b'AEGC 2021Short abstracts87: Automated facies classification in borehole log data corridor proposed as a fossil transfer fault and metal source along the mantle interface.Dr ROMAN BELOBORODOV 1, Dr James Gunning2, Dr Marina Pervukhina3, Dr Michael Ben Clennell2, Dr Irina Emelyanova2 andA stratigraphic marker of the caldera collapse enables Dr Juerg Hauser4 correlation of the spectrum of mineral systems including conglomerate facies that collapsed into IOCG systems.1 CSIRO Deep Earth Imaging Future Science Platform2 CSIRO Energy The Zircon Alteration Index (ZAI = 40Zr/Hf) is a robust 3 CSIRO search tool that is universally applicable to the OME spectrum 4 CSIRO Minerals of deposit styles and hosts requiring less assay samples and drilling for future targeting. The exclusive association of Hf Solving geophysical inverse problems typically involveswith Zr in zircon enables wholerock analysis of the Zr/Hf ratio supplying prior information to tackle the non-uniquenessto measure the amount of hydrothermal overprinting of the and tighten the distribution of possible solutions. A library ofinherited volcanic or detrital zircon in a host rock and hence rock physics models is a very specific type of prior informationproximity to a mineral target. Downhole variation of ZAI and that is for example required in seismic inversion algorithmslithologies enables lateral or vertical target vectors to be often that simultaneously recover facies distributions and physicaladded to the proximity measure.rock properties (e.g. Joint Impedance and Facies inversion). Among the features captured by these models are the depthThe ZAI Tool and strato-tectonic vectoring have been validated dependency of rock properties and associated uncertainties.for the Stuart Shelf IOCG systems with a comprehensive study But where do these rock physics models come from and howof 35 holes in varying proximities to known IOCG deposits. can we derive their parameters objectively? In this work, wePreliminary target ranges are assigned to the ZAI values.approach rock typing (i.e. rock physics model selection) and fitting of property depth trends as a joint problem. In our89: Constraining gravity inversion with lower-rock physics models, we account for the depth dependency of common petrophysical properties due to compactiondimensional seismic information: Imaging the eastern and diagenetic effects such as cementation, variable clayYilgarn Cratoncontent, and overpressure. Rock type-specific depth trends are modelled by the most appropriate rock physics modelMissmahtab Rashidifard 1, Dr Jeremie Giraud2,3, Dr Mark selected from the supplied library. The joint problem isLindsay4,5, Prof Mark jessell4,5 and Dr Vitaliy Ogarko6solved using the Expectation Maximisation algorithm which1 Centre of Exploration Targeting (School of Earth Sciences), simultaneously performs classification of the supplied boreholeUniversity of Western Australia, 35 Stirling Highway, Crawley, data into the rock types and fitting of the selected models. InWA, 6009, Australiathis manner, the identified facies for an appraisal well in the2 Centre of Exploration Targeting (School of Earth Sciences), The North West Shelf of Australia are consistent with the geologicalUniversity of Western Australia, 35 Stirling Highway, Crawly, WA, interpretation and rock physics model trends accurately fit6009, Australiathem. Further to this the selected and fitted rock physics3 Mineral Exploration Cooperative Research Centre, School of models also capture the stiffening of the shales with depthEarth Sciences, The University of Western Australia, 35 Stirling which is a known feature of the rocks in this region. Our resultsHighway, WA Crawley 6009, Australiaemphasise the objectivity of our approach, its ability to capture4 Centre of Exploration Targeting, School of Earth Sciences, the underlying geology, and illustrate its direct relevance forUniversity of Western Australia, 35 Stirling Highway, Perth 6009 downstream seismic inversion algorithms. WA, Australia5 Mineral Exploration Cooperative Research Centre (MinEx CRC), 88: New mineral system vectors for revitalised copper- School of Earth Sciences, University of Western Australia, 35 gold discovery in the Gawler Craton Stirling Highway, Perth 6009 WA, Australia6 International Centre for Radio Astronomy Research, University of Mr John Anderson 1 Western Australia, 35 Stirling Highway, Perth 6009 WA, Australia1 GSA Boundary parametrization of the subsurface from The combination of a new strato-tectonic model for the Olympicgeological observations and geophysical inversions is Metallogenic Event (OME) and zircon-based geochemical toolone of the main goals of 3D geological modelling. Several is a significant step-change for ore vectoring for a spectrum ofapproaches have been developed for geometric inversion IOCG and coeval deposit styles in the Gawler Craton. and joint inversion of geophysical datasets. However, the robust, quantitative integration of models and datasets The revised model proposes the Paris-Nankivel epithermal- with different spatial coverage, resolution, and levels of porphyry belt is formed at the same time as Olympic Dam onsparsity remains challenging. One promising approach the margins of a super caldera filled with upper Gawler Rangefor recovering the boundary of geological units is the Volcanics (GRV). Prior subduction tectonics produced precursorutilisation of potential field level-sets inversion method. We epithermal-porphyry conditions on the southern shoulderfocus on constraining 3D gravity inversion with sparse 2D of the caldera, whereas IOCGs formed on the northern andseismic images that allow us to account for uncertainty in eastern margins with haematite- or magnetite-dominatedinterpretations.systems respectively forming on the shoulder or in hotter more reduced conditions under the GRV blanket within the caldera. We use a level-set approach to recover the geometry of an arbitrary number of geological bodies using data from the The epithermal/porphyry and IOCG belts are both fluorine- geologically complex Yamarna terrane (Yilgarn craton, Western anomalous and connected by a conductive magneto-telluricAustralia). The study focuses on the eastern zone of the area AUGUST 2021 PREVIEW 76'