Quantitative Mineral Resource Assessment Research Articles

Quantitative resource assessment of hydrothermal gold deposits based on 3D geological modeling and improved volume method: Application in the Jiaodong gold Province, Eastern China

Quantitative assessment of deep mineral resources is important for the mineral exploration decisions of governments and companies. Complex structural controls make the volume method difficult to apply to hydrothermal gold deposits. Quantitative assessment of Au resources in hydrothermal goldfields remains a challenging task. Here we proposed a quantitative assessment approach for hydrothermal gold deposits via an improved volume method combined with 3D geology modeling. A highly reliable 3D model of ore-controlling structure was first constructed to obtain the spatial association between Au mineralization and structure. On this basis, we made an optimal quantitative estimation of the ore-bearing ratio and similarity index, which are the most critical parameters in the volume method, before evaluating gold resources. Specifically, (1) an ore-bearing ratio prediction model was established by support vector machine based on measured data and 3D models, which was further applied in predicting the ore-bearing ratio of the evaluation area at depth and peripherals; (2) the calculation of the similarity index was improved by novelly using the Mahalanobis distance of the regional geochemical data with regard to the similar geochemical anomalies of gold mineralization in adjacent space. This proposed method was applied to quantitatively assess the gold resources in the Jiaojia and Dayingezhuang goldfields in the Jiaodong gold province, China, where gold deposits show significant structure controls on mineralization. The results of gold grade prediction are statistically significantly correlated to measured values by the Wilcoxon signed rank test, showing the model for gold grade prediction can be extensible in the deep parts. Our approach produced similarity indices for the model and evaluation areas at Jiaojia and Dayingezhuang that accurately reflected the geology complex. The above lines suggest that the proposed approach can be used to estimate the gold resources of Jiaodong. Potential gold resources in the Jiaojia and Dayingezhuang districts were estimated to be 1221.82 t and 254.95 t.

Developments in Quantitative Assessment and Modeling of Mineral Resource Potential: An Overview

The special issue entitled “Developments in Quantitative Assessment and Modeling of Mineral Resource Potential” is composed of 17 papers that cover a diverse range of approaches to mineral resource assessment, including mainly multivariate statistical analysis, fractal and multifractal modeling, geostatistical modeling, machine learning, mathematical morphology and 3D mineral exploration. This introductory article first provides an overview of the developments and existing methods in quantitative assessment of mineral resources. Then, brief introductions of each of the 17 papers are provided. These papers can be grouped into three themes: (1) multifractal theory for mineral resource assessment; (2) machine learning for mineral prospectivity mapping; and (3) GIS-based 3D modeling for mineral exploration. The 17 papers either proposed novel methods or demonstrated innovative applications of existing methods.

Mineral deposit discovery order and three-part quantitative assessments

Larger oil pools tending to be discovered earlier in an exploration play suggests the same pattern might exist for mineral deposits and could be used in predicting sizes of undiscovered deposits in mineral assessments. The volume of individual petroleum pools is highly correlated with surface projection area of pools in basins. The gradual additions to individual oil pool reserves over time adds to the appearance of larger pools being discovered earlier.Comparisons of surface projected areas of mineral deposits to their tonnages showed significant positive relationships in all 10 deposit types analyzed, suggesting that larger deposits should be discovered earlier than small deposits.Analysis of deposits consistent with three-part mineral assessments identified 9 combinations of mineral deposit types in large regions each containing multiple geological permissive tracts showing negative and 1 positive relationships of deposit size with discovery date significant at the 1% level. Twenty other tests of regions containing multiple permissive settings had either negative or positive relationships, none significantly different from those that might occur by chance. The large regions are mostly based on political boundaries. These results suggest mineral deposit discovery order is not the same as observed in oil pool exploration.The widely employed three-part quantitative mineral resource assessments are an obvious choice to benefit from patterns of declining deposit sizes with order of discovery. The 30 tests of relationships of discovery dates to deposit sizes demonstrated here were performed with deposits consistent with those in three-part assessments, but the large areas are not consistent with permissive tracts used in these assessments because they also contain substantial non-permissive geology.In 100 permissive tracts assessed with three-part assessments of multiple deposit types located throughout the world, the median number of known well-explored deposits is 1 and 90 percent of tracts report less than 9 deposits. The number of well-explored deposits in three-part assessed tracts tends to be quite small, limiting any ability to recognize a discovery order versus size relationship.In a three-part assessment of undiscovered porphyry copper deposits of South America, only 7 of 26 delineated tracts contained more than 2 known deposits and only 1 had a significant negative relationship between tonnage of known deposits and year of discovery (p = 0.04). Most predicted undiscovered deposits in this tract were expected to be under extensive unexplored post-mineralization cover, meaning the general grade and tonnage model should be applied because the discovery order process starts over. Projection of deposit sizes based on discovery order would provide a biased estimate of the undiscovered deposit sizes in this case. Thus, although a discovery order versus size relationship could exist in three-part mineral assessments, only rarely might the pattern be useful to predict sizes of undiscovered deposits.

