AUTHORS: Gessner, K.
ABSTRACT: The Mount Isa Inlier is a deformed and metamorphosed Proterozoic rift system in Queensland, Australia, which is extraordinary rich in base metals, and has considerable gold and uranium resources. Here it is suggested that the metal prospectivity of the Mt Isa Inlier is closely related to the preferential formation of vertical permeability, which formed as a consequence of the deformation of hot and mechanically decoupled lithosphere in a sequence of extensional and contractional events. Enrichment of heat- producing elements in pre-rift basement resulted in an upper crust geothermal gradient of up to 50 °C/km, leading to strong vertical partitioning of mechanical behaviour in extension and shortening of the continental lithosphere. During the structural evolution of the Mount Isa Inlier, vertical permeability was enhanced significantly parallel to steepened fold limbs, reactivated foliation, and damage zones along high-angle fault systems. Vertical permeability generates short fluid pathways across gradients of pressure, temperature, and chemical composition; favoring the formation of high grade and high tonnage hydrothermal deposits. The link between thermally weakened crust, steep tectonic grain and mineral prospectivity is likely to play a key role in many other mineral provinces.
KEYWORDS: Mount Isa, Continental lithosphere, Proterozoic metal provinces
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