XU Chang-hao1, LIN Yan-hai2,3*, YU Tao4, FAN Bing-liang5
(1. Department of Geology College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China;
2. Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources Laboratory, Xining 810012, China;
3. Qinghai Geological Survey Institute, Xining 810012, China;
4. College of Science, Tibet University, Lhasa 850000, China;
5. Geothermal Geological Survey Party, Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, China)
Abstract: In this paper, the LA-ICP-MS zircon U-Pb isotopic ages and petrogeochemical characteristics of biotite monzogranites, porphyritic monzogranites, and fine-grained granites in the Xiaya intrusions in Eastern Tibet have been studied. The results show that the Xiaya intrusions is characterized with multi-stage intrusions in a period from Late Cretaceous to Paleogene (73.6±0.8－60.6±1.6 Ma). The intrusive rocks are generally depleted in Ba, Nb, Sr, P, Ti, etc., but relatively enriched in Rb, Th, U, etc., with some characteristics of I-type granite and A-type granite. They all belong to the highly differentiated calc-alkaline granite with transitional characteristics of I type and A type granites. The F and B rich fluids derived from the late-stage high differentiation evolved granitic magma are the main W-bearing fluids in this area with the time of W-mineralization limited in a period from Late Cretaceous to Paleogene (76.6－60.6 Ma). The intrusions only provide heat energy, but not ore-forming materials to the Pb, Zn, Ag mineralization in the surrounding area. The Xiaya intrusions were formed in a transitional process from the collisional environment to intraplate environment, which is related to the transformation of the Lancangjiang island arc and Changdu micro block from the late-orogenic and syn-collisional tectonic environment to the intracontinental rift environment.
Keywords: The Xiaya intrusions; petrogeochemical characteristics; zircon U-Pb dating; petrogenesis; tungsten mineralization
ACTA MINERALOGICA SINICA Vol. 40, No.6, 2020, page 649-663
