汉诺坝榴辉岩相石榴辉石岩——岩浆底侵作用新证据

Eclogite facies garnet-pyroxenolite xenolith in Hannuoba area: New evidence of magma underplating

汉诺坝榴辉岩相石榴辉石岩捕虏体的产状、层状堆晶构造和粒状变晶结构 ,以及具有幔源成因的矿物学、REE地球化学特征和温压条件表明 ,其深部过程是由幔源岩浆底侵于上地幔顶部 ,形成镁铁质堆晶岩 ,再经榴辉岩相变质而成 ,它与下地壳底部的麻粒岩相镁铁质堆晶岩 ,提供了岩浆底侵作用和壳 -幔过渡带存在的新证据。

Eclogite facies garnet-pyroxenolite xenoliths in Hannuoba area show the typical layered cumulate structures and crystalloblastic textures of granulite facies. The mineral compositions, equilibrated P-T conditions and REE geochemistry of the xnolith reveal its mantle-derived genesis. All these facts indicate that the mantle-derived magma underplates in the top of the upper mantle and forms the mafic cumulate, then the cumulate experiences some metamorphism of eclogite facies. The eclogite facies xenolith, accomponied with the granulite facies xenolith, provides new evidence of the existence of the crust-mantle transitional zone.