Pub Date : 2020-06-23DOI: 10.1080/25726838.2020.1783740
Rhys S. Davies, R. Schodde, J. Sykes, D. Groves, A. Trench, M. Dentith
ABSTRACT The United States Geological Survey (USGS) Three-part Undiscovered Mineral Resource Assessment provides a framework for estimating undiscovered mineral endowment. Previous studies that applied the Three-part Assessment to estimate the undiscovered orogenic gold endowment of the Sandstone Greenstone Belt, Western Australia, have relied upon dated or expert-derived grade-tonnage models. Here, several assessments are conducted using local grade-tonnage models, comprising known orogenic gold deposits within the entire Yilgarn Block and several individual terranes with contrasting lithosphere- to terrane-scale characteristics. These models are generated through comprehensive review of historical exploration, resource and production data. Based on these models, the Sandstone Greenstone Belt is estimated to contain significant undiscovered gold mineralisation, with a median total endowment of between 166 and 298 t gold, and mean of 167–319 t gold. Although these updated grade-tonnage models provide an approximately 80 per cent variation in predicted gold endowment, it is still evident that the belt remains an under-explored region within the Yilgarn Block, Western Australia.
{"title":"Predicting grade-tonnage characteristics of undiscovered mineralisation: application of the USGS Three-part Undiscovered Mineral Resource Assessment to the Sandstone Greenstone Belt of the Yilgarn Block, Western Australia","authors":"Rhys S. Davies, R. Schodde, J. Sykes, D. Groves, A. Trench, M. Dentith","doi":"10.1080/25726838.2020.1783740","DOIUrl":"https://doi.org/10.1080/25726838.2020.1783740","url":null,"abstract":"ABSTRACT The United States Geological Survey (USGS) Three-part Undiscovered Mineral Resource Assessment provides a framework for estimating undiscovered mineral endowment. Previous studies that applied the Three-part Assessment to estimate the undiscovered orogenic gold endowment of the Sandstone Greenstone Belt, Western Australia, have relied upon dated or expert-derived grade-tonnage models. Here, several assessments are conducted using local grade-tonnage models, comprising known orogenic gold deposits within the entire Yilgarn Block and several individual terranes with contrasting lithosphere- to terrane-scale characteristics. These models are generated through comprehensive review of historical exploration, resource and production data. Based on these models, the Sandstone Greenstone Belt is estimated to contain significant undiscovered gold mineralisation, with a median total endowment of between 166 and 298 t gold, and mean of 167–319 t gold. Although these updated grade-tonnage models provide an approximately 80 per cent variation in predicted gold endowment, it is still evident that the belt remains an under-explored region within the Yilgarn Block, Western Australia.","PeriodicalId":43298,"journal":{"name":"Applied Earth Science-Transactions of the Institutions of Mining and Metallurgy","volume":"129 1","pages":"91 - 110"},"PeriodicalIF":1.0,"publicationDate":"2020-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/25726838.2020.1783740","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48043193","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 : 2020-05-26DOI: 10.1080/25726838.2020.1765538
A. Cabral, Matheus de Oliveira, Thaís Keuffer Mendonça
ABSTRACT Gibbsite, typically a clay-sized mineral in lateritic profiles, occurs as crystals between 50 and 150 µm across in druse-like cavities that characterise veins hosted in lateritised Cenozoic sediments, exposed along a road cut in the Quadrilátero Ferrífero of Minas Gerais, Brazil. Both the veins and the host rock, a red diamictite, contain gibbsite, but the drusy gibbsite in the former is remarkably larger than the matrix gibbsite in the latter. It is suggested that the coarser gibbsite is a low-temperature hydrothermal mineral. The coarse grain size of gibbsite and its occurrence in veins comprise important criteria to recognise hydrothermal overprint of low temperature on lateritic profiles.
