b'AEGC 2021Short abstractsdrill hole databases into new lithological classes using textualbelt of WAs North Eastern Goldfields. Gold was first discovered comments. This approach uses drill hole database comments toin the mid-1890s predominantly from underground operations extract general topics that can then be used as learning featuresactive between 1987 and 1997 when the mine closed. Several in a supervised machine learning approach. The featuresfactors culminated in the mines closure including a diminishing are used in combination with a few re-logged control holes,resource and a prevailing (incorrect) model that the Highway with the desired lithological labels, to produce a new set ofFault terminated mineralisation. Minor exploration was carried lithological entries. out for 20 years until the projects revival by Bellevue Gold The extracted concepts from the LSA model give key insightsLimited in 2017.into the geological relationships and the supervised learningWith a new geological model and during their maiden drill model produces consistent lithological entries to a set of controlprogramme, the projects potential was confirmed with holes. This novel approach could greatly benefit explorationshallow, high-grade intercepts down-plunge of historical lodes. projects with considering historical data by unifying thousandsGold mineralisation at the Tribune lode was discovered in the of disparate and inconsistent entries into a new usablesecond drill programme, followed shortly after by the Viago lithological legend. and Deacon discoveries.Mineralisation is hosted in Archean tholeiitic basalts, with 273: Spatio-temporal distribution of igneous rocks andminor sediments and felsic intrusions, metamorphosed seismic facies analysis of buried volcanoes of the Prawnto upper greenschist to amphibolite facies. Gold occurs in Platform, offshore Otway Basin gently plunging, high-grade ore shoots associated with semi-massive to massive pyrrhotite chalcopyrite, and folded and Mr Yakufu Niyazi 1, Dr Ovie Emmanuel Eruteya2, Dr Mark Warne1boudinaged quartz veins, developed within steeply west-and Dr Daniel Ierodiaconou1 dipping shear zones and conjugate low-angle shears.1 Deakin University High pyrrhotite content and its correlation with gold 2 University of Geneva mineralisation is an uncommon characteristic of orogenic lode Volcanic rocks occur in different types of sedimentary basins,gold deposits in the Eastern Goldfields. Petrophysical testing of especially those evolving from lithospheric stretching. Whilehistorical core samples was completed in 2017 and confirmed volcanoes and other igneous rocks are widespread in thethe strong conductivity and chargeability contrast between the onshore Otway Basin, well-preserved volcanoes have not beentarget mineralisation and host rock.documented in the offshore portion of the basin. Here, weDHEM surveys acquired in 1992-1993 included significant analysed high-quality 2D and 3D seismic reflection datasetsanomalies from off-hole conductors located below and to the to investigate the origin and spatio-temporal distribution ofsouth of the mine that remained untested until 2019. These are the igneous rocks in the Prawn Platform, offshore Otway Basin.now known to be associated with the Viago lode.Nineteen volcanoes, ranging from ~90400 m in height and 1.86 km in diameter, occur at three stratigraphic levels: lateAcquisition of modern high-powered DHEM data has become Eocene, mid-Oligocene, and early Miocene. While the igneousstandard practice to identify strongly conductive, high-grade sills are relatively small (~0.211 km2), and located immediatelygold mineralisation and to vector drilling. Over 200 drillholes beneath the volcanoes, implying a synchronous intrusionhave been surveyed over a 2km strike length. Deacon is a direct activity with the volcanoes. Seismo-geomorphological analysisDHEM discovery.indicates these are shield volcanoes fed by dykes. Distinct seismic facies characterise these buried volcanoes, including280: Investigation of old pollution site along the Swan the chaotic central face that represents the main volcanic eruption centre, outward-dipping moderate amplitudeRiver, Perth, Western Australia using the Loupe TEM reflections of tuff cone, and chaotic reflections at the distalsystemflanks representing the pyroclastic mass-wasting deposits. Interestingly, seismic facies of interbedded extrusive andDr Michael Hatch 1, Mr Gregory Street2, Mr Andrew Duncan3, Dr sedimentary rocks are mainly observed within volcanoesAaron Davis4 and Mr Gavan McGrath5over 250 m high, and are associated with gullies along their1 University of Adelaideflanks, indicating these volcanoes may have been subject to2 ASEG AIG GSAerosion. The discovery of these buried volcanoes extends our3 EMIT,Loupe Geophysicsunderstanding of magmatism in the Otway Basin, especially4 CSIROregarding the offshore extension of the Older Volcanics. 5 WA Department of Biodiversity, Conservation and Attractions279: Using modern downhole EM to discover high- In this study, data were collected using a new transient-electromagnetic system (TEM) over an area in Perth, along grade, narrow vein lodes in an historical gold field,the Swan River, that was polluted by industry in the 1960s Bellevue Gold Project, Western Australia and 1970s, and then remediated by the Western Australian government in the 1990s. A fertiliser plant and a landfill Ms Anne Tomlinson 1 and Mr Gregory John Maude2 were located approximately 1 km to the northwest of the 1 AIG, ASEG study site (upgradient for the groundwater in the area) 2 Southern Geoscience Consultants and the groundwater was heavily affected by both. Other geophysical data sets have been collected over the area Bellevue Mine is located 35 km northwest of Leinster within therecently and will be compared with the Loupe results as part highly gold- and nickel-endowed Agnew-Wiluna greenstoneof this study.AUGUST 2021 PREVIEW 110'