Australian Journal of Earth Sciences最新文献

{"title":"Reply to the discussion by Gell and Finlayson (2023)","authors":"R. Bourman, C. Murray-Wallace, Christopher J. Wilson, L. Mosley, J. Tibby, D. D. Ryan, E. D. De Carli, A. Tulley, A. Belperio, D. Haynes, A. Roberts, C. Westell, E. Barnett, S. Dillenburg, L. Beheregaray, P. Hesp","doi":"10.1080/08120099.2023.2175908","DOIUrl":"https://doi.org/10.1080/08120099.2023.2175908","url":null,"abstract":"R. P. Bourman , C. V. Murray-Wallace , C. Wilson , L. Mosley , J. Tibby , D. D. Ryan , E. D. De Carli , A. Tulley , A. P. Belperio , D. Haynes , A. Roberts , C. Westell , E. J. Barnett , S. Dillenburg , L. B. Beheregaray and P. A. Hesp School of Earth, Atmospheric and Life Sciences, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, Australia; Department of Geography, Environment and Population, University of Adelaide, Adelaide, Australia; Beach and Dune Systems (BEADS) Laboratory, College of Science and Engineering, Flinders University, Bedford Park, Australia; College of Humanities Arts and Social Sciences, Flinders University, Bedford Park, Australia; Centre for Australian Biodiversity and Heritage (CABAH), Adelaide, Australia; School of Biological Sciences, University of Adelaide, Adelaide, Australia; Sprigg Geobiology Centre, University of Adelaide, Adelaide, Australia; Department of Geography and Environmental Science, University of Southampton, Southampton, UK; Copper Search Ltd., Norwood, Australia; School of Physical Sciences, University of Adelaide, Adelaide, Australia; Geosciences Institute, Federal University of Rio Grande do Sul, Porto Alegre, Brazil; Molecular Ecology Laboratory (MELFU), College of Science and Engineering, Flinders University, Bedford Park, SA, Australia","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45063516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discussion of Bourman, R. P., Murray-Wallace, C. V., Wilson, C., Mosley, L., Tibby, J., Ryan, D. D., De Carli, E. D., Tulley, A., Belperio, A. P., Haynes, D., Roberts, A., Westell, C., Barnett, E. J., Dillenburg, S., Beheregaray, L. B., Hesp, P. A. (2022). Holocene freshwater history of the Lower River Murray and its terminal lakes, Alexandrina and Albert, South Australia, and its relevance to contemporary environmental management. <i>Australian Journal of Earth Sciences, 69</i>(6), 605–629","authors":"P. A. Gell, C. M. Finlayson","doi":"10.1080/08120099.2023.2175907","DOIUrl":"https://doi.org/10.1080/08120099.2023.2175907","url":null,"abstract":"Click to increase image sizeClick to decrease image size Disclosure statementNo potential conflict of interest was reported by the author(s).","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136041785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dolomitisation under an arid climate at low sea-level: a case study of the Lei 4 Member of the Middle Triassic Leikoupo Formation, Western Sichuan Depression, China","authors":"Y. Qing, S. Li, Z. Liao, Y. Li, Z. Lv, X. Song, Q. Cao","doi":"10.1080/08120099.2023.2173653","DOIUrl":"https://doi.org/10.1080/08120099.2023.2173653","url":null,"abstract":"Abstract The origin of dolostones from the Lei 4 Member (T2l4) of the Middle Triassic Leikoupo Formation in the Western Sichuan Depression is unclear. The occurrence and genetic evolution of dolostones in T2l4 were analysed by polarised thin-sections and cathodoluminescence, major- and trace-element, scanning electron microscope, and carbon, oxygen and strontium isotope analyses. The study results are summarised as follows. (1) The dolostones were mainly precipitated in three stages of <40 °C, 40–60 °C and 60–80 °C, corresponding with three paleodepth ranges of 167–300 m, 433–1000 m and 1067–1433 m. The micritic dolostones and the fabric-retentive dolostones (algal dolostone, granular dolostone) mainly formed in a near-surface–shallow-burial environment, and the crystalline dolostones were mainly formed under intermediate burial conditions. (2) 87Sr/86Sr ratios are equivalent to that of the Middle Triassic seawater, Sr/Ba and V/Ni ratios >1, Na notably higher than that in coexisting limestones of T2l4, and the dolostones always coexist with evaporative minerals such as gypsum, indicating that dolomitisation fluids mainly originated from evaporative concentrated seawater. (3) The dolostones mainly inherit materials from precursor limestones based on trace-element distribution patterns, and carbon and oxygen isotope values that are consistent with coexisting limestones of T2l4. (4) Mediated by micro-organisms during the syngenetic period, micritic dolostones and some algal dolostones were formed by replacing aragonites and calcites. During shallow burial, concentrated seawater rich in Mg2+ from the supratidal–intertidal