b'AEGC 2021Short abstractswhere active structures represent pathways for migration and121: 3D Bedrock model utilising multi-channel analysis deposition of mineralising fluids exsolved from an intrusiveof surface waves to assist the land development porphyry system at depth. Faults and shear zones variably hostindustry in greater Melbourne, VICelevated Cu-Au-AsAgNiCo dependant on orientation during the porphyry emplacement event; veins do not appearMr Tavis Lavell 1to host substantial metal anomalism.1 GBG Maps Pty LtdBy comparing the orientations of active versus inactive structures, an overall NW-SE directed axis for maximumA common problem across greater Melbournes expanding land compressive stress is interpreted at the time of mineralisation.development, both residential and commercial, is encountering The results of this work imply that porphyry intrusion andsites that have incredibly stiff and undulating bedrock. This is mineralisation occurred within a compressive D1a stress regime,experienced on sites with Newer Volcanic Basalt which accounts during VanDieland collision, and prior to D1b extensionalfor two thirds of greater Melbourne, the weathered profile of tectonism. The collision event and associated disruptionthese once lava flows produces a highly variable depth and to subduction zone processes are therefore implicated instrength bedrock interface.triggering porphyry emplacement. These findings will be important for understanding the prospectivity of the Stavely ArcThe acquisition of bedrock survey data has been shown to reduce and targeting future exploration activity. site uncertainty, unforeseen earthwork costs and financial risk. Working hand in hand with traditional intrusive geotechnical 120: Exploring links between thermal maturity andmethods, the Multi-channel Analysis of Surface Waves (MASW) method can connect the dots between boreholes generating 2D electrical properties of organic-rich shales geological cross-sections of the subsurface. These 2D cross-sections Dr Claudio Delle Piane 1, Dr Matthew Josh2, Dr Julien Bourdet2,when combined can create a 3D subsurface model of the bedrock.Dr David, N. Dewhurst2 and Dr M. Ben Clennell2 This data can be presented in a variety of ways, including 1 CSIRO Energy, Deep Earth Imaging contour plots in either elevation or depth below ground level 2 CSIRO Energy (BGL), overlying clay volumetric calculations to user friendly 3D AutoCAD files which can be encompassed with a topography The petrophysical signature of organic-rich shales ismodel. Producing a very comprehensive site classification determined by their mineral and organic matter assemblagepackage, a useful tool for the investigatory stage for any land and the nature and distribution of fluids in the pore space.development project.Electrical properties have been widely used as an effective proxy for detection of organic matter and hydrocarbons in shales via interpretation of wireline logs. Up to thermal123: The role of geophysics in the discovery of the maturities within the oil window, the so-called delta logGonneville PGE-Ni-Cu-Co-Au Deposit, Julimar, Western R method (Passey etal., 1990) is used to estimate organicAustraliarichness of potential source rocks from the sonic and the resistivity wireline log curves. However, at higher thermalMr Jacob Paggi 1, Dr Kevin Frost2 and Mr Bruce Kendall2maturities, the organic components of the sediments undergo chemical and structural reorganization involving loss of1 Armada Exploration Serviceshydrogen and oxygen and aromatization of the organic2 Chalice Mining Limitedcomponent leading to changes in density and to dramaticThe Gonneville deposit is a significant new PGE-nickel-copper-decreases in electrical resistivity. These influences, especiallycobalt-gold sulphide deposit discovered by Chalice Mining in at thermal maturities consistent with and beyond the gas2020. Located only 70 km northeast of Perth, Western Australia, generation window, are not effectively accounted for init represents the first major discovery of magmatic sulphide petrophysical log interpretation. It follows that an in-depthmineralisation within the Julimar Complex, in the newly defined understanding of the links between thermal maturity andWestern Yilgarn Ni-Cu-PGE Province.petrophysical properties is desirable to achieve meaningful interpretation of downhole logs acquired in organic-rich shalesGeophysics has played a major role in the initial discovery, spanning a wide range of thermal maturity. delineation and understanding of the Gonneville deposit under lateritic cover. Chalice originally staked the project We show examples of hydrocarbon prospective shalesin 2018 on the basis of a previously unrecognised, 26 km characterized through an integrated petrophysical,long, mafic-ultramafic intrusive complex interpreted petrological, and nanoanalytical approach showing howfrom open-file aeromagnetic surveys. In 2019, a moving-anomalously low resistivity is related to a conductive,loop electromagnetic survey conducted over a discrete connected network of partially graphitised bitumen and1.6 km0.8 km magnetic anomaly detected multiple EM not to commonly assumed accessory conductive mineralsconductors, some of which were interpreted to represent such as pyrite. This interpretation is verified by several casea massive sulphide source. An RC drilling programme studies on prospective organic-rich shales that have beencommenced in March 2020, with the first hole drilled into the exposed to high thermal maturation induced by either deepstrongest conductor intersecting massive, matrix and stringer burial conditions (Appalachian Basin, USA; Sichuan Basin,sulphide mineralisation reporting 19 m @ 8.4g/t Pd, 1.1g/t Pt, China), or contact metamorphism (Beetaloo Basin, Australia).2.6% Ni, 1.0% Cu and 0.1% Co from 48 m downhole. Multiple These results can help better define prospective areas ofhigh-grade massive-matrix-heavy disseminated sulphide hydrocarbon accumulation in sedimentary basins as well aszones have since been intersected in the Gonneville Intrusion, potentially identify false positives in the geophysical signaturealong with widespread, lower-grade disseminated sulphide of mineralization under cover. mineralisation.AUGUST 2021 PREVIEW 82'