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野外地质露头观测资料、裂缝测井资料的综合解释及钻井岩心观察描述表明,鄂尔多斯盆地中东部地区奥陶系裂缝普遍发育。依据现有资料,在研究区划分了横山、靖边和安塞三个裂缝发育区,裂缝以多期共轭“x”节理(裂缝)和高角度斜交裂缝为特征。不同区块裂缝的发育方向不尽相同,可能是多期构造运动的结果。平面上裂缝(节理)走向大致可分为近EW向、近SN向、NNW向、NW向、NE向和NNE向等,且其中一组共轭“x”节理(裂缝)走向具有明显的左旋特征。根据各期应力场特征来看,该组裂缝可能是燕山运动的产物。

Characteristics of Fracture Systems in Ordovician in Central-east E'erduosi Basin

Through systematically observing the field outcrop fractures and core fractures and comprehensively analyzing the fracture logging data,it is indicated that the fractures are widely distributed over Ordovician in Central-East E'erduosi Basin.According to the existing data,three fracture development areas i.e.Hengshan,Jingbian and Anzhai fracture development areas are divided up in research region and these fractures are composed of multiple-stage conjugated "X" joints (fractures) and high-angle oblique crossing fractures.The fracture extending direction in different regions is not very much alike,which may be the result of multiple-stage structural movements.Fracture (joint) strikes may be roughly divided into approximate west-east,approximate north-south,north-northwest,northwest,northeast and north-northeast,etc.,in which the strike of a group of conjugated "X" joints (fractures) possess obvious sinistral property.According to the characteristics of stress fields in various stages,it is shown that this group of fractures might be the product of Yanshan movement.