Earth Science Frontiers ›› 2018, Vol. 25 ›› Issue (6): 152-164.DOI: 10.13745/j.esf.sf.2018.11.1

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Geochronology, rock geochemistry and tectonic setting of intermediate-acid intrusive rocks from the Jigongcun molybdenum mining area, Tibet.

WANG Jian,WEI Qirong,CI Qiong,ZHENG Qiuping,WANG Xudong,JI Xuefeng,XU Huan   

  1. 1. Faculty of Earth Resources, China University of Geosciences(Wuhan), Wuhan 430074, China 
    2. Second Geological Survey, Tibet Institute of Geological Survey, Lhasa 850000, China
  • Received:2018-09-05 Revised:2018-11-01 Online:2018-11-30 Published:2018-11-30
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Abstract: The Jigongcun molybdenum mine is located in the southern part of the GangdiseXiachayu late YanshanHimalaya magmatic arc zone. In this paper, we studied the intermediate-acid rocks widely distributed in the mining area and carried out a systematic investigation on field geological survey, petrology, LA-ICP-MS zircon U-Pb dating and geochemical characteristics of these rocks. The findings indicate that the Jigongcun intermediate-acid rocks are mainly quartz diorite and some granodiorite. The rocks LA-ICP-MS zircon U-Pb age of 51.8±0.5 Ma suggests they were formed in the Eocene (E2) period. They have low K (K2O content ranges 1.66%2.44%) and high Na (Na2O content ranges 3.58%4.06%) contents and belong to calc-alkaline-high potassium calc-alkaline series with quasi-aluminum-weak aluminous characteristics. The ΣREE contents vary greatly (53.6117)×10-6 with light REE enrichment, represented by right-inclined REE distribution mode, and (La/Yb)N value of 3.907.31. No obvious Ce and Eu anomalies were observed (Ce/Ce*=0.921.17; Eu/Eu*=0.961.15), while the trace-element spider diagram shows positive Rb, Th, U and K and negative Ba, Nb, Ta, P and Ti anomalies. The Jigongcun intermediate-acid rocks belong to I-type granite, and formed from the partial melting of the lower basaltic crust due to thickening of the crust, in the subduction and collision environment of the Indo-Eurasian plate.


Key words: intermediate-acid intrusive rocks, zircon U-Pb dating, rock geochemistry, tectonic setting, Jigongcun molybdenum mining area, Tibet

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