{"title":"Gibbsite as low-temperature hydrothermal overprint on lateritised Cenozoic sediments, Quadrilátero Ferrífero of Minas Gerais, Brazil","authors":"A. Cabral, Matheus de Oliveira, Thaís Keuffer Mendonça","doi":"10.1080/25726838.2020.1765538","DOIUrl":"https://doi.org/10.1080/25726838.2020.1765538","url":null,"abstract":"ABSTRACT Gibbsite, typically a clay-sized mineral in lateritic profiles, occurs as crystals between 50 and 150 µm across in druse-like cavities that characterise veins hosted in lateritised Cenozoic sediments, exposed along a road cut in the Quadrilátero Ferrífero of Minas Gerais, Brazil. Both the veins and the host rock, a red diamictite, contain gibbsite, but the drusy gibbsite in the former is remarkably larger than the matrix gibbsite in the latter. It is suggested that the coarser gibbsite is a low-temperature hydrothermal mineral. The coarse grain size of gibbsite and its occurrence in veins comprise important criteria to recognise hydrothermal overprint of low temperature on lateritic profiles.","PeriodicalId":43298,"journal":{"name":"Applied Earth Science-Transactions of the Institutions of Mining and Metallurgy","volume":"129 1","pages":"154 - 160"},"PeriodicalIF":1.0,"publicationDate":"2020-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/25726838.2020.1765538","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42143368","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 : 2020-05-21DOI: 10.1080/25726838.2020.1767473
Saâd Soulaimani, S. Chakiri, A. Manar, Ayoub Soulaimani, A. Miftah, M. Boujamaoui
ABSTRACT Geophysical data processing further constrained inversion is evolving progressively prevalent in geoscience domains for three-dimensional modelling and resources evaluation. The process is based on the magnetic and gravity data processing further constrained Cartesian cut cell inversion to discern the maximum of information about HAJJAR deposit in order to calculate its tonnage. This article exhibits data and inversion processing technique for tonnage calculation based on an important geophysical magnetic and gravity surveys of defined extent of HAJJAR region, which presents a great benefit to save time and have accurate and realistic results to a same case. Otherwise, the potential-field signatures of what are regarded to be geologically expressive features are sought within the magnetic and gravity data. The preliminary stage for tonnage calculation was residual anomaly processing and depth estimation of the orebody using spectral analysis method. However, progressing towards extracting the deposit signature, the used method leads to invest the gravity signature of the orebody in adequacy with the magnetic signature. Finally, the tonnage calculation was developed by constrained Cartesian cut cell inversion using Voxi Earth ModellingTM. Obtained results were very important, given their qualitative and quantitative accuracy, which give an added value for the governmental geological and geophysical survey.
{"title":"Gravity and magnetic data processing further constrained inversion for 3D modelling and tonnage calculation","authors":"Saâd Soulaimani, S. Chakiri, A. Manar, Ayoub Soulaimani, A. Miftah, M. Boujamaoui","doi":"10.1080/25726838.2020.1767473","DOIUrl":"https://doi.org/10.1080/25726838.2020.1767473","url":null,"abstract":"ABSTRACT Geophysical data processing further constrained inversion is evolving progressively prevalent in geoscience domains for three-dimensional modelling and resources evaluation. The process is based on the magnetic and gravity data processing further constrained Cartesian cut cell inversion to discern the maximum of information about HAJJAR deposit in order to calculate its tonnage. This article exhibits data and inversion processing technique for tonnage calculation based on an important geophysical magnetic and gravity surveys of defined extent of HAJJAR region, which presents a great benefit to save time and have accurate and realistic results to a same case. Otherwise, the potential-field signatures of what are regarded to be geologically expressive features are sought within the magnetic and gravity data. The preliminary stage for tonnage calculation was residual