西藏冈底斯地区早第三纪林子宗群火山岩地球化学特征及成因  

Geochemical Features and Genesis of the Linzizong Group Volcanic Rocks of the Early Tertiary in Gangdise,Tibet

作　　者：王天武[1] 李才[1] 杨德明[1] 

机构地区：[1]长春科技大学地球科学学院,130026

出　　处：《地质论评》1999年第S1期966-971,共6页Geological Review

基　　金：原地质矿产部资助(编号9501101)项目

摘　　要：西藏冈底斯地区广泛分布一套林子宗群(E_1-2lz)的海陆交互相和陆相、以安山岩为主的火山岩。伴生的侵入岩为石英二长岩—花岗岩系列岩石。岩石地球化学研究表明,区内火山岩呈较好的钙碱性演化趋势。其FeO^*/MgO值】2.0,K₂O/Na₂O】0.6,K₂O含量在1.38以上;微量分析结果表明,其含量具高钾火山岩特征;稀土配分呈右倾型,具明显的Eu负异常,同位素年龄在38.2～63.8 Ma之间。综合以上特征认为该火山岩是陆-陆碰撞造山作用中大陆边缘火山活动的产物。In the Gangdise area distribute extensively a suite of intermediate acidity volcanic rocks of the Early Tertiary Linzizong Group, belonging to paralic facies or continental facies. The main rock type is andesite ,while there are associated intrusive rocks including adamellite—granite series. From the geochemical research of the rocks, we can infer that the volcanic rocks of this region mostly belong to subalkali series,showing apparent evolution tendency towards the calc-alkaline suite. For most volcanic rocks,FeO~* /MgO>2. 0, K_2O/Na_2O>0. 6 and K_2O>1.38%, which indicates a continuous rising trend from intermediate to acidity. Analysis of frace elements showshigh-K contents and right oblique REE partition curves in addition to obvious negative euanomaly with isotopic ages of 38. 2～65.0 Ma. All of these present an active epicontinental feature of the volcanic rocks in this area. Basedon the geochemical characteristics and regional structure evolution of the volcanic rocks in this region, it is clear that the emergence of the rocks in this area is due to the activities of volcanos on the continental margin during the process of the contient-continent collision.

关 键 词：林子宗群火山岩 地球化学特征 成因 西藏 

分 类 号：P588.14[天文地球—岩石学]