帕米尔构造结塔什库尔干碱性杂岩同位素年代学研究  

The geochronology of Taxkorgan alkalic complex, Pamir syntax.

作　　者：柯珊[1,2] 罗照华[1,2] 莫宣学[2] 张文会[2] 梁涛[2] 詹华明[2] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]中国地质大学地球科学与资源学院,北京100083

出　　处：《岩石学报》2008年第2期315-324,共10页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(2002CB412603);教育部博士点新教师基金(20070491518);中国地质大学(北京)青藏高原创新团队和国家自然科学基金项目(40472038)资助成果

摘　　要：利用高精度锆石SHRIMP U-Pb法测定了帕米尔构造结中东部塔什库尔干碱性杂岩的年龄,岩体不同岩石类型的年龄均为11Ma,与野外证据吻合。通过与该杂岩体钾长^(40)Ar/^(39)Ar等时线年龄(23Ma、13Ma)对比研究,^(40)Ar/^(39)Ar定年结果明显偏老,认为是由于钾长石中含有过剩氩所致,并分析了过剩氩存在的可能原因。因此塔什库尔干碱性杂岩的活动时代可以确定为11Ma,而且钾长石不宜作为该杂岩体测年的理想对象。结合岩体的成因及构造意义,认为在11Ma前,帕米尔构造结地区已具有加厚下地壳的特征。We obtain the precise ages, liMa, of different rock types from the Taxkorgan alkalic complex, Middle East of Pamir syntax by using SHRIMP U-Pb zircon, which is consisted with the field evidence. ^40Ar/^39 Ar dating of K-feldspar was also be used for this complex, Comparison between the two methods shows that the ^40Ar/^39 Ar i sochrone ages （23 Ma and 13 Ma） are obviously older than these of zircons, suggesting that the K-feldspar may probably have excess argon. Thus the K-feldspar is not the favorable object for ^40Ar/^39Ar dating to this alkalic complex with the possible reasons for excess argon presence, Therefore, the time of emplacement of the Taxkorgan alkalic complex could be confirmed as 1 1 Ma. To combine with its petrogenesis, the Pamir syntax was already characterized with a thickened lower crust at least before 11 Ma.

关 键 词：帕米尔 塔什库尔干 碱性杂岩 SHRIMP U—Pb年龄 过剩氩 

分 类 号：P597.3[天文地球—地球化学]