玄武岩成分变异原因

笔者等研究发现山东栖霞和浙江西垄两地新生代玄武岩中分别产有奇特的富钾霞石质和富透长石质熔体玻璃地幔捕虏体,而且它们与寄主玄武岩之间有强烈的混染反应.表明玄武岩浆不是一元系岩浆,而是不同期多元系岩浆.多元系所占比例差别很大,决定了玄武岩浆成分的多样性.另外,此玄武岩成分也很特别:①不见斜长石,主要是铬透辉石(Mg质太多)；②含有较多霞石；③全岩SiO2低,37％ ～39％.此玄武岩应称为透辉石岩.

The Cause of Comoposition Anomalies of Basalt

Through basalt studies, sampled from Qixia (Shandong Province) and Xilong(Zhejiang Province), we found that K riched nepheline melt glass xenoliths and sanidine melt glass xenoliths,which have contaminated the host basalt magma and resulted in formation of shonshonites. These basalts have not plagioclase, which consist mainly of Cr diopside and nepheline. The SiO2 content in basalt is low (37%~39%).