The nature of the Carpentaria Conductivity Anomaly

The Carpentaria Conductivity Anomaly (CCA) is a significant conductivity anomaly in Queensland extending from the Gulf of Carpentaria through to the Simpson Desert. The broad nature of the CCA suggests an origin rooted in tectonic scale processes. The CCA is on the eastern edge of the Mount Isa Province, coincident with the Gidyea Structure which marks the contact between the subsurface Numil terrane and the Mount Isa terrane. The endowment of copper within reach of the CCA is significant, Iron Oxide Copper Gold deposits hosted in the Eastern Succession are clustered in a belt within the hanging wall to the Gidyea Structure. The Cloncurry and Cloncurry Extension MT surveys were carried out between 2016 - 2021 and collected 996 sites on a 2 km grid. These data are located across the location of the Gidyea Structure, mainly within the hanging wall. Three-dimensional MT inversions were carried out on the full data array using ModEM on the NCI supercomputing infrastructure. Inversion models contain a prominent linear conductor to the east of the Gidyea Structure, several pipelike conductors within the resistive Mount Isa crust, and a belt of elevated conductivity associated with the Quamby Fault in the west. The conductivity feature to the east of the Gidyea Structure represents the upper crustal expression of the CCA. Postulated sources of the CCA are enhanced fluid flow and alteration proximal to the Gidyea Structure, or metamorphism of Paleoproterozoic carbonaceous deep-water sediments preserved proximal to the Gidyea Structure. The subsequent inversion and metamorphism of these basins have generated a suite of linear and pipe-like conductive features adjacent to the Gidyea Structure zone which extends to mid-crustal levels but is also coincident with known graphitic metasediments.