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Mark J. Mihalasky

Publications and source records attributed to Mark J. Mihalasky.

At least 19 recordsLinked to original sources
USGS2026

Uranium—Deposits, production and resources, market dynamics, and supply chain risks

Introduction Interest in nuclear power for the generation of electricity has risen with the increase in the need for more diverse baseload power, enhanced energy security, and the development of new technologies, such as small modular reactors (SMRs), which could provide power for remote areas, industrial applications, and artificial intelligence (AI) data centers. In 2024, the U.S. Department of Energy received $2.7 billion in congressional funding to bolster the domestic uranium production and nuclear fuel supply chain and address reliance on imports from foreign suppliers. In 2025, the U.S. Government issued several Executive and Secretary’s orders aimed at revitalizing the U.S. nuclear sector. If SMRs are to be as widely deployed in the United States and worldwide as envisioned, demand for uranium (nuclear reactor fuel) will likely increase. After the Fukushima nuclear accident in 2011, the market spot price of uranium began a decline, followed by a decrease in U.S. and global uranium exploration and mine development expenditures that led to a uranium supply deficit until 2020, when prices started to recover, prompting a resurgence in uranium exploration and development. In January of 2024, the uranium spot price rose to a 17-year high $106 (U.S. dollars) per pound of U3O8 (triuranium oxide, commonly known as “yellowcake”), which is expected to increase uranium exploration, mine development, and uranium production domestically and worldwide.

Fact Sheet↗
USGS2018

Rare earth element and rare metal inventory of central Asia

Rare earth elements (REE), with their unique physical and chemical properties, are an essential part of modern living. REE have enabled development and manufacture of high-performance materials, processes, and electronic technologies commonly used today in computing and communications, clean energy and transportation, medical treatment and health care, glass and ceramics, aerospace and defense, and metallurgy and chemical refining. Central Asia is an emerging REE and rare metals (RM) producing region. A newly compiled inventory of REE-RM-bearing mineral occurrences and delineation of areas-of-interest indicate this region may have considerable undiscovered resources.

Fact Sheet↗
USGS2018

World distribution of uranium deposits

Deposit data derived from IAEA UDEPO (http://infcis.iaea.org/UDEPO/About.cshtml) database with assistance from P. Bruneton (France) and M. Mihalasky (U.S.A.). The map is an updated companion to "World Distribution of Uranium Deposits (UDEPO) with Uranium Deposit Classification, IAEA Tech-Doc-1629". Geology was derived from L.B. Chorlton, Generalized Geology of the World, Geological Survey of Canada, Open File 5529 , 2007. Map production by M.C. Fairclough (IAEA), J.A. Irvine (Austrailia), L.F. Katona (Australia) and W.L. Slimmon (Canada). World Distribution of Uranium Deposits, International Atomic Energy Agency, Vienna, Austria. Cartographic Assistance was supplied by the Geological Survey of South Australia, the Saskatchewan Geological Survey and United States Geological Survey to the IAEA. Coastlines, drainage, and country boundaries were obtained from ArcMap, 1:25 000 000 scale, and are copyrighted data containing the intellectual property of Environmental Systems Research Institute (ESRI). The use of particular designations of countries or territories does not imply any judgment by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries. Any revisions or additional geological information known to the user would be welcomed by the International Atomic Energy Agency and the Geological Survey of Canada.

Report↗
USGS2017

Spatiotemporal analysis of changes in lode mining claims around the McDermitt Caldera, northern Nevada and southern Oregon

Resource managers and agencies involved with planning for future federal land needs are required to complete an assessment of and forecast for future land use every ten years. Predicting mining activities on federal lands is difficult as current regulations do not require disclosure of exploration results. In these cases, historic mining claims may serve as a useful proxy for determining where mining-related activities may occur. We assess the utility of using a space–time cube (STC) and associated analyses to evaluate and characterize mining claim activities around the McDermitt Caldera in northern Nevada and southern Oregon. The most significant advantage of arranging the mining claim data into a STC is the ability to visualize and compare the data, which allows scientists to better understand patterns and results. Additional analyses of the STC (i.e., Trend, Emerging Hot Spot, Hot Spot, and Cluster and Outlier Analyses) provide extra insights into the data and may aid in predicting future mining claim activities.

Nevada, Oregon↗
USGS2017

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 80 million pounds of U 3 O 8 have been produced and about 60 million pounds of identified producible U 3 O 8 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.

