Pub Date : 2019-12-01DOI: 10.1080/22020586.2019.12073037
David C. M. Fox, S. Spinks, M. Pearce, M. Vaillant, R. Thorne, M. Barham, M. Aspandiar
Summary Carlow Castle is a Cu-Co-Au deposit situated within the western Pilbara Craton of Western Australia. Whilst Carlow Castle is the oldest discovered copper deposit in the Pilbara region, having been initially discovered in 1882, no detailed study of the ore mineralisation has ever been undertaken. After being long abandoned, a recent drilling campaign through 2018 uncovered an economically significant and geologically complex system of Cu-Co-Au mineralisation with a current resource estimate for Carlow Castle of 7.7Mt @ 1.06g/t Au, 0.51% Cu, and 0.08% Co, making it one of Australia’s most significant Cu-Co-Au deposits. This mineralisation was analysed using a variety of geochemical and mineralogical techniques in order to provide the first constraint on its genesis. This analysis suggests that Carlow Castle is a hydrothermal Cu-Co-Au deposit, with mineralisation hosted in sulphide-rich quartz veins throughout a pervasively chloritised shear zone in an Archaean mafic volcano-sedimentary sequence. Within these ore veins, the sulphide mineralogy is dominated by pyrite (FeS2), chalcopyrite (CuFeS2), chalcocite (Cu2S), and cobaltite (CoAsS). Here we present the findings of the first detailed study on the nature of the Cu-Co-Au mineralisation at Carlow Castle and propose an orogenic model for the genesis of this unique deposit. It is proposed that the orogenic event that gave rise to Carlow Castle is related to the initial assembly of the Pilbara Craton during the Archean.
卡洛城堡是位于西澳大利亚皮尔巴拉克拉通西部的一个铜钴金矿床。虽然卡洛城堡是皮尔巴拉地区发现的最古老的铜矿床，最初发现于1882年，但从未对矿石成矿进行过详细的研究。在被遗弃了很长一段时间之后，最近的一次钻探活动发现了一个具有经济意义和地质复杂的Cu-Co-Au矿化系统，目前Carlow Castle的资源估计为770万吨，Au 1.06g/t, Cu 0.51%， Co 0.08%，使其成为澳大利亚最重要的Cu-Co-Au矿床之一。利用各种地球化学和矿物学技术对这种矿化进行了分析，以便对其成因提供第一个约束。这一分析表明，Carlow Castle是一个热液型Cu-Co-Au矿床，其矿化分布在太古宙基性火山-沉积序列中遍布绿泥化剪切带的富含硫化物的石英脉中。在这些矿脉中，硫化物矿物学以黄铁矿(FeS2)、黄铜矿(CuFeS2)、辉铜矿(Cu2S)和钴矿(CoAsS)为主。在这里，我们提出了对Carlow Castle的Cu-Co-Au矿化性质的首次详细研究结果，并提出了这个独特矿床成因的造山模型。认为卡洛城堡的形成与太古宙皮尔巴拉克拉通的初始组合有关。
{"title":"The genesis of Carlow Castle: A unique Australian orogenic Cu-Co-Au deposit in the Archean Pilbara Craton","authors":"David C. M. Fox, S. Spinks, M. Pearce, M. Vaillant, R. Thorne, M. Barham, M. Aspandiar","doi":"10.1080/22020586.2019.12073037","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073037","url":null,"abstract":"Summary Carlow Castle is a Cu-Co-Au deposit situated within the western Pilbara Craton of Western Australia. Whilst Carlow Castle is the oldest discovered copper deposit in the Pilbara region, having been initially discovered in 1882, no detailed study of the ore mineralisation has ever been undertaken. After being long abandoned, a recent drilling campaign through 2018 uncovered an economically significant and geologically complex system of Cu-Co-Au mineralisation with a current resource estimate for Carlow Castle of 7.7Mt @ 1.06g/t Au, 0.51% Cu, and 0.08% Co, making it one of Australia’s most significant Cu-Co-Au deposits. This mineralisation was analysed using a variety of geochemical and mineralogical techniques in order to provide the first constraint on its genesis. This analysis suggests that Carlow Castle is a hydrothermal Cu-Co-Au deposit, with mineralisation hosted in sulphide-rich quartz veins throughout a pervasively chloritised shear zone in an Archaean mafic volcano-sedimentary sequence. Within these ore veins, the sulphide mineralogy is dominated by pyrite (FeS2), chalcopyrite (CuFeS2), chalcocite (Cu2S), and cobaltite (CoAsS). Here we present the findings of the first detailed study on the nature of the Cu-Co-Au mineralisation at Carlow Castle and propose an orogenic model for the genesis of this unique deposit. It is proposed that the orogenic event that gave rise to Carlow Castle is related to the initial assembly of the Pilbara Craton during the Archean.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"35 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":"82524355","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: 10.1080/22020586.2019.12073078
