青藏高原羌塘中部果干加年山一带晚三叠世花岗岩的特征拉萨市堆龙德庆县却桑地区早中三叠世查曲浦组层序厘定及其构造意义

拉萨却桑地区的原早中三叠世查曲浦组由下部碳酸盐岩和上部火山岩组成，下部碳酸盐岩产丰富的化石，时代为早—中三叠世，上部火山岩无古生物和年代学资料，根据叠置关系作为查曲浦组上部，时代也为早—中三叠世，并且成为该地区经典地层层序而被广泛引用。最近在原查曲浦组上部火山岩段玄武质安山岩中获得248Ma±4Ma的锆石SHRIMP U-Pb年龄，厘定原查曲浦组上部火山岩时代为早三叠世，原查曲浦组存在倒转，火山岩段应位于碳酸盐岩段之下，其下与列龙沟组整合过渡，证明该区二叠系与三叠系是连续沉积的，进一步说明早三叠世该区存在岩浆活动。查曲浦组层序的厘定对探讨冈底斯地区构造演化过程具有重要意义。

Determination of the formation sequence of Chaqupu Formation of Early-Middle Triassic in the Quesang area, Tibet, China, and its tectonic significance

Original Chaqupu Formation of Early-Middle Triassic in the Quesang area of Lhasa is composed by the lower part carbonate rocks which contain abundant Early-Middle Triassic fossils and the upper part volcanic rocks with no information on paleontology or chronology. Based on their stratigraphic overlying relationship, the volcanic rocks were determined as the upper part of Chaqupu Formation, and its age was determined to be Early-Middle Triassic, which has become a classical formation sequence locally and been widely used. Recently, SHRIMP U-Pb zircon dating was carried on the zircons of basaltic andesites of the volcanic rocks in the upper part of original Chaqupu Formation. The dating results show that these rocks were formed in Early Triassic (248Ma±4Ma), so the original Chaqupu Formation is a inversion tectonic, and the volcanic rocks used be under the carbonate rocks and contact conformably with Lielonggou Formation of Permian, which is a trustworthy evidence of the continuous deposition in this area from Permain to Triassic and further shows that this area existed magmatic activities in Early Triassic. The determination of the sequence of Chaqupu Formation has important significances in studying the evolution process of the Gangdise area.