Texas↗
USGS2017

Undiscovered porphyry copper resources in the Urals—A probabilistic mineral resource assessment

A probabilistic mineral resource assessment of metal resources in undiscovered porphyry copper deposits of the Ural Mountains in Russia and Kazakhstan was done using a quantitative form of mineral resource assessment. Permissive tracts were delineated on the basis of mapped and inferred subsurface distributions of igneous rocks assigned to tectonic zones that include magmatic arcs where the occurrence of porphyry copper deposits within 1 km of the Earth's surface are possible. These permissive tracts outline four north-south trending volcano-plutonic belts in major structural zones of the Urals. From west to east, these include permissive lithologies for porphyry copper deposits associated with Paleozoic subduction-related island-arc complexes preserved in the Tagil and Magnitogorsk arcs, Paleozoic island-arc fragments and associated tonalite-granodiorite intrusions in the East Uralian zone, and Carboniferous continental-margin arcs developed on the Kazakh craton in the Transuralian zone. The tracts range from about 50,000 to 130,000 km 2 in area. The Urals host 8 known porphyry copper deposits with total identified resources of about 6.4 million metric tons of copper, at least 20 additional porphyry copper prospect areas, and numerous copper-bearing skarns and copper occurrences. Probabilistic estimates predict a mean of 22 undiscovered porphyry copper deposits within the four permissive tracts delineated in the Urals. Combining estimates with established grade and tonnage models predicts a mean of 82 million metric tons of undiscovered copper. Application of an economic filter suggests that about half of that amount could be economically recoverable based on assumed depth distributions, availability of infrastructure, recovery rates, current metals prices, and investment environment.

Urals↗
USGS2016

Geology and mineral resources of the Sheldon-Hart Mountain National Wildlife Refuge Complex (Oregon and Nevada), the Southeastern Oregon and North-Central Nevada, and the Southern Idaho and Northern Nevada (and Utah) Sagebrush Focal Areas: Chapter B in Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming

Summary The U.S. Department of the Interior has proposed to withdraw approximately 10 million acres of Federal lands from mineral entry (subject to valid existing rights) from 12 million acres of lands defined as Sagebrush Focal Areas (SFAs) in Idaho, Montana, Nevada, Oregon, Utah, and Wyoming (for further discussion on the lands involved see Scientific Investigations Report 2016–5089–A). The purpose of the proposed action is to protect the greater sage-grouse ( Centrocercus urophasianus ) and its habitat from potential adverse effects of locatable mineral exploration and mining. The U.S. Geological Survey Sagebrush Mineral-Resource Assessment (SaMiRA) project was initiated in November 2015 and supported by the Bureau of Land Management to (1) assess locatable mineral-resource potential and (2) to describe leasable and salable mineral resources for the seven SFAs and Nevada additions. This chapter summarizes the current status of locatable, leasable, and salable mineral commodities and assesses the potential of selected locatable minerals in lands proposed for withdrawal that span the Nevada, Oregon, Idaho, and Utah borders. In this report, the four study areas evaluated were (1) the Sheldon-Hart Mountain National Wildlife Refuge Complex SFA in Washoe County, Nevada, and Harney and Lake Counties, Oregon; (2) the Southeastern Oregon and North-Central Nevada SFA in Humboldt County, Nevada, and Harney and Malheur Counties, Oregon; (3) the Southern Idaho and Northern Nevada SFA in Cassia, Owyhee, and Twin Falls Counties, Idaho, Elko County, Nevada, and Box Elder County, Utah; and (4) the Nevada additions in Humboldt and Elko Counties, Nevada.

Idaho, Nevada, Oregon, Utah↗
USGS2016

Book review: Mineral resource estimation

Mineral Resource Estimation is about estimating mineral resources at the scale of an ore deposit and is not to be mistaken with mineral resource assessment, which is undertaken at a significantly broader scale, even if similar data and geospatial/geostatistical methods are used. The book describes geological, statistical, and geostatistical tools and methodologies used in resource estimation and modeling, and presents case studies for illustration. The target audience is the expert, which includes professional mining geologists and engineers, as well as graduate-level and advanced undergraduate students. Review info: Mineral Resource Estimation . By Mario E. Rossi, Clayton V. Deutsch . 2014 . ISBN 978-1-4020-5716-8 332 pp.

