济阳坳陷埕东凸起基底岩石组合、原岩恢复及地质意义

Rock association,protolith restoration of basement rocks in Chengdong salient,Jiyang depression and its geological significance

济阳坳陷埕东凸起太古界基底分布广泛,岩石类型丰富。岩心及显微薄片观察表明,岩石组合以花岗片麻岩、二长片麻岩和黑云母斜长片麻岩等各类片麻岩和石英闪长岩、花岗闪长岩等古老岩浆岩为主,少量石英岩、变粒岩等变质表壳岩以及云煌细晶岩、钾长花岗岩等年轻侵入岩脉。岩石地球化学分析及区域对比揭示,各类片麻岩的原岩为中酸性侵入岩,属于TTG质片麻岩,而石英岩和变粒岩属于变质表壳岩范畴,原岩为沉积岩。基底岩石构造样式为片麻岩或侵入岩形成构造穹窿,规模较小的变质表壳岩零星分布在周边。盆地基底岩石组合、变质岩原岩恢复与构造样式分析表明,渤海湾盆地覆盖区基底性质与露头区相似,是华北克拉通变质基底重要组成部分。这些认识对弄清盆地基底潜山油藏储层特征与展布具有重要指导作用,为深入研究变质岩潜山内幕油藏储层演化规律提供了依据。

The basement rocks are wildly distributed in Chengdong salient, Jiyang depression,with many varieties of rock types. Observation of cores and thin sections indicate that the basement rocks are mainly composed of gneisses such as granitic gneiss, monzogranite gneiss, biotite plagiogneiss, and older magmatic rocks like quartz diorite, granodiorite, with a little quartzite, leptynite, and younger vein rocks such as lamprophyres, feldspar granites. Analyses of geochemistry and regional correlation study exhibit that the protoliths of gneisses are intermediate-acid intrusive rocks belonging to TTG. The quartzite and leptynite are metamorphosed supracrustal rocks,whose protoliths are sediments. Structural style of basement rocks is that TTG gneisses are as tectonic domes, but supracrustal rocks fragmentary distributing around. According to rock association, protolith restoration and structural style of basement rocks,it can be concluded that the basement of Bohai Bay Basin is an important part of North China Craton＇s. Besides this, it has the immensely guiding role to research on reservoir characteristics and distribution law of basement, and- provides evidence for further study of inner buried hill of metamorphic rocks.