GEOCHEMISTRY
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Geoscience Australia currently uses two commercial petroleum system modelling software packages, PetroMod https://www.software.slb.com/products/petromod and Zetaware http://www.zetaware.com, to undertake burial and thermal history modelling on wells in Australian sedimentary basins. From the integration of geological (age-based sedimentary packages, uplift and erosional events), petrophysical (porosity, permeability, and thermal conductivity) and thermal (downhole temperature, heat flow, vitrinite reflectance, and Tmax) input data, to name the most significant, a best-fit model of the time-temperature history is generated. Since the transformation of sedimentary organic matter (kerogen) into petroleum (oil and gas) is a chemical reaction, it is governed by chemical kinetics i.e. time and temperature (in the geological setting pressure is of secondary importance). Thus, the use of chemical kinetics associated with a formation-specific, immature potential source rock (where available) from the basin of interest is considered a better practical approach rather than relying on software kinetic defaults, which are generally based on the chemical kinetics determined experimentally on Northern Hemisphere organic matter types. As part of the Australian source rock and fluids atlas project being undertaken by the Energy Systems Group’s Exploring for the Future (EFTF) program, compositional kinetics (1-, 2-, 4- and 14-component (phase) kinetics) were undertaken by GeoS4, Germany. The phase kinetics approach is outlined in Appendix 1. This report provides the compositional kinetics for potential source rocks from the Ordovician Goldwyer (Dapingian–Darriwilian) Formation and the Bongabinni (Sandbian) Formation, Carribuddy Group, Canning Basin, Western Australia.
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As part of the Onshore Energy Systems Group’s program, organic maturation levels were determined using polar compounds from potential source rocks from the Georgina and Canning basins. The Early Paleozoic organic matter is devoid of the vitrinite maceral so unsuitable of the measurement of the industry-standard vitrinite reflectance (Ro%) measurement.
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A predictive model of weathering intensity or the degree of weathering has been generate over the Australian continent. The model has been generated using the Random Forest decision tree machine learning algorithm. The algorithm is used to establish predictive relationships between field estimates of the degree of weathering and a comprehensive suite of covariate or predictive datasets. The covariates used to generate the model include satellite imagery, terrain attributes, airborne radiometric imagery and mapped geology. The weathering intensity model is an estimate of the degree of surface weathering only. The interpretation of the weathering intensity is different for in-situ or residual landscapes compared with transported materials within depositional landscapes. In residual landscapes, weathering process are operating locally whereas in depositional landscapes the model is reflecting the degree of weathering either prior to erosion and subsequent deposition, or weathering of sediments after being deposited. The degree of surface weathering is particularly important in Australia where variations in weathering intensity correspond to the nature and distribution of regolith (weathered bedrock and sediments) which mantles approximately 90% of the Australian continent. The weathering intensity prediction has been generated using the Random Forest decision tree machine learning algorithm. The algorithm is used to establish predictive relationships between field estimates of the degree of weathering and a comprehensive suite of covariate or predictive datasets. The covariates used to generate the model include satellite imagery, terrain attributes, airborne radiometric imagery and mapped geology. Correlations between the training dataset and the covariates were explored through the generation of 300 random tree models. An r-squared correlation of 0.85 is reported using 5 K-fold cross-validation. The mean of the 300 models is used for predicting the weathering intensity and the uncertainty in the weathering intensity is estimated at each location via the standard deviation in the 300 model values. The predictive weathering intensity model is an estimate of the degree of surface weathering only. The interpretation of the weathering intensity is different for in-situ or residual landscapes compared with transported materials within depositional landscapes. In residual landscapes, weathering process are operating locally whereas in depositional landscapes the model is reflecting the degree of weathering either prior to erosion and subsequent deposition, or weathering of sediments after being deposited. The weathering intensity model has broad utility in assisting mineral exploration in variably weathered geochemical landscapes across the Australian continent, mapping chemical and physical attributes of soils in agricultural landscapes and in understanding the nature and distribution of weathering processes occurring within the upper regolith. <b>Value: </b>Weathering intensity is an important characteristic of the earth's surface that has a significant influence on the chemical and physical properties of surface materials. Weathering intensity largely controls the degree to which primary minerals are altered to secondary components including clay minerals and oxides. In this context the weathering intensity model has broad application in understanding geomorphological and weathering processes, mapping soil/regolith and geology. <b>Scope: </b>National dataset which over time can be improved with additional sites for training and thematic datasets for prediction.