Economic Geology↗
USGS2015

Porphyry copper assessment of northeast Asia: Far East Russia and northeasternmost China: Chapter W in Global mineral resource assessment

The U.S. Geological Survey assesses resources (mineral, energy, water, environmental, and biologic) at regional, national, and global scales to provide science in support of land management and decision making. Mineral resource assessments provide a synthesis of available information about where mineral deposits are known and suspected to be in the Earth’s crust, which commodities may be present, and estimates of amounts of resources in undiscovered deposits. A probabilistic mineral resource assessment of undiscovered resources associated with porphyry copper deposits in northeast Asia—composed mainly of Far East Russia and a small part of northeasternmost China—was completed as part of a global mineral resource assessment. Porphyry copper deposits are the main source of copper globally. Russia is an important source of copper, consistently ranking as 6th, 7th, or 8th in world production since 2000, and ranked 7th in 2014. Most of this production has been from magmatic copper-nickel-platinum-group element, volcanogenic massive sulfide, and sediment-hosted copper deposit types. The purpose of the assessment was to (1) compile a database of known deposits and significant prospects, (2) delineate permissive areas (tracts) for undiscovered porphyry copper deposits that may be present in the upper kilometer of the Earth’s crust, and (3) provide probabilistic estimates of amounts of copper (Cu), molybdenum (Mo), gold (Au), and silver (Ag) that could be contained in undiscovered porphyry copper deposits in the tracts. The assessment was completed by the U.S. Geological Survey in collaboration with geologists from the Russian Academy of Sciences and industry consultants. The database of known deposits, significant prospects, and prospects includes an inventory of mineral resources in two known porphyry copper deposits, as well as key characteristics derived from available exploration reports for 70 significant porphyry copper prospects and 86 other prospects. Resource and exploration and development activity are updated with information current through February 2013.

Scientific Investigations Report↗
USGS2015

Porphyry copper assessment of the Central Asian Orogenic Belt and eastern Tethysides: China, Mongolia, Russia, Pakistan, Kazakhstan, Tajikistan, and India: Chapter X in Global mineral resource assessment

The U.S. Geological Survey collaborated with international colleagues to assess undiscovered resources in porphyry copper deposits in the Central Asian Orogenic Belt and eastern Tethysides. These areas host 20 known porphyry copper deposits, including the world class Oyu Tolgoi deposit in Mongolia that was discovered in the late 1990s. The study area covers major parts of the world’s largest orogenic systems. The Central Asian Orogenic Belt is a collage of amalgamated Precambrian through Mesozoic terranes that extends from the Ural Mountains in the west nearly to the Pacific Coast of Asia in the east and records the evolution and final closure of the Paleo-Asian Ocean in Permian time. The eastern Tethysides, the orogenic belt to the south of the Central Asian Orogenic Belt, records the evolution of another ancient ocean system, the Tethys Ocean. The evolution of these orogenic belts involved magmatism associated with a variety of geologic settings appropriate for formation of porphyry copper deposits, including subduction-related island arcs, continental arcs, and collisional and postconvergent settings. The original settings are difficult to trace because the arcs have been complexly deformed and dismembered by younger tectonic events. Twelve mineral resource assessment tracts were delineated to be permissive for the occurrence of porphyry copper deposits based on mapped and inferred subsurface distributions of igneous rocks of specific age ranges and compositions. These include (1) nine Paleozoic tracts in the Central Asian Orogenic Belt, which range in area from about 60,000 to 800,000 square kilometers (km 2 ); (2) a complex area of about 400,000 km 2 on the northern margin of the Tethysides, the Qinling-Dabie tract, which spans central China and areas to the west, encompassing Paleozoic through Triassic igneous rocks that formed in diverse settings; and (3) assemblages of late Paleozoic and Mesozoic rocks that define two other tracts in the Tethysides, the 100,000 km 2 Jinsajiang tract and the 300,000 km 2 Tethyan-Gangdese tract. Assessment participants evaluated applicable grade and tonnage models and estimated numbers of undiscovered deposits at different confidence levels for each permissive tract. The estimates were then combined with the selected grade and tonnage models using Monte Carlo simulations to generate probabilistic estimates of undiscovered resources. Additional resources in extensions of deposits with identified resources were not specifically evaluated. Assessment results, presented in tables and graphs, show amounts of metal and rock in undiscovered deposits at selected quantile levels of probability (0.95, 0.9, 0.5, 0.1, and 0.05 confidence levels), as well as the arithmetic mean and associated standard deviations and variances for each tract. This assessment estimated a total of 97 undiscovered porphyry copper deposits within the assessed permissive tracts. This represents nearly five times the 20 known deposits. Predicted mean resources that could be associated with these undiscovered deposits are about 370,000,000 metric tons (t) of copper, 10,000 t of gold, 7,700,000 t of molybdenum, and 120,000 t of silver. The assessment area is estimated to contain about five times as much copper in undiscovered deposits as has been identified to date. This report includes a summary of the data used in the assessment, a brief overview of the geologic framework of the area, descriptions of permissive tracts and known deposits, maps, and tables. A geographic information system database that accompanies this report includes the tract boundaries and known porphyry copper deposits, significant prospects, and prospects. Assessments of overlapping younger rocks and adjacent areas are included in separate reports available on-line at http://minerals.usgs.gov/global/ .

