Isotope Geochemistry
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Newer version v1.1 available at eCat <a href="https://pid.geoscience.gov.au/dataset/ga/147720">147720</a> Isotopic data from rocks and minerals have the potential to yield unique insights into the composition and evolution of the Earth's crust and mantle. Time-integrated records of crust and mantle differentiation (as preserved by the U-Pb, Sm-Nd and Lu-Hf isotopic systems, for example) are important in a wide range of geological applications, especially when successfully integrated with other geological, geophysical, and geochemical datasets. However, such integration requires (i) compilation of comprehensive isotopic data coverages, (ii) unification of datasets in a consistent structure to facilitate inter-comparison, and (iii) easy public accessibility of the compiled and unified datasets in spatial and tabular formats useful and useable by a broad range of industry, government and academic users. This constitutes a considerable challenge, because although a wealth of isotopic information has been collected from the Australian continent over the last 40 years, the published record is fragmentary, and derived from numerous and disparate sources. Unlocking and harnessing the collective value of isotopic datasets will enable more comprehensive and powerful interpretations, and significantly broaden their applicability to Earth evolution studies and mineral exploration. As part of the Exploring for the Future (EFTF) program (https://www.ga.gov.au/eftf), we have designed a new database structure and web service system to store and deliver full Lu-Hf isotope and associated O-isotope datasets, spanning new data collected during research programs conducted by Geoscience Australia (GA), as well as compiled literature data. Our approach emphasises the links between isotopic measurements and their spatial, geological, and data provenance information in order to support the widest possible range of uses. In particular, we build and store comprehensive links to the original sources of isotopic data so that (i) users can easily track down additional context and interpretation of datasets, and (ii) generators of isotopic data are appropriately acknowledged for their contributions. This system delivers complete datasets including (i) full analytical and derived data as published by the original author, (ii) additional, normalised derived data recalculated specifically to maximise inter-comparability of data from disparate sources, (iii) metadata related to the analytical setup, (iv) a broad range of sample information including sampling location, rock type, geological province and stratigraphic unit information, and (v) descriptions of (and links to) source publications. The data is delivered through the Geoscience Australia web portal (www.portal.ga.gov.au), and can also be accessed through any web portal capable of consuming Open Geospatial Consortium (OGC)-compliant web services, or any GIS system capable of consuming Web Map Services (WMS) or Web Feature Services (WFS). This Record describes the database system and web service tables. It also contains full tabulated datasets for data compiled from the North Australian Craton as part of the EFTF program. These data are predominantly micro-analytical zircon analyses which are linked at the spot-level across Lu-Hf, O, and U-Pb measurements. This data release comprises 5974 individual analyses from 149 unique rock samples.
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This report presents the results of an elemental and carbon and oxygen isotope chemostratigraphy study on three historic wells; Kidson-1, Willara-1 and Samphire Marsh-1, from the southern Canning Basin, Western Australia. The objective of this study was to correlate the Early to Middle Ordovician sections of the three wells to each other and to wells with existing elemental and carbonate carbon isotope chemostratigraphy data from the Broome Platform, Kidson and Willara sub-basins, and the recently drilled and fully cored stratigraphic Waukarlycarly 1 well from the Waukarlycarly Embayment.
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<div>Geoscience Australia’s Exploring for the Future (EFTF) 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 EFTF program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.</div><div>The onshore Canning Basin in Western Australia was the focus of a regional hydrocarbon prospectivity assessment undertaken by the EFTF program dedicated to increasing investment in resource exploration in northern Australia, with the objective being to acquire new data and information about the potential mineral, energy and groundwater resources concealed beneath the surface. As part of this program, significant work has been carried out to deliver pre-competitive data in the region including new seismic acquisition, drilling of a stratigraphic well, and geochemical analysis from historic exploration wells.</div><div>As part of this program, a compilation of the compound-specific isotopic compositions of crude oils from 30 petroleum wells in the Canning Basin have been completed. The samples were analysed in Geoscience Australia’s Isotope and Organic Geochemistry Laboratory and the collated results are released in this report. This report provides additional stable carbon and hydrogen isotopic data to build on the oil-oil correlations previously established by Edwards and Zumberge (2005) and Edwards et al. (2013). This information can be used in future geological programs to determine the origin of the crude oils, and hence increase our understanding of the Larapintine Petroleum Supersystem, as established by Bradshaw (1993) and Bradshaw et al. (1994).</div><div><br></div>
