Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12072937
T. Wise, S. Thiel, R. Dutch, M. Pawley, K. Robertson
Summary We integrate seismic tomographic models and filtered gravity anomaly maps to investigate the compositional variations in the SCLM of Australia. We find zones of relative enrichment and depletion coinciding with the spatial extent of major thermal events. Anomalous regions of enrichment may represent subduction metasomatism of the lithospheric mantle, or refertilisation due to asthenospheric upwelling. Regions of apparent depletion signify high-degree melt extraction from a previously more enriched lithosphere.
{"title":"Metasomatic/depletion events affecting Cratons and “cratons”","authors":"T. Wise, S. Thiel, R. Dutch, M. Pawley, K. Robertson","doi":"10.1080/22020586.2019.12072937","DOIUrl":"https://doi.org/10.1080/22020586.2019.12072937","url":null,"abstract":"Summary We integrate seismic tomographic models and filtered gravity anomaly maps to investigate the compositional variations in the SCLM of Australia. We find zones of relative enrichment and depletion coinciding with the spatial extent of major thermal events. Anomalous regions of enrichment may represent subduction metasomatism of the lithospheric mantle, or refertilisation due to asthenospheric upwelling. Regions of apparent depletion signify high-degree melt extraction from a previously more enriched lithosphere.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"118 1","pages":"1 - 4"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88021270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073164
J. Pearce, T. Blach, G. Dawson, Y. Melnichenko, G. Southam, S. Golding, J. Bahadur, D. Paterson
Summary Shale oil and gas is of recent interest in Australia, and the Roseneath, Epsilon and Murteree (REM) shales of the Cooper Basin, Australia, are unconventional gas targets. Shales have a high proportion of porosity in the submicron scale and hydraulic stimulation of USA shales has historically employed high volumes of water with dilute HCl, proppants and various chemicals. Supercritical (sc) CO2 has also been used as a fracture fluid in water sensitive formations. In addition, shales may contain high concentrations of potentially toxic or regulated components such as U, As, Pb, or BTEX which may be released to production water. Improper disposal or treatment of waste water has caused recent environmental concerns in the USA. REM shales were characterised with various techniques including high resolution synchrotron XFM for association of metals with specific minerals. Several metals and As were associated with sulphides in coal pores; Mn with siderite, and Pb with pyrite cements. Shales were reacted with dilute HCl or scCO2-water +/- SO2. The fraction of SANS gas accessible meso-pores was highest in the Epsilon Formation core. Siderite dissolved in HCl reactions, and the fraction of open meso-pores increased. Fe-rich precipitates formed in scCO2 reactions and mesopores partly closed. Mobilised concentrations of Pb, Fe, U, and Na were highest from the reactions with dilute HCl. Understanding the mineral sources of metals and their potential release with different fracture fluids may result in better predictions and mitigation options for production water. Reactions of minerals such as siderite, and sulphides may release regulated metals to production water.
{"title":"Experimental acid and scCO2 reactions of Roseneath, Epsilon and Murteree gas shales: Opening or closing of gas accessible pores and metal release to water","authors":"J. Pearce, T. Blach, G. Dawson, Y. Melnichenko, G. Southam, S. Golding, J. Bahadur, D. Paterson","doi":"10.1080/22020586.2019.12073164","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073164","url":null,"abstract":"Summary Shale oil and gas is of recent interest in Australia, and the Roseneath, Epsilon and Murteree (REM) shales of the Cooper Basin, Australia, are unconventional gas targets. Shales have a high proportion of porosity in the submicron scale and hydraulic stimulation of USA shales has historically employed high volumes of water with dilute HCl, proppants and various chemicals. Supercritical (sc) CO2 has also been used as a fracture fluid in water sensitive formations. In addition, shales may contain high concentrations of potentially toxic or regulated components such as U, As, Pb, or BTEX which may be released to production water. Improper disposal or treatment of waste water has caused recent environmental concerns in the USA. REM shales were characterised with various techniques including high resolution synchrotron XFM for association of metals with specific minerals. Several metals and As were associated with sulphides in coal pores; Mn with siderite, and Pb with pyrite cements. Shales were reacted with dilute HCl or scCO2-water +/- SO2. The fraction of SANS gas accessible meso-pores was highest in the Epsilon Formation core. Siderite dissolved in HCl reactions, and the fraction of open meso-pores increased. Fe-rich precipitates formed in scCO2 reactions and mesopores partly closed. Mobilised concentrations of Pb, Fe, U, and Na were highest from the reactions with dilute HCl. Understanding the mineral sources of metals and their potential release with different fracture fluids may result in better predictions and mitigation options for production water. Reactions of minerals such as siderite, and sulphides may release regulated metals to production water.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"13 1","pages":"1 - 4"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80030768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073250