Scientific Investigations Report↗
USGS2012

Porphyry copper assessment of the Mesozoic of East Asia: China, Vietnam, North Korea, Mongolia, and Russia: Chapter G in Global mineral resource assessment

The U.S. Geological Survey (USGS) collaborated with the China Geological Survey (CGS) to conduct a mineral resource assessment of Mesozoic porphyry copper deposits in East Asia. This area hosts several very large porphyry deposits, exemplified by the Dexing deposit in eastern China that contains more than 8,000,000 metric tons of copper. In addition, large parts of the area are undergoing active exploration and are likely to contain undiscovered porphyry copper deposits. Three tracts were delineated to be permissive for Mesozoic porphyry copper deposits in East Asia: the Manchuride, Coastal Pacific, and East Qinling tracts, all Jurassic through Cretaceous in age. The tracts are based on mapped and inferred subsurface distributions of igneous rocks that define areas where the occurrence of porphyry copper deposits is possible. These tracts range in area from about 170,000 to about 1,400,000 km 2 . Although maps at a variety of scales were used in the assessment, the final tract boundaries are intended for use at a scale of 1:1,000,000. These Mesozoic deposits in East Asia all formed in post-subduction environments, environments newly recognized as permissive for the occurrence of porphyry copper deposits. Based on the grade, tonnage, and geologic characteristics of the known deposits, two tracts, Manchuride and Coastal Pacific, were evaluated using the general (Cu-Mo-Au) porphyry copper grade and tonnage model. The East Qinling tract was evaluated using the molybdenum-rich (Cu-Mo) model. Assessment participants estimated numbers of undiscovered deposits at different levels of confidence for each permissive tract. These estimates were then combined with the selected grade and tonnage models using Monte Carlo simulation to generate quantitative probabilistic estimates of undiscovered resources. Resources in future extensions of deposits with identified resources were not specifically evaluated. Assessment results, presented in tables and graphs, show mean amounts of metal and rock in undiscovered deposits at different quantile levels, as well as the arithmetic mean for each tract. This assessment estimated a mean total of about 44 undiscovered porphyry copper deposits within the assessed permissive tracts in East Asia. This represents nearly 4 times the 12 known deposits. Predicted mean (arithmetic) resources that could be associated with these undiscovered deposits are about 198,000,000 metric tons (t) of copper and about 3,900 t of gold, as well as byproduct molybdenum and silver. The reported identified resources for those 12 known deposits total about 23,000,000 t of copper and about 850 t of gold. The assessment area is estimated to contain nearly nine times as much copper in undiscovered porphyry copper deposits as has been identified to date. This report includes an overview of the assessment results and summary tables. Descriptions of each tract are included in appendixes, with estimates of numbers of undiscovered deposits, and probabilistic estimates of amounts of copper, molybdenum, gold, and silver that could be contained in undiscovered deposits for each permissive tract. A geographic information system that accompanies the report includes tract boundaries and a database of known porphyry copper deposits and prospects.

