【摘要】 林子宗火山岩是发育在青藏高原南部冈底斯带的古近纪火山岩,被认为代表了新特提斯洋俯冲消减结束过渡到印度-亚洲大陆碰撞过程的产物,其确切的时代对于限制印度-亚洲大陆的碰撞时限具有重要意义.对冈底斯带中部朱诺地区的林子宗火山岩进行了系统的LA-ICP-MS锆石U-Pb年代学、元素和Sr-Nd同位素地球化学研究,获得的林子宗火山岩的典中组、年波组和帕那组LA-ICP-MS锆石U-Pb年龄分别为64.8±1.6Ma、59.7±1.8Ma和48.9±0.8Ma.元素和同位素地球化学结果表明,朱诺地区各组特征与区域上特征相似,其中典中组和年波组火山岩属于钙碱性和高钾钙碱性系列,具有岛弧火山岩特点;帕那组出现大量的钾玄岩,属于同碰撞火山岩.证明前人提出的雅鲁藏布江地区洋盆闭合和印度-亚洲大陆碰撞开始时间为50Ma左右的观点.更多还原

【Abstract】 The Paleogene volcanic rock in Linzizong Group is developed in the Gangdise belt,southern Tibet plateau and it is deemed to represent the result of Neo-Tethys from its subduction to the India-Asia collision.Its precise age is significant to constrain the time of the India-Asia collision.Herein a systematic study,including zircon U-Pb ages,major and trace elements and Sr-Nd isotopic geochemistry,has been done to volcanic rock from Linzizong Group in Zhunuo area in middle Gangdise belt.We obtain Linzizong Group volcanic rock LA-ICP-MS zircon U-Pb data showing the following ages:the Dianzhong Formation,64.8±1.6 Ma,the Nianbo Formation,59.7±1.8 Ma,the Pana Formation,48.9±0.8 Ma.The data of elementary and isotopic geochemistry suggest that the characteristics of these formations in Zhunuo area are similar to regional characteristics.Among them,Dianzhong and Nianbo formations are calc-alkalic and high-K calc-alkalic rocks with characteristics of arc-island volcanic rocks.Pana Formation contains shoshonite and is syn-collision volcanic rock.It is proved that suture of the Yarlung Zangbo oceanic basin and the beginning of collision between India and Asia were about 50 Ma.更多还原