Linking gold mineralization to regional-scale drivers of mineral systems using in situ U-Pb geochronology and pyrite LA-ICP-MS element mapping
2019
Proterozoic orogens commonly host a range of hydrothermal ores that form in diverse tectonic settings at
different times. However, the link between mineralization and the regional-scale tectonothermal evolution
of orogens is usually not well understood, especially in areas subject to multiple hydrothermal events.
Regional-scale drivers for mineral systems vary between the different classes of hydrothermal ore, but all
involve an energy source and a fluid pathway to focus mineralizing fluids into the upper crust. The Mount
Olympus gold deposit in the Proterozoic Capricorn Orogen of Western Australia, was regarded as an
orogenic gold deposit that formed at ca. 1738 Ma during the assembly of Proterozoic Australia. However,
the trace element chemistry of the pyrite crystals closely resembles those of the Carlin deposits of Nevada,
with rims that display solid solution gold accompanied by elevated As, Cu, Sb, Hg, and Tl, surrounding
gold-poor cores. New SHRIMP U-Pb dating of xenotime intergrown with auriferous pyrite and ore-stage
alteration minerals provided a weighted mean 207 Pb*/ 206 Pb* date of 1769 +/- 5 Ma, interpreted as the age of
gold mineralization. This was followed by two discrete episodes of hydrothermal alteration at 1727 +/-7Ma
and 1673 +/- 8 Ma. The three ages are linked to multiple reactivation of the crustal-scale Nanjilgardy Fault
during repeated episodes of intracratonic reworking. The regional-scale drivers for Carlin-like gold
mineralization at Mount Olympus are related to a change in tectonic regime during the final stages of the
intracratonic 1820-1770 Ma Capricorn Orogeny. Our results suggest that substantial sized Carlin-like gold
deposits can form in an intracratonic setting during regional-scale crustal reworking.
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