LA-ICP-MS zircon U-Pb age and geochemical characteristics of Jiada potas-sic volcanic rocks in Zhongba terrane, Tibet

Cenozoic potassic volcanic rocks are widely distributed in the Tibetan Plateau, mainly in northern Tibet and Lhasa block with a few reports in Zhongba terrane. The study of Jiada potassic volcanic rocks found in Zhongba terrane shows that the rocks are almost exclusively trachyte, and the magma erupted incessantly by overflowing and erupting. These rocks are also characterized by high potassium and high aluminum, rich LILE, LREE and Sr, and poor HFSE, Y and Yb, with Eu negative anomaly. Their geochemi-cal characteristicss are similar to those of typical adkite rocks. The LA-ICP-MS zircon U-Pb age of trachyandesites is 17.03±0.32Ma, which means that these volcanic rocks were formed in Miocene. The Jiada potassic magma was derived from partial melting of thickened crust. The rocks represent post-collisional tectonic setting and extension environment.