b'AEGC 2021Short abstractsthat shorter sweeps with wider bandwidth are used. This1 Curtin Universitytheoretically reduces the strength of the harmonics, suggesting2 CSIROpotentially more aggressive slips. Conversely, coal targets usually contain more near offsets and groundroll, and requireProduction from ultra-low permeable gas shale reservoirs is more high frequency signal for desired resolution. These factorsfeasible only through hydraulic fracturing stimulation. Slip imply that harmonics may have a greater relative impact. along a pre-existing natural network of fractures/faults with the injection of hydraulic fluid is mostly controlled by the To determine which factors are most important thisfrictional properties of the shale. We studied the deformation investigation has utilised modelling, ground force analysis,characteristics of the Goldwyer shale formation at in-situ stress and real data. This has allowed us to gain an understandingconditions by performing a series of multistage triaxial tests to of the characteristics of Vibroseis harmonics in coal-scaleunderstand compositional controls on fault slip accompanying environments and from this develop a methodology forhydraulic fracturing. The Coulomb friction coefficient is derived optimising high-production seismic surveys. from the post-failure axial displacement and the angle of the final failure plane. When the clay and total organic content 132: Multi-scale magnetotelluric surveysmapping(TOC) of the studied shale samples are above ~40% by volume, from the lithosphere to the near surface for mineralthe friction coefficient approaches a value of 0.6, while below systems this threshold it is higher. This change suggests a transition from a grain-bearing to a clay-bearing structure. Therefore, we Dr Wenping Jiang 1, Mr Jingming Duan2, Mr Anthony Schofield1,can directly estimate the slip tendency of natural faults and Dr Ross C Brodie1 and Mr Andy Clark1 fractures in gas shale reservoirs from their clay and TOC content.1 Geoscience Australia Keywords: frictional coefficient, deformation, clay, TOC, fault 2 Mineral Systems Branch, Geoscience Australia slip, Goldwyer shaleMagnetotellurics is one of few techniques that can provide multi-scale datasets to understand mineral systems. We134: Overprinting of remanence in Paleozoic rocks of have used long-period data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) as a first- the Lachlan Orogen in southeast Australiaorder reconnaissance survey to resolve large-scale lithosphericMr Umer Habib 1, Dr Robert Musgrave2 and Dr Sebastien Meffre1architecture for mapping areas of mineral potential in northern Australia. A 3D resistivity model reveals a broad conductivity1 University of Tasmaniaanomaly extending from the Tennant Region to the Murphy2 Geological Survey of New South WalesProvince in the lower crust and upper mantle, representing a potential fertile source region for mineral systems. We thenThe Lachlan orocline hypothesis has been proposed to explain undertook a higher-resolution infill magnetotelluric surveythe tectonic evolution of southeast Australia where the Lachlan to refine the geometry of major structures, and to investigate ifOrogen has been transformed into an N-shaped curve due to the deep conductive structure is connected to the near surfaceconvergence and rotation about a vertical axis driven by the by crustal-scale fluid pathways. Resistivity models reveal twoslab retreat and indentation of a micro-continent during middle prominent conductors in the resistive host whose combinedPalaeozoic. A recent positive palaeomagnetic orocline test responses result in the lithospheric-scale conductivity anomalysuggests ~ 90 of clockwise relative block rotation occurred during mapped in the AusLAMP model. The resistivity contrasts coincidethe Late Silurian/Early Devonian. This study was undertaken to test with major structures preliminarily interpreted from seismicthe orocline hypothesis using a detailed palaeomagnetic analysis reflection and potential field data. Most importantly, conductiveaided with x-ray study for magnetic mineralogy in Palaeozoic structures coinciding with major faults in this region extend fromrocks of Victoria and New South Wales. Four demagnetisation the lower crust to the near surface. This observation stronglybehaviours have been established (labelled A, B, C and D). The suggests that the major faults are deep-penetrating structuresbehaviour A is associated with loss of most natural remanent that potentially acted as pathways for transporting metalliferousmagnetisation (NRM) around of 200oC, whilst the B express loss fluids to the upper crust where they could form mineral deposits.of NRM at 450C, indicating that NRM is possibly carried by a This result indicates high prospectivity for major minerallow-temperature weathering product, most likely maghemite. deposits in the vicinity of these major faults. In addition, weBehaviour C is attributed to the high temperatures of distinct used high-frequency data to estimate cover thickness to assistunblocking (520 C-690 C). Samples with D behaviour exhibit with stratigraphic drill targeting which, in turn, will validate thea complete NRM loss at 100 C, suggesting very poor magnetic models and improve our understanding of basement geology,stability. Hysteresis data confirmed that the NRM behaviour cover sequences and mineral potential. This study demonstratesB and C specimens have elevated coercivities and remain that integration of geophysical data from multiscale surveys is anunsaturated above 300 mT, implying that hematite carries a effective approach to scale reduction during mineral explorationsignificant proportion of the remenace. The principal aim of the in covered terranes. study failed due to the presence of an overprint which masked the original depositional remanence. The sites in the Ordovician This abstract is published with the permission of the CEO,rocks for central Victoria and Macquarie Arc plot within the Geoscience Australia confidence error limit of Devonian palaeopoles for the Australian continent. Back-scattered electron images and X-ray analysis 133: Compositional control on frictional properties ofof the selected samples from each site suggested that detrital Goldwyer shale reservoir rocks magnetite/titanomagnetite, and (diagenetic?)/altered hematite carries magnetic remanence. This alteration could be the result of Mr Partha Pratim Mandal 1, Prof Reza Rezaee1, Dr Mustafa Sari2massive fluid expulsion events during late Bindian-Tabberabberan and Dr Joel Sarout2 orogenic event in Devonian which reset the original remanence.85 PREVIEW AUGUST 2021'