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Throughout New Zealand, the Torlesse Supergroup forms an extensive Permian to Cretaceous accretionary wedge of rather monotonous, sandstone-dominated turbidites. In contrast to contemporaneous rocks in neighbouring terranes within the accretionary wedge, the turbidites have less intermediate-volcaniclastic compositions, and show more quartzose, continent-derived, plutonic provenances. Petrographic, geochemical, isotopic and detrital mineral age characteristics all indicate that they did not originate at the contemporary Gondwanaland margin in New Zealand, but rather, constitute a suspect terrane (Torlesse Terrane), having sediment sources elsewhere along the margin. This latter subject has been controversial, with sediment sources suggested in Antarctica, southern South America and northeast Australia, but detailed Torlesse detrital mineral (zircon and mica) age data and bulk rock Sr-isotope patterns can be best matched for the most part with Carboniferous, Permian and Triassic sources in the New England Orogen, and the remainder with Cambrian and Ordovician sources in its hinterland.
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As recognised by the Academy of Science's UNCOVER group in their `Searching the Deep Earth' document, a goal for geoscientific advancement in Australia is a `holistic understanding of our continent so that we might better predict the location of large-scale mineral systems. This view included the investigation of Australia's lithospheric architecture to establish a whole-of-lithosphere architectural framework as a priority. An important component of the Earth's lithosphere is the crust, most of which is clearly inaccessible. Just as the study of basaltic rocks has provided insight into the earth's mantle, granites provide a (not always wholly transparent) window into the middle and lower continental crust. Studies of these rocks are enhanced by isotopic tracers, such as Samarium-Neodymium, which can affectively `see through' the granite to provide constraints on crustal formation, and enable us to map the Australian crust. This approach and the application of Samarium-Neodymium isotope data were used by Geoscience Australia for the Archean Yilgarn Craton of Western Australia. Studies in that region showed that regional scale Samarium-Neodymium signatures in felsic igneous rocks (tonalite to granite and volcanic equivalents) were not only able to map crustal architecture but that this architecture had unexpected correlations with mineralisation. The successful results in the Yilgarn Craton, coupled with the UNCOVER focus, warranted that this approach be extended to the whole of the continent to test its general applicability for crustal mapping and predicting mineralisation. A database of Sm-Nd isotopic data, and associated metadata, for >2650 samples of Australian rocks was compiled from published and unpublished sources. This included location, unit, geochronology and bibliographic data and metadata for all data points; this dataset is available for download at www.ga.gov.au. Data were compiled for a range of lithologies, including felsic and mafic igneous rocks, sedimentary rocks, as well as some mineral data. Just over 1630 of these data points were from felsic igneous rocks which had reliable locational details and a reasonable estimated or known magmatic age. A comparison of the magmatic ages from these samples with compilations of Australian igneous rock ages showed a generally good agreement confirming the representative nature of the compiled Nd data set.
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Inland sulfidic soils have recently formed throughout wetlands of the Murray River floodplain associated with increased salinity and river regulation (Lamontagne et al., 2006). Sulfides have the potential to cause widespread environmental degradation both within sulfidic soils and down stream depending on the amount of carbonate available to neutralise acidity (Dent, 1986). Sulfate reduction is facilitated by organic carbon decomposition, however, little is known about the sources of sedimentary organic carbon and carbonate or the process of sulfide accumulation within inland sulfidic wetlands. This investigation uses stable isotopes from organic carbon (13C and 15N), inorganic sulfur (34S) and carbonate (13C and 18O) to elucidate the sources and cycling of sulfur and carbon within sulfidic soils of the Loveday Disposal Basin.