S. Johnson
Summary State- and federal-generated pre-competitive geoscience data is critical for exploration success. These relatively low-cost but high-quality regional-scale datasets ultimately reduce the financial risk to explorers by reducing the search space and allowing a more targeted use of exploration expenditure. In Western Australia, over 20 years of geological mapping and associated research in the Capricorn Orogen has led to a robust understanding of the orogen architecture and its temporal and thermal evolution. Recent in situ geochronology work in the northern part of the orogen, has bridged the gap between prospect-scale ‘exploration’ geoscience data with regional- and province-scale data, ultimately leading to a better understanding of the regional-scale drivers and pathways for gold mineralization in this part of the orogen. This information is critical for exploration models as it opens up older parts of the northern Capricorn basins that were traditionally considered unprospective, and refines and focusses exploration strategies to target the major crustal structures and their ancillary structures.
{"title":"Twenty years of pre-competitive geoscience data in the Capricorn Orogen: the link between mineral systems and crustal evolution","authors":"S. Johnson","doi":"10.1080/22020586.2019.12073250","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073250","url":null,"abstract":"Summary State- and federal-generated pre-competitive geoscience data is critical for exploration success. These relatively low-cost but high-quality regional-scale datasets ultimately reduce the financial risk to explorers by reducing the search space and allowing a more targeted use of exploration expenditure. In Western Australia, over 20 years of geological mapping and associated research in the Capricorn Orogen has led to a robust understanding of the orogen architecture and its temporal and thermal evolution. Recent in situ geochronology work in the northern part of the orogen, has bridged the gap between prospect-scale ‘exploration’ geoscience data with regional- and province-scale data, ultimately leading to a better understanding of the regional-scale drivers and pathways for gold mineralization in this part of the orogen. This information is critical for exploration models as it opens up older parts of the northern Capricorn basins that were traditionally considered unprospective, and refines and focusses exploration strategies to target the major crustal structures and their ancillary structures.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"88 1","pages":"1 - 3"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86109352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073052
J. S. Holmes, J. L. Grigson
Summary The Pilgangoora lithium-tantalum project encompasses a globally significant Li-Ta pegmatite district which formed in the late-Mesoarchaean, along the western margin of the East Pilbara Terrane in Western Australia. Regional field mapping, coupled with local petrographic and micro-analytical investigation into lithium and tantalum mineralisation at Pilgangoora, have allowed a first step towards developing a mineral system-type model for rare-metal pegmatites, that looks beyond the internal features of the trap site, and considers factors such as the triggers, potential sources, and pathways of rare-metal pegmatite magmas. The Li-Ta pegmatite sheets and dykes at Pilgangoora are composite bodies of three paragenetically distinct magmatic phases, each showing differing degrees of ductile strain. The intrusions are structurally controlled and were emplaced within the strain halo of a regional shear zone that is kinematically distinct from, and overprinting of, deformational structures and fabrics belonging to earlier orogenic events in the East Pilbara Terrane. A crystallisation age of 2845 ± 4 Ma for tantalite, obtained during this study, is ~15 m.y. younger than a proximal pluton of the high-K Split Rock Supersuite. This seemingly rules out direct derivation of the rare-metal pegmatite magma from what has traditionally been considered the most likely parent granitic intrusive suite. Along with the evidence for multi-phase parageneses, such a timing relationship is at odds with the currently accepted paradigm for rare-metal pegmatite genesis. The new constraints on rare-metal pegmatite genesis identified as part of this study form valuable exploration criteria, which may be applied locally to locate additional resources and, longer term, more strategically to review and target lithium-bearing pegmatite fields throughout Western Australia.
