藏南邛多江地区花岗岩地球化学特征及成因类型  

Genetic Type and Geochemical Features of Granitoid Intrusions Occurring in the Qiongduojinag Area,Southern Tibet

作　　者：聂凤军[1] 胡朋[1] 江思宏[1] 刘妍[1] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037

出　　处：《地质学报》2006年第9期1342-1354,共13页Acta Geologica Sinica

基　　金：国家重点基础发展规划"973"项目(编号2002CB412606)资助成果

摘　　要：本文以邛多江变质核杂岩中花岗岩为研究对象、分别对仲格耐和倾日二长花岗岩体及相关岩脉的代表性全岩样品主元素、微量元素和稀土元素进行了系统测定。研究结果表明,所研究的2处花岗岩环(株)无论在岩相学和矿物学上,还是在元素地球化学方面均兼具壳幔型花岗岩特点,部分微量元素的特征比值和稀土元素分布型式完全可与高钾钙—碱性系列火成岩相对比。根据全岩样品的矿物学和地球化学特征,可以推断,仲格耐和倾日花岗岩环(株)是深源岩浆与地壳浅部岩(体)层相互作用的结果,而并非是泥质类岩石通过深熔和岩浆结晶分异的产物。仲格耐和倾日花岗岩体的成岩作用与后碰撞造山作用晚期阶段大规模拆离构造活动有关,属后碰撞造山环境中的壳幔型花岗岩。Located at easternmost part of the Tethyan--Himalayan tectonic belt, the Qiongduojiang is one of the most important parts of southern Tibet metallogenic province, and has been considered as one of the key parts of the southern Tibet detachment system. Phanerozoic granitoid intrusions of varying size and occurrence are well--developed duo to multiple orogenic events from early Paleozoic to Tertiary. Some of these intrusions show an intimate relation with various metamorphic core complexes. To clarify the genetic type and geochemical features, two typical monzogranite bodies, that are associated with the Qiongduojiang metamorphic core complex, have been selected for the geochemical studies. Systematic chemical analyses on a number of fresh whole--rock samples from the Zhonggenai monzogranite ring and Qingri monzogranite stock indicate that both of these two rock bodies bear the characteristics of mantle--and crust--derived granitoid intrusions, not only in petrological observations and mineralogical assemblage, but also in major, trace and rare earth elements. The characteristic ratios of some trace element agree well with the typical shoshonitic igneous rocks. Based on the geochemical studies, combined with field geological evidences, we concluded that both the Zhonggenai monzogranite ring and Qingri monzogranite stock could be the result of the interaction of deep--rooted granitoid magma （mantle--derived ？） and upper crust. Most of these granitoid intrusions occurring in the Qiongduojiang area were emplaced along a detachment zone during a large--scale extensional tectonic event caused by the Miocene post--collision orogeny （Mid--Himalayan time period）. Meanwhile, some of these granitoid intrusions played an important role during the formation of various metamorphic core complex occurring in southern Tibet.

关 键 词：藏南 邛多江 二长花岗岩 元素地球化学 成因类型 

分 类 号：P588.121[天文地球—岩石学]