河北平山阜平群夕线石钾长浅粒岩深熔作用的微区矿物学标志

河北省平山县阜平群是一套高角闪岩相岩石。根据宏观现象，某些地段曾经历过深熔作用过程。深熔效应以小觉地区的夕线石钾长浅粒岩最为典型。通过电子显微镜观测确认，所研究的夕线石钾长浅粒岩经受了深熔作用的改造，具有丰富而显著的微区矿物学标志。主要表现为前存矿物，如钾长石、条纹长石、石英、钠长石、黑云母和磁铁矿等，不同程度地被熔蚀，主要组成元素发生迁移和重组，沿矿物的解理、裂隙及粒间形成夕线石、石英、云母、长石、金红石等再结晶相。在深熔过程中，元素的迁移有两种可能形式：①选择性地从前存矿物晶格中移出；②通过前存矿物的熔融。Fe、Ti等元素从黑云母中移出，形成再结晶磁铁矿和金红石；Si、AI等元素则从黑云母和长石中移出，形成夕线石和再结晶石英。

Micro-area Mineral ogical Characteristics of Anatectic Sillimanite-K-feldspar Leucogranulitite in the Fuping Group at Pingshan, Hebei Province

The Fuping Group in Pingshan County, Hebei Province, is a suite of high-grade amphibolite-facies rocks. From its micro-features, the rocks underwent anatexis in some areas. The effect of the anatexis is most promi- nent in sillimanite-K- feldspar leucogranulitite (leptite) of the Xiaojue area. The electron microscopic observation shows that the sillmanite-K- feldspar leucogranulitite studied has been modified in the process of anatexis. There appear many distinct micro-area mineralogical characteristics which are mainly different degrees of corrosion of pre-existing minerals such as K-feldspar (Kf1), perthite, quartz (Q1), albite (Ab1), biotite (Bi1) and magnetite (Mt1) , remobilization and reconstitution of the main component elements and formation of recrystal-lized minerals, e, g. sillimanite, quartz, mica, feldspar and rutile along the cleavages and fissures of the minerals and in their interstices. There are two possible mechanisms of element remobilization in the process of anatexis: (1) selective removal from the lattices of the pre-existing minerals, and (2) melting of pre-existing minerals. Fe and Ti removed from biotite formed the recrystallized magnetite (Mt2) and rutile, while Si and Al removed from the biotite and feldspar formed sillimanite (Sill) and quartz (Q2).