Zircon U-Pb Geochronology, Geochemistry And Tectonic Setting Of The Eshan Granite With Mo Mineralization In Yunnan Province

The study area is located in the southwest of Yangtze paraplatform, the lower-middle part of kunyang rift and in the limit of Luzhijiang fracture and Puduhe fracture. Eshan granite is located in the south of Kangdian axis and belonging to a part of the Kangdian axis granite. Based on the analysis results of petrography, major elements, trace elements, rare earth elements, Sr-Nd isotopes, LA-ICP-MS U-Pb zircon dating, molybdenite Re-Os metallogenic dating and other studies, we obtained that ZHM1 granites are flesh red and medium to coarse-grained granite, while ZHM2 granites are the gray and medium to coarse-grained granite. Both are characterized by high alkali and rich silicon contents,belonging to high potassium calc-alkaline and peraluminous granite and rish in trace elements in Rb, U, K,Ta, Pb, Hf, loss of Nb, Ti, P,Ba, La. Both total rare earth elements content are low, rich in light rare earth elements(LREE); exhibiting moderate negative Eu anomalies; Sr-Nd isotopes show that flesh redgraniteand gray granite belong to S type granites; Through the analysis of the ore-forming elements,Eshan flesh redgranite(rich in Sb, Bi, Sn, Cu, W, Cr, As,B, Pb) and gray granite granite(rich in Bi, Cu, Sn, W, Cr, Sb, B) have more types of the forming elements,with higher strength of enrichment and good metallogenic prospect(2) By the method of LA-ICP-MS zircon U-Pb isotope dating, the forming age of flesh red granite and gray granite are 746±34 Ma and 746±30 Ma, respectively, which belong to the early sinian period.(3) By the method of molybdenite Re-Os dating, the ore-forming age is 827.9-835.1Ma, which belong to the late Qingbaikou period of the late Proterozoic(4) The Eshan flesh red granite and gray granite genesis are highly fractionated S type granite, The source rocks may have been formed from partial melting of pelite-rich the upper crust(5) R1 and R2 figure, Rb/30-Hf-3Ta figure, Y+Yb-Rb figure, Yb+Ta-Rb figure, etc., reflect the background of the study area is in the conversion of syn-collision tectonic into post-collisionaland extensional tectonics environment. In late proterozoic era(1200-1000 Ma), the world’s major continents gathered to Rodinia supercontinent, greenville orogeny which is respected by the Jinning movement in China, urged the near continental blocks to combine together, then leaded to the formation of unified Yangtze basement, and generated Syn-collisional S type granite simultaneously. Under the background of Rodinia supercontinent cracking in Early neoproterozoic, thewestern Yangtze was also cracking, The tectonic environment of the area changed from compressive to tensile environment, associated a series of granite magmatic activities, including the granite magmatic of the study area.