安徽女山幔源橄榄岩捕虏体Re-Os同位素地球化学  

Re-Os geochemistry of mantle peridotite xenoliths from Nushan

作　　者：支霞臣[1] Reisberg L 徐夕生[3] 

机构地区：[1]中国科学院壳幔物质和环境重点实验室中国科学技术大学地球和空间科学学院,安徽合肥230026 [2]法国国家科学研究中心南锡岩石学和地球化学研究中心,法国南锡54501 [3]南京大学地球科学系,江苏南京210093

出　　处：《中国科学技术大学学报》2007年第8期945-952,共8页JUSTC

基　　金：国家自然科学基金(40473008;40572036)资助

摘　　要：Re-Os同位素体系可以为研究大陆岩石圈地幔形成和演化提供重要制约.女山12个地幔橄榄岩全岩样品测得Re含量为19×10^-12～306×10^-12, Os含量为0.81×10-9～2.42×10^-9, 187^Os/188^Os比值为0.114 90～0.131 02, 187^Re/188^Os比值为0.037～1.517. 两个石榴子石-尖晶石二辉橄榄岩的Os同位素组成与原始上地幔（PUM）的现代值0.129 6相似, 其余的尖晶石二辉橄榄岩、方辉橄榄岩, 和角闪石、金云母-尖晶石二辉橄榄岩等的Os同位素组成都低于PUM现代值, Os同位素模式年龄为早元古代.实性和隐性地幔交代作用对女山幔源橄榄岩捕虏体的Os同位素组成没有明显影响. 橄榄岩捕虏体代表的女山地区岩石圈地幔是元古代岩石圈地幔经过减薄作用后的残留部分. 橄榄岩中Re-Os体系扰动是近期事件.Geochemistry of Re-Os isotopic systematics may offer strong constraints on origin and evolution of subcontinental lithospheric mantle. 12 mantle peridotite samples from Nushan, eastern Anhui, were analysed for Re-Os isotopic systematics. The Re concentrations vary from 19 ×10^-12 to 306 ×10^-12 and the Os concentrations vary from 0.81 ×10^9 to 2.42 ×10^9 for the sample set. The 187^Os/188^Os ratios range from 0. 114 90 to 0. 131 02 and 187^Re/188^Os ratios range from 0. 037 to 1. 517. The 187^Os/188^Os ratios of 2 garnet-spinel lherzolite are slightly higher than 0. 129 6, the present value of primitive upper mantle （PUM）. The others including spinel lherzolite, harzburgite, amphibole-and-phlogopite-spinel lherzolite are lower than 0. 1296. The Os isotope model age of Nushan lithospheric mantle formation was estimated as early proterozoic. The Os isotopic compositions of mantle peridotite xenoliths were not effected significantly by the mode or cryptical mantle metasomatism. The disturbance of Re-Os isotope system resulted from the relatively recent event.

关 键 词：RE-OS同位素 模式年龄 地幔过程 橄榄岩捕虏体 安徽女山 

分 类 号：P597[天文地球—地球化学]