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Scientific Investigations Report 2010–5090–X

Prepared in cooperation with the China Geological Survey, the Centre for Russian and Central EurAsian Mineral Studies, and the Russian Academy of Sciences

Porphyry Copper Assessment of the Central Asian Orogenic Belt and Eastern Tethysides—China, Mongolia, Russia, Pakistan, Kazakhstan, Tajikistan, and India

By Mark J. Mihalasky, Steve Ludington, Jane M. Hammarstrom, Dmitriy V. Alexeiev, Thomas P. Frost, Thomas D. Light, Gilpin R. Robinson, Jr., Deborah A. Briggs, John Wallis, and Robert J. Miller, with contributions from Arthur A. Bookstrom, Andre Panteleyev, Andre Chitalin, Reimar Seltmann, Yan Guangsheng, Lian Changyun, Mao Jingwen, Li Jinyi, Xiao Keyan, Qiu Ruizhao, Shao Jianbao, Shai Gangyi, and Du Yuliang

Thumbnail of and link to report PDF (48.8 MB)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 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 on-line at http://minerals.usgs.gov/global/.

First posted March 24, 2015

  • Report PDF (22 MB)
  • Tabloid Figure 1 PDF (15.7 MB)
    Map of the study area in central and eastern Asia, showing geographic features mentioned in this report
  • Tabloid Figure E1 PDF (826 kB)
    [pages 1, 2 of 3] Correlations among geologic time division duration and symbols as used in Russia (Katalog Mineralov, 2005), China (Ma and others, 2002), and Mongolia (Mineral Resources Authority of Mongolia and others, 1998)
  • Appendix B XLS (153 kB)
    Excel Workbook for Deposits, Significant Prospects, and Prospects for the Porphyry Copper Assessment of the Central Asian Orogenic Belt and Eastern Tethysides

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Suggested citation:

Mihalasky, M.J., Ludington, Steve, Hammarstrom, J.M., Alexeiev, D.V., Frost, T.P., Light, T.D., Robinson, G.R., Jr., Briggs, D.A., Wallis, J.C., and Miller, R.J., with contributions from Bookstrom, A.A., Panteleyev, Andre, Chitalin, Andre, Seltmann, Reimar, Guangsheng, Y., Changyun, L., Jingwen, M., Jinyi, L., Keyan, X., Ruizhao, Q., Jianbao, S., Gangyi, S., and Yuliang, D., 2015, Porphyry Copper Assessment of the Central Asian Orogenic Belt and eastern Tethysides—China, Mongolia, Russia, Pakistan, Kazakhstan, Tajikistan, and India: U.S. Geological Survey Scientific Investigations Report 2010–5090–X, 106 p. and spatial data, http://dx.doi.org/10.3133/sir20105090X.

ISSN 2328-0328 (online)



Contents

Abstract

Introduction

Terminology

Porphyry Copper Deposit Models

Permissive Tracts for Porphyry Copper Deposits

Assessment Data

Geologic Framework

Exploration History

Tract Delineation

Estimating Numbers of Undiscovered Deposits

Assessment of Tracts in the Central Asian Orogenic Belt and Eastern Tethysides

Assessment of Tracts in the Tethyside Region

Summary of Probabilistic Assessment Results

Discussion

Acknowledgments

References

Appendixes (5)

Figures (44)

Tables (19)


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