Evaluation Of Mineral Resources Research Articles

Effect of Phosphatization on Element Concentration of Cobalt-Rich Ferromanganese Crusts

A detailed study on a small scale of the effect of phosphatization on the chemistry of marine cobalt-rich ferromanganese crusts supplies useful information for the evaluation and comprehensive utilization of crust mineral resources. Sub-samples from top to bottom of a 10-cm thick sample from the NW Pacific Magellan seamount were taken at 5 mm intervals. The concentration profiles of ore-forming and rare earth elements show that obvious differences exist between young unphosphatized crusts and old phosphatized crusts. In the old crusts Fe, Mn, Si, Al, Zn, Mg, Co, Ni and Cu elements are depleted and Ca, P, Sr, Ba and Pb elements are enriched. The order of depletion is Co > Ni > Mg > Al > Mn > Si > Cu > Zn > Fe, while the order of enrichment is P > Ca > Ba > Pb > Sr. The phosphate mineral controls the concentration variation of the ore-forming elements in crusts and causes loss of the main ore-forming elements such as Co and Ni. The phosphatization also affects the abundance of REEs in the crusts. REEs are more abundant and the content of Ce in old crusts is higher than that in young crusts, however, the pattern of REEs and their fractionation characteristics in new and old crusts are not fundamentally changed. A Y-positive anomaly in old crusts has no relationship to the phosphatization.

Re‐Os Dating of the Pulang Porphyry Copper Deposit in Zhongdian, NW Yunnan, and Its Geological Significance

Abstract The Pulang porphyry copper deposit is located in the Zhongdian island are belt, NW Yunnan, in the central part of the Sanjiang area, SW China, belonging to the southern segment of the Yidun island arc belt on the western margin of the Yangtze Platform. In the Yidun island arc, there occur well‐known “Gacun‐style” massive sulfide deposits in the northern segment and plenty of porphyry copper deposits in the southern segment, of which the Pulang porphyry copper deposit is one of the representatives. Like the Yulong porphyry copper deposit, this porphyry copper deposit is also one of the most important porphyry copper deposits in the eastern Qinghai‐Tibet Plateau. But it is different from other porphyry copper deposits in the eastern Qinghai‐Tibet Plateau (e.g. those in the Gangdise porphyry copper belt and Yulong porphyry copper belt) in that it formed in the Indosinian period, while others in the Himalayan period. Because of its particularity among the porphyry copper deposits of China, this porphyry copper deposit is of great significance for the study of the basic geology and the evaluation and prediction of mineral resources in the Zhongdian island arc belt. However, no accurate chronological data are available for determining the timing of mineralization of the porphyry copper deposit. By field observation in the study area and Re‐Os dating of molybdenite and K‐Ar dating of hydrothermal minerals and whole rock from the typical geological bodies, the timing of mineralization of the porphyry copper deposit has systematically been determined for the first time. The K‐Ar age for the hydrothermal mineralization of biotite‐quartz monzonitic porphyry that has undergone patassic silicate (biotite and K‐feldspar) alteration ranges from 235.4±2.4 to 221.5±2.0 Ma and the Re‐Os age for molybdenite in the quartz‐molybdenite stage is ∼213±3.8 Ma. These data are very close to each other, suggesting that the ore‐forming processes of the Pulang porphyry copper deposit was completed in the Indosinian. But the K‐feldspar K‐Ar age of the main orebodies suggests that the hydrothermal activity related to porphyry copper mineralization continued till ∼182.5±1.8 Ma. This indicates that the lifespan of the hydrotthermal system related to porphyry copper mineralization may have lasted at least 40 Ma. This hydrothermal thermal system with such a long lifespan may be one of the necessary conditions for forming large porphyry copper deposits with a high grade. No late Yanshanian and/or Himalayan magmatism (mineralization) were superimposed in the Pulang porphyry copper deposit.