Tungsten skarn mineral resource assessment of the Great Basin region of western Nevada and eastern California

A new quantitative mineral resource assessment for tungsten, a critical mineral commodity with highly concentrated production and a moderate risk of global supply disruption, was conducted for the Great Basin region of western Nevada and eastern California. This assessment was part of a larger effort focusing on three regions in the United States and represents the first study of domestic tungsten resources and mineral potential in over twenty years. By integrating geology, bedrock and stream sediment geochemistry, geophysics, and remote sensing data with recently developed software tools and analyses, estimates of undiscovered tungsten skarn deposits in permissive tracts are combined with grade and tonnage distributions of known deposits to generate probabilistic estimates of undiscovered resources. Identified resources in the Great Basin region total 168 thousand metric tons (kt) of tungsten trioxide (WO3), including 116 kt of past production and 52 kt remaining in place. Consistent with the historic significance of the Great Basin region as a past producer containing a large portion of U.S. identified resources, undiscovered resources are likely to occur adjacent to known deposits and prospects and at unexplored depths. Undiscovered deposits are estimated to contain median resources of 940 kt of WO3 with a 90% probability of at least 420 kt and a 10% probability of at least 1.7 million metric tons (Mt), of which 240 kt to 1.1 Mt may be economic to extract. Based on a 20-year average price, median recoverable undiscovered resources are estimated at 570 kt WO3 equivalent with a net present value of $3 billion U.S. dollars. The methods, data, results, and economic significance of the assessment contribute to a scientific understanding of a critical mineral resource with direct implications for policy and land management decisions.

Tungsten skarn potential of the Yukon-Tanana Upland, eastern Alaska, USA—A mineral resource assessment

Tungsten (W) is used in a variety of industrial and technological applications and has been identified as a critical mineral for the United States, India, the European Union, and other countries. These countries rely on W imports mostly from China, which leaves them vulnerable to supply disruption. Consequently, the U.S. government has a current initiative to understand domestic resource potential. The eastern Alaska portion of the Yukon-Tanana Upland (YTU), is prospective for W skarn deposits, the major source of global W supply. The regional geology consists of juxtaposed Paleozoic lithotectonic packages that were reaccreted to North America in the Mesozoic. Multiple subsequent episodes of arc-related magmatism intruded the lithotectonic packages, accompanied by W skarn formation mostly associated with 100–90 Ma intrusions; major W skarn deposits in Canada are part of the same metallogenic event (e.g., Mactung, Cantung). In this paper, we present an assessment for undiscovered W skarn resources for parts of the lesser-explored western (Alaskan) portion of the YTU.We used GIS proximity analysis to map the intersection of pluton and carbonate-bearing rocks to define three permissive tracts for W skarn deposits. The permissive tracts were qualitatively assessed by mineral potential mapping using region-wide sediment geochemistry and mineral concentrate datasets. This analysis showed that much of the western YTU has high potential for undiscovered W skarn deposits, whereas the eastern and southern YTU had only isolated areas of medium to high potential. Historical production and the quality of the geochemistry data of the western YTU tract (ca. 9200 km2) permitted a quantitative assessment of undiscovered W resources. Probabilistic estimates by a panel of 20 experts predicted a 70% chance of one to three undiscovered W skarn deposits in the western YTU tract. The rationale for favorability employed by the expert panel included favorable lithology, previous production, clustering of previously mined deposits, W placers in the area, lack of recent exploration, pan concentrates containing W minerals, and W geochemical anomalies. Estimates were combined with a global grade and tonnage model for W skarns in a Monte Carlo simulation and provided a median estimate of undiscovered resources of 94 kt WO3. If the undiscovered W skarn deposits are located close to infrastructure (e.g., near Fairbanks, or close to roads and/or power grid), application of an economic filter indicates that the median total economically recoverable WO3 is 63 kt with a net present value (NPV) of $330 million USD (2008 dollars). Whereas if deposits are far from infrastructure, median recoverable WO3 is only 30 kt and the NPV is $44 million.Our models for contained WO3 resources and NPV estimates for the western YTU tract are considerably lower than the known resources in skarns in adjacent areas in Canada. Estimates for the western YTU are also lower than preliminary estimates for undiscovered W skarn deposits in areas of the western conterminous United States. We speculate that lower permeability and continuity of favorable carbonate rock horizons in the relatively higher-grade metamorphic country rocks in the Alaska portion of the YTU may explain some of the differences in prospectivity. More detailed geologic mapping, modern geochemistry, and geophysical surveys are needed to refine the resource potential of the whole YTU. Regardless, quantitative mineral resource assessment provides a useful tool for making first-order regional estimates of undiscovered resources, identifying target areas for new data acquisition, and guiding research on the fundamental controls of district-scale metallogenic endowments.

