阳信洼陷构造岩浆演化与油气聚集

TECTONO-MAGMATIC EVOLUTION OF YANGXIN DEPRESSION AND ITS HYDROCARBON ACCUMULATION

阳信洼陷在老第三纪存在陡坡带、洼陷带及缓坡带，属左旋张担应力场作用下的箕状断陷；新第三纪转变为右旋压扭应力场作用下的整体拗陷。洼陷经历了幔隆张裂、初始裂谷、裂谷裂陷及坳陷四个发育阶段，发育三期基性超基性岩浆喷发，其演化趋势是从孔店期到馆陶期碱质增加、酸度减少，反映岩石圈不断扩张变薄的过程。注陷最有利于油气生成聚集的构造演化期是裂陷期。

Yangxin Depression was a typical half-graben in the Eogene. Three tectonic zones inthe depression, including steep-slope, depreessed and senile slope zones, resulted fromsinistral tenso-shear stress.In the Neogene, the faults that controlled the depressionchanged from extensional normal faults into compressive dextral strike-slip fsults,the depression then depressed in its entirety,and hence it is characterized by fault-subSidence inits lower-part but depression in its upper part. Three-stase magmatite developed in the depression: andisite basalt in the 4th member of the Shahejie Formation; quartz-tholeiiticbdsalt and olivine tholeiitic basalts in the 3rd member of the Shahejie Formation and alkalic ultrabasic rock in the Guantao Formation.The tectonic evolution preocess of Yangxin Depression could be divided into following four stages:extenso-fracturing of mantle uplifting, proto-rifting,riftins-subsiding anddepressing. The most favourable stage for hydrocarbon formation and accumulation wasrifting-subsiding stage.