Late Permian carbonate concretions in the marine siliciclastic sediments of the Ravnefjeld Formation, East Greenland

This investigation of carbonate concretions from the Late Permian Ravnefjeld Formation in East Greenland forms part of the multi-disciplinary research project Resources of the sedimentary basins of North and East Greenland (TUPOLAR; Stemmerik et al. 1996, 1999). The TUPOLAR project focuses on investigations and evaluation of potential hydrocarbon and mineral resources of the Upper Permian – Mesozoic sedimentary basins. In this context, the Upper Permian Ravnefjeld Formation occupies a pivotal position because it contains local mineralisations and has source rock potential for hydrocarbons adjacent to potential carbonate reservoir rocks of the partly time-equivalent Wegener Halvø Formation (Harpøth et al. 1986; Surlyk et al. 1986; Stemmerik et al. 1998; Pedersen & Stendal 2000). A better understanding of the sedimentary facies and diagenesis of the Ravnefjeld Formation is therefore crucial for an evaluation of the economic potential of East Greenland.

Precambrian geology of the northern Nagssugtoqidian orogen, West Greenland: mapping in the Kangaatsiaq area

The Nagssugtoqidian orogen and its transition into the Rinkian orogen to the north were the main focus of the field activities of the Geological Survey of Denmark and Greenland (GEUS) in West Greenland in the summer of 2001. This work was carried out within the framework of the Survey’s three-year programme of bedrock mapping and mineral resource evaluation to enhance the understanding of the Archaean and Palaeoproterozoic crustal evolution in the transition zone between the Nagssugtoqidian and Rinkian orogens (Fig. 1). The work in the field season of 2001 comprised geological mapping of the 1:100 000 Kangaatsiaq map sheet described in this paper (Fig. 2), an investigation of the supracrustal rocks at Naternaq / Lersletten (Østergaard et al. 2002, this volume), a geochronological reconnaissance of the southern Rinkian orogen in the northern Disko Bugt region (Garde et al. 2002, this volume), a resource evaluation of the Nagssugtoqidian orogen (Stendal et al. 2002, this volume), a synthesis and interpretation of geophysical data of the central part of the Nagssugtoqidian orogen (Nielsen et al. 2002, this volume) and a report on investigations of the kimberlites and related intrusive rocks in the southern Nagssugtoqidian orogen and its foreland (Jensen et al. 2002, this volume).

Hydrothermal Alteration of the Saplica Volcanic Rocks, Sebinkarahisar, Turkey

A widespread, intense hydrothermal alteration zone has developed in the Cretaceous Saplica volcanics as a result of the intrusion of Late Cretaceous-Paleocene granitoids. The propylitic, phyllitic (sericitic), and argillic alteration along with hematite, silica polymorphs, and two types of tourmaline mineralization developed under a wide range of Eh and pH conditions. Alunite, kaolinite, and silica are abundant in the argillic alteration, whereas sericite dominates in the phyllic alteration. Most of the major alunite deposits are located along the periphery of the Saplica volcanic rocks and in addition contain alunite, kaolinite + quartz ± opal ± cristobalite. Illite and pyrite, barite, and gypsum also occur in small amounts. Major and trace elements are concentrated in, or were leached from, the volcanic rocks, depending upon the alteration types. In general, Al + K and Mg + Ca + Fe were enriched in the alunitic + sericitic and propylitic alteration types, respectively. On the other hand, Ca, Mg, and Fe were leached during argillic alteration, and Fe was concentrated in hematite formation. Strong leaching of Na was determined for alteration types. Silica generally decreased in argillitic (kaolinitic and alunitic) alteration zones. Most trace elements were mobile during hydrothermal alteration. Y, Sc, Mo, Cr, Co, Ni, and Zn tend to be mobile in acid aqueous systems, and thus are nearly absent in these alunitic alteration zones. In the surrounding kaolinitic envelope, these elements are present at background (average) or slightly higher concentrations. Rb and Sr contents are high in the alunitic and kaolinitic zones. Barium is highest near the alunite zone because of the relative insolubility of barite in acidic solutions. Pb and Cu contents increase in the propylitic zone. Such hydrothermal alteration zones can be used effectively in the exploration and evaluation of mineral resources of the eastern Black Sea region.