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This Record presents 40Ar/39Ar chronologic results acquired in support of collaborative regional geoscientific investigations and mapping programs conducted by Geoscience Australia (GA) and the Northern Territory Geological Survey (NTGS). Argon isotopic data and interpretations from hornblende, muscovite, and biotite from seven samples collected from the Aileron Province in ALCOOTA , HUCKITTA, HALE RIVER, and ILLOGWA CREEK in the Northern Territory are presented herein. The results complement pre-existing geochronological constraints from U–Pb zircon and monazite analyses of the same or related samples, and provide new constraints on the thermal and deformation history of the Aileron Province. Three samples (2003082017, 2003082021, 2003083040) were taken from ALCOOTA in the northeastern portion of the Aileron Province. Biotite in sample 2003082017 from the ca 1.81 Ga Crooked Hole Granite records cooling below 320–280°C at 441 ± 5 Ma. Biotite in sample 2003082021 from the ca 1.73 Ga Jamaica Granite records cooling below 320–280°C at or after 414 ± 2 Ma. Muscovite in sample 2003083040 from the Delny Metamorphics, which were deposited after ca 1.82 Ga and preserve evidence for metamorphism at ca 1.72 Ga and 1.69 Ga, records cooling below 430–390°C at 399 ± 2 Ma. The fabrics preserved in the samples from the Crooked Hole Granite and Delny Metamorphics are interpreted to have formed due to dynamic metamorphism related to movement on the Waite River Shear Zone, an extension of the Delny Shear Zone, during the Palaeoproterozoic. Portions of the northeastern Aileron Province are unconformably overlain by the Neoproterozoic–Cambrian Georgina Basin, indicating these samples were likely at or near the surface by the Neoproterozoic. Together, these data indicate that rocks of the Aileron Province in ALCOOTA were subjected to heating above ~400°C during the Palaeozoic. Two samples (2003087859K, 2003087862F) of exoskarn from an indeterminate unit were taken from drillhole MDDH4 in the Molyhil tungsten–molybdenum deposit in central HUCKITTA. The rocks hosting the Molyhil tungsten–molybdenum deposit are interpreted as ca 1.79 Ga Deep Bore Metamorphics and ca 1.80 Ga Yam Gneiss. They experienced long-lived metamorphism during the Palaeoproterozoic, with supersolidus metamorphism observed until at least ca 1.72 Ga. Hornblende from sample 2003087859K indicates cooling below 520–480°C by 1702 ± 5 Ma and may closely approximate timing of skarn-related mineralisation at the Molyhil deposit; hornblende from sample 2003087862F records a phase of fluid flow at the Molyhil deposit at 1660 ± 4 Ma. The Salthole Gneiss has a granitic protolith that was emplaced at ca 1.79 Ga, and experienced alteration at ca 1.77 Ga. Muscovite from sample 2010080001 of Salthole Gneiss from the Illogwa Shear Zone in ILLOGWA CREEK records cooling of the sample below ~430–390°C at 327 ± 2 Ma. This may reflect the timing of movement of, or fluid flux along, the Illogwa Shear Zone. An unnamed quartzite in the Casey Inlier in HALE RIVER has a zircon U–Pb maximum depositional age of ca 1.24 Ga. Muscovite from sample HA05IRS071 of this unnamed quartzite yields an age of 1072 ± 8 Ma, which likely approximates, or closely post-dates, the timing of deformation in this sample; it provides the first direct evidence for a Mesoproterozoic episode of deformation in this part of the Aileron Province.
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This Record presents new U–Pb geochronological data, obtained via Sensitive High Resolution Ion Micro Probe (SHRIMP), from 43 samples of predominantly igneous rocks collected from the East Riverina region of the central Lachlan Orogen, New South Wales. The results presented herein correspond to the reporting period July 2016–June 2020. This work is part of an ongoing Geochronology Project, conducted by the Geological Survey of New South Wales (GSNSW) and Geoscience Australia (GA) under a National Collaborative Framework agreement, to better understand the geological evolution and mineral prospectivity of the central Lachlan Orogen in southern NSW (Bodorkos et al., 2013; 2015; 2016, 2018; Waltenberg et al., 2019).
