新疆西克尔碧玄岩中的地幔橄榄岩包体  

Mantle peridotite xenoliths in basanite from Xikeer,Xinjiang.

作　　者：陈咪咪[1] 田伟[1] 潘文庆[2] 

机构地区：[1]北京大学地球与空间科学学院造山带与地壳演化教育部重点实验室,北京100871 [2]中石油塔里木油田公司勘探开发研究院,新疆库尔勒841000

出　　处：《岩石学报》2008年第4期681-688,共8页Acta Petrologica Sinica

基　　金：科技部973项目(2007CB411307);国家自然科学基金(40502009)资助.

摘　　要：在新疆西克尔地区发现了尖晶石相橄榄岩包体。这些包体的寄主岩石为碧玄岩,其K-Ar同位素年龄为19.76～21.90 Ma。岩相学和矿物化学研究表明西克尔橄榄岩包体具有典型的岩石圈地幔橄榄岩包体的特征。利用矿物温压计对包体的平衡温压进行估算,发现西克尔地幔橄榄岩包体的平衡温压为736～1017℃和1.7～2.2GPa,与西南天山托云地区晚白垩纪火山岩中尖晶石二辉橄榄岩包体(平衡温压为818～1113℃和1.5～2.0GPa)相比,具有温度明显偏低,而压力明显偏高的特点。这说明西克尔地区的地幔橄榄岩包体没有受到地幔热异常事件的影响,因此可以代表塔里木板块岩石圈地幔的原始性质。这对于研究塔里木盆地岩石圈地幔的热结构和地球化学特征以及塔里木盆地内大量幔源岩浆的成因具有重要意义。Spinel-facies mantle peridotite xenoliths are found in Xikeer, Xinjiang. These xenoliths are hosted by Cenozoic basanite, with K-Ar isotopic age of 19.76 - 21.90 Ma. As indicated by petrography and mineral chemistry, the peridotite xenoliths are typical mantle derived xenoliths. Equilibrium temperature and pressure calculated by several classical geothermometers and geobarometers show that temperature and pressure are 736 - 1017 ℃ and 1.7 - 2.2 GPa for the Xikeer Sp-lherzolite xenoliths, and, are 818 - 1113 ℃, 1.5- 2.0GPa for the Tuoyun Sp-lherzolite xenoliths. The Xikeer mantle xenoliths are distinguished from Tuoyun＇ s by its lower temperature and higher pressure, which implies that the subcontinental lithosperic mantle （SIAl） beneath Xikeer area has not affected by mantle thermal abnormity. The Xikeer mantle xenoliths can represent the primitive and unaltered SLM beneath Tarim block, hence they have significance on research of thermal structure and geochemistry of SLM beneath Tarim block, together with petrogenesis of large scale mantle derived magmatism.

关 键 词：西克尔 塔里木 碧玄岩 地幔包体 平衡温压 岩石圈地幔 

分 类 号：P588.125[天文地球—岩石学]