西湖凹陷新生代火成岩发育特征及区域背景分析

Characteristics and Regional Background of Cenozoic Igneous Rocks in Xihu Sag

东海西湖凹陷的勘探实践表明,凹陷内火成岩非常活跃,它发育于西湖凹陷构造运动的各个时期,其分布与发育对盆地、构造的形成演化和油气成藏都有影响。依据磁力资料及最新的钻井、地震等资料的近期研究成果揭示:西湖凹陷为新生代沉积盆地,火成岩分布广泛,具有南、东多北少的分布特征;已知钻井钻遇的火成岩主要为凝灰岩、安山岩与花岗岩,具有高密度、高电阻率与低自然伽马、低声波时差的特征;新生代岩浆岩活动分喜山早、中、晚3期,具有西早东晚,北早南晚特点,南部岩浆岩改造作用强;岩浆岩成分显示主体为板内或板缘岩浆岩。这些研究成果对西湖凹陷的油气地质研究具有指导作用。

The exploration activities in Xihu Sag of East China Sea revealed that igneous rocks are well developed and have activated in the different stages of the tectonic movement. Their distribution and development have affected the formation and evolution of the basin and structures as well as the hydrocarbon accumulation. The study of magnetic data and the latest drilling and seismic data shows that Xihu sag is a Cenozoic sedimentary basin and the igneous rocks are widespread distributed widely, with the characteris- tics of being common in the southern and eastern but scarce in the northern area; The igneous rock encountered by drilling wells are mainly tuff, andesite and granite, with the characteristics of high density and resistivity, low natural gamma and acoustic; the Ceno- zoic magma activity can be divided into three periods i.e. early Himalayan, middle Himalayan and late Himalayan, with the charac- teristics of the western and northern area being earlier than the eastern and southern area, strong reforming occurring in the southern; The compositions of magmatic rocks indicate they were produced in the environment of intra-plate or plate margin. These research results have the important guiding significance for the petroleum geology research in Xihu sag.