辽西义县组玻基方辉安山岩成因及其构造背景

Origin of sanukite from Yixian Formation in western Liaoning province and its tectonic settings.

辽西下白垩统义县组顶部有一套高镁的玻基方辉安山岩,它们在矿物组成和结构上存在一系列不平衡现象。斜方辉石和玻璃质的常量、微量元素研究揭示它们具有壳、幔不同来源的组分特征。本文采用下地壳、岩石圈地幔等不同来源熔体混合的观点解释斜方辉石的存在和玻基方辉安山岩的形成,根据研究区在玻基方辉安山岩快速喷发后出现的亏损地幔来源的玄武岩,笔者认为这是早白垩世末中国东部岩浆来源从富集岩石圈地幔向亏损的软流圈地幔转型的表现。

A suite of high-Mg sunukites occurred in the uppermost of Early Cretaceous Yixian Formation in western Liaoning Province, China, which show a series of disequilibrium phenomena in textures and their constituent minerals. Major and trace elemental compositions of the orthopyroxenes and glass （hyaline） in the sunukites reveal existence of mixing feature between magma of a crustal origin and that of a mantle derivation. This paper interpreted the existence of orthopyroxenes and the formation of sunukites in a point view of magma mixing between melt from the crust and that from the depleted mantle. According to the fact that rapid eruption of sunukitic magma followed by basaltic magma of depleted mantle origin in the studied area, we believed that the occurrence of these sunukites was a sigh of magma source sift from the enriched lithospheric mantle to the depleted asthenosphere in eastern China in the end of Early Cretaceous.