澜沧江结合带中二叠世达弄岩片的发现及特征

摘要

The Danong Slices are located in the Danong Valley and its vicinity in Leiwuqi County,eastern Tibet.Based on the study of the rock strata,SIMS zircon dating of the mylonitizaed chlorite schist is 272.8±2.4 Ma,which indicates that this suit of rocks formed at Middle Permian.The whole rock SiO2 change from 48.12% to 76.93%.Their original rock might be a basic-middle-acid volcanic rock series and the main part of this suit of rocks are belong to high K calc-alkaline series.Tectonic reconstraction by whole rock geochemical data suggests that Langcangjiang suture maybe develop at an island-arc environment in the Middle Permian.The discovery of this suit of rocks provides new basic information for the strata,magmatic activity and tectonic evolution of the Langcangjiang suture,Tibet.%达弄岩片出露于藏东类乌齐县达弄沟及其附近地区,经采样分析测得糜棱岩化绿泥片岩的SIMS锆石U-Pb年龄为272.8±2.4 Ma,表明这套岩石形成于中二叠世。岩石SiO2含量从48.12%到76.93%,它们的原岩可能为基性-中性-酸性的火山岩,岩石系列主体属于高钾钙碱性系列岩石,地球化学分析数据表明在中二叠世,澜沧江结合带为岛弧构造环境。达弄岩片的发现为澜沧江结合带地层对比、岩浆活动和构造演化提供了新的信息。