XIANG Kun;XUE Chuandong;YANG Tiannan;XIE Zhipeng;XIN Di;JIANG Lili;LAI Ruijuan;Department of Earth Sciences, Kunming University of Science and Technology;Institute of Geology, Chinese Academy of Geological Sciences (CAGS);
Department of Earth Sciences, Kunming University of Science and Technology;Institute of Geology, Chinese Academy of Geological Sciences (CAGS);
The tectonic setting of Cretaceous granitoids in the southeastern Tibet Plateau, east of the Eastern Himalaya Syntax, is debated. Exploration and mining of the Laba Mo–Cu porphyry-type deposit in the area has revealed Late Cretaceous granites. New and previously published zircon U–Pb dating indicate that the Laba granite crystallized at 89–85 Ma. Bulk-rock geochemistry, Sr–Nd isotopic data and in situ zircon Hf isotopic data indicate that the granite is adakitic and was formed by partial melting of thickened lower crust. The Ca, Fe, and Al contents decrease with increasing SiO2 content.These and other geochemical characteristics indicate that fractional crystallization of garnet under high-pressure conditions resulted in the adakitic nature of the Laba granite. Cretaceous granitoids are widespread throughout the Tibetan Plateau including its southeastern area, forming an intact curved belt along the southern margin of Eurasia. This belt is curved due to indenting by the Indian continent during Cenozoic, but strikes parallel to both the Indus–Yarlung suture zone and the Main Frontal Thrust belt. It is therefore likely that Cretaceous granitoids in both the Gangdese and southeastern Tibetan Plateau areas resulted from subduction of Neo-Tethyan lithosphere.
adakitic granite;;geochemistry;;garnet fractional crystallization;;Cretaceous;;Neo-Tethyan subduction;;southeastern Tibetan Plateau
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