Southern China's manganese resource assessment: An overview of resource status, mineral system, and prediction model

Manganese is, an important industrial mineral used in the manufacture of various products, including in the refinement of iron ore and as an alloy in steel. China has rich resources of manganese (Mn), with the majority of deposits located in southern China. The common types of Mn deposits are sedimentary, hydrothermally modified, and supergene. Exploring a suitable method to quantitatively assess the Mn mineral resources at the craton-scale is, therefore, an open challenge for the geologist. The purpose of this contribution is to present a framework for the region-scale assessment of manganese based on mineral-system analysis and the model-based synthetic volume method. The framework involves: (1) summarising the status of Mn resources in regions of southern China considered to be prospective for the metal; (2) constructing datasets based on mineral exploration; (3) completion of mineral-system analysis of Mn deposits in each prospective area; (4) establishing a prediction model based on mineral-system analysis; (5) construction of geographic information system (GIS) layers to represent the mineralisation processes; (6) using a mathematical model to conduct a spatial analysis of areas considered to be prospective; (7) estimation of mineral resources based on the synthetic volume method; and (8) delineation of “minimum potential area” (MPA) and the calculation of the total predicted resources. The innovations of this research are the translation of the ore-forming processes into mappable features in the geosciences datasets by applying the concept of mineral system, and quantitative assessment of the Mn mineral resources based on the assumption that the larger the volume of a trap, the more resources it probably holds. This framework was used for China’s “National Mineral Resources Assessment Initiative” in recent years, and help to assess the Mn mineral resources at the craton-scale, and determine the critical characteristic of the Mn deposits that can be used for the construction of model-based prospectivity mapping, especially in southern China, which can be used for manganese exploration.

Development and future prospects of quantitative mineral assessment in China

ABSTRACT Mineral potential assessment at the Earth’s surface has been an important research for geoscientists around the world in the past five decades. The fundamental aspects of mineral assessment at different scales can be associated with the following tasks, e.g., mineral potential mapping and estimation of mineral resources. This paper summarized the history and development in terms of theories, methods technologies and software platforms for quantitative assessment of mineral resources in China, e.g. comprehensive information methodology, geological anomaly, three-component quantitative prediction method, 5P ore-finding area, integrated information assessment method, nonlinear process modeling and fractals, three dimensional mineral potential mapping, etc. At last, to discuss the future of quantitative mineral assessment in an era of big data including platform for 3D visualization, analysis and sharing, new methods and protocols for data cleaning, information enhancement, information integration, and uncertainties and multiple explanations of multi-information. © 2019 China Geology Editorial Office.

GIS prospectivity mapping and 3D modeling validation for potential uranium deposit targets in Shangnan district, China

Integrating multi-source geoscience information (such as geology, geophysics, geochemistry, and remote sensing) using GIS mapping is one of the key topics and frontiers in quantitative geosciences for mineral exploration. GIS prospective mapping and three-dimensional (3D) modeling can be used not only to extract exploration criteria and delineate metallogenetic targets but also to provide important information for the quantitative assessment of mineral resources. This paper uses the Shangnan district of Shaanxi province (China) as a case study area. GIS mapping and potential granite-hydrothermal uranium targeting were conducted in the study area combining weights of evidence (WofE) and concentration-area (C-A) fractal methods with multi-source geoscience information. 3D deposit-scale modeling using GOCAD software was performed to validate the shapes and features of the potential targets at the subsurface. The research results show that: (1) the known deposits have potential zones at depth, and the 3D geological models can delineate surface or subsurface ore-forming features, which can be used to analyze the uncertainty of the shape and feature of prospectivity mapping at the subsurface; (2) single geochemistry anomalies or remote sensing anomalies at the surface require combining the depth exploration criteria of geophysics to identify potential targets; and (3) the single or sparse exploration criteria zone with few mineralization spots at the surface has high uncertainty in terms of the exploration target.