Scientific Investigations Report↗
USGS2011

Porphyry copper assessment of British Columbia and Yukon Territory, Canada: Chapter C in Global mineral resource assessment

The U.S. Geological Survey does regional, national, and global assessments of resources (mineral, energy, water, biologic) to provide science in support of land management and decision making. Mineral resource assessments provide a synthesis of available information about where mineral deposits are known and suspected to be in the Earth’s crust, which commodities may be present, and estimates of amounts of resources that may be present in undiscovered deposits. Canada is an important source of copper, consistently ranking as one of the top 10 world producers during the past decade (2000–2010). The preponderance of this production has been from porphyry-copper-type deposits in the western Canadian Cordillera. A probabilistic mineral resource assessment of undiscovered resources associated with porphyry copper deposits in western Canada was completed as part of a global mineral resource assessment. The purpose of the assessment was to (1) compile a database of known deposits and significant prospects, (2) delineate permissive areas (tracts) for undiscovered porphyry copper deposits that may be present in the upper kilometer (minimally) of the Earth’s crust, and (3) provide probabilistic estimates of amounts of copper (Cu), molybdenum (Mo), gold (Au), and silver (Ag) that could be contained in undiscovered porphyry copper deposits in the tracts. The study was done by the U.S. Geological Survey (USGS) in collaboration with geologists from the British Columbia Geological Survey, Yukon Geological Survey, and industry consultants. The database of known deposits and significant prospects includes an inventory of mineral resources in 89 known porphyry copper (and 2 related copper-bearing polymetallic vein) ore zones, representing 50 porphyry copper deposits, and lists key characteristics of 280 additional porphyry copper and related copper-bearing prospects, as indicated by currently available exploration results, which also are summarized. Resource and exploration and development activity are updated with information current through April 2010. The delineation of permissive tracts and probabilistic estimation of resources in undiscovered deposits were done using the USGS three-part mineral resource assessment approach. Permissive tracts are defined in accordance with descriptive models for porphyry copper deposits to include igneous rocks and known deposits and prospects within magmatic arcs related to convergent plate-margin boundary zones. Frequency distributions of total tonnages and average grades of thoroughly explored deposits were used as models for undiscovered deposits and include a new grade and tonnage model for calc-alkaline porphyry Cu±Mo±Au deposits in western Canada. Five permissive tracts for the occurrence of porphyry copper deposits were delineated: 2 island-arc tracts, 1 tract of transitional, mixed island-arc and continental arc affinities, and 2 continental arc tracts. In permissive tract 003pCu2001, calc-alkaline igneous rocks of Middle Triassic to Late Jurassic age in accreted island-arc terranes of the Intermontane belt are assessed for calc-alkaline porphyry Cu±Mo±Au deposits. The area of this tract is 175,250 km 2 . In 12 known deposits, the total reported tonnage of ore is 8,100 million metric tons (Mt) containing 24.6 Mt copper. An estimated 6.9 undiscovered deposits contain a calculated mean of 8.9 Mt copper and a median of 6.9 Mt copper. The spatial density for the 18.9 known plus estimated undiscovered deposits in this tract is approximately 11 deposits per 100,000 km 2 . In permissive tract 003pCu2002, alkaline igneous rocks of Middle Triassic to Late Jurassic age within the Intermontane accreted island-arc terranes are assessed for alkaline porphyry Cu-Au deposits. The area of this tract is 109,290 km 2 . In 12 known deposits the total reported tonnage of ore is 6,440 Mt, containing 20.9 Mt copper. An estimated 7 undiscovered deposits contain a calculated mean of 22 Mt copper and a median of 13 Mt copper. The spatial density for the 19 known plus estimated undiscovered deposits in this tract is approximately 17 deposits per 100,000 km 2 . In permissive tract 003pCu2003, calc-alkaline igneous rocks of Late Triassic to Early Cretaceous age within the accreted Insular terranes of mixed island-arc and continental arc affinities are assessed for calc-alkaline porphyry Cu±Mo±Au deposits. The area of this tract is 58,360 km 2 . The total tonnage of ore reported in the 2 known deposits is 1,160 Mt containing 3.17 Mt copper. An estimated 2.3 undiscovered deposits contain a calculated mean of 3 Mt copper and a median of 1.9 Mt copper. The spatial density for the 4.3 known plus estimated undiscovered deposits in this tract is approximately 7 deposits per 100,000 km 2 . In permissive tract 003pCu2004, calc-alkaline igneous rocks in continental magmatic arcs of Jurassic to Eocene age are assessed for porphyry Cu±Mo±Au deposits. The area of this tract is 639,500 km 2 . The total tonnage of ore reported for the 23 known deposits is 6,520 Mt containing 17.9 Mt copper. An estimated 9.6 undiscovered deposits contain a calculated mean of 13 Mt copper and a median of 11 Mt copper. The spatial density for the 32.6 known deposits plus the estimated undiscovered deposits in this tract is approximately 5 deposits per 100,000 km 2 . In permissive tract 003pCu2005, calc-alkaline igneous rocks in continental magmatic arcs of Oligocene to Pliocene age are assessed for porphyry Cu±Mo±Au deposits. The area of this tract is 32,840 km 2 . The total tonnage of ore reported for the 1 known deposit is 44.8 Mt containing 0.224 Mt copper. An estimated 1.4 undiscovered deposits contain a calculated mean of 1.8 Mt copper and a median of 0.72 Mt copper. The spatial density for the 2.4 known plus estimated undiscovered deposits in this permissive tract is approximately 7 deposits per 100,000 km 2 . Western Canada has been thoroughly explored for porphyry copper deposits. The total estimated copper contained in known deposits is about 66.8 Mt (based on 2010 data), as compared to a 49 Mt mean of estimated copper in undiscovered deposits and a 34 Mt median of estimated copper in undiscovered deposits. The copper contained in known porphyry copper deposits represents about 58 percent of the total of known and undiscovered porphyry copper deposits (based on mean values). About 86 percent of the increase in estimated copper resources between 1993 and 2009 resulted from the discovery of extensions to known deposits. Nevertheless, exploration for undiscovered deposits continues, especially in and around significant prospects and in parts of permissive tracts that are mostly hidden beneath younger volcanic, sedimentary, or vegetated surficial cover.