anomaly processing and depth estimation of the orebody using spectral analysis method. However, progressing towards extracting the deposit signature, the used method leads to invest the gravity signature of the orebody in adequacy with the magnetic signature. Finally, the tonnage calculation was developed by constrained Cartesian cut cell inversion using Voxi Earth ModellingTM. Obtained results were very important, given their qualitative and quantitative accuracy, which give an added value for the governmental geological and geophysical survey.","PeriodicalId":43298,"journal":{"name":"Applied Earth Science-Transactions of the Institutions of Mining and Metallurgy","volume":"129 1","pages":"133 - 146"},"PeriodicalIF":1.0,"publicationDate":"2020-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/25726838.2020.1767473","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44560539","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 : 2020-04-02DOI: 10.1080/25726838.2019.1607192
S. J. Walding, D. P. James, R. Dawson, R. Frutuoso
ered have been falling for decades. In addition, the demand for gold is increasing, especially where there is a growing consumer market in developing countries such as China and India. This makes it crucial to discover new gold deposits; however, the vast majority of surface deposits have been discovered, which means it is harder and more expensive to find deposits in the subsurface. Norway lies on the Fennoscandian shield, which contains an extensive wealth of minerals. This is explained by the geological evolution of this region, including the development of Precambrian supracrustals, intrusive rocks and Devonian intrusions that formed in major rift and orogenic settings. There are exploitable resources of gold in Norway, indicating that this country could be a significant supplier of gold (Eilu 2011). The quartz veins at the Bleka Mine in the Telemark region have reported grades of 35 g t Au, 45 g t Ag, 0.5% Bi and 1.5% Cu (NGU 2017). Other studies have estimated a reserve of 60,000 tonnes of ore with grades of 11 g t Au that could produce 233,000 oz of Au (Horvath 1943). These veins form the Bleka Main Vein System (BMVS) where they are hosted by the Svartdal Metagabbro, a large Proterozoic gabbroic sill complex. Another set of quartz veins, known as the Espelid vein system, is located 3 km north of the Bleka Mine; these veins are smaller, but are more numerous and may have a significant amount of gold that could be utilised. Scheelite, an important ore mineral of tungsten, was observed at Bleka and might be of economic importance, depending on its abundance (Dahlgren 2015). It is currently known that scheelite is abundant within the BMVS; however, it is unknown if it is abundant in the Espelid vein system or other quartz systems in the area as it superficially appears similar to quartz although it can be easily distinguished in darkness using short wave UV light (Søren and Tonny 1998). The project area, located northwest of the Bleka mine, contains the Svartdal Metagabbro that hosts the gold bearing quartz veins and scheelite. This gives the opportunity to explore the area for scheelite in the Espelid vein system or other gold bearing quartz veins. Geological mapping of the project area confirms the presence of quartz veins, along with their location, orientation and relationship with the Svartdal Metagabbro. A detailed petrographic and geochemical analysis of the quartz veins along with the Svartdal Metagabbro is currently being undertaken to better characterise the formation of the host rock and the quartz veins. Interpretation of data gathered from a geophysical survey of the Svartdal Metagabbro using an EM31 and magnetometer will show the location of quartz veins and their strike in the subsurface.