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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 Australian Government’s $225 million Exploring for the Future (EFTF) program is committed to supporting a strong economy, resilient society and sustainable environment for the benefit of Australians (https://www.ga.gov.au/eftf). At its heart, the program is about stimulating industry now to ensure a sustainable, long-term future for Australia through an improved understanding of the nation’s minerals, energy and groundwater resource potential. By gathering and analysing geological and geophysical data and making the results publicly available, the program supports regional development and informed decision making across Australia, resulting in jobs and growth. The Energy component of this program is designed to produce pre-competitive information to assist with the evaluation of the hydrocarbon resource potential of onshore basins and attract exploration investment to Australia. As part of the EFTF Natural Hydrogen module, molecular and isotopic analyses were undertaken by Geoscience Australia on natural gas samples from the wells Canunda 2 and Ralgnal 1 from the southwestern margin of the Patchawarra Trough in the Cooper Basin, with the raw data from these analyses being released in this report. Some data from these wells were included in the nationwide studies of helium and hydrogen, as published by Boreham et al. (2018; 2021), and build on previous studies that document the composition of Australian natural gases (Boreham et al., 2001). These data are available through the Geoscience Australia portal at https://portal.ga.gov.au/
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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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Although the Canning Basin has yielded minor gas and oil within conventional and unconventional reservoirs, the relatively limited geological data available in this under-explored basin hinder a thorough assessment of its hydrocarbon potential. Knowledge of the Paleozoic Larapintine Petroleum Supersystem is restricted by the scarcity of samples, especially recovered natural gases, which are limited to those collected from recent exploration successes in Ordovician and Permo-Carboniferous successions along the margins of the Fitzroy Trough and Broome Platform. To address this shortcoming, gases trapped within fluid inclusions were analysed from 121 Ordovician to Permian rock samples (encompassing cores, sidewall cores and cuttings) from 70 exploration wells with elevated mud gas readings. The molecular and carbon isotopic compositions of these gases have been integrated with gas compositions derived from open-file sources and recovered gases analysed by Geoscience Australia. Fluid inclusion C1–C5 hydrocarbon gases record a snapshot of the hydrocarbon generation history. Where fluid inclusion gases and recovered gases show similar carbon isotopes, a simple filling history is likely; where they differ, a multicharge history is evident. Since some fluid inclusion gases fall outside the carbon isotopic range of recovered gases, previously unidentified gas systems may have operated in the Canning Basin. Interestingly, the carbon isotopes of the fluid-inclusion heavy wet gases converge with the carbon isotopes of the light oil liquids, indicating potential for gas–oil correlation. A regional geochemical database incorporating these analyses underpins our re-evaluation of gas systems and gas–gas correlations across the basin. <b>Citation:</b> Boreham, C.J., Edwards, D.S., Sohn, J.H., Palatty, P., Chen, J.H. and Mory, A.J., 2020. Gas systems in the onshore Canning Basin as revealed by gas trapped in fluid inclusions. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.
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<div>The first ca. 2.2 billion years of Earth history saw significant change; from a water-world dominated by an anoxic atmosphere and tonalitic continents, to the exposed landmasses, oxygenated atmosphere, and granitic crust of the Paleoproterozoic. Precisely when, and how, these major changes occurred, remain some of the most important and controversial questions in modern geoscience. Here, we present an extensive new zircon U-Pb-Hf-O isotopic and trace element dataset from Earth’s largest preserved Archean continent, the Superior Craton, Canada. These data record a number of fundamental geochemical changes through time and indicate a major geological and geodynamic transition occurred toward the end of Archean, at ca. 2.7 Ga. Our data show that, at >2704–2695 Ma, the southern Superior Craton had juvenile εHf, light to mantle-like δ18O, low (Eu/Eu*)/Y (drier/shallower crust), reduced ΔFMQ, less continental initial-U (Ui)/Yb, and more mantle-like Ui/Nb. At ca. 2704–2695 Ma, there is a marked transition in multiple datasets, including increases in δ18O, (Eu/Eu*)/Y, ΔFMQ, Ui/Yb and Ui/Nb data, together with more distinct arc-like trace element trends. These data reveal that at 2.7 Ga there was an increase in: (1) continental surface weathering, supported by increased sedimentation at <2.68 Ga, (2) oxidized and hydrous magmatism, and (3) surface material in magma sources. Together, these observations suggest a major geodynamic transition from ‘vertical’ tectonics (sagduction, drips) to north-dipping subduction at 2.7 Ga. The increase in δ18O suggests that proximal continental crust, probably in the northern Superior Craton, became emergent at this time, an inference supported by detrital zircon geochronology. Hence, this dataset links major geodynamic change to the emergence of continental crust and the rise of more oxidized magmatism. These fundamental changes to the Earth’s surface environment, tectonics, and atmosphere at 2.7 Ga, provide evidence for an Earth systems turning-point at the end of the Neoarchean.</div> This Abstract was submitted/presented to the 2022 Specialist Group in Geochemistry, Mineralogy and Petrology (SGGMP) Conference 7-11 November (https://gsasggmp.wixsite.com/home/biennial-conference-2021)