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Initial lead isotope ratios from Archean volcanic-hosted massive sulfide (VHMS) and lode gold deposits and neodymium isotope model ages from igneous rocks from the geological provinces that host these deposits identify systematic spatial and temporal patterns, both within and between the provinces. The Abitibi-Wawa Subprovince of the Superior Province is characterized by highly juvenile lead and neodymium. Most other Archean provinces, however, are characterized by more evolved isotopes, although domains within them can be characterized by juvenile isotope ratios. Metal endowment (measured as the quantity of metal contained in geological resources per unit surface area) of VHMS and komatiite-associated nickel sulfide (KANS) deposits is related to the isotopic character, and therefore the tectonic history, of provinces that host these deposits. Provinces with extensive juvenile crust have significantly higher endowment of VHMS deposits, possibly as a consequence of higher heat flow and extension-related faults. Provinces with evolved crust have higher endowment of KANS deposits, possibly because such crust provided either a source of sulfur or a stable substrate for komatiite emplacement. In any case, initial radiogenic isotope ratios can be useful in predicting the endowment of Archean terranes for VHMS and KANS deposits. Limited data suggest similar relationships may hold in younger terranes.
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The Victoria and Birrindudu Basins of the Victoria River region, NW Northern Territory, represent a pair of stacked unmetamorphosed Palaeoproterozoic to Neoproterozoic basins unconformably overlying low-grade metamorphic basement. SHRIMP U-Pb analysis of detrital zircons provide a basis for lithostratigraphic correlations with other Proterozoic Basins across northern Australia. The Palaeoproterozoic Stirling Sandstone (basal Limbunya Group) is tentatively correlated with the Mount Charles Formation in the Tanami region. The Jasper Gorge Sandstone (basal Auvergne Group) correlates with basal units of the lower Cryogenian Supersequence 1 of the Centralian Superbasin (Heavitree Quartzite and its correlatives). A third correlation, previously proposed elsewhere and further explored here, suggests that the Duerdin Group may correlate with the upper Cryogenian ca. 635 Ma 'Marinoan' glacigenic units of Supersequence 3 of Centralian Superbasin. In particular, the Cryogenian pre-glacigenic Black Point Sandstone Member (basal Duerdin Group) is dominated by detrital zircons with age components characteristic of the Musgrave Complex, implying significant exhumation and erosion of the Musgrave Complex occurred, at least partially, prior to the end of the Cryogenian (<ca. 635 Ma) far earlier than generally thought. The latter two correlations suggest that the Victoria Basin in the Victoria River region represents yet another relic component of the extensive former Centralian Superbasin, at least during Cryogenian time. Sm-Nd whole rock determinations overwhelmingly, and unsurprisingly, are consistent with clastic derivation from the evolved North Australian Craton and, for the Black Point Sandstone Member, from the Musgrave Complex. A relatively juvenile signature ('Ndt ' +1) is observed coincident with aerial volcanism within the Birrindudu Basin at ca. 1640 Ma as has been recently noted in other Australian Palaeoproterozoic terrains.
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<div>A groundwater chemistry, regolith chemistry and metadata record for legacy geochemical studies over the southern Curnamona Province done by GA and partners as part of CRC LEME from 1999 to 2005, that was never fully released. This includes comprehensive groundwater chemistry from more than 250 bores in the Broken Hill region, containing physicochemical parameters, major and trace elements, and a suite of isotopes (34S, Pb, Sr, 18O, D). Recent work on this dataset (in 2021) has added hydrostratigraphic information for these groundwater samples. Also included is a regolith geochemistry dataset collected adjacent to some of the groundwater bores which tests the geochemical response of a range of different size fractions, depths and digests.</div>
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The Nolans Bore deposit, located in the Aileron Province of south-central Northern Territory, is a developing Australian rare earth element (REE) deposit. The deposit currently has a defined global resource of 30.2 Mt grading 2.8% rare earth oxides, 12.9% P2O5 and 200 ppm U3O8 (ASX:ARU 11/11/08). It consists of massive and brecciated fluorapatite veins that are up to 75-m-thick and hosted by ~1806 Ma granitic and metasedimentry units. Although initial drilling indicated that these veins dipped steeply to the NNW, more recent drilling has indicated a more complex 3D-vein configuration across the deposit. Even though apatite is the dominant mineral in the veins, the paragenesis is complex, with a massive zone of apatite-allanite-amphibole breccia, and numerous cross-cutting veins. The apatite hosts REE but it also typically contains abundant inclusions of other REE-bearing minerals, such as monazite and allanite along with other REE 'bearing phosphates, silicates and carbonates. Localised zones of higher grade REE mineralisation occur as intensely kaolinitised and clay altered rocks dominated by fine grained monazite and crandallite group minerals. A preliminary ~1240 Ma U-Pb age for apatite, which is interpreted as a minimum age, corresponds to a major period of global alkalic magmatism between 1300 and 1130 Ma. Low ?Nd and 87Sr/86Sr in the mineralisation are suggestive of EM-1 sources. The deposit is interpreted to be a carbonatite-related hydrothermal deposit. Fertilisation of the mantle to produce the EM-1 source may relate to subduction associated with older convergence along the southern margin of the North Australian Craton.