Lake sediment geochemical methods in the Canadian Shield, Cordillera and Appalachia

Abstract Lake sediment geochemistry has been used in Canada since the 1970s for mineral exploration and resource evaluation in glaciated regions of Appalachia, the Canadian Shield and the western Cordillera which are of low to moderate relief. Geochemical signatures of bedrock and mineralization within a lake’s catchment basin are commonly reflected in the chemical constituents of the organic-rich Holocene sediment which has been transported from source by a combination of mechanical and hydromorphic processes. Lake sediment geochemical surveys have been used successfully to discover base metal, Au, Mo, W, Sb, Sn, U, and REE mineralization. The scale of such surveys determines the size and density of lake sediment sampling. In regional surveys, large lithological targets such as greenstone belts or chemically distinctive intrusives can be identified by low density ( c. 1 per 10–15 km 2 ) sampling of relatively larger lakes. Smaller targets such as mineralized areas require higher density ( c. 1 per 4–5 km 2 ) sampling using a greater number of smaller lakes. Regional surveys are typically helicopter-borne, and employ a tubular grab sampler which permits rapid reconnaissance-scale coverage of large areas. Centre-basin profundal lake sediment, or gyttja, is an ideal sample medium because of its homogeneity and abundance of fine-grained organic matter, which complexes with many trace elements. Multi-element analytical techniques in common use include inductively coupled plasma emission spectrometry (ICP-ES), ICP mass spectrometry (ICP-MS) and instrumental neutron activation analysis (INAA). Reliability of data is assessed by analysis of known standards, site duplicates and sample splits. PC statistical software packages facilitate the interpretation of geochemical data, and desktop GIS packages aid in further interpretation and generation of multi-layer maps.

Appreciation of Contributions by Georges Matheron and John Tukey to a Mineral-Resources Research Project

Georges Matheron (1930–2000) and John Tukey (1915–2000) were among the most prominent mathematical statisticians of the 20th century. Both men produced numerous important new theoretical and practical results. This personal appreciation of their work concentrates on contributions to mineral-resources research and describes their influence on my work in mineral-resource evaluation studies at the Geological Survey of Canada (1966–1983).

Special Section on mining geophysics—Introduction

The Exploration 97 Conference held in Toronto in 1997 was a decennial event which provided a forum for review of advances in geophysics applied to mineral exploration and resource evaluation. This Special Section of Geophysics publishes a set of 16 papers, originally presented at that conference, which demonstrate recent advances in mineral exploration and mine geophysics.

Application of Artificial Neural Networks in Mineral Resource Evaluation

This paper explores the novel technique of artificial neural networks and their application to mineral resource evaluation. The primary objective of this exploratory work is concerned with cost minimization, especially in drilling. The objective is to reduce investment costs on projects before decisions on further development of a mineralization are made. A data set consisting of 163 sample locations for a bauxite deposit was collected and used for training and testing an artificial neural network model using the back propagation technique. This trained network was then used to predict known point values at specified locations. Results between actual and predictions were then compared for validation purposes. Same results are also compared with estimates obtained from a geostatistical technique (kriging). These results indicate that the ANN-based model predictions were in close agreement with actual results within the main zone of mineralization than at the boundaries. Finally, the validated model was used to predict values at unsampled locations in order to determine the feasibility of drilling in these locations. The investigation on the bauxite deposit shows that artificial neural networks can be used as a complementary decision tool in mining and earth sciences, not so much at an early stage of exploration as in the later stages of exploitation.

Mafic igneous rocks and mineralisation in the Palaeoproterozoic Ketilidian orogen, South-East Greenland: project SUPRASYD 1996

The multidisciplinary SUPRASYD project (1992–96) focused on a regional investigation of the Palaeoproterozoic Ketilidian orogenic belt which crosses the southern tip of Greenland. Apart from a broad range of geological and structural studies (Nielsen et al., 1993; Garde & Schønwandt, 1994, 1995; Garde et al., 1997), the project included a mineral resource evaluation of the supracrustal sequences associated with the Ketilidian orogen (e.g. Mosher, 1995). The Ketilidian orogen of southern Greenland can be divided from north-west to south-east into: (1) a border zone in which the crystalline rocks of the Archaean craton are unconformably overlain by Ketilidian supracrustal rocks; (2) a major polyphase pluton, referred to as the Julianehåb batholith; and (3) extensive areas of Ketilidian supracrustal rocks, divided into psammitic and pelitic rocks with subordinate interstratified mafic volcanic rocks (Fig. 1). The Julianehåb batholith is viewed as emplaced in a magmatic arc setting; the supracrustal sequences south of the batholith have been interpreted as either (1) deposited in an intra-arc and fore-arc basin (Chadwick & Garde, 1996), or (2) deposited in a back-arc or intra-arc setting (Stendal & Swager, 1995; Swager, 1995). Both possibilities are plausible and infer subduction-related processes. Regional compilations of geological, geochemical and geophysical data for southern Greenland have been presented by Thorning et al. (1994). Mosher (1995) has recently reviewed the mineral exploration potential of the region. The commercial company Nunaoil A/S has been engaged in gold prospecting in South Greenland since 1990 (e.g. Gowen et al., 1993). A principal goal of the SUPRASYD project was to test the mineral potential of the Ketilidian supracrustal sequences and define the gold potential in the shear zones in the Julianehåb batholith. Previous work has substantiated a gold potential in amphibolitic rocks in the south-west coastal areas (Gowen et al., 1993.), and in the amphibolitic rocks of the Kutseq area (Swager et al., 1995). Field work in 1996 was focused on prospective gold-bearing sites in mafic rocks in South-East Greenland. Three M.Sc. students mapped showings under the supervision of the H. S., while an area on the south side of Kangerluluk fjord was mapped by H. S. and W. M. (Fig. 4).