{"title":"Pilgangoora Lithium-Tantalum Project: deposit geology and new constraints on rare-metal pegmatite genesis","authors":"J. S. Holmes, J. L. Grigson","doi":"10.1080/22020586.2019.12073052","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073052","url":null,"abstract":"Summary The Pilgangoora lithium-tantalum project encompasses a globally significant Li-Ta pegmatite district which formed in the late-Mesoarchaean, along the western margin of the East Pilbara Terrane in Western Australia. Regional field mapping, coupled with local petrographic and micro-analytical investigation into lithium and tantalum mineralisation at Pilgangoora, have allowed a first step towards developing a mineral system-type model for rare-metal pegmatites, that looks beyond the internal features of the trap site, and considers factors such as the triggers, potential sources, and pathways of rare-metal pegmatite magmas. The Li-Ta pegmatite sheets and dykes at Pilgangoora are composite bodies of three paragenetically distinct magmatic phases, each showing differing degrees of ductile strain. The intrusions are structurally controlled and were emplaced within the strain halo of a regional shear zone that is kinematically distinct from, and overprinting of, deformational structures and fabrics belonging to earlier orogenic events in the East Pilbara Terrane. A crystallisation age of 2845 ± 4 Ma for tantalite, obtained during this study, is ~15 m.y. younger than a proximal pluton of the high-K Split Rock Supersuite. This seemingly rules out direct derivation of the rare-metal pegmatite magma from what has traditionally been considered the most likely parent granitic intrusive suite. Along with the evidence for multi-phase parageneses, such a timing relationship is at odds with the currently accepted paradigm for rare-metal pegmatite genesis. The new constraints on rare-metal pegmatite genesis identified as part of this study form valuable exploration criteria, which may be applied locally to locate additional resources and, longer term, more strategically to review and target lithium-bearing pegmatite fields throughout Western Australia.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"8 1","pages":"1 - 6"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88340745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073051
J. Vearncombe
Summary Criticism of the exploration and mining industry for failing to find enough new deposits and open new mines is misplaced. Significant growth in the size of gold Resources on many mines of the Yilgarn Craton has occurred well after the deposit was discovered and after mining had commenced. Brownfields exploration is commonly (but not always) socially, environmentally and politically acceptable. It is easier to add to an operation than it is to permit and fund a new operation. The record of successful brownfield exploration in Western Australia is outstanding with 100% to 1000% additions to endowment recorded at many gold operations in Western Australia in recent years. This success more than covers the perceived, but not proven, short fall from greenfield exploration.
{"title":"West Australian gold resources: crisis or hubris?","authors":"J. Vearncombe","doi":"10.1080/22020586.2019.12073051","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073051","url":null,"abstract":"Summary Criticism of the exploration and mining industry for failing to find enough new deposits and open new mines is misplaced. Significant growth in the size of gold Resources on many mines of the Yilgarn Craton has occurred well after the deposit was discovered and after mining had commenced. Brownfields exploration is commonly (but not always) socially, environmentally and politically acceptable. It is easier to add to an operation than it is to permit and fund a new operation. The record of successful brownfield exploration in Western Australia is outstanding with 100% to 1000% additions to endowment recorded at many gold operations in Western Australia in recent years. This success more than covers the perceived, but not proven, short fall from greenfield exploration.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"56 1","pages":"1 - 2"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87324886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073220
A. Costall, B. Teo, A. Pethick
Summary Divining has been used for centuries for groundwater and mineral prospecting. Historically, divining has been reliant on a rod, or pair of rods, accompanied by a particular individual. Recently, the use of fluid-bearing containers was cited as a viable water divining technique by a popular Indian ‘youtuber’. We numerically simulate the response from a coconut using an appropriate robust statistical method, similar to that deployed by the diviner in their videos. Coincidentally, a clear response in the rotation of the coconut is generated wherever the diviner desires. Our results indicate that divining is and remains at the whim of the practitioner. Unfortunately, this pseudo-science pervades in the modern day and discredits other methods of remote subsurface imaging.
