内蒙古集宁橄榄岩包体微区微量元素与Sr同位素特征及其岩石圈地幔演化的指示意义

发布时间：2018-03-14 18:31

本文选题：华北克拉通西部　切入点：集宁　出处：《地球科学》2017年04期 　论文类型：期刊论文

【摘要】：为完整了解华北克拉通的破坏程度和机制,加深对其西部陆块岩石圈地幔的研究十分重要,而位于华北克拉通西部集宁新生代碱性玄武岩中的地幔橄榄岩包体,为研究人员认识该地区的岩石圈地幔的性质和演化起到指示作用.运用LA-ICPMS和LA-MC-ICP-MS对集宁地区橄榄岩矿物进行原位微区测试,获得其主量、微量元素和Sr同位素成分的数据.根据矿物组成,可以将集宁地区的橄榄岩分为两类:第一类为贫单斜辉石橄榄岩(单斜辉石体积分数小于8%),它们经历了高程度的部分熔融,可能是古老难熔岩石圈地幔的残留;第二类为二辉橄榄岩(单斜辉石体积分数大于13%),其熔融程度低,代表了新生饱满的岩石圈地幔.第一类橄榄岩中单斜辉石REE含量整体偏低且轻微富集LREE,第二类橄榄岩中单斜辉石具有LREE富集和轻微亏损两种配分模式,大部分样品的核边有一定的强不相容元素及Sr同位素组成变化.这些微量元素和同位素特征都表明集宁橄榄岩包体经历过交代作用.(La/Yb)_N和Ti/Eu比值特征表明它们经历过多阶段的交代作用,交代介质有硅酸盐、碳酸盐熔/流体,这些交代介质可能为来源于古亚洲洋板块俯冲时释放的熔/流体.
[Abstract]:To understand the extent of damage and the mechanism of the North China Craton is complete, more research on the western block of the lithospheric mantle is very important, and is located in the western North China Craton of Jining Cenozoic basalts in the mantle peridotite xenoliths, nature and evolution for researchers in the area of the lithospheric mantle understanding pointing to the application. LA-ICPMS and LA-MC-ICP-MS of peridotite minerals in Jining by in-situ test, the main content, trace elements and Sr isotope composition data. According to the mineral composition of the peridotite in Jining area can be divided into two categories: the first is the poor clinopyroxene peridotite (clinopyroxene volume fraction is less than 8%), they experience the high degree of partial melting, may be difficult to remain the old lava stone circle of the mantle; second to two peridotite (clinopyroxene volume fraction greater than 13%), the low degree of melting, represents a new Life full of lithospheric mantle. The content of clinopyroxene peridotite in the first REE class overall low and slight enrichment of LREE, second types of peridotite in clinopyroxene with LREE enrichment and slight loss of two kinds of distribution patterns, most samples of nuclear boundary has certain strong incompatible elements and Sr isotope compositions of trace elements and these changes. Isotopic characteristics indicate that Jining peridotite xenoliths experienced metasomatism. (La/Yb) _N and Ti/Eu ratios indicate that they have experienced many stages of metasomatism, metasomatic medium with silicate carbonate melt / fluid, the account may be released in the medium from subduction of the paleo Asian Ocean plate when the melt / fluid.

【作者单位】：中国地质大学李四光学院;中国地质大学地球科学学院;中国地质大学地质过程与矿产资源国家重点实验室;
【基金】：国家重点基础研究发展计划(973计划)项目(No.2013CB429806) 国家自然科学基金项目(Nos.41125013,41530211) 中国地质大学(武汉)地质过程与矿产资源国家重点实验室基金项目(No.MSFGPMR2016)
【分类号】：P59;P588.125;P542.5

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