zone flowed downward owing to gravity along the platform and replaced the underlying carbonate rocks, promoting continuous growth of the early dolomites. In the intermediate burial period, the Mg2+-depleted dolomitisation fluid caused the early micritic and silt-crystalline dolostones to recrystallise into silt- or fine-crystalline dolostones with larger crystals and altered the fabric-retentive dolostones into crystalline dolostones. (5) The evaporative dolostones deposited in the near-surface environment are characterised by maximal enrichment of Fe, Sr and Na, the highest δ18O values, the lowest order degree and the highest Ca/Mg ratios. The reflux dolostones formed in a shallow-burial environment characterised by the lowest Fe, medium δ18O values and the lowest order degree. The burial dolostones that developed in the intermediate burial environment are characterised by relative enrichment of Fe and Mn, minimal Na, the lowest δ18O values, the highest order degree and medium Ca/Mg ratios. KEY POINTS The fabric-retentive dolostones mainly formed in a near-surface–shallow-burial environment, and the crystalline dolostones mainly formed under intermediate burial conditions. Dolomitisation fluids mainly originated from the evaporative concentrated seawater, and the dolostones inherit materials from the precursor limestones. Micritic ","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44980514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis of the Kalka, Ewarara and Gosse Pile layered intrusions, Musgrave Province, South Australia, and implications for magmatic sulfide prospectivity","authors":"W. Maier, B. Wade, S. Barnes, R. Dutch","doi":"10.1080/08120099.2023.2173292","DOIUrl":"https://doi.org/10.1080/08120099.2023.2173292","url":null,"abstract":"Abstract The Musgrave Province of central Australia was the focus of long-lived mantle upwelling that produced large volumes of magnesian basaltic to tholeiitic magma and their felsic derivatives. The Musgrave Province contains one of the greatest concentrations of mafic–ultramafic layered intrusions globally, grouped as the Giles intrusions. In the present paper, we study the magmatic ore potential of the Kalka, Gosse Pile and Ewarara layered intrusions located in South Australia. Ewarara and Gosse Pile appear to have relatively low potential for platnium-group element (PGE) reefs and magmatic Ni–Cu, based on lack of evident metal enrichment and the absence of a mafic–ultramafic transition zone that hosts most PGE reefs globally. However, mafic–ultramafic pipes within the intrusions that could have higher ore potential have not been studied by us. At Kalka, the mafic–ultramafic transition interval is exposed, rendering this intrusion potentially more prospective for PGE reefs. However, based on the available data, this zone appears to be barren. Instead, there are signs of PGE enrichment and metal ratio variation in the magnetite-bearing upper portion of the intrusion suggestive of undiscovered PGE reefs. This interpretation is consistent with subtle Cu–Pd enrichment of soils adjacent to the upper portion of the intrusion. KEY POINTS First assessment of magmatic ore potential of Kalka, Ewarara and Gosse Pile layered intrusions in South Australia. Kalka shows signs of PGE enrichment in upper, magnetite-bearing portion of intrusion, suggesting enhanced potential for a PGE reef. Ewarara and Gosse Pile appear to be less prospective for PGE–Ni–Cu, but picrite pipes remain unstudied.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46988312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Late Quaternary geological history of the Sydney estuary, Australia","authors":"G. Birch, S. Lound","doi":"10.1080/08120099.2023.2139756","DOIUrl":"https://doi.org/10.1080/08120099.2023.2139756","url":null,"abstract":"Abstract The present study provides valuable new information on the evolution of Sydney estuary by tracing the development of the complete marine–estuarine–fluvial system through a full glacial cycle (Last Interglacial, LIG, to the present Interglacial). Extensive seismic (361.3-line km) and sedimentological studies provided a sound foundation for production of a detailed litho- and seismic-stratigraphic record for the estuary. In the absence of reliable age data, a relative chronology was constructed based on Quaternary flooding surface elevations constrained by a recent local relative sea-level record supported by other global studies. A thick, ubiquitous estuarine unit deposited during the LIG period (MIS 5.5; 130–115 ka BP) was an important chronological marker horizon and played a critical role in controlling seismic interpretation and correlation throughout the estuary. Deposition during the MIS 5.1/5.3 interstadial period (100–80 ka BP) resulted