Prepared in cooperation with the Task Force for Business and Stability Operations, under the auspices of the U.S. Department of Defense and the Afghanistan Geological Survey Rare Earth Element Mineralogy, Geochemistry, and Preliminary Resource Assessment of the Khanneshin Carbonatite Complex, Helmand Province, Afghanistan Robert D. Tucker, Harvey E. Belkin, Klaus J. Schulz, Stephen G. Peters, and Kim P. Buttleman Open-File Report 2011–1207 USGS Afghanistan Project Product No. 200 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2011 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Suggested citation: Tucker, R.D., Belkin, H.E., Schulz, K.J., Peters, S.G., and Buttleman, K.P., 2011, Rare earth element mineralogy, geochemistry, and preliminary resource assessment of the Khanneshin carbonatite complex, Helmand Province, Afghanistan: U.S. Geological Survey Open-File Report 2011–1207, 50 p. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 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Contents Abstract ......................................................................................................................................................................... 1 1.0 Introduction ........................................................................................................................................................... 2 2.0 Geology of the Khanneshin Carbonatite Complex ................................................................................................ 2 2.1 Geologic Setting ................................................................................................................................................ 2 2.2 Geology ............................................................................................................................................................. 3 2.2.1 Rocks of the Central Vent ........................................................................................................................... 3 2.2.2 Volcanic and Volcano-Sedimentary Rocks ................................................................................................. 8 2.2.3 Satellitic Vents, Dikes, and Minor Intrusive Rocks ...................................................................................... 9 2.3 History of Igneous Activity ................................................................................................................................. 9 2.4 Metallogeny ......................................................................................................................................................10 3.0 The Zone of LREE Enrichment ............................................................................................................................10 3.1 Styles of LREE Mineralization ..........................................................................................................................21 3.2 Whole-Rock Geochemistry ...............................................................................................................................21 3.3 Mineralogy ........................................................................................................................................................30 3.4 Structural Control on Alkaline Igneous Magmatism and LREE Mineralization ..................................................41 4.0 Estimation of LREE Resources ............................................................................................................................42 4.1 Analysis of the Soviet-Defined Zone .................................................................................................................42 4.2 Analysis by Remote Sensing ............................................................................................................................47 5.0 Conclusions .........................................................................................................................................................48 6.0 References Cited .................................................................................................................................................49 Figures 1. Maps of southern Afghanistan showing the location of the Khanneshin carbonatite complex and the permissive tract of uranium-phosphorus-rare earth element mineralization in the Helmand Basin ................... 4 2. Geologic map of the Khanneshin carbonatite complex ..................................................................................... 5 3. Cross-sections through the Khanneshin carbonatite complex .......................................................................... 6 4. Field photographs showing the key rock types and relationships within the intrusive central vent and volcanic apron of the Khanneshin carbonatite complex .................................................................................... 7 5. Photographs of examples of type-1 rare earth element mineralization in the marginal zone of the intrusive central vent of the Khanneshin carbonatite complex ...................................................................22 6. Photographs of examples of type-2 mineralized dikes in the zone of light rare earth element enrichment of the Khanneshin carbonatite complex ........................................................................................26 7. Ternary diagrams of major-element concentration data at the Khanneshin carbonatite complex ....................27 8. Variation diagrams illustrating the difference in major and trace element concentrations among igneous rocks of the Khanneshin carbonatite complex ....................................................................................28 9. Graphs showing the magnitude of rare earth element enrichment in the marginal zone of the intrusive central vent of the Khanneshin carbonatite complex .......................................................................................30 10. Mineralogy and crystallization sequence of sample RT-11K-2, type-1 mineralization of the Khanneshin carbonatite complex ........................................................................................................................................32 11. Mineralogy and crystallization sequence of sample RT-11K-5, type-1 mineralization of the Khanneshin carbonatite complex ........................................................................................................................................35 12. Mineralogy and crystallization sequence of fluorite-bearing rocks of the Khanneshin carbonatite complex ...........................................................................................................................................................36 13. Mineralogy and crystallization sequence of the fluorine-rich intrusive dikes of the Khanneshin carbonatite complex ........................................................................................................................................38 iii 14. Mineralogy and crystallization sequence of the apatite-rich intrusive dikes of the Khanneshin carbonatite complex ........................................................................................................................................40 15. Maps showing the area of the identified light rare earth element prospect in the northeastern part of the central intrusive vent and the digital elevation topography of the northern part of the Khanneshin carbonatite complex ........................................................................................................................................45 Tables 1. Whole-rock major-, trace-, and rare earth element (REE) concentration data, traverses 1A and 1B, Khanneshin carbonatite complex, Afghanistan. ...............................................................................................11 2. Major-, trace-, and rare earth element (REE) concentration data, traverse 2, Khanneshin carbonatite complex, Afghanistan. .....................................................................................................................................................13 3. Major- and trace- , and rare earth element (REE) concentration data, traverse 3, Khanneshin carbonatite complex, Afghanistan. .....................................................................................................................................17 4. Table of minerals containing rare earth elements (REE), Sr, and Ba as major elements, Khanneshin carbonatite complex, Afghanistan. ...................................................................................................................26 5. Summary of barium, strontium, and light rare earth element (LREE) concentrations, barite-ankerite alvikite, Khanneshin carbonatite