Quantitative Geoscience and Geological Big Data Development: A Review

AbstractAfter long‐term development, mathematical geology has today become an independent discipline. Big Data science, which has become a new scientific paradigm in the 21st century, gives rise to the geological Big Data, i.e. mathematical geology and quantitative geoscience. Thanks to a robust macro strategy for big data, China's quantitative geoscience and geological big data's rapid development meets present requirements and has kept up with international levels. This paper presents China's decade‐long achievements in quantitative prediction and assessment of mineral resources, geoscience information and software systems, geological information platform development, etc., with an emphasis on application of geological big data in informatics, quantitative mineral prediction, geological environment and disaster management, digital land survey, digital city, etc. Looking ahead, mathematical geology is moving towards “Digital Geology”, “Digital Land” and “Geological Cloud”, eventually realizing China's grand “Digital China” blueprint, and these valuable results will be showcased on the international academic arena.

Genetic and grade and tonnage models for sandstone-hosted roll-type uranium deposits, Texas Coastal Plain, USA

The coincidence of a number of geologic and climatic factors combined to create conditions favorable for the development of mineable concentrations of uranium hosted by Eocene through Pliocene sandstones in the Texas Coastal Plain. Here 254 uranium occurrences, including 169 deposits, 73 prospects, 6 showings and 4 anomalies, have been identified. About 80million pounds of U3O8 have been produced and about 60million pounds of identified producible U3O8 remain in place. The development of economic roll-type uranium deposits requires a source, large-scale transport of uranium in groundwater, and deposition in reducing zones within a sedimentary sequence. The weight of the evidence supports a source from thick sequences of volcanic ash and volcaniclastic sediment derived mostly from the Trans-Pecos volcanic field and Sierra Madre Occidental that lie west of the region. The thickest accumulations of source material were deposited and preserved south and west of the San Marcos arch in the Catahoula Formation. By the early Oligocene, a formerly uniformly subtropical climate along the Gulf Coast transitioned to a zoned climate in which the southwestern portion of Texas Coastal Plain was dry, and the eastern portion humid. The more arid climate in the southwestern area supported weathering of volcanic ash source rocks during pedogenesis and early diagenesis, concentration of uranium in groundwater and movement through host sediments. During the middle Tertiary Era, abundant clastic sediments were deposited in thick sequences by bed-load dominated fluvial systems in long-lived channel complexes that provided transmissive conduits favoring transport of uranium-rich groundwater. Groundwater transported uranium through permeable sandstones that were hydrologically connected with source rocks, commonly across formation boundaries driven by isostatic loading and eustatic sea level changes. Uranium roll fronts formed as a result of the interaction of uranium-rich groundwater with either (1) organic-rich debris adjacent to large long-lived fluvial channels and barrier–bar sequences or (2) extrinsic reductants entrained in formation water or discrete gas that migrated into host units via faults and along the flanks of salt domes and shale diapirs. The southwestern portion of the region, the Rio Grande embayment, contains all the necessary factors required for roll-type uranium deposits. However, the eastern portion of the region, the Houston embayment, is challenged by a humid environment and a lack of source rock and transmissive units, which may combine to preclude the deposition of economic deposits. A grade and tonnage model for the Texas Coastal Plain shows that the Texas deposits represent a lower tonnage subset of roll-type deposits that occur around the world, and required aggregation of production centers into deposits based on geologic interpretation for the purpose of conducting a quantitative mineral resource assessment.

