Goldfields, Western Australia: examining the processes that produce nickel sulphide camps

[Truncated] This study investigates in detail what role both deep and shallow level lithospheric architecture played to permit the formation of the large abundance of komatiite-hosted nickel-sulphide deposits found in the north Eastern Goldfields of Western Australia during the Late Archaean. U-Pb age dates on zircons and Lu-Hf isotopic data were collected on zircons to investigate the deep-seated lithospheric processes. Multiple sulphur isotopes (δ³³S and δ³⁴S) from various sulphide reservoirs were collected to examine the shallow lithospheric processes that influenced the formation of these komatiite-associated nickel sulphides.

U-Pb age dates of felsic rocks from the north Eastern Goldfields reveal that felsic volcanism occurred within the Kalgoorlie Terrane between 2.920 – 2.705 Ga, with felsic volcanic activity peaking between 2.74-2.72 Ga. Ages in the Kurnalpi Terrane range from 2.69-2.675 Ga and agree with previous findings. In contrast, the ages of felsic rocks in the Burtville Terrane (2.807-2.690 Ga) and the geological relationships between these felsic rocks and the ultramafic rocks suggest that not all of the komatiites of the Burtville Terrane are coeval with those of the Kalgoorlie Terrane. The ages from this study indicate that there have been at least two komatiitic magmatic events associated with mineralization in the Eastern Goldfields (at ~2.80 and 2.705 Ga). An intervening third komatiitic event at 2.715 Ga is proposed. Furthermore, εHf ratios across the north Eastern Goldfields were found to be relatively restricted, ranging from -2 to +6. The lack of rocks older than 2.9 Ga and the paucity of inherited zircons prior to 3.0 Ga indicate that the Eastern Goldfields is a relatively juvenile superterrane. The lack of variation in εHf limits the usefulness of εHf mapping within the juvenile portions of the Eastern Goldfields Superterrane. The lack of variation of Hf isotopes may then be related to the repeated emplacement of mantle plumes over a 200 Ma time period.