周口坳陷构造特征与油气远景

STRUCTURAL FEATURE AND HYDROCARBON POTENTIAL OF ZHOUKOU DEPRESSION

这是一个横跨在华北地块与华北地块南缘构造带上的中新生代断坳型坳陷。中生代坳陷的形成与华北板块和扬子板块陆-陆碰撞引起的陆内火山活动及A型俯冲作用有关。新生代张剪性弧形断陷的形成是郯庐断裂系右行剪切平移运动和该区北西西向断裂左行剪切平移运动联合作用的结果。中部凹陷带是当前有利的油气勘探地区;对南部凹陷带的中生界和北部凹陷带的下古生界应加强工作。

Zhoukou Depression that crosses the two different tectonic units of North China massif and the southern marginal structural belt of the North China massif is the biggestdepression covering an area of 32000km^2 in the south part of North China Basin. In theMesozoic, NWW-trend tensile and compressive sags that filled with rapid accumulatedvolcanic--clastic rocks and oil--bearing molass formations developed in Runan, Tanzhuang-Shengqiu regions due to intracontinental volcanic activities and A-type subduction causedby continent-continent collision of North China Plate and Yangzhi Plate. In the Eogene,an arc-shaped tectonic framework protruding to south as a whole in the depression wascontrolled by tensile-wrench stress field. It contuins 2 uplifts alternated with 3 sags, in-cluding North part sag zone, Linying-Dancheng uplift zone, Central sag zone, Pingyu-Taihe uplift zone and South part sag zone from north to south. Each of the sag zones ismade up of several dustpan-shaped sags. It formed a group of dustpan-shaped sags withmulti-depocenter and multi-hydrocarbon generation center. The tensile-wrench arc-shapedtectonic system resulted from combined acting of dextral shear-wrench movement ofXiayi-Woyang-Macheng fault in Tanlou fault zone with sinistral shear-wrench movementof NWW trend fault in this region. Comprehensive studies indicate that the Central sag zone is favourable for hydrocar-bon exploration in the future. The Mesozoic System in the South sag zone and the LowerPaleozoic System in the North sag zone are prospective, and worthy to be further studied.