Magnetotellurics ('MT') is particularly applicable in the Curnamona Craton where copper-gold mineralisation is related to deep fault zones under extensive cover.
MT is a passive geophysical tool that is highly sensitive to minor interconnected conducting mineralogy and fluids, and thus is ideal for distinguishing between lithosphere of different degrees of enrichment. Additionally, the sensitivity to these minor phases means that fossil fluid pathways associated with the ascent of mineralising fluids and metals are detectable with MT.
The Jupiter MT anomaly (in the Curnamona Basin in South Australia) is a greenfield exploration play based on a prominent conductive zone that was first identified in a Havilah supported BBMT survey by the University of Adelaide and Geological Survey of South Australia during 2017.
The following images and text represents the results from BBMT (Broadband MT) undertaken during August 2017 re: the Jupiter MT anomaly target along with concise explanations of what C1, C2, C3, R1 represent.
C = Conductive zone or potential feeder zone (possible conduit for magmatic/ hydrothermal fluid flow) R = Resistive zone (e.g. granite)
A conductive sedimentary layer (C1) from the surface to ~200 m, thins to <100 m about 40 km along the profile. Below the sediments to 15 km there is a resistive upper crust (R1, R2 and R3) almost across the whole profile, except for a conductor (C3) located 80 – 100 km along the profile at a depth of 4 km. The lower crustal anomaly (C4) is widespread starting from a depth of 15 km which is probably the brittle-ductile boundary and extending to at least the Moho. Finally, there is a near vertical conductor (C2) 45 km along the profile that connects the most conductive part of the lower crust C4 to the near surface, where the sedimentary cover is thinnest.
A significant feature from the 2D resistivity inversion is C2 that has a footprint from the brittle-ductile boundary near 15 km above the C4 conductor, to the topographic basement high. A possible cause of this footprint is from fluids accumulating at and below the brittle-ductile boundary, until overpressure results in hydro-fracturing of the brittle crust above resulting in a conductive footprint from the alteration of fossil fluid pathways, usually through zones of weakness, which have previously been observed at mineral deposit locations such as Olympic Dam.
The mid-crust conductor, C3, is situated at the boundary near a major unnamed fault that is situated on the eastern edge of the 1590 Ma magmatic Benagerie Ridge that may have acted as a pathway for the fluids. It is possible to speculate that the large C3 conductor, of width ~15 km and possible extent > 100 km, might have resulted from a large scale thermal event that weakened the crustal rheology, and when compounded with paleo-stresses led to the eventual formation of the deep sub-basin C1 during the Cambrian period.
Havilah had said during the 2019 AGM Technical Presentation that it plans to extend collaboration with the University of Adelaide during calendar year 2020 to collect more detailed MT data (probably Audio-Magnetotellurics) that could be used to generate 2D and 3D models of the Jupiter MT conductive zone to potentially vector towards ore deposits.
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These are only my thoughts and it does not constitute investment advice. Before acting on any information you read and before making any financial or investment decisions, you should always consult your advisor(s) or other relevant professional experts.
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