柴达木盆地沉积体系发育的动力学机制及成藏效应

【作者】 李伟；

【导师】 刘宝珺； 陈洪德；

【作者基本信息】 成都理工大学 ， 古生物学与地层学， 2004， 博士

【摘要】 本文通过利用古地磁资料、野外地质调查资料与相应的分析化验资料等,研究了周边板块对柴达木微板块的作用与影响。本文首次提出了柴达木微板块在中生代主要受塔里木板块的影响,而新生代主要受羌塘板块及其以南板块的影响。作者认为塔里木板块在侏罗纪早期的迅速南移与中后期的顺时针旋转是柴达木侏罗纪盆地形成与迁移的主要动力;早侏罗世阿尔金断裂存在左行走滑构造运动,该构造运动也是早侏罗世早期板块边缘撕裂断陷形成的主要动力;古新世至始新世新特提斯洋首先在东端的闭合挤压以及羌塘地块短暂南移是柴达木此时局部拉分断陷盆地形成的主要动力。 首次提出柴达木盆地侏罗纪以来经历了9个形成与演化阶段,即经历了早侏罗世早期的板块边缘撕裂断陷期、早侏罗世中后期的板块边缘走滑断弯盆地期、中侏罗世的板块边缘断坳转化期、晚侏罗世-白垩纪挤压反转坳陷期、古新世-始新世的局部拉分断陷期、渐新世-中新世的走滑断陷期、上新世早中期断坳转化期、晚上新世挤压坳陷期及更新世-全新世的强烈挤压坳陷期等9个阶段。 首次从成盆动力学的角度系统总结了该盆地沉积充填的动力学特点,建立了不同时期的沉积充填动力学模式。通过沉积充填动力的分析,论述了沉积体系与充填动力变化对烃源岩、对储盖组合分布与发育类型的控制作用,认为强生物作用与弱物理作用的长期联合有利于形成巨厚的煤系烃源岩,弱化学与弱生物和极弱物理作用的联合促进了高丰度有机质的油页岩形成,强化学作用与弱生物和弱物理作用的长期联合有利于低丰度有机质泥岩烃源岩的形成和保存;沉积中心的大迁移不仅造成了侏罗系与上第三系烃源岩发育的分散性,而且造成储盖组合在同一方向上的迁移与有效性的变化。 在含油气系统思路的指导下,经过对盆地沉积体系变化规律的分析,提出了该盆地含油气系统划分的原则与新方案。认为柴达木盆地中新生界沉积体系的叠置与不断的迁移形成了7个含油气系统;并且不同盆地动力学机制下所形成的含油气系统在烃源岩发育与演化,以及油气的运聚规律上都存在明显的差异;柴北缘西段可靠的侏罗系双源并列型含油气系统(!)、西部下第三系多源叠合型可靠含油气系统(!)与第四系可靠的含生物成因天然气的含油气系统(!)仍然是最有利的含油气系统;上第三系上新统可能的多源叠瓦型含油气系统(·)与柴北缘东段可能的侏罗系双源叠合型含油气系统(·)将是存在一定勘探潜力的含油气系统,值得引起重视。更多还原

【Abstract】 This dissertation studied the function and influence of the peripheral plate to the Chaidamu tiny plate, by use of the palaeomagnetic data, the field geology survey data and the laboratory data etc. It firstly proposed that the Chaidamu tiny plate was affected by the Tarim plate in Mesozoic Era, but it was mainly influenced by Qiangtang plate and the south plate in Cenozoic Era. The fast movement of the Tarim plate to south in the Early Jurassic Epoch and clockwise rotation at the middle and late Jurassic Epoch was the main power of forming and moving for the Chaidamu basin in the Jurassic; and Aerjin fault in the early Jurassic Epoch subsisted left-walk strike-slip tectonic movement, which was the main power of forming of early Jurassic Epoch early plate edge ’s tear-fault depression. From the Palaeocene to Eocene Epoch, late Mediterranean sea’s eastern closed compression and Qiangtang block’s brief south movement was the main motive force of forming Chaidamu’s part of drawing and dividing faulted basin.The dissertation firstly proposed that the Chaidamu Basin had gone through 9 stages of forming and evolvement since Jurassic Period, i.e., the early plate edge ’s tear-fault depression in the early Early Jurassic Epoch; plate edge’s strike-slip fault basin period in the middle and late Early Jurassic Epoch ; plate edge’s fault sag transfer period in the Middle Jurassic Epoch; compression and twist sag period in the Late Jurassic Epoch to Cretaceous Period; local drawing and dividing faulted-sag period in the Paleocene to Eocene Epoch; strike-slip and fault depression of Mio-Oligocene age; early and metaphase of Pliocene fault sag transfer period; late Pliocene compression sag period and Pleistocene-Holocene Epoch’s intense compression sag period.It summarized this basin’s depositional infill of dynamics characteristics for the first time, established different phase’s depositional infill of dynamics model. By analyzing depositional infill of motive force, it discussed that depositional systems and depositional motive forces have control function to hydrocarbon source rock and the combination of reservoir and caprock’s distribution and developed types. Strong biological function combined perennially with weak physical function was in favor of forming huge thick coal更多还原