【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 0 Ma以前的认识更多还原

【Abstract】 The 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 ε 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.更多还原