Rank-Size Statistical Assessments of Undiscovered Gold Endowment in the Bendigo and Stawell Zones (Victoria) and the Mossman Orogen (Queensland), Australia: Comparison with Three-Part Assessment Results

The Bendigo and Stawell zones in Victoria and the Mossman Orogen in north Queensland host numerous orogenic gold deposits and are likely to contain significant undiscovered gold resources. This paper discusses applications of Zipf’s law to estimate the scale of residual gold endowment in each of the regions. Testing various plausible scenarios on whether or not the largest deposit in each region has been discovered and its endowment adequately evaluated provided some measure of uncertainty of assessment results. The Bendigo and Stawell zones are estimated to host 12 undiscovered ore fields with >31 t (1 Moz) of contained gold and another 35 undiscovered ore fields with >10 t (0.32 Moz) of gold, containing in total 1600 t (51 Moz) of gold. The total residual orogenic gold endowment of the Mossman Orogen is estimated to be between 3 and 30 t of gold, contained in extensions of known deposits and up to six significant undiscovered gold ore fields each containing >1 t of gold. These estimates are comparable to results of recent three-part quantitative mineral resource assessments for those areas.

Quantitative assessment of mineral resources by combining geostatistics and fractal methods in the Tongshan porphyry Cu deposit (China)

Three-dimensional (3D) geological, geostatistical, and fractal/multifractal modeling are combined for the identification of new exploration targets in the Tongshan porphyry Cu deposit (China): (1) A 3D geological model of the deposit includes the strata, faults, altered rocks, intrusive bodies, and three orebodies using geological map, cross-sections, borehole dataset, and magnetic inversion; (2) geostatistical analysis involves omnidirectional and vertical semi-variogram calculations of the orebody, ordinary kriging interpolation of the orebody and 3D trend modeling using the assay data; (3) fractal models consisting of Hurst exponent estimation of the continuity of vertical mineralization and its concentration–volume (C–V) fractal model separation mineralized zones in a 3D block model; and (4) interpretation and validation: magnetic inversion was utilized to constrain intrusive rock shape between cross-sections and additional interpret orebody geometry model by ordinary kriging interpolation method using Tongshan borehole dataset. The results indicate that (a) the Hurst exponent is useful for identifying the vertical continuity of mineralization (with the range between 0 and 1200m), (b) the C–V fractal model is useful for identifying thresholds of Cu values in oxidation-type, skarn-type, and magmatic-type orebodies in the Tongshan deposit, and (c) the 3D geological and trend model can be combined to recognize potential subsurface targets in the Tongshan deposit. The methods can be applied to estimate mineral resources through district-scale exploration.

Discovered and undiscovered gold endowment of Turkey: a quantitative mineral resource assessment using GIS and rank statistical analysis

An assessment of the discovered and undiscovered gold endowment of Turkey, a prolific sector in the Tethyan Metallogenic Belt, is developed from a comprehensive Geographic Information System database containing 402 gold deposits and prospects. The majority of the gold deposits and prospects are epithermal, porphyry, volcanic-associated massive sulfides, orogenic gold, and skarn systems. These five major deposit types form more than 90% of the known gold deposits and prospects. Just 87, corresponding to 21.6%, of the deposits and prospects in the data set have current calculated gold reserve and/or resources, containing a total of 54.885 Moz Au. Current gold reserves of the country are 21.447 Moz constituting 39.1% of the total gold resources, of which 17.1 Moz gold are contained in four deposits. Out of these 87 deposits and prospects, only 27 contain significant gold reserve and/or resources (defined as equal to or more than 0.32 Moz or 10 tons Au), and contain 91.8% of the total gold endowment of the country. The cumulative frequency distribution model of the gold endowment of Turkey abides by log-normal distribution. Observed and estimated 10th, 50th (median), and 90th percentiles of the data are 0.0046 Moz [0.0045 Moz estimated], 0.1030 Moz [0.0875 Moz], and 1.4969 Moz [1.6938 Moz], respectively. The 99th percentile of the data is 7.6444 Moz [18.9636 Moz]. The arithmetic mean of the known gold endowment is 0.657 Moz and the Swanson mean size is 0.492 Moz. The arithmetic mean of the 27 significant gold deposit or prospects is 1.94 Moz. Zipf’s law estimates of the undiscovered (residual) gold resources of Turkey are based on the current size of the largest, rank 1, gold deposit of Turkey, which is the Kisladag porphyry deposit that has 17.481 Moz gold endowment (including past production). Zipf’s law estimates a total of 88.261 Moz natural or total gold endowment, 57.133 Moz or 65% of which has already been found. This predicts at least 31.128 Moz residual or undiscovered gold resources to be found in Turkey, though the lack of full delineation of the rank 1 deposit, Kisladag, means that this figure is very conservative.