in deposition of fine-grained, estuarine sediments in the lower estuary and time-equivalent, fluvial-sourced estuarine and channel sediments, and marsh sediments in the upper and central estuary, respectively. The MIS 3 interstadial event did not play a significant role in sedimentation in Sydney estuary. An eolian dune field formed adjacent to the southern shores of the estuary during the last glacial (31–24 ka BP) when most of the sediment in the lower estuary had been removed by fluvial erosion. Transgressive marine sand, which deposited in the lower paleovalley after the ocean re-entered the estuary, experienced repeated erosion and infilling by laterally migrating paleoriver channels. A marine flood-tide delta now occupies the estuary mouth, and the lower and upper/central estuary are mantled in a veneer (mean 7 m) of Holocene sand and mud, respectively. KEY POINTS A relative chronology was based on Quaternary flooding surface elevations constrained by relative sea-level. First geological history of the Sydney estuary with a complete marine–estuarine–fluvial system. A late Quaternary estuary evolution through a full glacial cycle. Geological history includes an interstadial (MIS 5.3/5.1) estuarine sequence.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46395261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis and tectonic setting of Early Cretaceous mafic dykes in the North Qinling Orogenic Belt, central China: constraints on the lithospheric lower crust delamination","authors":"Y. N. Huang, D. Li, A. Xiao, S. M. Xu","doi":"10.1080/08120099.2023.2172609","DOIUrl":"https://doi.org/10.1080/08120099.2023.2172609","url":null,"abstract":"Abstract Late Mesozoic mafic dykes, which are widely developed in the North Qinling Orogenic Belt (NQOB), include abundant geodynamic information. This paper describes the mafic dykes that intrude the Late Jurassic granite in the Dayu and Kuyu areas, and reports important petrological constraints for the late Mesozoic tectonic transition from compression to extension in the NQOB. Three zircon U–Pb results show that the minimum ages of the mafic dykes are 139.8 ± 1.4 Ma, 137.4 ± 1.7 Ma and 133.4 ± 0.9 Ma, indicating that the emplacement age of the Dayu and Kuyu mafic dykes is 140–133 Ma. Petrogeochemical analyses suggest that the mafic dykes belong to the high-K calc-alkaline shoshonite series with low SiO2 (46.93–56.73 wt%), MgO (1.88–9.10 wt%) and TiO2 (1.17–1.82 wt%), and high Al2O3 (13.98–17.46 wt%), TFe2O3 (7.81–10.92 wt%) and K2O (1.28–4.78 wt%). The mafic dykes are enriched in large ion lithophile elements (e.g. Rb, Ba, K, La, Sr) and depleted in high-field-strength elements (e.g. Nb, Ta, Zr, Ti). These samples have the right-sloping chondrite-normalised rare earth element patterns, which suggest light rare earth element enrichment and heavy rare earth elements depletion with no obvious Eu anomalies (δEu = 0.94–1.11). The I Sr, ε Nd(t), ε Hf (t) and T DM2(crust) values are 0.7056–0.7060, −10.60 to −5.98, −14.1 to −2.8, and 1382.4 ± 25.1 to 2081.9 ± 47.6 Ma, respectively. Both elemental and isotopic geochemistry show that the formation of Dayu and Kuyu mafic dykes is due to the partial decompression melting of previously enriched lithospheric mantle during a delamination process. The mafic dykes have undergone fractionation crystallisation of Mg–Fe phase minerals during magma ascent, accompanied by some crustal contamination. Combined with the regional tectonic setting, we suggested that the NQOB experienced intra-continental extension during the Early Cretaceous. KEY POINTS Early Cretaceous (140–133 Ma) mafic dykes have been discovered in the middle part of the North Qinling Orogenic Belt. The remote effect of the Paleo-Pacific Plate subduction has reached the middle of the North Qinling Orogenic Belt. The North Qinling Orogenic Belt entered the extensional stage in the Early Cretaceous (140–133 Ma).","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42869314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A geophysically constrained crustal element map of East Antarctica between Enderby Land and Princess Elizabeth Land","authors":"Y. Giri, P. Betts, M. Radhakrishna, M. McLean, T. K. Biswal, R. Armit","doi":"10.1080/08120099.2023.2169957","DOIUrl":"https://doi.org/10.1080/08120099.2023.2169957","url":null,"abstract":"Abstract East Antarctica along with Greater India played a vital role in the accretion and breakup of the Indo-Antarctic landmasses during the supercontinents Nuna, Rodinia and Gondwana. Without geophysical potential field methods, interpreting the architecture of the ice-covered geological provinces of Antarctica is impossible. We present here a crustal element map of East Antarctica between Enderby Land and Princess