Related information measures for the associations of earth-science variables

A basic task in earth-science data integration is to quantify variable associations. Although manv measures have been used to determine the associations between quantitative variables, the ability to quantify qualitative attributes (e.g., categorical) is limited. Moreover, most traditional association measures are restricted to linear correlations or similarities, for example, correlation coefficient. The measures proposed in this report are designed on the basis of Shannon's entropy concepts, including directional related information, ordinary related information, and partial related information. The directional related information quantifies the association of one variable in terms of another. The ordinary related information determines the mutual association of two variables. The partial related information characterizes the association of an individual stale of one variable in terms of another variable. The properties of these measures are discussed and their sample estimates are derived from both maximum likelihood and Bayesian methods. The relations between these measures are illustrated by using synthetic examples. Two applications of these measures also are developed, including the selection of variables and evaluation of mineral resources. Finally, a case study is given to demonstrate the use of the measures in mineral resources evaluation.

The quantitive prediction and evaluation of mineral resources

The quantitive prediction and evaluation of mineral resources

Information structure analysis for quantitative assessment of mineral resources and the discovery of a silver deposit

We propose an information-structure-analysis (ISA) method to quantify the correlations between quantitative and qualitative variables as well as within each type of variable. This method is applied to the evaluation of mineral resources in the western Zheijiang Province of China. The district contains a number of silver-bearing Fe−Cu−Pb−Zn mineral deposits near igneous complexes and Fe→Cu→Pb→Zn zones away from the complexes. Silver anomalies occur not only in the known Fe−Cu−Zn−Pb deposits, but also in the country rock, suggesting the possible existence of silver deposits far from the igneous complexes.

Undiscovered unit regional resources of Gondwana coals in India

A parameter called Undiscovered Unit Regional Resources was formulated and studied for the Gondwana coal resources of India with a view to developing a quick method of estimating undiscovered mineral resources of a region superior to that of Unit Regional Value and Unit Regional Weight. Unit Regional Value and Unit Regional Weight have been used for the evaluation of undiscovered mineral resources of a region, but they give only a broad outlook and can sometimes lead to biased conclusions, particularly over small regions. Weighted Unit Regional Weight for a mineral or minerals based on the area of exposure of the relevant geological formation (s), together with the Unit Regional Reserves computed from already identified reserves yields a measure of greater accuracy in the form of Undiscovered Unit Regional Resources. The Undiscovered Unit Regional Resources of Gondwana coals in India were evaluated for different coal-bearing states of India taking West Bengal as standard, since the Ranigunj coalfield, the only producing coalfield in West Bengal, was found to have reached stage II of the economic life and could be considered as well developed in regard to coal exploitation. The study reveals that Undiscovered Unit Regional Resources give a more reliable estimate of the undiscovered resources of Gondwana coals in the different states of India than Unit Regional Weight and consequently shifts the priority of exploration. The Unit Regional Weight method highly underestimates the total undiscovered coal resources of India at less than 10 billion tonnes, which is very small compared to the already identified reserves of 157.4 billion tonnes.

What is a mineral resource?

