THE IMPLICATION OF SIMILARITIES AND SYSTEMATIC VARIATIONS AMONG THE MONOMETALLIC HIGH-FLUORINE PORPHYRY DEPOSITS IN THE EAST QINLING MOLYBDENUM BELT, CHINA

XIAO, Ping, China University of Mining and Technology, Beijing, 100083, China, FRIEHAUF, Kurt, Dept. Physical Sciences, Kutztown University, Kutztown, PA 19530, WANG, Yanbin, Scientific Cooperation, China University of Mining & Technology, D11, Xueyuan Road, Haidian District, Beijing, 100083, China and WANG, Cuizhi, College of Zijin Mining, Fuzhou University, 2 New Campus Road, Fuzhou, 350108, China, xiao@kutztown.edu

Situated on the southern margin of the North China Craton, mirroring the Yan-Liao molybdenum belt on the northern margin, and with more than 5million metric tons of explored Mo metal reserves, the East Qinling Molybdenum Belt (EQMB) is the largest molybdenum producing region in China. Molybdenum deposits in the EQMB include porphyry Cu-Mo, porphyry Mo, skarn Mo-W, and carbonatite deposits.

The five known major monometallic high-fluorine porphyry Mo deposits in the EQMB – Jinduicheng, Shijiawan, Leimengou, Yuchiling, and Donggou – bear a striking similarity in mineralization, hydrothermal alteration, and igneous geochemistry. Mineralization of four of the deposits is associated with a small granite porphyry stock, and the Yuchiling deposit is related to a composite granitoid batholith. Porphyries related to mineralization share broad likenesses in major elemental features (SiO₂- and Al2O₃-rich, MgO- and CaO-poor, TiO2 depletion, A/CNK > 1.1, (Na₂O+K₂O) > 7.5, (K₂O/Na₂O) > 1) and high LREE/HREE ratios.

The East Qinling Molybdenum Belt shows systematic variation along its axis. Published molybdenite Re-Os ages indicate mineralization progressed from west to east: Jinduicheng (138.3 ± 0.8 Ma), Shijiawan (138.0 ± 8 Ma), Leimengou (132.4 ± 1.9 Ma), Yuchiling (131.2 ± 1.4 Ma), and Donggou (116.0 ± 1.7 Ma). Re content of molybdenite and alkali-lime index decrease gradually, and Eu anomaly systematically increases eastward.

Prior researchers suggested that the five deposits formed at different times with different magmatic source regions (upper mantle, lower crust, and upper crust). Alternatively, we propose the systematic differences in geochemistry, mineralization age, REE pattern, and isotopic characteristics, may have resulted from magmas of similar primary source region that experienced progressively greater degrees of crustal interaction and fractionation during ascent, as post-orogenic extension of the Qinling Mountains progressed eastward.

Session No. 246--Booth# 18

Economic Geology (Posters)

Wednesday, 3 November 2010: 8:00 AM-6:00 PM

Hall D (Colorado Convention Center)

Geological Society of America Abstracts with Programs. Vol. 42, No. 5, p.580

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