XU Heng1,2, CUI Yin-liang1,3, ZHOU Jia-xi4, ZHANG Miao-hong2, JIANG Yong-guo3, WANG Gen-hou5, LIANG Ting-xiang2
(1. Faculty of Land Resources Engineering, Kunming University of Science and Technology, Kunming 650093, China;
2. Institute of Geological, Geophysical and Geochemical Exploration, Yunnan Nonferrous Metals Geological Bureau, Kunming 650216, China;
3. Yunnan Nonferrous Metals Geological Bureau, Kunming 650051, China;
4. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;
5. School of Geosciences and Resource, China University of Geology, Beijing 100083, China)
Abstract: Located in the middle of Jinshajiang-Red River alkali-rich porphyry metallogenic belt, Bijiashan copper deposit in Dali City, Yunnan province, China has made new breakthroughs associated with the porphyry Cu/Au ore prospecting. Based on detailed petrographic study, the paper carries out system geochemistry and geochronology of Bijiashan Cu deopit. The quartz-monzonite porphyry (QMP) associated with Cu/Au mineralization belongs to the quasi-aluminous and high-K series with alkali-rich (the average K2O+Na2O value is 9.97%), K-rich (the average K2O/Na2O ratio is 2.34) and quasi-aluminous (the average A/CNK values is 0.89) features. Trace element spider diagram displays enrichment of LILE (Rb, Ba, U, Th and Sr) and depletions of HFSE (Ta, Nb and Ti), which is consistent with continental crust. The rock displays Eu negative anomaly (the average value is 0.73), which is consistent with crust-mantle mixed granite. Litho-geochemical features suggest that the quartz-monzonite porphyry has crust-mantle mixing characteristics, of which the old crustal material melt partially is important. The zircon U-Pb dating (35.6±0.19 Ma) of quartz-monzonite porphyry by LA-ICP-MS is consistent with the magmatic period (45 to 30 Ma) of Jinshajiang-Honghe alkali-rich porphyry belt. The results further indicate that quartz-monzonite porphyry formed from the thickened lower crust and upper mantle melt partially under the tensional setting in India-Eurasian plate post-collision, which is related to the strike-slip tectonic events of Jinshajiang-Honghe fault.
Keywords: quartz-monzonite porphyry; zircon U-Pb age; petrogenesis; dynamic background; Bijiashan Cu deposit; Dali City
Email: cyl186@163.com
ACTA MINERALOGICA SINICA Vol. 35, No. 4, 2015, Page 439-446
