鄂尔多斯地块西缘中晚元古代沉积特征研究

发布时间：2018-07-05 05:56

  本文选题：中晚元古界 + 沉积环境　； 参考：《西北大学》2015年硕士论文

【摘要】：鄂尔多斯地块西部海槽中晚元古界沉积特征及形成演化研究,对元古代地壳演化不仅有重要的理论意义,而且对中新元古界油气勘探有重要的现实意义。本文以盆地动力学及沉积学理论为指导,以野外剖面、测井、地震、钻井、岩心及各种分析化验资料为基础,根据区域地层对比标志及沉积特征,结合古生物化石以及同位素年代学分析等资料对中新元古代地层进行了划分及对比,初步分析确定了各层系沉积相、沉积体系类型及特征。在对岩石样品进行有机地球化学的基础上,结合构造背景及岩相分析结果,对鄂尔多斯盆地中新元古界的生烃条件进行评价,取得以下新认识：据区域地层对比标志及沉积特征,结合古生物化石以及同位素年代学分析等将中新元古代划分为长城系蓟县系、震旦系(本区缺失青白口系)建立了全区地层格架。中新元古界以滨海一浅海相陆源砂质、泥质和碳酸岩为主体,很少有火山动。长城系主要为一套陆相—滨海相石英砂岩沉积,长城系物源主要来自于克拉通内部。蓟县系主要为碳酸盐潮坪沉积环境。震旦系为一套海相冰碛砾岩沉积。从长城纪-震旦纪鄂尔多斯地区中新元古代原型盆地范围及沉积厚度逐渐减小。中新元古代鄂尔多斯地区祁连海槽构造背景为大陆边缘坳陷,为拉性环境,贺兰裂陷仅是深入华北陆块内部的一个地堑型沉降带。鄂尔多斯地区祁连海槽中新元古界烃源岩可能发育的主要层位为蓟县系,蓟县系白云岩有机碳含量总体较低,为较差烃源岩；有机质类型为Ⅰ型,成熟度主要在1.51-4.68%之间,成熟度高,主要处于生气阶段。长城系发现灰黑色泥板岩层段,有机质丰度及热演化较高,为好的烃源岩。根据鄂尔多斯地区祁连海槽中新元古界原型盆地及烃源分析结果,盆地中新元古界油气勘探方向主要有两个方面：(1)、自生自储型气藏；(2)、上生下储型气藏。上生下储型气藏位于盆地北部伊盟隆起区,预测元古界自生自储气藏有利区位于盆地西南缘伸向盆地内的断陷槽内。
[Abstract]:The study on the sedimentary characteristics and formation and evolution of the Middle and late Proterozoic in the western trough of the Ordos Block has important theoretical significance not only for the evolution of the Proterozoic crust, but also for the exploration of oil and gas in the Middle and Neoproterozoic. This paper is guided by the theory of basin dynamics and sedimentology, based on field profile, logging, earthquake, drilling, core and various analytical and laboratory data, based on regional stratigraphic correlation markers and sedimentary characteristics. Combined with the data of paleontological fossils and isotopic chronological analysis, the MesoNeo-Neoproterozoic strata were divided and correlated, and the sedimentary facies, sedimentary system types and characteristics of each stratigraphic system were preliminarily determined. On the basis of organic geochemistry of rock samples, the hydrocarbon generation conditions of the Neoproterozoic in the Ordos Basin are evaluated in combination with the results of tectonic background and lithofacies analysis. According to the regional stratigraphic correlation markers and sedimentary characteristics, the MesoNeoproterozoic is divided into the Jixian system of the Great Wall system according to the paleontological fossils and isotopic chronology analysis. The stratigraphic framework of the whole area has been established by the Sinian system (missing Qingbaikou system). The Mesozoic Proterozoic was dominated by littoral-shallow-sea continental sandy, muddy and carbonatite, with little volcanic activity. The Great Wall system is mainly composed of a set of continental-coastal quartz sandstone deposits, and the Great Wall source mainly comes from the interior of the craton. Jixian system is mainly carbonate tidal flat sedimentary environment. The Sinian system is a set of marine moraine conglomerate deposits. From the Great Wall to Sinian Ordos area, the area of Mesoproterozoic archetype basin and sedimentary thickness gradually decrease. The tectonic setting of Qilian trough in MesoNeo-Neoproterozoic Ordos area is continental margin depression and tensile environment. Helan rift is only a graben subsidence zone deep into North China continental block. In the Qilian trough of Ordos area, the main formation of Neoproterozoic source rocks is Jixian system, the organic carbon content of dolomite in Jixian system is relatively low, and the organic matter type is type 鈪，

本文编号：2099201