ered几十年来一直在下降。此外，对黄金的需求正在增加，尤其是在中国和印度等发展中国家消费市场不断增长的地方。这使得发现新的金矿床变得至关重要；然而，绝大多数地表矿床都已被发现，这意味着在地下寻找矿床更加困难和昂贵。挪威位于芬诺斯堪的地盾上，该地盾含有丰富的矿产。这可以通过该地区的地质演化来解释，包括在主要裂谷和造山环境中形成的前寒武纪表壳、侵入岩和泥盆纪侵入体的发展。挪威有可开采的黄金资源，这表明该国可能是一个重要的黄金供应国（Eilu，2011年）。Telemark地区Bleka矿的石英脉报告品位为35 g t Au、45 g t Ag、0.5%Bi和1.5%Cu（NGU 2017）。其他研究估计储量为60000吨，品位为11克/吨Au，可生产233000盎司Au（Horvath 1943）。这些矿脉形成了Bleka主脉系统（BMVS），在那里它们由Svartdal变质辉长岩（一种大型元古代辉长岩岩床复合体）托管。另一组石英脉，称为Espelid脉系，位于Bleka矿以北3公里处；这些矿脉较小，但数量较多，可能有大量可利用的黄金。白钨矿是一种重要的钨矿石，在Bleka发现，根据其丰度，它可能具有经济重要性（Dahlgren 2015）。目前已知，白钨矿在BMVS中含量丰富；然而，尚不清楚它是否在Espelid矿脉系统或该地区的其他石英系统中丰富，因为它表面上看起来与石英相似，尽管在黑暗中使用短波紫外线可以很容易地区分它（Søren和Tonny，1998）。项目区位于Bleka矿的西北部，包含Svartdal变质辉长岩，其中含有含金石英脉和白钨矿。这为勘探Espelid矿脉系统中的白钨矿或其他含金石英脉提供了机会。项目区域的地质测绘证实了石英脉的存在，以及它们的位置、方向和与斯瓦尔达尔变质辉长岩的关系。目前正在对石英脉和Svartdal变辉长岩进行详细的岩相和地球化学分析，以更好地描述主岩和石英脉的形成特征。使用EM31和磁力计对Svartdal变质辉长岩地球物理调查收集的数据进行解释，将显示石英脉的位置及其在地下的走向。
{"title":"Exploration for magmatic Ni–Cu–Co sulphide deposits in a convergent tectonic setting – a case study in southeast Sweden","authors":"S. J. Walding, D. P. James, R. Dawson, R. Frutuoso","doi":"10.1080/25726838.2019.1607192","DOIUrl":"https://doi.org/10.1080/25726838.2019.1607192","url":null,"abstract":"ered have been falling for decades. In addition, the demand for gold is increasing, especially where there is a growing consumer market in developing countries such as China and India. This makes it crucial to discover new gold deposits; however, the vast majority of surface deposits have been discovered, which means it is harder and more expensive to find deposits in the subsurface. Norway lies on the Fennoscandian shield, which contains an extensive wealth of minerals. This is explained by the geological evolution of this region, including the development of Precambrian supracrustals, intrusive rocks and Devonian intrusions that formed in major rift and orogenic settings. There are exploitable resources of gold in Norway, indicating that this country could be a significant supplier of gold (Eilu 2011). The quartz veins at the Bleka Mine in the Telemark region have reported grades of 35 g t Au, 45 g t Ag, 0.5% Bi and 1.5% Cu (NGU 2017). Other studies have estimated a reserve of 60,000 tonnes of ore with grades of 11 g t Au that could produce 233,000 oz of Au (Horvath 1943). These veins form the Bleka Main Vein System (BMVS) where they are hosted by the Svartdal Metagabbro, a large Proterozoic gabbroic sill complex. Another set of quartz veins, known as the Espelid vein system, is located 3 km north of the Bleka Mine; these veins are smaller, but are more numerous and may have a significant amount of gold that could be utilised. Scheelite, an important ore mineral of tungsten, was observed at Bleka and might be of economic importance, depending on its abundance (Dahlgren 2015). It is currently known that scheelite is abundant within the BMVS; however, it is unknown if it is abundant in the Espelid vein system or other quartz systems in the area as it superficially appears similar to quartz although it can be easily distinguished in darkness using short wave UV light (Søren and Tonny 1998). The project area, located northwest of the Bleka mine, contains the Svartdal Metagabbro that hosts the gold bearing quartz veins and scheelite. This gives the opportunity to explore the area for scheelite in the Espelid vein system or other gold bearing quartz veins. Geological mapping of the project area confirms the presence of quartz veins, along with their location, orientation and relationship with the Svartdal Metagabbro. A detailed petrographic and geochemical analysis of the quartz veins along with the Svartdal Metagabbro is currently being undertaken to better characterise the formation of the host rock and the quartz veins. Interpretation of data gathered from a geophysical survey of the Svartdal Metagabbro using an EM31 and magnetometer will show the location of quartz veins and their strike in the subsurface.","PeriodicalId":43298,"journal":{"name":"Applied Earth Science-Transactions of the Institutions of Mining and Metallurgy","volume":"129 1","pages":"86 - 87"},"PeriodicalIF":1.0,"publicationDate":"2020-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/25726838.2019.1607192","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49491669","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 : 2020-04-02DOI: 10.1080/25726838.2019.1599198
C. S. Bishop, G. Jenkin, D. Duckworth
The frequency and grade of gold deposits being discovered have been falling for decades. In addition, the demand for gold is increasing, especially where there is a growing consumer market in devel...
