b'AEGC 2023Short abstractsFinding greenfield areas in the brownfield geochemicalThe paper presents recently acquired seismic cross-sections, database, Queensland. gravity modelling results (along regional profiles) and data from the recent wells. The new data is used to support the Joseph Tang concept that the LMC is an allochthonous unit thrust from the north whose relatively planar base is a major decollement. As a Geological Survey of Queensland result, it is proposed that the allochthon sits above a complex Geochemical exploration has been utilised in Queensland forof over-thrusted Australian Continental margin blocks including 70 years, targeting mainly the outcropping geology that coverssome that were likely to have once been part of the evolving approximately 30% of the State. The Geological Survey ofaccretionary wedge at the base of the Timor Trough. Building on Queensland has compiled and released 5.5 million geochemicalwork by previous authors, we show the rationale for a deep sub-and drill-hole data that have been extracted from explorationthrust test in the Suai Basin of southern Timor Leste.reports and academic publications. Although these data were intended to expedite exploration in Queensland, they have also led to a common misconception that all near-surface economicIsotope and geochemical fingerprinting of placer gold: deposits within the well-exposed and explored areas have beeninsights into the provenance and age.discovered, effectively and indirectly sterilising these groundsSvetlana TessalinaElena Hancock , Bryant Wareand Neal 1 1 2from further exploratory work. McNaughton2A thorough appraisal of the current exploration data1 WA Department of Mines, Industry Regulation and Safety demonstrates that most of the well-sampled areas in Queensland2 Curtin Universityare under-explored. Past exploration techniques applied mineralisation models of the time, targeting narrow searchWestern Australia hosts the fifth largest gold province in the corridors in which samples were analysed for a limited numberworld, and Australia as a whole is estimated to have the worlds of targeted elements. Identifying data gaps and the removal oflargest gold reserves (17% of the total world estimated gold poor-quality data expose extensive greenfield areas within thereserves). Over the last few decades, there has been a significant broader brownfield areas. The latter therefore remain essentiallyadvance in our understanding of geological, structural under-explored for such commodities. This fact necessitatesconditions and geochronological context of gold-bearing ore exploration focus on these under-explored regions, consideringaccumulation. The recent exploration surge for conglomerate the current demands for rare-earth, battery and technologygold in the Pilbara is mostly targeted at exploration and mining metals. An effective discriminant for data quality is to use theof palaeo-placers in siliciclastic sediments and sedimentary baseline elemental concentrations of geologic units as therocks. However, the question must be raised about the primary normalising factor to establish whether the geochemical resultssource of these gold nuggets and whether larger in-situ gold are sensitive enough for geochemical exploration. Low-precisiondeposits are yet to be discovered.data have detection limits few magnitudes above their rock background concentrations and are inappropriate for exploration. The recent Curtin-GSWA geochemical-isotopic collaborative study of native gold nuggets from WA placer gold deposits Re-sampling and/or re-assaying is/are necessary if existing(Tessalina etal., in press) has demonstrated our analytical samples have not been analysed for the desired commodity, ifcapability to produce a coherent set of trace element and target areas have not been sampled, or if the current data are ofisotopic data to fingerprint native gold. In our study, we low quality. As all data in the Queensland geochemical databaseinvestigated several gold grains from various locations in are referenced to a company or report, it is possible to trackWestern Australia (Pilbara and Yilgarn Cratons and Capricorn archival samples to previous explorers. If these samples are notOrogen) with the aim to establish the age and constrain available, field campaign will be required otherwise. the source of gold mineralisation directly from gold. The samples were analysed for Pb-Os isotopes, PGEs and other trace elements. One of the most important findings was the Recent exploration in the Timor-Leste frontier. establishment of reliable Pb-Pb model ages for some gold samples, as well as the characterisation of the source of Pb prior Randall Taylor 1, Jan Hulse2, Ana Belo2 and Jacinto Soares2 to mineralisation. This study demonstrates that the geochemical 1 Taylor Exploration Consultingand isotopic fingerprints could be useful for exploration of gold 2 Timor Resources sources to establish the source of alluvial gold nuggets and potentially identify transport corridorsOnshore hydrocarbon exploration in Timor Leste has resumed after a 50-year gap from the last well in 1972 by Timor Oil to Timor Resources recent drilling of Karau 1 and Kumbili 1 in theInsights into the deep crust across the Delamerian and Suai Basin. Encouragement from these new wells is providingLachlan Orogens derived from new magnetotelluric incentive to conduct further exploration targeting a deeperdata.sub-decollement play, first proposed in the 1970s. The play concept is subject to regional debate over the true nature ofStephanThiel 1,2,Suzanne Haydon3, Kate Brand4 and Tom Wise1the metamorphic rocks outcropping north of the Suai Basin.1 Geological Survey of South Australia Does the Lolotoi Metamorphic Complex (LMC) represent an2 The University of Adelaide allochthonous unit below which is an un-metamorphosed3 Geological Survey of Victoria prospective section, or is it composed of uplifted Australian4 Bureau of Meteorology continental margin material? New data acquired by Timor Resources is used to update the regional model and presentThe Geological Survey of Victoria (GSV) and Geological Survey support for the former concept. of South Australia (GSSA) are acquiring magnetotelluric (MT) FEBRUARY 2023 PREVIEW 144'