A. Davis, Juerg Hauser
Summary Borehole induction logs, together with lithology records, are valuable for inferring geological and geophysical features in the subsurface. They offer insight in the relationship between geology and geophysics, and are an important source of information for determining the success of a planned airborne electromagnetic (AEM) survey for recovering features of interest. Often, bore logs are used as the ‘ground-truth for an AEM system, and are employed for system selection pre-survey and ‘validation’ post-survey. We discuss the use of electromagnetic borehole logs for calibrating and validating AEM survey results in a sensible way: by comparing the measurements at the resolution power of the AEM system itself.
{"title":"Making EM systems and bore logs speak the same language","authors":"A. Davis, Juerg Hauser","doi":"10.1080/22020586.2019.12073078","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073078","url":null,"abstract":"Summary Borehole induction logs, together with lithology records, are valuable for inferring geological and geophysical features in the subsurface. They offer insight in the relationship between geology and geophysics, and are an important source of information for determining the success of a planned airborne electromagnetic (AEM) survey for recovering features of interest. Often, bore logs are used as the ‘ground-truth for an AEM system, and are employed for system selection pre-survey and ‘validation’ post-survey. We discuss the use of electromagnetic borehole logs for calibrating and validating AEM survey results in a sensible way: by comparing the measurements at the resolution power of the AEM system itself.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"61 5 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":"86385215","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: 10.1080/22020586.2019.12073188
M. Urosevic, S. Ziramov, R. Pevzner, K. Tertyshnikov, S. Yavuz, A. Egorov, A. Bóna, V. Shulakova, D. V. Gent
Summary Within the South West Hub Project we conducted a comprehensive integrated study to map the fault and fracture network surrounding the Harvey 3 well to obtain an understanding of their propensity to act as conduits for the injected CO2. Here we report only on the seismic investigations that had two objectives: The first one was to provide precise structural model for subsequent geomechanical studies. The second objective was design more environmentally friendly acquisition and overcome the land access issues. This is of a crucial importance at Harvey where farmers are opposed to any land disturbance that can affect their activities. We thus designed a comprehensive survey that addressed both objectives. The survey included a conventional component consisting of simultaneous recorded 3D surface and 3D VSP data sets and an alternative component that recorded multi-offset VSP survey along the public roads. 3D imaging results using diverse VSP geometries were compared to 3D surface data. Both products, borehole and surface 3D images, were used for the structural analysis. Multi-offset VSP survey on the other had was reanalysed using different decimation strategies for the purpose of optimising CO2 sequestration monitoring strategy. The main outcome of this analysis was the imaging concept that is limited only to public roads which bypasses access restriction and improves chance for better public acceptance in the future.