From Predictive Mapping of Mineral Prospectivity to Quantitative Estimation of Number of Undiscovered Prospects

AbstractThis paper proposes that the spatial pattern of known prospects of the deposit‐type sought is the key to link predictive mapping of mineral prospectivity (PMMP) and quantitative mineral resource assessment (QMRA). This proposition is demonstrated by PMMP for hydrothermal Au‐Cu deposits (HACD) and by estimating the number of undiscovered prospects for HACD in Catanduanes Island (Philippines). The results of analyses of the spatial pattern of known prospects of HACD and their spatial associations with geological features are consistent with existing knowledge of geological controls on hydrothermal Au‐Cu mineralization in the island and elsewhere, and are used to define spatial recognition criteria of regional‐scale prospectivity for HACD. Integration of layers of evidence representing the spatial recognition criteria of prospectivity via application of data‐driven evidential belief functions results in a map of prospective areas occupying 20% of the island with fitting‐ and prediction‐rates of 76% and 70%, respectively. The predictive map of prospective areas and a proxy measure for degrees of exploration based on the spatial pattern of known prospects of HACD were used in one‐level prediction of undiscovered mineral endowment, which yielded estimates of 79 to 112 undiscovered prospects of HACD. Application of radial‐density fractal analysis of the spatial pattern of known prospects of HACD results in an estimate of 113 undiscovered prospects of HACD. Thus, the results of the study support the proposition that PMMP can be a part of QMRA if the spatial pattern of discovered prospects of the deposit‐type sought is considered in both PMMP and QMRA.

Methods of Three-part Quantitative Assessments of Undiscovered Mineral Resources: Examples from Victoria, Australia

Quantitative mineral resource assessments following the 3-part form rely on grade and tonnage models and probabilistic estimates of the number of undiscovered deposits. Assessments completed in Victoria, Australia, indicate that undiscovered mineral resources can be effectively estimated using grade and tonnage sub-models constructed using only medium- and large-tonnage deposits. Numbers of undiscovered deposits can be estimated on the basis of expert judgement or entirely by statistical means. Appropriate mathematical aggregation of individual expert views, expressed at interactive expert workshops, provides robust estimates of the number of undiscovered deposits. Underestimation of uncertainty, which is common in expert judgement, can be compensated by the statistical modification of individual interval estimates. In this study, the linear opinion pool was used as a simple and robust method of mathematical aggregation of multiple expert estimates of the number of undiscovered deposits. A general regression model, which estimates numbers of undiscovered deposits based on the size of the geologically permissive area and the median deposit tonnage, provided results generally compatible with those based on expert judgement or local deposit density models.

Quantitative Mineral Resource Assessments: An Integrated Approach.: DONALD A. SINGER and W. DAVID MENZIE. Pp. 232. 2010. Oxford University Press. ISBN 978-0-19-539959-2. Price US$74.00.

This book is the result of almost 40 years of effort the authors have made to develop an integrated approach to mineral resource assessments, principally working with the U.S. Geological Survey. The authors’ goal was to provide information valuable to users or practitioners of these types of assessments and, overall, they have done a fine job with this book. Although they emphasize the importance of quantitative mineral resource assessments (QRAs) and the details about how they are developed, principally being focused on the needs of government decision makers, the value of the book for exploration managers is much more than the authors intended. The QRAs have been developed to provide a rational, fact-based analysis of the potential for discovery of mineral resources on public lands. This information is important to people making informed decisions about land use and policy. The authors have developed a stepwise, three-part approach to QRAs: (1) using models of tonnages and grades to estimate possible tonnages and grades of undiscovered deposits, (2) …

Quantitative mineral resource assessment of undiscovered PGE resources in Finland