{"title":"Can you use a coconut to find groundwater?","authors":"A. Costall, B. Teo, A. Pethick","doi":"10.1080/22020586.2019.12073220","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073220","url":null,"abstract":"Summary Divining has been used for centuries for groundwater and mineral prospecting. Historically, divining has been reliant on a rod, or pair of rods, accompanied by a particular individual. Recently, the use of fluid-bearing containers was cited as a viable water divining technique by a popular Indian ‘youtuber’. We numerically simulate the response from a coconut using an appropriate robust statistical method, similar to that deployed by the diviner in their videos. Coincidentally, a clear response in the rotation of the coconut is generated wherever the diviner desires. Our results indicate that divining is and remains at the whim of the practitioner. Unfortunately, this pseudo-science pervades in the modern day and discredits other methods of remote subsurface imaging.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"3 1","pages":"1 - 3"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75404018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073001
David. Pratt, K. Blair McKenzie, A. White
Summary Most regional scale magnetic maps are dominated by the magnetic characteristics of steeply dipping basement units truncated by an unconformity surface. It is easy to demonstrate that 80 to 90% of each total field magnetic anomaly is contributed by this intersecting surface. We approach this problem by mapping the boundaries between contrasting magnetic units along each line in the magnetic survey using the full precision of the line data and 3D information from the magnetic gradient tensor. Additionally, we derive the azimuth of each boundary, depth to the unconformity and magnetic properties of the anomalous units. The segments are overlain on any image such as existing geological maps, satellite imagery, gravity or magnetic imagery to provide a new geological interpretation concept. This method provides a new way to interpret new and old magnetic surveys. Eigenvector analysis of the magnetic tensor and normalised source strength (NSS) are combined with an artificial intelligence (AI) approach to estimate the basement properties. The method is applied to full tensor magnetic survey data or a grid of the total magnetic intensity data is processed using FFT transformations to derive the magnetic gradient tensor. These data are used as input to the pre-trained AI process for calculation of depth, width, azimuth, magnetic susceptibility and magnetisation direction. The rock properties and depth information can be used for 3D visualisation of the unconformity and 2D mapping of the magnetic lithology of the unconformity surface.
{"title":"An AI approach to automated magnetic formation mapping beneath cover","authors":"David. Pratt, K. Blair McKenzie, A. White","doi":"10.1080/22020586.2019.12073001","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073001","url":null,"abstract":"Summary Most regional scale magnetic maps are dominated by the magnetic characteristics of steeply dipping basement units truncated by an unconformity surface. It is easy to demonstrate that 80 to 90% of each total field magnetic anomaly is contributed by this intersecting surface. We approach this problem by mapping the boundaries between contrasting magnetic units along each line in the magnetic survey using the full precision of the line data and 3D information from the magnetic gradient tensor. Additionally, we derive the azimuth of each boundary, depth to the unconformity and magnetic properties of the anomalous units. The segments are overlain on any image such as existing geological maps, satellite imagery, gravity or magnetic imagery to provide a new geological interpretation concept. This method provides a new way to interpret new and old magnetic surveys. Eigenvector analysis of the magnetic tensor and normalised source strength (NSS) are combined with an artificial intelligence (AI) approach to estimate the basement properties. The method is applied to full tensor magnetic survey data or a grid of the total magnetic intensity data is processed using FFT transformations to derive the magnetic gradient tensor. These data are used as input to the pre-trained AI process for calculation of depth, width, azimuth, magnetic susceptibility and magnetisation direction. The rock properties and depth information can be used for 3D visualisation of the unconformity and 2D mapping of the magnetic lithology of the unconformity surface.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"1 1","pages":"1 - 9"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77168121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073117
J. Gorter, M. Orchard, R. Nicoll, D. Ferdinando