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<div>Exploring for the Future (EFTF) is an Australian Government program led by Geoscience Australia, in partnership with state and Northern Territory governments, and aimed at stimulating exploration now to ensure a sustainable, long-term future for Australia through an improved understanding of the nation’s minerals, energy and groundwater resource potential. </div><div>The EFTF program is currently focused on eight interrelated projects, united in growing our understanding of subsurface geology. One of these projects, the Barkly–Isa–Georgetown project, will deliver new data and knowledge to assess the mineral and energy potential in undercover regions between Tennant Creek, Mount Isa and Georgetown. Building on the work completed in the first four years of the Exploring for the Future program (2016-2020), the project undertook stratigraphic drilling in the East Tennant and South Nicholson regions, in collaboration with MinEx CRC and the Northern Territory Geological Survey (NTGS). This work tests geological interpretations and the inferred mineral and energy potential of these covered regions. Geoscience Australia is undertaking a range of analyses on physical samples from these drill holes including geochemistry and geochronology. </div><div>The South Nicholson National Drilling Initiative (NDI) Carrara 1 drill hole is the first drillhole to intersect the Proterozoic rocks of the Carrara Sub-Basin, a depocentre newly discovered in the South Nicholson region based on interpretation from seismic surveys acquired as part of the EFTF. It is located on the western flanks of the Carrara Sub-basin on the South Nicholson Seismic line 17GA-SN1, reaching a total depth of 1751 m, intersecting ca. 630 m of Cambrian Georgina Basin overlying ca. 1100 m of Proterozoic carbonates, black shales and minor siliciclastics.</div><div>The NDI BK10 drill hole is the tenth drill hole drilled as part of the East Tennant project aimed to constrain the East Tennant basement geology and calibrate predictive mineral potential maps to further our understanding of the prospectivity of this region. NDI BK10 reached a depth of 766 m and intersected basement at 734 m. Overlying these basement metasediments of the Alroy Formation, the drillhole intersected about 440 m of Proterozoic rocks underlain by ca. 300 m rocks of Cambrian age from the Georgina Basin.</div><div>During coring of NDI Carrara 1 and NDI BK10, cores containing oil stains were identified and sent for geochemical analysis to Geoscience Australia. This report presents the geochemical data from these oil stains including biomarker and isotopic data.</div>
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As part of the Exploring for the Future (EFTF) program, a chemostratigraphic framework for the Officer Basin was developed that correlates inorganic geochemical sequences between exploration wells. The Officer Basin spans 525,000 km<sup>2</sup> across Western Australia and South Australia, where it remains an unproven frontier basin which has seen little exploration. The objective of this study was to undertake a bulk rock elemental chemostratigraphy study on ten historic wells in order to better correlate the Neoproterozoic and Cambrian sections. Ten study wells, five from Western Australia and five from South Australia, were selected, and core (241) and cuttings (1,245) samples were acquired from their respective state core libraries. All samples were analysed using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), resulting in quantitative data for 50 elements. The approximate proportions of dolomite, clastics, halite and anhydrite for the samples were derived using stoichiometric geochemical calculations. Halite was identified in some formations based on mud log and wireline data, but was not always preserved in the cuttings samples. This non-detection of halite resulted in poor matches between the wireline gamma ray (GR) and ChemGR profiles for halite-bearing units in some wells (e.g. Dragoon-1, Mulyawara-1, and Yowalga-3). Key element and ratios utilised to subdivide the strata were principally chosen to highlight changes in sediment provenance, climatic, and organic matter changes, as they typically have the best correlation potential over a greater distance. The stratigraphy within the study wells has been subdivided into eight chemostratigraphic mega-sequences referred to as MS1 to MS8, which are further subdivided into a total of twenty-four sequences. Mega-Sequences MS1 to MS4 broadly correspond to the published Neoproterozoic–Cambrian Centralian Supersequences (CS1 to CS4). While overall there is broad agreement between these two schemes, there are also sections where the stratigraphy has been reassigned. For example, within Kutjara-1, the section previously assigned to Centralian Supersequence CS2, and equivalent to the Cryogenian Tapley Hill Formation, is assigned to Mega-Sequence MS3 (not MS2). Within MS4, the lithostratigraphically defined members of the Observatory Hill Formation show some significant variation to the chemostratigraphy, with differences occurring within sequences MS4-S3, MS4-S4 and MS4-S5 (e.g. Birksgate-1; Trainor Echo-1). Mega-Sequence MS6 encompasses the Mount Chandler Sandstone in Trainor Echo-1 in the east and the lithological lateral equivalent Lennis Sandstone in Lungkarta-1/ST1 and Yowalga-1 in the west; however, these two argillaceous sandstones are chemically distinct. Carbonate-containing samples from three wells (Birksgate-1, Yowalga-3, and Giles-1) were analysed for their δ13Ccarb and δ18Ocarb isotope signature using Isotope-Ratio Mass Spectrometry (IRMS), with results from the least altered carbonates being of sufficient quality to attempt preliminary age dating. Comparison of the Officer Basin isotope data to global type sections enabled tentative correlation of the Yowalga-3 carbonates to the Tonian and late Ediacaran, and the Birksgate-1 carbonates to the early Cambrian. The geochemistry analyses from 10 basin-wide wells provide a robust dataset that has been used to confirm which sections correlate within the existing lithostratigraphic and sequence stratigraphic framework. This study also highlights where further work needs to be undertaken to elucidate the spatial and temporal relationships of some Cryogenian and early Cambrian sections across the entire basin, given that rocks of these ages contain both potential source and reservoir rocks for petroleum generation and accumulation.