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We present a new geological map of Warrumbungle Volcano created from volcanic facies field mapping, new geophysical, geochemical, and geochronological data as well as data from previous studies. Field mapping and petrography defined 19 volcanic and 2 mixed volcanic-sedimentary facies. Facies identification and distribution in conjunction with geochemical analyses indicate an early shield-forming phase of predominantly mafic and intermediate lavas and pyroclastic deposits, and minor felsic lavas deposited on an irregularly eroded basement of Surat and Gunnedah basin rocks. The shield was subsequently intruded by felsic intermediate to felsic magmas that formed dykes and other intrusions including possible cryptodomes, and also erupted as lava domes and block-and-ash-flow deposits. A radial dyke swarm cross-cuts most units, although is concentrated within basement sandstone surrounding the central area of the volcano, suggesting late inflation accompanied by dyke emplacement. Geochemistry indicates differentiation of a single although repeatedly recharged alkaline magmatic suite. Fractionation of olivine, Ti-magnetite and clinopyroxene occurred in mafic magmas, and after reaching 62 wt% SiO2 crystallisation of apatite and alkali feldspar took place. A new U-Pb zircon SHRIMP magmatic crystallisation age of 16.25 +/- 0.12 Ma on a felsic block-and-ash flow deposit is in agreement with the recalculated 40Ar/39Ar isochron dates of previous workers. Based on our mapping and the use of volcanic facies to define mappable units, we recommend the previous Warrumbungle Volcanics be elevated from formation to group status and renamed the Warrumbungle Volcanic Complex.
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This database contains geochemical analyses of over 7000 samples collected from or near mineral deposits from 60 countries, compiled by the Critical Minerals Mapping Initiative (CMMI), a collaboration between Geoscience Australia (GA), the Geological Survey of Canada (GSC) and the United States Geological Survey (USGS). Data was compiled from a number of publicly-available sources, including federal and provincial government mineral deposit and geochemistry databases, and the ore samples normalised to average crustal abundance (OSNACA) database compiled by the Centre for Exploration Targeting at the University of Western Australia. Geochemical data cover the majority of the periodic table, with metadata on analytical methods and detection limits. Where available, sample descriptions include lithology, mineralogy, and host stratigraphic units. Mineral deposits are classified according to the CMMI mineral deposit classification scheme (Hofstra et al., 2021). Location information includes deposit or prospect name, and sampling location (i.e., mine, field site, or borehole collar). This dataset will be updated periodically as more data become available. Geoscience Australia: D Champion, O Raymond, D Huston, M Sexton, E Bastrakov, S van der Wielen, G Butcher, S Hawkins, J Lane, K Czarnota, I Schroder, S McAlpine, A Britt Geological Survey of Canada: K Lauzière, C Lawley, M Gadd, J-L Pilote, A Haji Egeh, F Létourneau United States Geological Survey: M Granitto, A Hofstra, D Kreiner, P Emsbo, K Kelley, B Wang, G Case, G Graham Geological Survey of Queensland: V Lisitsin
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The Precambrian Pine Creek Orogen and Arnhem Province represent two of the oldest basement terrains in northern Australia and are often considered to be devoid of major tectonic or deformational activity since the cessation of regional metamorphism in the Paleoproterozoic. A major caveat in the current hypothesis of long lived structural inactivity is the absence of published low temperature thermochronological data and thermal history models for this area. Here we report the first apatite U–Pb, fission track and (U–Th–Sm)/He data for igneous samples from both the Pine Creek Orogen and Arnhem Province, complemented with apatite geochemistry data acquired by electron microprobe and laser ablation mass spectrometry methods, and present detailed multi-kinetic low temperature thermal history models. Low-temperature thermal history models for the Pine Creek Orogen and Arnhem Province reveal a distinct phase of denudation coeval with the Paleozoic Alice Springs Orogeny, suggesting that this orogenic event impacted a larger area of the Australian crust than previously perceived. Minor localised Mesozoic thermal perturbations proximal to the Pine Creek Shear-Zone record evidence for Mesozoic reactivation contemporaneous with modelled mantle driven subsidence and the onset of sedimentation in the Money Shoal Basin, while the Arnhem Province samples demonstrate no evidence of Mesozoic thermal perturbations. <b>Citation:</b> Angus L. Nixon, Stijn Glorie, Alan S. Collins, Jo A. Whelan, Barry L. Reno, Martin Danišík, Benjamin P. Wade, Geoff Fraser; Footprints of the Alice Springs Orogeny preserved in far northern Australia: an application of multi-kinetic thermochronology in the Pine Creek Orogen and Arnhem Province. <i>Journal of the Geological Society</i> 2020;; 178 (2): jgs2020–173. doi: https://doi.org/10.1144/jgs2020-173
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As part of the Onshore Energy Systems Group’s program, late gas (methane) and compositional kinetics (1-, 2-, 4- and 14-component (phase) kinetics) were undertaken by GeoS4, Germany. The phase kinetics approach is outlined in Appendix 1. This report provides the data required to access the shale gas potential of source rocks from the Georgina Basin, Australia.
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<div>This record one in a series of reports detailing the geochemical and mineralogical results of sampling collected at mine waste sites across Australia as part of Geoscience Australia's Exploring for the Future program. It presents new data and information regarding the tenor rare earth elements, ore commodities (lead, zinc and silver) and other trace metals, at the Cannington silver and lead mine located in Queensland’s Northwest Minerals Province.</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>