橄榄岩-熔体的相互作用:岩石圈地幔组成转变的重要方式  

Peridotite-melt interaction:an important mechanism for the compositional transformation of lithospheric mantle

作　　者：张宏福[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029

出　　处：《地学前缘》2006年第2期65-75,共11页Earth Science Frontiers

基　　金：国家自然科学基金委员会杰出青年科学基金项目(40225009);国家自然科学基金委员会大陆动力学重点项目(40534022)

摘　　要：橄榄岩-熔体/岩浆的相互作用常被用来解释蛇绿岩套橄榄岩、造山带橄榄岩、超镁铁质侵入杂岩体、地幔橄榄岩捕虏体中某些具有不平衡结构和矿物组成的岩石的形成过程。橄榄岩-熔体的反应主要有两种方式,即消耗橄榄石(和单斜辉石)生成斜方辉石或消耗斜方辉石生成橄榄石(和单斜辉石)。反应的结果不仅造成矿物百分含量的变化,而且造成矿物组成的变化;后者更重要但未引起足够的重视。华北东部中生代玄武质岩石中具有环带状结构的橄榄石和辉石捕虏晶,特别是具有环带状结构的地幔橄榄岩捕虏体的发现,暗示这种橄榄岩-熔体的相互作用在华北东南部中生代岩石圈地幔中很可能普遍存在,为岩石圈地幔组成转变和快速富集的重要方式。这是全球首例由橄榄岩-熔体相互反应造成的岩石圈地幔大规模的组成变化。反应熔体来源途径主要有地壳来源和软流圈地幔来源。来源不同的熔体与橄榄岩的反应造成的组成变化完全不同。Peridotite-melt/magma interaction has usually been used to interpret the petrogenesis for those rocks that have disequilibrated textures and mineral compositions, which range from ophiolitic peridotites, orogenic peridotites, ultra-mafic intrusive complexes, to mantle xenoliths. There are two major types of peridotite-melt reaction： i.e. dissolution of olivine （and clinopyroxene） and precipitation of orthopyroxene, or dissolution of orthopyroxene and precipitation of olivine （and clinopyroxene）. The result of the reaction leads not only to a change in mineral percentages, but also to a change in mineral compositions; the latter has not been paid enough attention. The discovery of zoned mantle olivine and pyroxene xenocrysts, especially zoned mantle peridotitic xenoliths in Mesozoic basaltic rocks from eastern North China, indicates that peridotite-melt interaction was widespread in Mesozoic lithospheric mantle beneath the southeastern North China craton. Such interaction could be an important mechanism for the compositional transformation and rapid enrichment of the lithospheric mantle. This is the first case in the world for large-scale compositional changes of the lithospheric mantle resulting from peridotite-melt interaction. The reactant melts were mainly derived from two sources： crustal materials and/or asthenosphere. Reaction of peridotites with melts from different sources results in different com- positional changes.

关 键 词：华北东部 中生代 捕虏晶和捕虏体 橄榄岩-熔体反应 岩石圈地幔 

分 类 号：P588.12[天文地球—岩石学]