Discovery of the granulite xenoliths in Cenozoic volcanic rocks from Hoh Xil, Tibetan plateau

摘要

Two-pyroxene granulite and clinppyroxene granulite xenoliths have been recently discovered in the Late Paleogene to Neogene volcanic rocks (with ages in the range of 4.27 ～ 44. 60 Ma) that outcropped in Hoh Xil, central Tibetan plateau. Based on the electron microprobe analysis data, the xenoliths provide constraints for the formation equilibrium temperatures of the two-pyroxene granulite being about 783 to 818 ℃ as determined by two-pyroxene thermometry and the forming pressure of the clinopyroxene granulite being about 0.845 to 0.858 GPa that is equivalent to 27.9 ～ 28.3 km depth respectively. It indicates that these granulite xenoliths represent the samples from the middle part of the thickened Tibetan crust. This discovery is important and significant to making further discussion on the component and thermal regime of the deep crust of the Tibetan plateau.