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秦岭发现金刚石:横贯中国中部巨型超高压变质带新证据及古生代和中生代两期深俯冲作用的识别
引用本文:杨经绥,许志琴,裴先治,史仁灯,吴才来,张建新,李海兵,孟繁聪,戎合.秦岭发现金刚石:横贯中国中部巨型超高压变质带新证据及古生代和中生代两期深俯冲作用的识别[J].地质学报,2002,76(4):484-495.
作者姓名:杨经绥  许志琴  裴先治  史仁灯  吴才来  张建新  李海兵  孟繁聪  戎合
作者单位:1. 中国地质科学院地质研究所大陆动力学实验室,北京,100037
2. 长安大学地质调查院,西安,710054
基金项目:国土资源部“十五”重点科技项目(编号20020201),科技部大陆钻探预研究和“973项目”资助的成果
摘    要:在秦岭北带榴辉岩及其围岩片麻岩的锆石中发现金刚石和大量石墨包裹体。金刚石具典型的1331~1334cm~(-1)拉曼谱峰。变质金刚石的发现证明秦岭北带榴辉岩及其围岩片麻岩经历了超高压变质作用,其俯冲深度>120 km。片麻岩锆石的SHRIMP定年表明,锆石核部代表岩浆事件的年龄或之前的残核年龄为1200~1800 Ma,超高压变质新增生边部的年龄为507±38 Ma,属早古生代。认为北秦岭超高压变质带与印支期大别超高压变质带(240~200 Ma)是时空上两个带。北秦岭超高压变质带向西可以与南阿尔金—柴北缘早古生代(490~440Ma)超高压变质带相连,向东与大别西北部的熊店和浒湾早古生代榴辉岩(420~400 Ma)相连,组成一条沿中央造山带北部分布的加里东期超高压变质带。认为主要分布在大别山南部的印支期超高压变质带应与南秦岭的高压蓝片岩带相连,组成一条分布在中央造山带南部的印支期高压超高压变质带。北秦岭超高压变质带的发现,为中央造山带存在一条西起阿尔金,东至苏鲁的近4000 km的世界上最大的一条超高压变质带的确定提供了新的关键性证据。而沿中央造山带分布的两条超高压变质带说明:①中国南北大陆在早古生代就已拼接在一起,其后,又有印支期的俯冲和碰撞叠加,加里东期超高压变质带主要分布在北部,后者在南部,两者时

关 键 词:金刚石  榴辉岩  UHP  激光拉曼  SHRIMP  秦岭  中央造山带
修稿时间:2002年7月21日

Discovery of Diamond in North Qinling: Evidence for a Giant UHPM Belt across Central China and Recognition of Paleozoic and Mesozoic Dual Deep Subduction between North China and Yangtze Plates
YANG Jingsui,XU Zhiqin,PEI Xianzhi,SHI Rendeng,WU Cailai ZHANG Jianxin,LI Haibing,MENG Fancong,RONG He Laboratory of Continental Dynamics,Institute of Geology,CAGS,Beijing, College of Geological Survey,Chang'' an University,Xi''an.Discovery of Diamond in North Qinling: Evidence for a Giant UHPM Belt across Central China and Recognition of Paleozoic and Mesozoic Dual Deep Subduction between North China and Yangtze Plates[J].Acta Geologica Sinica,2002,76(4):484-495.
Authors:YANG Jingsui  XU Zhiqin  PEI Xianzhi  SHI Rendeng  WU Cailai ZHANG Jianxin  LI Haibing  MENG Fancong  RONG He Laboratory of Continental Dynamics  Institute of Geology  CAGS  Beijing  College of Geological Survey  Chang' an University  Xi'an
Institution:YANG Jingsui,XU Zhiqin,PEI Xianzhi,SHI Rendeng,WU Cailai ZHANG Jianxin,LI Haibing,MENG Fancong,RONG He Laboratory of Continental Dynamics,Institute of Geology,CAGS,Beijing, College of Geological Survey,Chang' an University,Xi'an
Abstract:There is a giant Central Orogenic Belt (COB) in central China, which extends over 4000 km from West Kunlun on the west, through Altun, Qinlian, Qinling, and Dabie, to Sulu on the east. This paper is to report that micro-grains of diamond were discovered as inclusions in zircons from both eclogite and its gneissic country rocks in North Qinling, middle part of COB. SHRIMP U-Pb dating of zircons from granitic gneiss yielded 507 ?8 Ma for metamorphic rims and 1200~1800 Ma for relic magmatic or old cores, suggesting an Early Paleo-zoic ultrahigh pressure metamorphic event. The discovery indicated that supracrusts in North Qinling have been subducted to depths >120 km, which together with an Early Paleozoic suture reported in the region suggests an ealy collision between North China Plate and Yangtze Plate. Previous study indicates that an over 350 km long coesite-bearing UHP terrane of Early Paleozoic age has been discovered in Altun and Qilian, west part of COB, and an over 1000 km long diamond- and coesite-bearing UHP terrane of both Early Paleozoic and Trias-sic ages was developed in Dabie-Sulu, east part of the COB. This new microdiamond occurrence forms a bridge between two ultra-high pressure metamorphic terranes recognized in the western and eastern parts of China, thereby confirming the existence of the World's largest ultra-high pressure metamorphic belt extending >4000 km. The existence of such a belt, where the ultra-high pressure metamorphic events are dated from west to east as 500 Ma (South Altun) , 495 Ma (North Qaidam) , 507 Ma (North Qinling, this study) , or, 420~400 Ma (Qinling and northern Dabie) and 240-200 Ma (southern Dabie and Sulu) suggests that in general at least two events of large-scale plate subduction and collision, i. e. , Early Paleozoic and Mesozoic, between the North and South China plates have been recorded. Similar evidence of repeated subduction to and exhumation from great depths occurs in Western Europe in the Variscan and Alpine orogenies of Mesozoic and Tertiary ages. These examples of very deep subduction during recurrent continental collision along belts extending thousands of km suggest that UHPM is probably a common rather than an exceptional occurrence during continental colli-sion, with significant implications for processes of plate tectonic reorganization and mantle mixing over time.
Keywords:diamond  eclogite  Laser Raman Spectroscopy  Qinling  central erogenic belt
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