在South West Hub项目中，我们进行了一项全面的综合研究，绘制了Harvey 3井周围的断层和裂缝网络，以了解它们作为注入二氧化碳管道的倾向。在这里，我们只报道有两个目标的地震调查:第一个是为后续的地质力学研究提供精确的结构模型。第二个目标是设计更环保的收购并克服土地获取问题。这对哈维来说至关重要，因为农民反对任何可能影响他们活动的土地干扰。因此，我们设计了一项全面的调查，以解决这两个目标。该调查包括一个传统组件，包括同时记录的3D表面和3D VSP数据集，以及一个替代组件，记录沿公共道路的多偏移VSP调查。使用不同VSP几何形状的三维成像结果与三维表面数据进行了比较。这两种产品，井眼和表面的3D图像，都被用于结构分析。另一方面，为了优化CO2固存监测策略，使用不同的抽取策略对多偏移VSP调查进行了重新分析。这项分析的主要结果是成像概念，它仅限于公共道路，绕过了通行限制，提高了未来公众接受的机会。
{"title":"Subsurface characterisation for future CCS applications using uncommon 3D surface and borehole seismic survey geometries at Harvey, Western Australia","authors":"M. Urosevic, S. Ziramov, R. Pevzner, K. Tertyshnikov, S. Yavuz, A. Egorov, A. Bóna, V. Shulakova, D. V. Gent","doi":"10.1080/22020586.2019.12073188","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073188","url":null,"abstract":"Summary Within the South West Hub Project we conducted a comprehensive integrated study to map the fault and fracture network surrounding the Harvey 3 well to obtain an understanding of their propensity to act as conduits for the injected CO2. Here we report only on the seismic investigations that had two objectives: The first one was to provide precise structural model for subsequent geomechanical studies. The second objective was design more environmentally friendly acquisition and overcome the land access issues. This is of a crucial importance at Harvey where farmers are opposed to any land disturbance that can affect their activities. We thus designed a comprehensive survey that addressed both objectives. The survey included a conventional component consisting of simultaneous recorded 3D surface and 3D VSP data sets and an alternative component that recorded multi-offset VSP survey along the public roads. 3D imaging results using diverse VSP geometries were compared to 3D surface data. Both products, borehole and surface 3D images, were used for the structural analysis. Multi-offset VSP survey on the other had was reanalysed using different decimation strategies for the purpose of optimising CO2 sequestration monitoring strategy. The main outcome of this analysis was the imaging concept that is limited only to public roads which bypasses access restriction and improves chance for better public acceptance in the future.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"27 1","pages":"1 - 5"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82839160","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: 10.1080/22020586.2019.12072950
Kristofer Davis
Summary The application of a growing body style of inversion within the program VPmg is presented. The body begins by a seed and grows until there are no eligible neighbours or the data misfit criterion is fit. In this case, the assumptions of source location and physical property are specifically given by drillhole intersects with the body. This style of inversion is useful for reinverting data after drilling in order to produce a more realistic model. The program VPmg allows for density and magnetic susceptibly to be recovered through physical property domains. The algorithm is shown to be promising through two examples: one with density contrast and one with magnetic susceptibility. In summary, the application is another style of inversion that is added to the current hands-on approach to inversion that is performed through VPmg.