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The Nolans Bore deposit, located in the Aileron Province of south-central Northern Territory, is an emerging Australian rare earth development. It consists of steeply northwest dipping apatite veins hosted by ~1806 Ma granite gneiss. A preliminary ~1240 Ma U-Pb age for apatite may correspond to a major global period of alkalic magmatism between 1300 and 1130 Ma, including emplacement of the Bayan Obo deposit in China. Low ?Nd and 87Sr/86Sr in the mineralisation is reminiscent of modern EM-1 ocean island basalts and may indicate a link to carbonatitic magmatism. Oxygen isotope thermometry indicates a mineralisation temperature of 410°C, with '18Ofluid of ~8.0'. Fertilisation of the mantle to produce the EM-1 source may relate to subduction associated with convergence along the southern margin of the North Australian Craton.
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Natural gas is Australia's third largest energy resource after coal and uranium but despite this economic importance, the gas origin is not always recognized. To address this, isotope and geochemistry data have been collated on 850 natural gases from all of Australia's major gas provinces with proposed source ages spanning the earliest Paleozoic to the Cenozoic. Unaltered natural gases have a thermogenic origin ('13C methane ranges between -49 and -27'; 'D methane ranges between -290 and -125'). Microbially altered natural gases were identified primarily on the basis of 13C and D enrichments in propane and/or 13C depletion in methane and/or 13C enrichment in CO2. The carbon isotopic composition of the gas source has been estimated using '13C iso-butane as a surrogate for '13C kerogen while for gases where biodegradation is moderate to severe, '13C neo-pentane provides an alternative measure. The '13C kerogen of gas source rocks range from -47 to -22' with the older Paleozoic sources and marine kerogen amongst the most depleted in 13C. The '13C CO2 also provides an insight into crustal- and mantle-derived components while '15N N2 (-6.0 to 2.3' for N2 up to 47 %) distinguish between organic and inorganic (groundwater) inputs. This dataset provides a better understanding on the source and preservation history of Australian gas accumulations with direct implications on improving exploration success.
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Intrusive and extrusive, predominantly felsic, magmatism of Carboniferous to Permian age occurs throughout the north Queensland region (Figure kennedy), and comprises the most widespread and voluminous magmatic event in the region. The great bulk of the exposed KIA is concentrated in the Townsville-Cairns-Cooktown-Georgetown-Charters Towers-Burdekin Falls regions (Figure Kennedy)-within the early-mid-Palaeozoic Hodgkinson and Broken River Provinces, the Etheridge Province and associated Proterozoic provinces, and in the northern part of the Thomson Orogen including the Greenvale, Charters Towers, and Barnard Provinces, and the northern Drummond Basin. The boundary between the northern Drummond Basin and Connors (nNEO) Subprovince is taken to be the Millaroo Fault Zone (MFZ). Geophysical data (and limited geochronology) show that Carboniferous-Permian granites also form a westerly trending belt-the Townsville-Mornington Island Belt (TMIB; originally Townsville-Mornington Island Igneous Belt), which extends under cover from north of Mount Surprise, at least as far as Mornington Island in the Gulf of Carpentaria, transecting regional trends (Wellman, 1992, 1995; Wellman et al., 1994). There is also recent geochronological evidence for KIA magmatism in the environs of the Millungera Basin (Neumann & Kositcin, 2011). Outcrop is discontinuous in the belt extending northwards from Cairns up Cape York Peninsula, to the islands of Torres Strait (and beyond) but geophysical evidence implies there is more extensive magmatism under cover.