b'AEGC 2021Short abstractsSamples from each deposit were generally collected from270: Post-rift magmatism on the continental shelf multiple boreholes, at a downhole spacing ranging fromof the Otway Basin and implications for the igneous continuous (phosphorites) to 10-50 m (base metal deposits - toplumbing systems in sedimentary basinscharacterise the entire range from high-grade mineralisation to distal alteration and background). Major and trace elementMr Yakufu Niyazi 1, Dr Mark Warne1 and Dr Daniel Ierodiaconou1geochemistry (for up to 67 elements) was consistently characterised using a combination of exploration industry- 1 Deakin Universitystandard digestion methods and analytical techniques:Various types of igneous rocks have been frequently encountered four-acid digestion and ICP-MS / OES (48 elements), lithiumduring hydrocarbon exploration of sedimentary basins along metaborate fusion and ICP-MS / OES (31 elements), fire assayrifted passive margins, and their impacts on the hydrocarbon and ICP-MS (Au, Pt. Pd), Leco furnace (C, S), KOH fusion - ionmaturation and migration processes are diverse. Buried volcanoes chromatography (F) and Aqua regia - ICP-MS (Hg, Se, Te). generally act as migration pathways, whilst magma intrusions Sediment-hosted Cu deposits are generally significantly enrichedare often associated with source rock maturation. Importantly, in Co; IOCGin Co (and sometimesREEs, Re, In); sediment- the high acoustic velocity and density of igneous intrusions, hosted Zn-Pbin Ge (In, Ga) and phosphoritesin REE. introduces imaging problems. Therefore, understanding the The programme is ongoing in North-east Queensland,igneous plumbing styles within the sediments, remained crucial expanding the largest internally consistent public database offor hydrocarbon exploration for frontier basins. Combining the Queenslands mineral deposit geochemistry. seismic reflection surveys with magnetic datasets, in this study we identified six intrusive sills, seven lava flows and feeder dykes beneath them. Thirty cones to trapezium-shaped and twenty-269: Complex recharge mechanisms creatingseven dome to eye-shaped mounds are also identified and contradictory tracer signals in a large karst aquifer inbased on their magnetic and seismic-geomorphic attributes, are northern Australia elucidated by a multi-tracer study interested as monogenetic volcanoes and hydrothermal vents, respectively. The igneous complexes were emplaced between Dr Axel Suckow 1, Dr Alec Deslandes1, Dr Christoph Gerber1, Drmid-Eocene to mid-Miocene, while the hydrothermal vents are Cornelia Wilske2, Dr Sebastien Lamontagne1, Dr Yang Guo-Min3mainly of mid-Eocene. Most of the volcanic/hydrothermal vents and Dr Jiang Wei3 are linked to the underlying rift related faults via vertical zones of disruption, which are interpreted as feeder dykes or hydrothermal 1 CSIRO Land and Water fluid pipes, respectively. The scattered distribution of sills and 2 University of Adelaide dyke-dominated volcanoes of this study, contrasts to most of the 3 University of Science and Technology of China (USTC) recent studies that highlight the importance of the lateral magma The Beetaloo Sub-Basin in the Northern Territory of Australiatransportation in sedimentary basins. Our comparison with has one of the largest Australian prospective resources of shalethe neighbouring Bight Basin, suggests that he thin crust but gas in the Velkerri formation at 2 km to 2.5 km depth. Therelatively thick sediment layers of the Bight Basin, facilitated the shallowest aquifer covering this basin is the up to 300 m thicklateral transportation of magma and promoted sill-fed volcanism, Cambrian Limestone Aquifer (CLA), extending over more thanwhile the magma ascending through thick crust but relatively 800 km, with groundwater flow direction from the dry savannathin sediment layers of the Otway Basin, produced sufficient climate in the southeast to the monsoon-dominated climate inmagma pressure and promoted the predominantly dyke-fed the northwest. Both the pastoral industry of the region as welligneous plumbing system. This work highlights the critical role of as shale gas industry will use water from the CLA and a robustbasin structures, such as continental crust, sedimentary thickness, water balance for this aquifer is needed. and faults, in controlling the distribution, morphology and style of post-rift igneous plumbing processes in magma-poor margins.Tracer findings in the karstified CLA are counter-intuitive: radiocarbon concentrations increase instead of decreasing272: Using comment field entries in drill hole database in groundwater flow direction. Tritium is generally low, but detectable in the north, whereas modern gas tracers CFCs, SF 6 to automatically re-log lithologies; application of Latent and H1301 are high throughout the aquifer, indicating highSemantic Analysis and Supervised Learningexcess air and suggesting more recent recharge than tritium. Radiogenic helium is present in several bores, indicating upwardMr Jean-philippe Paiement 1fluid flow that cannot be further quantified due to a lack of1 Mira Geoscience Ltdobservations in deeper formations. To shed further light on the recharge conditions, samples for 85Kr and 39Ar were taken. 85KrOften times, geological modelling on projects with extensive results indicate a wide range of concentrations from detectionhistorical data is plagued by over complexified lithological limit to modern. dictionaries and inconstancies in the logging. In order to be able The recharge model in best agreement with the data suggeststo properly interpret and model the geology, geologists often a strong regional recharge gradient from south to north,have to reclassify the lithological entries into a new legend by a further complicated locally by direct recharge into sinkholes.combination of re-logging, reading of comments and a certain This creates water level fluctuations over wide areas, causingamount of guessing. Coming up with an automated way of large excess air and allowing the anthropogenic gas tracers toreclassifying the lithological entries to a consistent legend that exchange with the recent atmosphere in the unsaturated zone,is meaningful for modelling as always been a challenge.while recharge is not actually happening. Tritium and 85Kr areBy using Latent Semantic Analysis (LSA), a technique that uses therefore considered as the most reliable recharge indicators,natural language processing in order to analyze relationships whereas CFCs, SF 6and H1301 mainly indicate the gas exchangebetween a set of entries and the words they contain to interpret process. a set of more general concepts, we propose a workflow to relog 109 PREVIEW AUGUST 2021'