柯坪玄武岩的岩石学、地球化学、Nd、Sr、Pb同位素组成与岩石成因  

Petrology, Geochemistry and Petrogenesis of the Kalpin Basalts and Their Nd, Sr and Pb Isotopic Compositions

作　　者：姜常义[1] 张蓬勃[1] 卢登蓉[1] 白开寅[1] 王瑶培[1] 唐索寒[2] 王进辉[2] 杨淳[2] 

机构地区：[1]长安大学造山带成矿研究所,西安710054 [2]中国地质科学院地质研究所,北京100037

出　　处：《地质论评》2004年第5期492-500,共9页Geological Review

基　　金：国家重点基础研究发展规划项目(编号2001CB409800)"九五"国家重点科技攻关项目(编号99-111-01)联合资助的成果。

摘　　要：柯坪玄武岩位于塔里木板块西缘,产于下二叠统库普库兹曼组和开派兹雷克组中。岩石化学组成以富集TFeO、TiO2、P2O5和SiO2不饱和为特征。大部分样品属碱性玄武岩系列,个别属拉斑玄武岩系列。它们的稀土元素和微量元素显示了板内拉张环境玄武岩的地球化学特征。εNd(t)=-1.73--3.69,εSr(t)=+27.56-+56.87,206Pb／204Pb=17.87-18.02,207Pb／204Pb=15.45-15.53,208Pb／204Pb=38.22-38.49。Nd、Sr、Pb同位素组成证明柯坪玄武岩源自于前寒武纪的富集型大陆岩石圈地幔。而且,这种情况在塔里木盆地及周缘地区十分发育的镁铁质岩浆岩中具有广泛的代表性。据此,可以将新疆南部和北部划分为两个明显不同的同位素地球化学省。南部省以富集型地幔的同位素组成为特征,而北部省以亏损型地幔的同位素组成为特征。分属于这两个省的古生代晚期阶段岩浆岩有可能不是同一个地质过程的产物。The Kalpin basalts, located on the western margin of the Tarim plate, occur in the Lower Permian Kupukuziman Formation and Kaipaizileike Formation. Their petrochemical compositions are characterized by remarkably enriched TFeO, TiO2, P2O5 and unsaturated SiO2. Most of the samples belong to the alkali.basalt series and only one sample belongs to tholeiite series. The REE and trace element geochemical features show that the Kalpin basalts occur in a within-plate extensional setting. εNd(t) - - 1. 73 to -3. 69, εsr(t) = + 27. 56 to +56.87, = 17.87 - 18.02, 207Pb/204Pb =15.45 - 15.53, 208Pb/204Pb = 38.22 - 38.49. These Nd, Sr and Pb isotopic compositions show that the Kalpin basalts are derived from the Precambrian enriched-type continental lithospheric mantle. And this case is representative among the well-developed mafic magmatic rocks in the Tarim Basin and its peripheral areas. Accordingly, the northern and southern parts of Xinjiang can be divided into two obviously different isotopic geochemical provinces: the northern province is characterized by isotopic compositions of the depleted mantle, whereas the southern province by isotopic compositions of the enriched mantle. The Late Paleozoic magmatic rocks separately belonging to the two provinces cannot be oroducts of the same p-eolopical orocess.

关 键 词：玄武岩 岩石学 地球化学 同位素地球化学 二叠纪 

分 类 号：P588.1[天文地球—岩石学] P59[天文地球—地质学]