辽宁盖县梁屯-矿洞沟碱性正长岩杂岩体的U-Pb和Sm-Nd年龄及其地质意义  

U-Pb and Sm-Nd isotopic ages of an alkaline syenite complex body in Liangtun-Kuangdongguo, Gai County, Liaoning Province, China and their geological significance.

作　　者：蔡剑辉[1,2] 阎国翰[1] 牟保磊[1] 许保良[1] 邵宏翔[1] 许荣华[3] 

机构地区：[1]北京大学地球与空间科学学院 [2]中国地质科学院矿产资源研究所北京100037 [3]中国科学院地质与地球物理研究所

出　　处：《岩石学报》2002年第3期349-354,共6页Acta Petrologica Sinica

基　　金：国家自然科学基金项目 ( 4 0 0 72 0 2 4493 73 170 )资助

摘　　要：辽宁梁屯 -矿洞沟杂岩体主要由辉石正长岩、霓辉正长岩和霓辉角闪正长岩等碱性岩石组成 ,具有全岩 Rb- Sr等时线年龄 186 6± 115 Ma和 ISr=0 .70 4 9的同位素特征 ,是我国目前报道的最古老的碱性正长岩类。本文报道了该岩体的锆石U- Pb和全岩 Sm- Nd同位素测试资料 ,获得了锆石 U- Pb同位素年龄为 185 7± 2 0 Ma、Sm- Nd等时年龄为 1787± 180 Ma、εNd(t) =- 4 .8～ - 5 .0的数据。它们反映出该杂岩体形成年龄的上限为 185 7± 2 0 Ma、下限不小于 1787± 180 Ma,来源于富集地幔物质。基于这些数据并结合区域地质资料分析 ,作者提出了华北地台北缘古元古宙存在有富集地幔储库 ,以及辽河群主体形成于 190 0The complex body in Liangtun-Kuangdongguo, Liaoning Province, China, mainly consists of alkaline rocks such as pyroxene syenite, aegirite-augite syenite and aegirite-augite-hornblende syenite. According to the previous whole rock Rb-Sr isochron age data of 1866+/-115Ma with I-Sr=0.7049, it is the oldest alkaline syenite reported in China up to now. The data of Zircon U-Pb and whole rock Sm-Nd data reported in this paper show that the complex body has a U-Pb isotopic age of 1857+/-20Ma, and a whole rock Sm-Nd isochron age of 1787+/-180Ma, with a epsilon(Nd)(t) value between -4.8 and -5.0. This means that the complex originated from enriched mantle material, with the upper limit age of 1857+/-20Ma. So the authors suggest that during early Proterozoic era an enriched mantle reservoir existed in the North China platform, and the main part of the Liaohe Group was formed before 1900Ma.

关 键 词：辽宁 碱性正长岩 锆石U-PB年龄 全岩Sm-Nd等时线年龄 富集地幔 

分 类 号：P588.12[天文地球—岩石学] P597[天文地球—地质学]