五台山-恒山地区繁峙玄武岩岩石学特征及构造意义

Petrologic Characteristics and Tectonic Implications of Fanshi Basalts in the Wutaishan-Hengshan Area

为了探讨滹沱河地区新生代的陆壳演化特征,在野外地质调查的基础上,开展了繁峙玄武岩的岩相学、岩石主微量元素地球化学研究。结果表明,繁峙玄武岩为一套钠质亚碱性-碱性系列的基性火山岩,形成于大陆板内裂谷的板块构造环境;繁峙玄武岩的岩浆来源于地幔物质的部分熔融与下地壳组分部分熔融的混合;繁峙玄武岩形成于太平洋板块向欧亚板块俯冲的动力学背景,标志在始新世-渐新世,滹沱河裂陷开始发育。深入探讨繁峙玄武岩的岩浆作用特征、物质来源和岩浆作用的构造环境,对揭示五台山-恒山地区的陆壳演化特点,具有重要的意义。

A detailed investigation of petrography and geochemistry of major and trace ele- ments of Fanshi basahs has been carried out on the basis of field observation, which aimed to shed light on continental crustal evolution in Hutuohe area during Cenozoic era. The results show that Fanshi basalts are basic volcanic rocks characterized by sodic subalkaline to alkaline series, and are formed in tectonic setting of continental intraplate rifting. Additionally, the magma of the basalts is derived from the mixing of partial melting of mantle and lower crust component. Fur- thermore,Fanshi basalts were closely associated with the subduction of the Pacific plate beneath the Eurasian plate, and Hutuohe rifting began to develop from Eocene to Oligocene.