{"title":"Application of growing-body potential-field inversion from drillholes","authors":"Kristofer Davis","doi":"10.1080/22020586.2019.12072950","DOIUrl":"https://doi.org/10.1080/22020586.2019.12072950","url":null,"abstract":"Summary The application of a growing body style of inversion within the program VPmg is presented. The body begins by a seed and grows until there are no eligible neighbours or the data misfit criterion is fit. In this case, the assumptions of source location and physical property are specifically given by drillhole intersects with the body. This style of inversion is useful for reinverting data after drilling in order to produce a more realistic model. The program VPmg allows for density and magnetic susceptibly to be recovered through physical property domains. The algorithm is shown to be promising through two examples: one with density contrast and one with magnetic susceptibility. In summary, the application is another style of inversion that is added to the current hands-on approach to inversion that is performed through VPmg.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"186 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":"91528913","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: 10.1080/22020586.2019.12073098
K. Hill, J. Cunneen, R. Farrington
Summary A regional, high-quality seismic traverse from the coast to oceanic crust across the Bight Basin has been assembled and interpreted in detail, then balanced, restored, decompacted and replaced at paleo-water depths. The Late Cretaceous Ceduna Delta developed above a Late Jurassic-Early Cretaceous rift basin in three stages punctuated by significant pulses of uplift and erosion across areas >100 km wide and with up to 1 km of erosion. The Cenomanian White Pointer delta prograded into deepening water and hence underwent gravitational collapse. This was terminated in the Santonian when the Antarctic margin was pulled out from below, thus supplying heat to a remnant thicker outer margin crust causing doming and erosion. Importantly, this established the saucer-shaped geometry of the Ceduna Delta that persisted throughout its development, so that any hydrocarbons generated in the southern half of the basin would have migrated towards this outer margin high. The Tiger Formation was deposited in shallow water in a full rift basin prior to breakup which was followed by regional thermal subsidence. The Hammerhead delta developed on the newly formed passive margin, but was terminated by another pulse of uplift and erosion, perhaps associated with a Paleogene change in plate motion at the end of the Cretaceous. Finite element modelling of this proposed tectonic evolution will test its validity and predict hydrocarbon generation and migration through time.
{"title":"The Bight Basin, evolution and prospectivity II; seismic, structure and balanced sections","authors":"K. Hill, J. Cunneen, R. Farrington","doi":"10.1080/22020586.2019.12073098","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073098","url":null,"abstract":"Summary A regional, high-quality seismic traverse from the coast to oceanic crust across the Bight Basin has been assembled and interpreted in detail, then balanced, restored, decompacted and replaced at paleo-water depths. The Late Cretaceous Ceduna Delta developed above a Late Jurassic-Early Cretaceous rift basin in three stages punctuated by significant pulses of uplift and erosion across areas >100 km wide and with up to 1 km of erosion. The Cenomanian White Pointer delta prograded into deepening water and hence underwent gravitational collapse. This was terminated in the Santonian when the Antarctic margin was pulled out from below, thus supplying heat to a remnant thicker outer margin crust causing doming and erosion. Importantly, this established the saucer-shaped geometry of the Ceduna Delta that persisted throughout its development, so that any hydrocarbons generated in the southern half of the basin would have migrated towards this outer margin high. The Tiger Formation was deposited in shallow water in a full rift basin prior to breakup which was followed by regional thermal subsidence. The Hammerhead delta developed on the newly formed passive margin, but was terminated by another pulse of uplift and erosion, perhaps associated with a Paleogene change in plate motion at the end of the Cretaceous. Finite element modelling of this proposed tectonic evolution will test its validity and predict hydrocarbon generation and migration through time.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"77 1","pages":"1 - 5"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90100062","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: 10.1080/22020586.2019.12073025
D. Allen
Summary Vehicle towed transient TEM systems have opened up possibilities of comprehensive mapping of groundwater resources at farm scale. At this scale airborne TEM usually has too much setup cost and conventional TEM conducted on foot is usually too laborious and rarely economically viable. Interpretation of data requires understanding of diverse geology, from alluvial geomorphology, volcanogenic deposition, weathering and erosion processes and the often complex combination of these. Further, impacts on the data by fences, buried cables and modelling imperfections must be separated from geological impact. Typically, it is the detail of the survey that renders it interpretable rather than system quality alone.
