陆相断陷湖盆的成岩圈闭──以泌阳凹陷下第三系核桃园组三段为例

DIAGENETIC TRAPS IN FAULT-DEPRESSED LACUS BASIN: Take Eh_3 Member in Biyang Depression as an Example

泌阳凹陷下第三系核桃园组三段现多处于晚成岩阶段“Ａ”亚期─“Ｂ”亚期，与成岩圈闭形成关系较密切的成岩作用为胶结作用和溶解作用。常见的胶结物以碳酸盐的分布最广、含量最高，溶解作用以晚期深埋溶解作用为主，表现为由有机质演化产生的酸液对碳酸盐胶结物、长石等的溶解。成岩圈闭形成的关键在于遮挡层的存在，核桃园组三段砂体相带多变，不同部位的胶结、溶解作用有所差异，在晚成岩“Ａ”亚期，碳酸盐胶结物的胶结作用和溶解作用同时进行，常在扇体中部分支河道砂体主休部位发生溶解，而在侧缘、端部及上翘方向发生沉淀胶结，形成胶结遮挡带。根据成岩圈闭的特点，可将其划分为３大类，即与岩性尖灭有关的成岩圈闭、与断层有关的成岩圈闭、透镜型成岩圈闭，并可进一步细分为９个亚类。影响成岩圈闭形成的因素有沉积相、溶蚀作用、成岩作用、流体性质、断层作用及排替压力等，其中以沉积相、成岩作用及流体性质为主要影响因素。

Biyang Depression is a typical continental fault-depressed lacustrine basin. The Eh3 member in the depression is in the A ~ B substages of late diagenesis, the cementation and solution of the diagensis bear close relation with the formation of diagenetic traps. Carbonate is the main cement; deep burial solution in the late diagenetic stage is the major solution types. The existence of shielding bed is the key factor of forming the diagenetic traps. According to their characteristics, the diagenetic traps could he divided into three types such as the traps relating to lithologic pinch out, fault and lenticular types. These traps could be further divided into 9 subtypes. The factors that effected the formation of the traps include sedimentary facies, diagenesis, the features of fluid, solution, faulting and expulsive pressure. Among them, sedimentary facies, diagencsis and the feature of fluid at-c the main factors.