{"title":"The controls on the formation of gold-bearing hydrothermal quartz veins at the Bleka Concession, Telemark, Norway","authors":"C. S. Bishop, G. Jenkin, D. Duckworth","doi":"10.1080/25726838.2019.1599198","DOIUrl":"https://doi.org/10.1080/25726838.2019.1599198","url":null,"abstract":"The frequency and grade of gold deposits being discovered have been falling for decades. In addition, the demand for gold is increasing, especially where there is a growing consumer market in devel...","PeriodicalId":43298,"journal":{"name":"Applied Earth Science-Transactions of the Institutions of Mining and Metallurgy","volume":"129 1","pages":"85 - 86"},"PeriodicalIF":1.0,"publicationDate":"2020-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/25726838.2019.1599198","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60141560","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 : 2020-04-02DOI: 10.1080/25726838.2020.1761693
S. Jowitt
{"title":"Editorial","authors":"S. Jowitt","doi":"10.1080/25726838.2020.1761693","DOIUrl":"https://doi.org/10.1080/25726838.2020.1761693","url":null,"abstract":"","PeriodicalId":43298,"journal":{"name":"Applied Earth Science-Transactions of the Institutions of Mining and Metallurgy","volume":"129 1","pages":"55 - 55"},"PeriodicalIF":1.0,"publicationDate":"2020-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/25726838.2020.1761693","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47820362","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 : 2020-02-14DOI: 10.1080/25726838.2020.1727126
V. M. Silva, João Felipe Coimbra Costa Leite
ABSTRACT Geoscientific datasets can contain individual data for more than 50 different chemical elements. The association between these variables is as important as their individual values. However, it is commonly overlooked that the observed covariance may be overestimated due to correlated errors. Dependent errors arise from many sources, such as the segregation process of minerals associated with these variables during delimitation, extraction, and preparation steps. This study extends a classical model composed of grade-independent (additive) and grade-proportional (multiplicative) errors to a generalised multivariate model that can estimate the real variance, covariance, and correlation from observations affected by shared errors. The use of estimates of the real covariance is recommended when the study objective is to evaluate or estimate the association between processes instead of the association between observations. A numerical example illustrates the bias in statistics and discusses the relevance of considering shared errors in linear regression and kriging.
{"title":"Sampling error correlated among observations: origin, impacts, and solutions","authors":"V. M. Silva, João Felipe Coimbra Costa Leite","doi":"10.1080/25726838.2020.1727126","DOIUrl":"https://doi.org/10.1080/25726838.2020.1727126","url":null,"abstract":"ABSTRACT Geoscientific datasets can contain individual data for more than 50 different chemical elements. The association between these variables is as important as their individual values. However, it is commonly overlooked that the observed covariance may be overestimated due to correlated errors. Dependent errors arise from many sources, such as the segregation process of minerals associated with these variables during delimitation, extraction, and preparation steps. This study extends a classical model composed of grade-independent (additive) and grade-proportional (multiplicative) errors to a generalised multivariate model that can estimate the real variance, covariance, and correlation from observations affected by shared errors. The use of estimates of the real covariance is recommended when the study objective is to evaluate or estimate the association between processes instead of the association between observations. A numerical example illustrates the bias in statistics and discusses the relevance of considering shared errors in linear regression and kriging.","PeriodicalId":43298,"journal":{"name":"Applied Earth Science-Transactions of the Institutions of Mining and Metallurgy","volume":"129 1","pages":"147 - 153"},"PeriodicalIF":1.0,"publicationDate":"2020-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/25726838.2020.1727126","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42090334","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 : 2020-01-02DOI: 10.1080/25726838.2019.1694326
C. A. S. Oliveira, J. Kloeckner, Á. L. Rodrigues, M. Bassani, J. F. Coimbra Leite Costa
ABSTRACT Mining projects often contain secondary data spatially correlated with the main variable of interest (primary). These secondary data are usually more densely sampled than the primary (heterotopic) dataset, as they are cheaper and faster to obtain. In this situation, the use of secondary data in geostatistical modelling improves the quality of the final estimated/simulated models. The main geostatistical methodology used to integrate these two types of data is cokriging, which requires the joint modelling of direct and cross variograms using the linear model of coregionalisation (LMC). This article shows a methodology for estimation/simulation with heterotopic secondary data that does not require the LMC. The spatial continuity will be described by covariance tables (direct and cross). A case study is presented to compare the proposed methodology with the estimates/simulations using the LMC. The results were satisfactory, as the estimated and simulated models with covariance tables were properly validated.
