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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
| Content Provider | Semantic Scholar |
|---|---|
| Author | Mihalasky, Mark J. Ludington, Steve D. Hammarstrom, Jane M. Alexeiev, Dmitriy V. Frost, Thomas P. Light, Thomas D. Robinson, Gilpin R. Briggs, Deborah A. Wallis, John C. Miller, Robert J. Bookstrom, Arthur A. Panteleyev, Andre Chitalin, Andre Seltmann, Reimar Guang-Sheng, Yan Changyun, Lian Jing-Wen, Mao Jin-Yi, Li Ke-Yan, Xiao Rui-Zhao, Qiu Jianbao, Shao Gangyi, Shai Yu-Liang, Du |
| Copyright Year | 2015 |
| Abstract | 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 Porphyry Copper Assessment of the Central Asian Orogenic Belt and Eastern Tethysides—China, Mongolia, Russia, Pakistan, Kazakhstan, Tajikistan, and India By Mark J. Mihalasky1, Steve Ludington1, Jane M. Hammarstrom1, Dmitriy V. Alexeiev2, Thomas P. Frost1, Thomas D. Light1, Gilpin R. Robinson, Jr.1, Deborah A. Briggs1, John Wallis1, and Robert J. Miller1, with contributions from Arthur A. Bookstrom1, Andre Panteleyev3, Andre Chitalin4, Reimar Seltmann5, Yan Guangsheng6, Lian Changyun6, Mao Jingwen7, Li Jinyi6, Xiao Keyan6, Qiu Ruizhao6, Shao Jianbao6, Shai Gangyi6, and Du Yuliang6 1U.S. Geological Survey, United States. 2Russian Academy of Sciences, Moscow, Russia. 3XDM Resources, Inc. 4Consultant. 5Centre for Russian and Central EurAsian Mineral Studies, Natural History Museum, London, United Kingdom. 6China Geological Survey, Beijing, China. 7Chinese Academy of Geological Sciences, Beijing, China. range in area from about 60,000 to 800,000 square kilometers (km2); (2) a complex area of about 400,000 km2 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 km2 Jinsajiang tract and the 300,000 km2 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 online at http://minerals.usgs.gov/global/. 2 Porphyry Copper Assessment of the Central Asian Orogenic Belt and Eastern Tethysides Introduction The U.S. Geological Survey (USGS) conducted a probabilistic mineral resource assessment of undiscovered resources in porphyry copper deposits in parts of the Central Asian Orogenic Belt (CAOB) and eastern Tethysides as part of its global mineral resource assessment project (GMRAP). The purpose of the assessment was to (1) compile a database of known porphyry copper deposits and significant prospects, (2) delineate geology-based permissive areas (tracts) for undiscovered porphyry copper deposits at a scale of 1:1,000,000, (3) estimate numbers of undiscovered deposits within those permissive tracts, and (4) provide probabilistic estimates of amounts of copper (Cu), molybdenum (Mo), gold (Au), and silver (Ag) that could be contained in those undiscovered deposits. This report describes an assessment of undiscovered resources in porphyry copper deposits for the CAOB and eastern Tethysides (figs. 1 and 2). The assessment describes permissive areas for porphyry copper deposits in Russia, Mongolia, and China, as well as small areas in Pakistan, Kazakhstan, Tajikistan, and India. In some cases, very small parts of tracts extend into Kyrgyzstan, Afghanistan, and Myanmar. The study was conducted in cooperation with the China Geological Survey (CGS), the Centre for Russian and Central EurAsian Mineral Studies (CERCAMS), and colleagues from the Russian Academy of Sciences and industry consultants. The assessment was done using a three-part form of mineralresource assessment based on established mineral deposit models (Singer, 1993, 2007a, b; Singer and Berger, 2007; Singer and Menzie, 2010). Geographic areas (permissive tracts) are delineated using geologic, mineral occurrence, geochemical, and geophysical data to identify areas with features typical of the type of deposit under consideration. The amount of metal in undiscovered deposits is estimated using grade and tonnage models derived from information about known deposits. Probabilistic estimates of numbers of undiscovered deposits are consistent with the known deposits that define grade and tonnage models (Singer, 2007a). Numbers of undiscovered deposits at various quantiles (degrees of certainty) are estimated by an assessment team of experts using a variety of strategies, such as counting the number and ranking the favorability of significant prospects and comparing the spatial density of known deposits and expected undiscovered deposits to that of known deposits in similar, well-explored regions (Singer, 2007b). Probable amounts of undiscovered resources are then estimated by combining estimates of numbers of undiscovered deposits with grade and tonnage models using a Monte Carlo simulation process (Root and others, 1992; Bawiec and Spanski, 2012; Duval, 2012). This report primarily addresses Paleozoic through Triassic porphyry copper deposits in central and eastern Asia. Readers are referred to separate porphyry copper assessment reports on adjacent and overlapping areas. These include reports on (1) the Mesozoic of East Asia in China, Vietnam, North Korea, Mongolia, and Russia (Ludington and others, 2012b) that describe Yanshanian events in the eastern part of the study area, (2) the Cenozoic of the Tibetan Plateau (Ludington and others, 2012a), (3) the Paleozoic of Kazakhstan (Berger and others, 2014), (4) the Late Triassic through Holocene Tethys region of western and southern Asia (Zürcher and others, in press), and (5) the Paleozoic through Holocene of northeast Asia in Far East Russia and northeasternmost China (Mihalasky and others, in press). Terminology The terminology used in this assessment follows the definitions used in the 1998 assessment of undiscovered deposits of gold, silver, copper, lead, and zinc in the United States (U.S. Geological Survey National Mineral Resource Assessment Team, 2000), as well as mineral resource definitions used by the U.S. Bureau of Mines and U.S. Geological Survey (1980) and geologic definitions found in Bates and Jackson (1997). The terminology is intended to represent standard definitions and general usage by the minerals industry and the resourceassessment community. Some countries in the world recently have adopted more rigorous definitions of terms for estimating mineral resources and mineral reserves and for reporting exploration information to comply with legal mandates (for example, see Committee for Mineral Reserves International Reporting Standards, 2004). • Mineral occurrence—A locality where a useful mineral or material is found. A mineral concentration, usually (but not necessarily) considered in terms of some commodity (such as copper or gold) that is considered to be of value to someone, somewhere, or that is of scientific or technical interest. It can be said to have an anomalous concentration of one or more commodities. Enough information may be available to allow for classification as a specific deposit type or suite of deposit types. • Mineral deposit—A mineral concentration of sufficient size and grade that it might, under the most favorable of circumstances, be considered to have potential for economic development. • Undiscovered mineral dep |
| File Format | PDF HTM / HTML |
| DOI | 10.3133/sir20105090x |
| Alternate Webpage(s) | https://pubs.usgs.gov/sir/2010/5090/x/pdf/sir2010-5090-X.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