Abstract Mineral resource evaluation is one of a whole spectrum of quantitative methods which have been used since biblical times for the purpose of improving the process required to aid problem-solving and to increase the quality of strategic management decisions at all levels. Such evaluation leads to the classification of mineral resources. It is important to have a clear knowledge of how mineral resources are classified and what the classification nomenclature actually means to ensure decisions are based on a sound understanding of criteria applied. As interest for investment in mineral resource development spreads into Eastern Europe and the former Soviet Union, the need for some form of harmonization in terminology, nomenclature, criteria, as well as the approach to the classification process for the definition of mineral resources has again been highlighted. The approach to quantitative studies is discussed, and guidelines are given that may improve mineral reserve and resource estimates so that implementation failure of mining projects can be avoided. Approaches to the classification of mineral resources are reviewed along with the uses made of such mineral resource information. The argument is put for a standard approach to mineral resource classification and consistency of international nomenclature with a discussion of some of the related problems. Principles are established which may suggest a way forward illustrated by a recent major resource assessment project.

Mineral Resource Evaluation 93

Report of a joint Mineral Deposit Studies Group and Geosciences Information Group meeting in association with the Institution of Mining and Metallurgy (Midlands Section), held on 6 and 7 April 1993 in the Geology Department at Leicester University. The meeting was organized by Michael K.G. Whateley and Peter K. Harvey. After the first Mineral Resource Evaluation meeting held in Cardiff in March 1991, it became clear that there was a large, interested group of geologists, engineers and financial experts who have a common interest in mineral resource evaluation. It appeared timely to repeat the conference; this second meeting therefore was convened to discuss methods in mineral resource evaluation and describe case histories. This successful international meeting brought together all those who are involved in the day to day exploration and evaluation of mineral deposits in addition to those who are responsible for their economic evaluation and for mine feasibility and design studies. The two-day meeting included 31 papers, six posters and commercial displays by nine companies. A Special Publication of the Geological Society will be published within about a year from the date of the meeting. The meeting attracted over 100 speakers and delegates from Ireland, the Netherlands, USA, Portugal, Germany, Malawi, Canada, Ghana, Sweden, Bulgaria, Belgium, England, Scotland and even Wales. The theme of the conference was to discuss methods of mineral deposit evaluation, and to follow this with case histories from around the world. The conference started with a keynote address by G. Riddler (British Geological Survey) on

A preliminary application of weights of evidence in gold exploration in Xiong-er Mountain Region, He-Nan Province

Weights of evidence modeling for combining indicator patterns in mineral resource evaluation is based on an application of Bayes' rule. Two weights are defined for each indicator pattern and Bayes' rule is applied repeatedly to combine indicator patterns. If all patterns are conditionally independent with respect to deposits, the logit of the posterior probability can be calculated as the sum of the logit of the prior probability plus the weights of the overlay patterns. The information to be integrated for gold exploration in Xiong-er Mountain Region comes from a geological map, an interpreted map of a Thematic Mapper (TM) image, and the locations of known gold deposits. Favorable stratigraphic units, structural control factors, and alteration factors are considered. The work was conducted on an S600 I2S image-processing system. FORTRAN programs were developed for creating indicator patterns, statistical calculations, and pattern integration. Six indicator patterns were selected to predict mineral potential. They are conditionally independent according to pairwiseG2 tests, and an overall chi-square test. The potential area predicted using the 32 known deposits generally coincides with the prospect areas determined by geological fieldwork.

Combining indicator patterns in weights of evidence modeling for resource evaluation

The weights of evidence model for combining indicator patterns in mineral resource evaluation is briefly explained with emphasis on the effect of undiscovered deposits on the estimation of the weights and posterior probabilities. A group of six statistical tests is proposed for analyzing the interaction of two or three indicator patterns with the point pattern for mineral deposits. A distinction is made between statistics that depend on choice of unit cell size and those that are approximately or completely independent of it. Finally, weights of evidence are compared to regression coefficients obtained by means of the logistic model.

A Comparison of Spatial Thematic Map Approaches Used for Mineral Resource Exploration and Evaluation

A Comparison of Spatial Thematic Map Approaches Used for Mineral Resource Exploration and Evaluation

Geological setting of Precambrian supracrustal belts: a fundamental part of mineral resource evaluation in Greenland

In Precambrian shield areas the economic potential of supracrustal rocks is well documented, and some of the world's largest metal deposits are found within these sequences. The Black Angel lead-zinc stratabound mineralisation at Mårmorilik in central West Greenland (71° 10'N, Fig. 1), hosted in the Proterozoic Karrat Group, is one commercial enterprise that confirms that this potential can be realised in Greenland. In last year's volume of Report of Activities, Thomassen (1991a) gave a history of the geology and mineral exploration of the Black Angel deposit.