AEGC Conference 2021

    Published on May 30th, 2021

    Consultant Geologist, Dr Rob Holm will present at the AEGC Conference 2021 on ‘The Structural controls on late Cambrian mineralisation in the Stavely Arc’ between September 15-20, 2021 at the Brisbane Convention and Exhibition Centre in Queensland, Australia.

    This 4-day program will feature keynotes speakers, concurrent sessions, posters presentations and workshops delivered by leading experts in their respective streams.

    Under the conference theme of Geoscience for a Sustainable World, the AEGC will attract a large number of international and national delegates and organisations from across the spectrum of Australasian geosciences representing industry, government and academia. We expect to be able to include dedicated streams for Australian basins, resourcing a sustainable energy challenge, data, innovation and technology, high-quality resources for future generations, and developing the future workforce.

    The conference is jointly hosted by the Australian Institute of Geoscientists (AIG), Australian Society of Exploration Geophysicists (ASEG), and Petroleum Exploration Society of Australia (PESA).

    Dr Holm is set to present on Saturday 18 September at 8.30am AEST.

    ABSTRACT – Structural Controls on late Cambrian Mineralisation in the Stavely Arc

    The middle-late Cambrian Stavely Arc forms the eastern boundary of the Delamerian Orogen in Victoria, Australia. A pulse of mineralised magmatism at ca. 500 Ma coincided with the collision of VanDieland and related deformation. Porphyry intrusion during this event has previously been inferred, from tectonic reconstructions, to coincide with a change from D1a transpression to D1b transtension, with intrusions having exploited transtensional structures. The outcropping area of the Stavely Arc is a small proportion of the total terrane, and informative outcrops and data are sparse, providing limited supporting evidence to date.

    This work presents new insights into the structural geology of the Stavely Arc during porphyry emplacement. A bottom-up approach is informed by structural observations and exploration activity from the Thursday’s Gossan-Cayley Lode Project of Stavely Minerals Limited (ASX:SVY). This data-orientated approach utilises measured structures and assay results from exploration drilling, as opposed to a top-down approach interpreted from the regional geodynamics.

    An evaluation of mineralised versus non-mineralised structures was used as a proxy for active versus inactive structures, where active structures represent pathways for migration and deposition of mineralising fluids exsolved from an intrusive porphyry system at depth. Faults and shear zones variably host elevated Cu-Au-As±Ag±Ni±Co dependant on orientation during the porphyry emplacement event; veins do not appear to host substantial metal anomalism.

    By comparing the orientations of active versus inactive structures, an overall NW-SE directed axis for maximum compressive stress is interpreted at the time of mineralisation. The results of this work imply that porphyry intrusion and mineralisation occurred within a compressive D1a stress regime, during VanDieland collision, and prior to D1b extensional tectonism. The collision event and associated disruption to subduction zone processes are therefore implicated in triggering porphyry emplacement. These findings will be important for understanding the prospectivity of the Stavely Arc and targeting future exploration activity.

    ABOUT THE PRESENTER

    Robert Holm

    Dr Rob Holm
    Consultant Geologist

    Robert is an expert geologist with an extensive and diverse background encompassing both the minerals and oil and gas sectors. He specialises in structural geology, drawing on experience ranging from Archean Gold systems to recent and actively forming analogues across the SW Pacific, to investigate mineral systems across multiple spatial and temporal scales. Robert also has expertise in unravelling the metallogenesis and prospectivity of complex tectonic settings through multidisciplinary methods that include, but are not limited to, structural geology and geodynamics, geophysical interpretation, petrology, geochemistry and isotope systematics, and geochronology. He uses these skills coupled with strong analytical and problem-solving skills to deliver integrated geological solutions in project generation and deposit targeting. Robert also draws from experience exceeding 10 years in geoscience training and education that has gained recognition and multiple awards to offer workshops and training programs that can be developed to cater for the specific needs of a client.

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