Summary The Cunaloo Limestone Member of the Locker Shale (Kockatea Shale facies) from the Carnarvon Basin contains a distinctive conodont zone also seen in the informally named ‘Limestone Marker’ in the lower Kockatea Shale of the northern Perth Basin. The boundary between the Induan (Dienerian) and the Olenekian (Smithian) is selected at the base of the incoming of the conodont Novispathodus waageni eowaageni in this core and provides an important biostratigraphic correlation point between the two basins. The Cunaloo Limestone Member contains Novispathodus dieneri-Neospathodus waageni- Scythogondolella milleri conodont zone species and this correlates with upper Bed 32 at the type section of the Permian-Triassic transition at the Meishan Permian-Triassic stratotype section D in China, dated by zircon U/Pb as about 251.5 Ma. This suggests an absolute age correlation of the lower part of the Kraeuselisporites saeptatus palynological zone in the southern Carnarvon Basin. This conodont zone is Smithian in age. A thin, apparently discontinuous, previously un-named limestone appears above the Cunaloo Limestone Member and is within the K. saeptatus zone. This carbonate unit becomes more prominent towards the north and contains conodonts, mostly fragmentary, of Smithian age. It is here named the Lawley Limestone Member. The Chiosella timorensis conodont zone occurs within Core 1 in the Candace Member of Cunaloo-1 and lies within the basal Tigrisporites playfordii palynozone. The First Appearance Datum (FAD) of the conodont C. timorensis has been proposed as an index for the worldwide recognition of the Olenekian-Anisian Boundary (OAB), although the species occurs first with upper Spathian Haugi Zone ammonoids. Nevertheless, it is a good approximation of the OAB, and therefore places the earliest occurrence of the T. playfordii palynozone in Western Australia at around the end of the Spathian-earliest Anisian (Aegean), about 247.2 Ma. A younger limestone, the Sholl Limestone Member of the Locker Shale facies, is recognised only from the Carnarvon Basin. This carbonate lies within the T. playfordii zone, but conodonts recovered from the unit are not age diagnostic. The Sholl Limestone is missing in several wells below sandstones of younger Triassic age, and in one case may be faulted out (e.g. Hampton-1). Recognition of these Early Triassic limestones allows a better stratigraphic understanding of those regions from the marine realm in the northern Perth and Carnarvon basins.
{"title":"Significance of Early Triassic conodont zones from Western Australia","authors":"J. Gorter, M. Orchard, R. Nicoll, D. Ferdinando","doi":"10.1080/22020586.2019.12073117","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073117","url":null,"abstract":"Summary The Cunaloo Limestone Member of the Locker Shale (Kockatea Shale facies) from the Carnarvon Basin contains a distinctive conodont zone also seen in the informally named ‘Limestone Marker’ in the lower Kockatea Shale of the northern Perth Basin. The boundary between the Induan (Dienerian) and the Olenekian (Smithian) is selected at the base of the incoming of the conodont Novispathodus waageni eowaageni in this core and provides an important biostratigraphic correlation point between the two basins. The Cunaloo Limestone Member contains Novispathodus dieneri-Neospathodus waageni- Scythogondolella milleri conodont zone species and this correlates with upper Bed 32 at the type section of the Permian-Triassic transition at the Meishan Permian-Triassic stratotype section D in China, dated by zircon U/Pb as about 251.5 Ma. This suggests an absolute age correlation of the lower part of the Kraeuselisporites saeptatus palynological zone in the southern Carnarvon Basin. This conodont zone is Smithian in age. A thin, apparently discontinuous, previously un-named limestone appears above the Cunaloo Limestone Member and is within the K. saeptatus zone. This carbonate unit becomes more prominent towards the north and contains conodonts, mostly fragmentary, of Smithian age. It is here named the Lawley Limestone Member. The Chiosella timorensis conodont zone occurs within Core 1 in the Candace Member of Cunaloo-1 and lies within the basal Tigrisporites playfordii palynozone. The First Appearance Datum (FAD) of the conodont C. timorensis has been proposed as an index for the worldwide recognition of the Olenekian-Anisian Boundary (OAB), although the species occurs first with upper Spathian Haugi Zone ammonoids. Nevertheless, it is a good approximation of the OAB, and therefore places the earliest occurrence of the T. playfordii palynozone in Western Australia at around the end of the Spathian-earliest Anisian (Aegean), about 247.2 Ma. A younger limestone, the Sholl Limestone Member of the Locker Shale facies, is recognised only from the Carnarvon Basin. This carbonate lies within the T. playfordii zone, but conodonts recovered from the unit are not age diagnostic. The Sholl Limestone is missing in several wells below sandstones of younger Triassic age, and in one case may be faulted out (e.g. Hampton-1). Recognition of these Early Triassic limestones allows a better stratigraphic understanding of those regions from the marine realm in the northern Perth and Carnarvon basins.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"37 1","pages":"1 - 4"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76586706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073137
S. Özaydın, K. Selway
Summary The magnetotelluric method is the most sensitive geophysical tool in detecting the hydration state of the mantle. Therefore, improved interpretations of electrical conductivity distribution within the Earth is a key measure that has to be taken in order to have a better grasp on lithopsheric-scale geodynamic concepts and the nature of mineralising agents. Progress towards this goal requires detailed comparisons between MT models and xenolith data in order to understand the controls on mantle electrical conductivity. In this study, new magnetotelluric models from southern Africa were utilised to constrain the composition and hydrogen content by comparing forward models based on the experimental studies made on mantle minerals at high P-T conditions. Many relations between the experimental parameters and information from xenolith data were tested to improve the capabilities of magnetotellurics as an exploration tool in the lithospheric mantle of cratons.