Elizabeth Land (Indo-Antarctica tectonic element) using aerogeophysical data interpretation. The data reveal distinct anastomosing geophysical provinces that correlate with sparse geological data. Our crustal element map shows the Oygarden Province and the Northern and Southern Rayner provinces are arcuate belts that wrap around the Archean Napier Province. These provinces represent the remnants of an accretionary tectonic margin, which evolved between ca 1300 Ma and 900 Ma. The arcuate geometry of these Meso- to Neoproterozoic provinces formed during the collision with the Napier Province, which represents a microcontinent. This collision triggered widespread extension and ultra-high temperature metamorphism in the Northern and Southern Rayner provinces. The southernmost provinces include the Fisher Province, Lambert Province and a transition zone. The provinces are truncated by a suture zone with the Archean Ruker Province, following north-dipping subduction during the Meso- to Neoproterozoic. Our interpretation provides a template upon which to correlate geological provinces with the terranes on the conjugate eastern Indian margin. KEY POINTS An aeromagnetic interpretation is given for Enderby Land and Princess Elizabeth Land of East Antarctica. Napier Province is a microcontinent that collided with the Rayner Province during a ca 1000 Ma orogenic event. A new interpretation of potential field data suggests anastomosing provinces accreted as part of a collisional event. New structures/piercing points are identified at the Mawson Coast and in Kemp Land.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46993436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shale gas potential of Ordovician marine Pingliang shale and Carboniferous–Permian transitional Taiyuan-Shanxi shales in the Ordos Basin, China","authors":"H. Nie, Q. Chen, P. Li, W. Dang, J. C. Zhang","doi":"10.1080/08120099.2023.2170466","DOIUrl":"https://doi.org/10.1080/08120099.2023.2170466","url":null,"abstract":"Abstract The assessment of shale gas potential for the Ordovician Pingliang Formation and Carboniferous–Permian Taiyuan and Shanxi formations in the northwest margin of Ordos Basin, China provides insight into how fluctuation in depositional environments has a significant role on lithofacies and shale gas potential. To investigate the shale gas potential, a series of measurements (i.e. Rock-Eval pyrolysis, maceral composition analyses and X-ray powder diffraction, etc.) on representative outcrop samples were conducted to characterise shale properties. The organic matter from marine Pingliang shale is predominantly type I with a strong predominance of sapropelinite, whereas the transitional Taiyuan-Shanxi shales are dominated by types II to III kerogen. Furthermore, the Pingliang shale is characterised as a ‘poor’ source rock mainly owing to the lower total organic carbon (TOC) content (average 0.79 wt%) and higher maturity [average 1.78% in vitrinite reflectance (R o)], while the transitional Taiyuan-Shanxi shales are mostly characterised as ‘fair’ source rocks, and some samples with high TOC content (more than 2.0 wt%) present good source rocks. It is also found that the sedimentary environment, as a key factor determining the organic matter and TOC content, inevitably influences the type and content of minerals in shale, and controls the shale gas potential. For example, the transitional argillaceous Taiyuan-Shanxi shales are significantly different from the siliceous Pingliang shales, specifically, total clay content for the former is more than 50 wt%, while the latter is rich in quartz content (more than 70 wt%). Additionally, the quartz and clay contents of the Taiyuan shale range widely, especially the smectite content of I–S ML. The barrier coastal facies in the Taiyuan Formation are more conducive to the enrichment and preservation of organic matter because the Shanxi shale was deposited in shallow delta facies with a greater terrestrial influence. Conclusively, the Taiyuan and Shanxi formations have relatively good exploitation potential for shale gas, especially the relatively high TOC content (average 2.45 wt%) and moderate R o value (average 1.25%). For future exploration, selecting areas with relatively large shale thickness, high brittle mineral content, stable tectonics and better preservation conditions are key to optimising favourable exploration areas for shale gas. KEY POINTS The shale gas potentials of the argillaceous Taiyuan-Shanxi shales and siliceous Pingliang shale are compared. The influence of sedimentary facies on reservoir parameters of marine and transitional shales is established. This is a first detailed comparison of the marine and transitional shale gas potential in the northwest margin of Ordos Basin, China.