{"title":"Use of heterotopic secondary data in geostatistics using covariance tables","authors":"C. A. S. Oliveira, J. Kloeckner, Á. L. Rodrigues, M. Bassani, J. F. Coimbra Leite Costa","doi":"10.1080/25726838.2019.1694326","DOIUrl":"https://doi.org/10.1080/25726838.2019.1694326","url":null,"abstract":"ABSTRACT Mining projects often contain secondary data spatially correlated with the main variable of interest (primary). These secondary data are usually more densely sampled than the primary (heterotopic) dataset, as they are cheaper and faster to obtain. In this situation, the use of secondary data in geostatistical modelling improves the quality of the final estimated/simulated models. The main geostatistical methodology used to integrate these two types of data is cokriging, which requires the joint modelling of direct and cross variograms using the linear model of coregionalisation (LMC). This article shows a methodology for estimation/simulation with heterotopic secondary data that does not require the LMC. The spatial continuity will be described by covariance tables (direct and cross). A case study is presented to compare the proposed methodology with the estimates/simulations using the LMC. The results were satisfactory, as the estimated and simulated models with covariance tables were properly validated.","PeriodicalId":43298,"journal":{"name":"Applied Earth Science-Transactions of the Institutions of Mining and Metallurgy","volume":"129 1","pages":"15 - 26"},"PeriodicalIF":1.0,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/25726838.2019.1694326","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49433535","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 : 2020-01-02DOI: 10.1080/25726838.2019.1708666
O. Erten, D. Renard, L. McAndrew
ABSTRACT The precise prediction of the footwall variability of a lateritic bauxite seam is of critical importance for the quantification of ferricrete dilution and ore loss that is likely to occur during mining activity. However, the majority of bauxite deposits have economic drillhole intercepts that are too widely spaced to reflect the accurate contact variability, resulting in uncertainties in the in-situ ore volume and the characteristics of the ore being sent to the refinery. In a case study, the seam attributes were modelled using drillhole data and geophysical information through univariate and bivariate geostatistical approaches. The uncertainties in the volumes of ore, dilution and loss were assessed through conditional simulation. The results indicated that the in-situ ore volume was predicted more accurately when the secondary information was incorporated. The realisations suggested a high local variability in the footwall contact, which is the source of dilution and loss considering the selectivity and operating constraints.
{"title":"Modelling of bauxite seam attributes and quantifying in-situ ore volume uncertainty in the presence of geophysical information","authors":"O. Erten, D. Renard, L. McAndrew","doi":"10.1080/25726838.2019.1708666","DOIUrl":"https://doi.org/10.1080/25726838.2019.1708666","url":null,"abstract":"ABSTRACT The precise prediction of the footwall variability of a lateritic bauxite seam is of critical importance for the quantification of ferricrete dilution and ore loss that is likely to occur during mining activity. However, the majority of bauxite deposits have economic drillhole intercepts that are too widely spaced to reflect the accurate contact variability, resulting in uncertainties in the in-situ ore volume and the characteristics of the ore being sent to the refinery. In a case study, the seam attributes were modelled using drillhole data and geophysical information through univariate and bivariate geostatistical approaches. The uncertainties in the volumes of ore, dilution and loss were assessed through conditional simulation. The results indicated that the in-situ ore volume was predicted more accurately when the secondary information was incorporated. The realisations suggested a high local variability in the footwall contact, which is the source of dilution and loss considering the selectivity and operating constraints.","PeriodicalId":43298,"journal":{"name":"Applied Earth Science-Transactions of the Institutions of Mining and Metallurgy","volume":"129 1","pages":"41 - 51"},"PeriodicalIF":1.0,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/25726838.2019.1708666","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45405802","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 : 2020-01-02DOI: 10.1080/25726838.2019.1708665
M. Zauner, A. Weller, M. Halisch
ABSTRACT Several core plugs from a 1243 m-deep borehole penetrating the Westwater Canyon Member of the Morrison Formation in New Mexico (USA) have been investigated by various petrophysical methods to evaluate the potential of extracting deeply buried sandstone-hosted uranium deposits by in situ recovery (ISR). Petrophysics and mineralization patterns of the host rock in the target aquifer are crucial parameters for ISR amenability and were determined according to the ISR feasibility criteria. Mineralogical investigations revealed a secondary uranium mineralization mainly coating the silica grains of the arkosic sandstone and some interstitial pore fillings. The differences between mineralized and non-mineralized sandstone plugs are highlighted by nuclear magnetic resonance (NMR), X-ray microcomputed tomography, and spectral induced polarization (SIP). The NMR results show a doubling of the clay- and capillary-bound water and a decease of free-fluid porosity of mineralized samples. A correlation of mineralization grade and polarization is observed through the SIP investigations.
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