南秦岭花岗岩锆石U-Pb定年及其地质意义  

Zircon U-Ph dating of granitoids from South Qinling, Central China and their geological significance

作　　者：孙卫东[1] 李曙光[1] Yadong Chen 李育敬 

机构地区：[1]中国科学技术大学地球和空间科学系 [2]Geochronolgy Lab,Royal Ontario Museum,100 Queen‘s Park,Ontario Canada [3]陕西省区调队,陕西咸阳712009

出　　处：《地球化学》2000年第3期209-216,共8页Geochimica

基　　金：国家自然科学基金!(49472144)

摘　　要：锆石Ｕ－Ｐｂ定年结果表明，南秦岭勉－略构造带以北迷坝、光头山和东江口等花岗岩体形成于三叠纪（２０６～２２０ Ｍａ），与南秦岭勉－略构造带洋盆的闭合时代及大别山超高压变质时代基本一致，显示了它们的形成与勉－略古生代洋盆闭合后及华南陆块与华北陆块碰撞之间的内在联系。它支持华南和华北两大陆块最终在印支期碰撞的观点。Qinling-Dabie orogenic belt is well known for the diamond and coesite-bearing ultrahigh-pressure metamorphic rocks found in Dabie Mountains and their east counterpart, Su-Lu terrane. The evolution of this famous EW-striking orogenic belt has been a controversial issue for many years, especially on when did the collision event between North and South China Blocks happened. The debating is mainly caused by the complexity of the orogenic belt. Qinling is a multisystem orogenic belt with two mountain chains and two sutures. The north suture lies along the Shan-Dan fault, it's a Caledonia suture. The south suture consists of Mian-Lue ophiolite complex belt and Bashan fault. It is believed to be the west counterpart of Dabie Triassic ultrahigh pressure metamorphic belt. One important key to solve the debating is to check whether those granitoids along the north part of Mian-Lue Suture in South Qinling are Devonian or Triassic. Zircons from 6 granitoids, such as Miba, Guangtoushan, Dongiiangkou, all through the -400 km long granitoid belt along the north part of Mian-Lue Suture are dated by zircon U-Pb method. Crystallization ages show that they were all formed at Triassic (206 - 220 Ma). This is consistent with the closure age Of the oceanic basin along Mian-Lue Suture and the metamorphic ages of ultrahigh-pressure metamorphic rocks in Dabie Mountains. It shows the relationship between the formation of these granitoids and the closure of the Mina-Lue Paleozoic ocean basin and support the Triassic collision between the South and North China Blocks.

关 键 词：花岗岩 锆石 碰撞时代 南秦岭 铀-铅定年 

分 类 号：P588.121[天文地球—岩石学] P597.1[天文地球—地质学]