Most of the known platinum group element (PGE) resources in Finland are in contact-type and reef-type deposits in 2.45 Ga mafic–ultramafic layered intrusions. These intrusions are also estimated to contain the majority of possibly existing, yet undiscovered PGE resources in Finland. The undiscovered Pt, Pd, Au, Ni, and Cu resources in contact-type and reef-type deposits were estimated down to 1000 m depth using a three-part quantitative assessment method. This included the delineation of 19 contact-type and 24 reef-type permissive tracts, the formulation of a grade-tonnage model for the contact-type deposits and a separate model for each reef-type tract, estimation of the number of undiscovered deposits for each permissive tract, and Monte Carlo simulation to estimate the frequency distributions of metal tonnages in the undiscovered deposits. The expected number of undiscovered contact-type deposits is 29 and that of reef-type deposits is 23. At the 50% probability level, the total undiscovered PGE resources of Finland are estimated to be at least 5600 t Pt, 12,000 t Pd, 430 t Au, 4.2 Mt Ni, and 5.7 Mt Cu. At the 90% probability level, the corresponding tonnages are 720 t Pt, 1700 t Pd, 59 t Au, 0.87 Mt Ni, and 0.91 Mt Cu. More than 80% of the Pt + Pd in the undiscovered resources are estimated to be in reef-type deposits. The known PGE resources in Finland are 259 t Pt + Pd in six contact-type deposits, plus 69 t Pt + Pd in the atypical Kevitsa deposit. These figures indicate that the presently known deposits account for approximately 2% of the total assessed PGE resources in Finland. They suggest that significant potential exists for the discovery of additional PGE resources in the country.

Progress in integrated quantitative mineral resource assessments

Three-part resource assessments, begun over 30 years ago, provide a framework for making decisions concerning mineral resources under conditions of uncertainty. The parts include general locations of undiscovered deposits that are delineated from a deposit type's geologic setting; frequency distributions of tonnages and grades of well-explored deposits that serve as models of grades and tonnages of undiscovered deposits, and number of undiscovered deposits that are estimated probabilistically by type. Recently improved deposit density models show how to make probabilistic estimates of numbers of undiscovered deposits. Significant progress has been made showing how to reduce uncertainty and risk by the practical integration of the fundamental kinds of information needed by decision-makers. The approach is founded on internally consistent mineral deposit models that help convert the output of assessments into forms helpful to decision-makers. This integration of models and methods is a source of strength that reduces the chances of biased estimates, but it is also a burden, requiring careful development of models and applications of methods. Before decisions are made on where to explore, decisions must be made about what to explore for and whether it is worth the risk.

Quantitative Mineral Resource Assessment of Copper, Molybdenum, Gold, and Silver in Undiscovered Porphyry Copper Deposits in the Andes Mountains of South America.: C.G. CUNNINGHAM, E.O. ZAPPETTINI, WALDO VIVALLO S., C.M. CELADA, J. QUISPE, D.A. SINGER, J.A. BRISKEY, D.M. SUTPHIN, M. GAJARDO M., A. DIAZ, C. PORTIGLIATI, V.I. BERGER, R. CARRASCO, and K.J. SCHULZ. U.S. Geological Survey Open-File Report 2008-1253. Pp.

The U.S. Geological Survey (USGS), in collaboration with international partners, has embarked on a campaign to estimate the amount of undiscovered non-fuel mineral resources on planet Earth. The justification for this exercise is that policy makers in the United States and other interest groups need to know how much material remains to be mined, and the likely locations of these “undiscovered deposits.” A product of this on-going exercise is USGS open-file report 2008-1253, Quantitative Mineral Resource Assessment of Copper, Molybdenum, Gold, and Silver in Undiscovered Porphyry Copper Deposits in the Andes Mountains of South America . This report has been written in collaboration with the geological surveys of Argentina, Chile, Colombia, Ecuador, and Peru, and can be downloaded from the Internet at no cost. This book starts with a 67-page report that summarizes the rationale for and methodologies employed during this study, together with a synthesis of the results for the entire South American …

Quantitative Prediction for Deep Mineral Exploration

On reviewing the characteristics of deep mineral exploration, this article elaborates on the necessity of employing quantitative prediction to reduce uncertainty. This is caused by complexity of mineral deposit formational environments and mineralization systems as increase of exploration depth and incompleteness of geo-information from limited direct observation. The authors wish to share the idea of “seeking difference” principle in addition to the “similar analogy” principle in deep mineral exploration, especially the focus is on the new ores in depth either in an area with discovered shallow mineral deposits or in new areas where there are no sufficient mineral deposit models to be compared. An on-going research project, involving Sn and Cu mineral deposit quantitative prediction in the Gejiu area of Yunnan Province, China, was briefly introduced to demonstrate how the “three-component” (geoanomaly-mineralization diversity-mineral deposit spectrum) theory and non-linear methods series in conjunction with advanced GIS technology, can be applied in multi-scale and multi-task deep mineral prospecting and quantitative mineral resource assessment.