British Columbia, Yukon Territory↗
USGS2004

Assessment of metallic mineral resources in the Humboldt River Basin, Northern Nevada, with a section on Platinum-Group-Element (PGE) potential of the Humboldt mafic complex

The Humboldt River Basin is an arid to semiarid, internally drained basin that covers approximately 43,000 km2 in northern Nevada. The basin contains a wide variety of metallic and nonmetallic mineral deposits and occurrences, and, at various times, the area has been one of the Nation's leading or important producers of gold, silver, copper, mercury, and tungsten. Nevada currently (2003) is the third largest producer of gold in the world and the largest producer of silver in the United States. Current exploration for additional mineral deposits focuses on many areas in northern Nevada, including the Humboldt River Basin.

Nevada↗
USGS2004

Spatial databases of the Humboldt Basin mineral resource assessment, northern Nevada

This report describes the origin, generation, and format of tract map databases for deposit types that accompany the metallic mineral resource assessment for the Humboldt River Basin, northern Nevada, (Wallace and others, 2004, Chapter 2). The deposit types include pluton-related polymetallic, sedimentary rock-hosted Au-Ag, and epithermal Au-Ag. The tract maps constitute only part of the assessment, which also includes new research and data for northern Nevada, discussions on land classification, and interpretation of the assessment maps. The purpose of the assessment was to identify areas that may have a greater favorability for undiscovered metallic mineral deposits, provide analysis of the mineral-resource favorability, and present the assessment of the Humboldt River basin and adjacent areas in a digital format using a Geographic Information System (GIS).

Open-File Report↗
USGS2002

A reconnaissance method for delineation of tracts for regional-scale mineral-resource assessment based on geologic-map data

The U.S. Geological Survey (USGS) is proposing to conduct a global mineral-resource assessment using geologic maps, significant deposits, and exploration history as minimal data requirements. Using a geologic map and locations of significant pluton-related deposits, the pluton-related-deposit tract maps from the USGS national mineral-resource assessment have been reproduced with GIS-based analysis and modeling techniques. Agreement, kappa, and Jaccard's C correlation statistics between the expert USGS and calculated tract maps of 87%, 40%, and 28%, respectively, have been achieved using a combination of weights-of-evidence and weighted logistic regression methods. Between the experts' and calculated maps, the ranking of states measured by total permissive area correlates at 84%. The disagreement between the experts and calculated results can be explained primarily by tracts defined by geophysical evidence not considered in the calculations, generalization of tracts by the experts, differences in map scales, and the experts' inclusion of large tracts that are arguably not permissive. This analysis shows that tracts for regional mineral-resource assessment approximating those delineated by USGS experts can be calculated using weights of evidence and weighted logistic regression, a geologic map, and the location of significant deposits. Weights of evidence and weighted logistic regression applied to a global geologic map could provide quickly a useful reconnaissance definition of tracts for mineral assessment that is tied to the data and is reproducible.

Natural Resources Research↗