{"title":"Groundwater applications of towed TEM in diverse geology at farm scale","authors":"D. Allen","doi":"10.1080/22020586.2019.12073025","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073025","url":null,"abstract":"Summary Vehicle towed transient TEM systems have opened up possibilities of comprehensive mapping of groundwater resources at farm scale. At this scale airborne TEM usually has too much setup cost and conventional TEM conducted on foot is usually too laborious and rarely economically viable. Interpretation of data requires understanding of diverse geology, from alluvial geomorphology, volcanogenic deposition, weathering and erosion processes and the often complex combination of these. Further, impacts on the data by fences, buried cables and modelling imperfections must be separated from geological impact. Typically, it is the detail of the survey that renders it interpretable rather than system quality alone.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"100 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":"80591850","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: 10.1080/22020586.2019.12073212
S. Hazarika, A. Singh, Bhawanisingh G. Desai
Summary The present study is aimed at understanding the petrophysical properties of shale such as porosity, permeability, capillary pressure and mineralogy of fine-grained sediment. It is a common perception that tight shale formation has good source rock properties, also with current energy scenario unconventional play are being sought for shale gas prospects. In context to this the Upper Jurassic Jhuran formation which is primarily a Shale dominated facies has been investigated for unconventional aspect in the Kachchh Basin. Jhuran formation is supposedly the source rock for the Kachchh Basin. Previous studies have indicated the hydrocarbon generation potential in the offshore part of the basin which is of thermogenic nature. Therefore a number of experiments to ascertain the flow storage and migration properties are carried out which include Routine Core Analysis such as Helium Porosimetry, Liquid Permeability as well as Special Core Analysis like Spontaneous and Forced Imbibition. The higher Quartz content preserve the porosity while compaction which is validated in porosity and Permeability measurements. The Capillary pressure curve gives an indication of the randomness and inter connectivity of the sparse void spaces in the shale. Conductometric titration was used to determine Cation Exchange capacity which helps in understanding the swelling characteristics under different drilling scenario. Ultimately, critical details regarding unconvectional reservoir quality can aid in the design of better and more efficient for shale gas recovery methods.
{"title":"Characterization and identification of petrophysical parameters of Shales from Jhuran Formation, Kachchh Basin, India","authors":"S. Hazarika, A. Singh, Bhawanisingh G. Desai","doi":"10.1080/22020586.2019.12073212","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073212","url":null,"abstract":"Summary The present study is aimed at understanding the petrophysical properties of shale such as porosity, permeability, capillary pressure and mineralogy of fine-grained sediment. It is a common perception that tight shale formation has good source rock properties, also with current energy scenario unconventional play are being sought for shale gas prospects. In context to this the Upper Jurassic Jhuran formation which is primarily a Shale dominated facies has been investigated for unconventional aspect in the Kachchh Basin. Jhuran formation is supposedly the source rock for the Kachchh Basin. Previous studies have indicated the hydrocarbon generation potential in the offshore part of the basin which is of thermogenic nature. Therefore a number of experiments to ascertain the flow storage and migration properties are carried out which include Routine Core Analysis such as Helium Porosimetry, Liquid Permeability as well as Special Core Analysis like Spontaneous and Forced Imbibition. The higher Quartz content preserve the porosity while compaction which is validated in porosity and Permeability measurements. The Capillary pressure curve gives an indication of the randomness and inter connectivity of the sparse void spaces in the shale. Conductometric titration was used to determine Cation Exchange capacity which helps in understanding the swelling characteristics under different drilling scenario. Ultimately, critical details regarding unconvectional reservoir quality can aid in the design of better and more efficient for shale gas recovery methods.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"16 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":"91134136","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: 10.1080/22020586.2019.12073055
J. Meyers, Sharna Riley, W. Groome
Summary Detailed airborne electromagnetic (VTEM), gravity and passive seismic HVSR surveying, followed up by RC and diamond drilling, has identified an isolated circular and geologically young meteorite impact crater filled with sediments and located next to the town of Coolgardie in Western Australia. It was discovered in 2017 (Meyers, 2017), is 800 m in diameter and estimated to be >140 m deep based on passive seismic results, because only angled drilling was carried out for gold exploration along the western side of the crater. The crater has been filled with impact debris and sedimentary deposits to form a flat modern topographic feature. The pre-impact bedrock is Archean greenstone, which hosts numerous gold occurrences and mines surrounding the crater. The crater is filled with a polymict impact breccia of mixed greenstone rocks from below and surrounds near its base. A thin (<2 m) tuffaceous