西藏那曲蛇绿岩地幔源区的碳质球粒陨石型Os同位素特征及其意义

被引：5

作者：

黄启帅 ^{[1
,2
]}

史仁灯 ^{[1
]}

刘德亮 ^{[1
,2
]}

张晓冉 ^{[1
,2
]}

樊帅权 ^{[1
,2
]}

丁林 ^{[1
]}

机构：

[1] 中国科学院青藏高原研究所大陆碰撞与高原隆升实验室

[2] 中国科学院研究生院

来源：

科学通报 | 2012年 / 33期

关键词：

Re-Os同位素; 尖晶石; 蛇绿岩; 那曲; 西藏;

D O I：

暂无

中图分类号：

P585 [岩石鉴定、分析];

学科分类号：

摘要：

尖晶石具有高Os低Re含量的特性,能够抵抗变质、蚀变和风化作用对其Os同位素组成的影响,其Os同位素组成的测量值可以代表形成时的初始Os同位素组成.本文尝试用同一堆晶序列纯橄岩中尖晶石Os同位素组成和辉长岩中锆石年龄来反演地幔源区的Os同位素组成,为认识大洋岩石圈的形成和演化提供重要证据.西藏那曲蛇绿岩是新特提斯蛇绿岩的一部分,位于班公湖-怒江缝合带中段,形成于成熟的弧后盆地,其中发育同一堆晶序列的纯橄岩和辉长岩.辉长岩中锆石U-Pb年龄为183.7±1Ma.纯橄岩的全岩和分选出的尖晶石的Os同位素组成非常一致,排除了后期混染作用的影响,可以代表对流上地幔Os同位素组成.与碳质球粒陨石对比,尖晶石的?Os为?0.2～?0.3,表明那曲蛇绿岩的地幔源区为碳质球粒陨石型对流上地幔.因此,青藏高原大陆岩石圈主体属于残留的特提斯大洋岩石圈,是由中生代软流圈地幔顶部转化形成.这是首次运用能准确定年的堆晶岩中尖晶石Re-Os同位素组成来反演蛇绿岩地幔源区性质的研究实例.

引用

页码：3154 / 3161

页数：8

共 38 条

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