东昆仑造山带花岗岩类Pb-Sr-Nd-O同位素特征  

Pb-Sr-Nd-O Isotope Characteristics of Granitoids in East Kunlun Orogenic Belt

作　　者：刘成东[1] 莫宣学[1] 罗照华[1] 喻学惠[1] 谌宏伟[1] 李述为[1] 赵欣[1] 

机构地区：[1]中国地质大学

出　　处：《地球学报》2003年第6期584-588,共5页Acta Geoscientica Sinica

基　　金：中国地质调查局重点项目"花岗岩重大地质问题研究"(编号 2 0 0 113 90 0 0 18);国家重点基础研究发展规划项目 (G19980 40 80 0 ;2 0 0 2CB412 60 0 )资助

摘　　要：本文报道了东昆仑造山带三叠纪辉长岩、花岗岩类及其包裹体的Pb、Sr、Nd和O同位素组成。东昆仑造山带花岗质岩石全岩和长石Pb同位素组成相差不大 ,具明显的造山带Pb同位素特征 ;Sr同位素初始值 (ISr)变化于 0 .70 14 4～ 0 .70 972之间 ,暗示幔源成因 ;εNd值变化于 - 4 .4 9939～ - 9.192 5 8之间 ,具壳源成因特点 ;Nd同位素模式年龄 (tDM)在 1.38～ 1.76 1Ga之间 ,与中元古代变质岩相当 ;O同位素组成变化范围 7.8～ 9.5 ,表明花岗岩类成岩物质主要来自地壳。综合岩石的同位素组成 ,结合矿物学、岩石地球化学的研究 ,表明花岗岩浆主要起源于地壳 ,但与来自地幔的基性岩浆曾发生过混合作用 。This paper reports Pb, Sr, Nd and O isotopic compositions of gabbro and granitoids formed in East Kunlun orogenic belt in Triassic. Granitoids and potassic feldspar have similar Pb isotopic compositions. Studies show that they were formed in an orogenic environment.Initial ( 87Sr/ 86Sr)t ratios range from 0.70144 to 0.70972,and εNd values from -4.49939 to -9.19258. Nd isotopic model ages (t DM) vary from 1.38 Ga to 1.761 Ga, being close to the age of mesoproterozoic metamorphic rocks. O isotopic compositions range from 7.8 to 9.5, indicating that the granitoids were derived from the crust. Based on all isotope data and mineralogical as well as petrochemical studies, it is held that the granitoids were mainly derived from the crust and mixed with the mantle-derived materials. The mixing process between the crust materials and the mantle-derived materials is responsible for the nearly identical isotope compositions.

关 键 词：花岗岩成因 岩浆混合作用 同位素 东昆仑 

分 类 号：P597[天文地球—地球化学] P588.115[天文地球—地质学]