looking ejecta layer occurs at the boundary between the impact breccia and underlying in situ brecciated greenstone bedrock (high Mg basalt and ultramafic lava). This transition zone is also imaged as two “bedrock” layers in passive seismic HVSR cross-sections. The impact breccia is overlain by a very thick deposit of anoxic peat and carbonised wood fragments containing framboidal pyrite, as well as slump blocks of greenstone rocks, starting from over 120 m deep to a depth of 14 m from surface, where this organic layer is capped by a fine clay deposit, which was likely transported into the crater after its raised rim was breached by erosion. The crater and its fill deposits cannot explain the entire circular gravity anomaly low of -5mGal, and the brecciated in situ greenstone bedrock around and below the crater is modelled to contribute to the gravity anomaly low. It is estimated that the meteorite projectile was about 40 m in diameter, came from an easterly trajectory, and impacted Coolgardie between the Miocene to Pleistocene, with age dating and Ir analysis of the impact layer and overlying plant material soon to be carried out. A high-resolution ground magnetic survey using 10 m line spacing was carried out to try and detect large iron meteorite fragments, but only a weak and diffuse anomaly pattern occurs at the crater centre, indicating that the meteorite was highly fragmented on impact and/or later demagnetised by weathering. A vertical diamond drillhole down the centre of the crater is required to properly study this relatively young impact structure and analyse the preserved plant material filling the crater over a vertical column of 100 m or more, continuously recording local environmental changes over a considerable time period.
{"title":"Geophysical expression of the Meyers Crater, a new meteorite impact crater discovered in the Coolgardie Goldfield of Western Australia","authors":"J. Meyers, Sharna Riley, W. Groome","doi":"10.1080/22020586.2019.12073055","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073055","url":null,"abstract":"Summary Detailed airborne electromagnetic (VTEM), gravity and passive seismic HVSR surveying, followed up by RC and diamond drilling, has identified an isolated circular and geologically young meteorite impact crater filled with sediments and located next to the town of Coolgardie in Western Australia. It was discovered in 2017 (Meyers, 2017), is 800 m in diameter and estimated to be >140 m deep based on passive seismic results, because only angled drilling was carried out for gold exploration along the western side of the crater. The crater has been filled with impact debris and sedimentary deposits to form a flat modern topographic feature. The pre-impact bedrock is Archean greenstone, which hosts numerous gold occurrences and mines surrounding the crater. The crater is filled with a polymict impact breccia of mixed greenstone rocks from below and surrounds near its base. A thin (<2 m) tuffaceous looking ejecta layer occurs at the boundary between the impact breccia and underlying in situ brecciated greenstone bedrock (high Mg basalt and ultramafic lava). This transition zone is also imaged as two “bedrock” layers in passive seismic HVSR cross-sections. The impact breccia is overlain by a very thick deposit of anoxic peat and carbonised wood fragments containing framboidal pyrite, as well as slump blocks of greenstone rocks, starting from over 120 m deep to a depth of 14 m from surface, where this organic layer is capped by a fine clay deposit, which was likely transported into the crater after its raised rim was breached by erosion. The crater and its fill deposits cannot explain the entire circular gravity anomaly low of -5mGal, and the brecciated in situ greenstone bedrock around and below the crater is modelled to contribute to the gravity anomaly low. It is estimated that the meteorite projectile was about 40 m in diameter, came from an easterly trajectory, and impacted Coolgardie between the Miocene to Pleistocene, with age dating and Ir analysis of the impact layer and overlying plant material soon to be carried out. A high-resolution ground magnetic survey using 10 m line spacing was carried out to try and detect large iron meteorite fragments, but only a weak and diffuse anomaly pattern occurs at the crater centre, indicating that the meteorite was highly fragmented on impact and/or later demagnetised by weathering. A vertical diamond drillhole down the centre of the crater is required to properly study this relatively young impact structure and analyse the preserved plant material filling the crater over a vertical column of 100 m or more, continuously recording local environmental changes over a considerable time period.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"33 1","pages":"1 - 5"},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89745284","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: 10.1080/22020586.2019.12073243
Qingtian Lü, Guixiang Meng, Jiayong Yan, Jinhua Zhao, Xuejing Gong
Summary Financed by the SinoProbe, a national collaborative multidisciplinary Earth science research project in China, the authors has conducted multi-scale and integrated geophysical exploration across the middle and lower reaches of Yangtze Metallogenic Belt (YMB) in east China. The data range in scale from terrane, district to camp or mine. The methods included broad band seismic, reflection seismic profiling, magnetotelluric sounding and gravity and magnetic modelling. The results provide first-order insights into the physical and structural properties of the lithosphere and upper mantle beneath the YMB, and thus provide in depth understanding of the deep processes that control the initiation and evolution of intra-continental mineral system.
