阿尔泰造山带南缘镁铁质—超镁铁质杂岩体的Sr、Nd、O同位素地球化学及其源区特征探讨  

Sr,Nd and O Isotope Geochemistry of the Mafic—Ultramafic Complexes in the South Margin of Altay Orogenic Belt and Discussion on Their Sources

作　　者：张招崇[1] 闫升好[2] 陈柏林[3] 何立新 何永胜 周刚 柴凤梅[5] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国地质科学院地质力学研究所,北京100081 [4]新疆地质矿产局第四地质大队,阿尔泰836500 [5]中国地质大学,北京100083

出　　处：《地质论评》2006年第1期38-42,共5页Geological Review

基　　金：国家305项目(编号2001BA609A-07-02);国家自然科学基金资助项目(编号40572047);教育部新世纪优秀人才支持计划(NCET-04-0728)的成果

摘　　要：对阿尔泰造山带南缘喀拉通克和锡泊渡两个杂岩体的Sr—Nd-O同位素研究表明，两个杂岩体的同位素特征相似，均具有低的（^87Sr／^86Sr），和高的εNd（t）值（6．3～9．1），表明其来源于亏损的软流圈地幔，但是其δ^18O值（‰）大多大于6（5．4～10．2），表明有地壳物质的加入。Sr和O同位素表明，这种地壳物质的混入主要是源区的混入。根据Nd同位素模式年龄以及区域构造演化特征，可能是混入有早期俯冲的洋壳（可能是早古生代）的亏损地幔熔融的结果。然而，与锡泊渡杂岩体不同的是，喀拉通克杂岩体局部还经历了上部地壳的混染作用。此外，额尔齐斯深大断裂南北两侧镁铁质-超镁铁质杂岩体源区特征的相似性可能暗示了该断裂可能不是阿尔泰造山带和准噶尔造山带的分界线。The Sr, Nd and O isotopic compositions of the Kalatongke and Xibodu mafic-ultramafic complexes from the south margin of Altay orogenic belt show that they have similar isotopic compositions, characterized by low （^87Sr/^86Sr）t and high εNd （t） value （6. 3- 9. 1）. It suggests that they were derived from depleted asthenospheric mantle. However, most of the samples have the δ18O values 〉6‰ （5. 4‰-10. 2‰）, indicating the involvement of crustal materials. A combination of Sr and O isotopic data shows the incorporation of crustal materials into depleted mantle. They were produced by the melting of depleted mantle by the incorporation of subducted oceanic crust, and this incorporation might occur in the Early Paleozoic time in the light of their Nd model ages and regional tectonics. The Kalatongke complex might have undertaken the contamination of upper crust whereas the Xibodu complex had not been had any signature of contamination of upper crust. In addition, the similarities of the sources of the two complexes, which were located at the north and south sides of the regional Irtysh fault zone respectively suggest that this fault might not be the boundary between the Altay and Zhunggar orogenic belts.

关 键 词：镁铁质-超镁铁质杂岩体 SR ND O同位素 源区 阿尔泰造山带 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学]