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46093348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New age constraints for the Tommy Creek Domain of the Mount Isa Inlier, Australia","authors":"A. Brown, C. Spandler, T. Blenkinsop, C. Fergusson","doi":"10.1080/08120099.2023.2171124","DOIUrl":"https://doi.org/10.1080/08120099.2023.2171124","url":null,"abstract":"Abstract The Tommy Creek Domain is a complex, yet little studied, terrane in the Eastern Subprovince of the Mount Isa Province, northwest Queensland Australia. In this study, we take advantage of modern low-cost and rapid geochronology techniques to undertake an iterative dating approach integrated with detailed fieldwork to define the ages and extents of numerous lithologies and units of the Tommy Creek Domain. This includes some units not previously identified, lithologies previously grouped together based on field observations but now shown to have multiple distinct ages and dates not commonly represented in Mount Isan time–space plots. We identify an episode of felsic magmatism at ca 1640 Ma, and multimodal intrusions (ca 1615 Ma) immediately preceding the onset of the Isan Orogeny. A major rock package of the Tommy Creek Domain, the Milo beds, are characterised here as the youngest pre-Isan Orogeny sedimentary unit in the Eastern Subprovince (1660–1620 Ma), confirming that sedimentation and possibly rifting continued after deposition of the Soldiers Cap, Mount Albert and Kuridala groups (ca 1690–1650 Ma) before the onset of the Isan Orogeny (ca 1600 Ma). The Milo beds are thus age equivalent to the Mount Isa and McNamara groups of the Western Succession. There is evidence of a compositional shift in sedimentation coincident with the ca 1640 Ma Riversleigh Inversion event, previously only observed in the Western Subprovince in the Lawn Hill Platform. The application of geochronology as part of the mapping workflow can assist with differentiating geological units in terranes where field evidence is ambiguous and can aid in the focusing of objectives for field campaigns to enable the best possible interpretations to be made. KEY POINTS New ages constrain the Milo beds in the Tommy Creek Domain as the youngest stratigraphy in the Eastern Subprovince of the Mount Isa Province. The Milo beds are age equivalents of the McNamara and Mount Isa groups of the Western Subprovince of the inlier. Recognition of felsic and mafic intrusions with ca 1640 Ma and ca 1615 Ma ages. Evidence for Riversleigh Inversion event ca 1640 in the Eastern Subprovince.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44437182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Foliation boudinage structures in the Mount Isa Cu system","authors":"B. J. Williams, T. Blenkinsop, R. Lilly, M. Thompson, P. Ava, C. Fergusson","doi":"10.1080/08120099.2022.2153384","DOIUrl":"https://doi.org/10.1080/08120099.2022.2153384","url":null,"abstract":"Abstract Small-scale foliation boudinage structures occur in rocks that were sampled in drill core from the Mount Isa Cu deposit, northwest Queensland. The necks of foliation boudinage structures plunge gently to the north and south as a result of layer normal shortening and layer parallel extension of the steeply west-dipping Urquhart Shale. Detailed petrographic analysis of the foliation boudinage structures has identified an initial rim of quartz and dolomite, followed by infill and replacement by pyrrhotite and minor chalcopyrite. Foliation boudinage structures formed after dolomitisation and silicification of the shale. They occur most commonly in the unaltered Urquhart Shale where the anisotropy and homogeneity provided by the shale layering is still intact. Infilling of the structures occurred during protracted silica-dolomite alteration, pyrrhotite and chalcopyrite mineralisation. The paragenesis of the foliation boudinage structures is consistent with the established paragenesis of the main Cu mineralisation. Foliation boudinage structures formed over the period from shortening during D4a through to the main Cu mineralisation during D4b west-northwest–east-southeast sinistral-reverse shortening. The timing of foliation boudinage is consistent with a current kinematic model for the Mount Isa system. KEY POINTS First record of foliation boudinage structures at Mount Isa. Foliation boudinage structures with sulfide-dominated infills. Foliation boudinage structures formed as a result of progressive deformation from a D4a dextral-reverse through to D4b sinistral-reverse slip. Foliation boudinage structures are associated with the timing and kinematics of Cu mineralisation at Mount Isa.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47436439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}