{"title":"The lithospheric structure and deep processes of the Mesozoic mineral systems in east China: constrained from integrated geophysical data","authors":"Qingtian Lü, Guixiang Meng, Jiayong Yan, Jinhua Zhao, Xuejing Gong","doi":"10.1080/22020586.2019.12073243","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073243","url":null,"abstract":"Summary Financed by the SinoProbe, a national collaborative multidisciplinary Earth science research project in China, the authors has conducted multi-scale and integrated geophysical exploration across the middle and lower reaches of Yangtze Metallogenic Belt (YMB) in east China. The data range in scale from terrane, district to camp or mine. The methods included broad band seismic, reflection seismic profiling, magnetotelluric sounding and gravity and magnetic modelling. The results provide first-order insights into the physical and structural properties of the lithosphere and upper mantle beneath the YMB, and thus provide in depth understanding of the deep processes that control the initiation and evolution of intra-continental mineral system.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"14 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":"90123769","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: 10.1080/22020586.2019.12073214
A. King
Summary Microseismics – the detection and characterisation of mining-induced fracture events in the rockmass – is widely used to improve geotechnical understanding of the rockmass response to mining, and for hazard assessment of rockbursts and roof falls. These uses of microseismics require that the seismic events be accurately located, which can only be done using an accurate velocity model. In sedimentary environments, seismic velocity is typically anisotropic, usually being somewhat faster in a horizontal direction than in the vertical direction. However, anisotropy is seldom taken into account when processing microseismic data, resulting in locations of seismic events which can be significantly in error. This paper presents a technique for inverting a set of calibration shots with known location, along with a set of mining-induced seismic events, for an anisotropic velocity model. An example of the differences in event location is shown, illustrating the potential geotechnical significance.
{"title":"The effects of seismic anisotropy on mining seismology","authors":"A. King","doi":"10.1080/22020586.2019.12073214","DOIUrl":"https://doi.org/10.1080/22020586.2019.12073214","url":null,"abstract":"Summary Microseismics – the detection and characterisation of mining-induced fracture events in the rockmass – is widely used to improve geotechnical understanding of the rockmass response to mining, and for hazard assessment of rockbursts and roof falls. These uses of microseismics require that the seismic events be accurately located, which can only be done using an accurate velocity model. In sedimentary environments, seismic velocity is typically anisotropic, usually being somewhat faster in a horizontal direction than in the vertical direction. However, anisotropy is seldom taken into account when processing microseismic data, resulting in locations of seismic events which can be significantly in error. This paper presents a technique for inverting a set of calibration shots with known location, along with a set of mining-induced seismic events, for an anisotropic velocity model. An example of the differences in event location is shown, illustrating the potential geotechnical significance.","PeriodicalId":8502,"journal":{"name":"ASEG Extended Abstracts","volume":"13 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":"75641499","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}
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