{"title":"Utilising 3-D magnetotelluric models of southern African mantle to constrain hydrogen content and compositional variations.","authors":"S. Özaydın, K. Selway","doi":"10.1080/22020586.2019.12073137","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073137","url":null,"abstract":"Summary The magnetotelluric method is the most sensitive geophysical tool in detecting the hydration state of the mantle. Therefore, improved interpretations of electrical conductivity distribution within the Earth is a key measure that has to be taken in order to have a better grasp on lithopsheric-scale geodynamic concepts and the nature of mineralising agents. Progress towards this goal requires detailed comparisons between MT models and xenolith data in order to understand the controls on mantle electrical conductivity. In this study, new magnetotelluric models from southern Africa were utilised to constrain the composition and hydrogen content by comparing forward models based on the experimental studies made on mantle minerals at high P-T conditions. Many relations between the experimental parameters and information from xenolith data were tested to improve the capabilities of magnetotellurics as an exploration tool in the lithospheric mantle of cratons.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"34 1","pages":"1 - 3"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82444564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12072960
Daniel Eremenco, R. Mortimer, Edna Mead
Summary The Carlow Castle deposit is located 40 kilometres east of Karratha, Western Australia. The deposit is shear hosted in the Ruth Well Mafic Formation, part of the Roebourne Group. It is interspersed with metagabbro intrusions and brecciated chert cataclastites. Carlow Castle contains Au, Cu and Co mineralisation. Data from a Sub-Audio Magnetic (SAM) survey was acquired in both galvanic and inductive configurations to map structural responses over known mineralisation. On-time Magnetometric Conductivity (MMC), Total Magnetic Intensity (TMI) and Off-time Galvanic Source Electromagnetic (GSEM) data were extracted from the galvanic dipole configuration. Off-time Inductive Source Electromagnetic (ISEM) data were extracted from the loop source configuration. MMC data were combined, modelled and interpreted to rank structural targets around existing Au and Cu mineralisation. This was used in conjunction with Co soil geochemistry as a vectoring tool for further cobalt mineralisation. The MMC data was successful in increasing level of detail over the project. ISEM and GSEM were also compared with previously highlighted VTEM anomalism. Five high and seven medium priority targets were identified for follow up with further drilling.
Carlow Castle矿床位于西澳大利亚州Karratha以东40公里处。该矿床位于Roebourne Group的Ruth Well Mafic组中。分布有变长岩侵入体和角砾岩碎裂岩。卡洛城堡含金、铜和钴矿化。从亚音频磁(SAM)调查中获得了电流和感应配置的数据，以绘制已知矿化的结构响应图。实时磁导率(MMC)、总磁强度(TMI)和非实时电源电磁(GSEM)数据从电偶极子结构中提取。断开时感应源电磁(ISEM)数据从环路源配置中提取。对MMC数据进行组合、建模和解释，以对现有Au和Cu矿化周围的结构目标进行排序。这与Co土壤地球化学结合使用，作为进一步钴矿化的矢量工具。MMC数据成功地提高了项目的详细程度。ISEM和GSEM还与先前突出的VTEM异常进行了比较。确定了5个高优先目标和7个中等优先目标，以便进一步钻探。
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