Lithospheric Mantle
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<div>Diamond exploration over the past decade has led to the discovery of a new province of kimberlitic pipes (the Webb Province) in the Gibson Desert of central Australia. The Webb pipes comprise sparse macrocrystic olivine set in a groundmass of olivine, phlogopite, perovskite, spinel, clinopyroxene, titanian-andradite and carbonate. The pipes resemble ultramafic lamprophyres (notably aillikites) in their mineralogy, major and minor oxide chemistry, and initial 87Sr/ 86Sr and <em>ε</em>Nd-<em>ε</em>Hf isotopic compositions. Ion probe U-Pb geochronology on perovskite (806 ± 22 Ma) indicates the eruption of the pipes was co-eval with plume-related magmatism within central Australia (Willouran-Gairdner Volcanic Event) associated with the opening of the Centralian Superbasin and Rodinia supercontinent break-up. The equilibration pressure and temperature of mantle-derived garnet and chromian (Cr) diopside xenocrysts range between 17 and 40 kbar and 750–1320°C and define a paleo-lithospheric thickness of 140 ± 10 km. Chemical variations of xenocrysts define litho-chemical horizons within the shallow, middle, and deep sub-continental lithospheric mantle (SCLM). The shallow SCLM (50–70 km), which includes garnet-spinel and spinel lherzolite, contains Cr diopside with weakly refertilized rare earth element compositions and unenriched compositions. The mid-lithosphere (70–85 km) has lower modal abundances of Cr diopside. This layer corresponds to a seismic mid-lithosphere discontinuity interpreted as pargasite-bearing lherzolite. The deep SCLM (>90 km) comprises refertilized garnet lherzolite that was metasomatized by a silicate-carbonatite melt.</div><div><br></div><div>Geoscience Australia’s Exploring for the Future program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.</div><div><br></div><div><strong>Citation:</strong></div><div>Sudholz, Z. J., et al. (2023). Petrology, age, and rift origin of ultramafic lamprophyres (aillikites) at Mount Webb, a new alkaline province in Central Australia. <i>Geochemistry, Geophysics, Geosystems</i>, 24, e2023GC011120.</div><div>https://doi.org/10.1029/2023GC011120</div>
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The Exploring for the Future program Showcase 2024 was held on 13-16 August 2024. Day 2 - 14th August talks included: <b>Session 1 - Architecture of the Australian Tectonic Plate</b> <a href="https://youtu.be/a8jzTdNdwfk?si=OWNlVR-FLDhF1GVM">AusArray: Australian lithosphere imaging from top to bottom</a> - Dr Alexei Gorbatov <a href="https://youtu.be/j5ox8Ke5n6M?si=YkfDno2xmZXueS1b">AusLAMP: Mapping lithospheric architecture and reducing exploration space in Australia</a> - Jingming Duan <a href="https://youtu.be/qZ6wjzx_dNc?si=NjDEzvqyEeM24-E8">Constraining the thermomechanical and geochemical architecture of the Australian mantle: Using combined analyses of xenolith inventories and seismic tomography</a> - Dr Mark Hoggard <b>Session 2 - Quantitative characterisation of Australia's surface and near surface</b> <a href="https://youtu.be/nPfa_j3_dos?si=mktfIJWXeLElIOK4">AusAEM: The national coverage and sharpening near surface imaging</a> - Dr Anandaroop Ray <a href="https://youtu.be/SU6ak98JvAw?si=DQPovulHa4poqcm0">Unlocking the surface geochemistry of Australia</a> - Phil Main <a href="https://youtu.be/Xtm45CT6e-s?si=JHU7J-ktgVrbj1Ke">Spotlight on the Heavy Mineral Map of Australia</a> - Dr Alex Walker <b>Session 3 – Maps of Australian geology like never before</b> <a href="https://youtu.be/aRISb1YYigU?si=3byJbqW0qRTqCB8-">An Isotopic Atlas of Australia: Extra dimensions to national maps</a> - Dr Geoff Fraser <a href="https://youtu.be/khSy-WAkw-w?si=F-Y67FX3jXN5zZaz">First continental layered geological map of Australia</a> - Dr Guillaume Sanchez <a href="https://youtu.be/Z3GlCJepLK4?si=k_tbaKdmxGBmoSro">An integrated 3D layered cover modelling approach: Towards open-source data and methodologies for national-scale cover modelling</a> - Sebastian Wong View or download the <a href="https://dx.doi.org/10.26186/149800">Exploring for the Future - An overview of Australia’s transformational geoscience program</a> publication. View or download the <a href="https://dx.doi.org/10.26186/149743">Exploring for the Future - Australia's transformational geoscience program</a> publication. You can access full session and Q&A recordings from YouTube here: 2024 Showcase Day 2 - Session 1 - <a href="https://www.youtube.com/watch?v=EHBsq0-pC8c">Architecture of the Australian Tectonic Plate</a> 2024 Showcase Day 2 - Session 2 - <a href="https://youtube.com/watch?v=xih4lbDk-1A">Quantitative characterisation of Australia's surface and near surface</a> 2024 Showcase Day 2 - Session 3 - <a href="https://www.youtube.com/watch?v=qeTLc1K-Cds">Maps of Australian geology like never before</a>