宿东向斜“挤压弯滑—顶托平移”构造形成机制及验证

The Structure Formation Mechanism and Verification of“Trending Extrusion Bending Slip-Trending Translation”in Sudong Syncline

宿东向斜形似不对称哑铃,在区域地质图上显得格外醒目,其成因值得关注。文章通过区域大地构造演化背景梳理和宿东向斜构造组合分析,探讨宿东向斜成因,并结合朱仙庄煤矿构造发育特征加以验证。结果表明:宿东向斜可以划分为四类变形区,包括NE翼整体变形区、SW翼挤入变形区、SW翼挤出变形区和SW翼正常变形区;宿东向斜形成经历了两个关键变形期,即SW向挤压应力持续作用下先后发生的,以层间弯滑调节为特征的宿东向斜和“X”型共轭断裂形成期(挤压弯滑期)和因宿南箱状向斜东南弯折端顶托而沿“X”型共轭断裂平移为特征的挤入挤出期(顶托平移期);朱仙庄煤矿8^(#)煤层煤镜质组反射率光率体记录了形成向斜各期应力的来源方向;8^(#)煤层不同变形类型和程度层滑构造的规律分布是对宿东向斜“挤压弯滑—顶托平移”形成机制的良好响应。提出了一种基于煤层底板等高线的断层走向断距计算方法,并据此定量表征朱仙庄煤矿南部断层的平移方向和距离,进一步验证宿东向斜顶托平移机制。

The Sudong syncline is shaped like an asymmetric dumbbell.This special shape stands out on geological map and makes its genesis worthy of investigation.Based on the analysis of regional tectonic evolution background and the structural analysis of Sudong syncline,we discuss the genesis of Sudong syncline,which is further verified by combining the tectonic development characteristics of Zhuxianzhuang Coal Mine.The results show that the Sudong syncline can be divided into four deformation zones including NE limb integral deformation zone,SW limb extrusion deformation zone,SW limb extrusion deformation zone and SW limb normal deformation zone.Sudong syncline formation involved two key deformation stages.that is,deformation under the continuous SW directed compression:a Sudong Syncline characterized by interlayer bending adjustment and“X”conjugated fracture formation period(Extrusion bending stage),and the trending of strip of the southeast Sunan box syncline with the“X”type conjugate fracture translation characterized by intrusion and extrusion period(Trending Translation stage).The Coal vitrinite reflectance indicatrix in the 8^(#)coal seam of Zhuxianzhuang Coal Mine records the direction of stress in each stage of syncline formation.The regular distribution of bedding slip in different deformation types and degrees of the 8^(#)coal seam is a good response to the formation mechanism of“trending extrusion bending slip-trending translation”in Sudong syncline.We propose a method for calculating the along-strike fault offset which is based on the contour of coal seam floor.Using this method,the translation direction and offset of the fault in the southern Zhuxianzhuang Coal Mine were quantitatively characterized and the mechanism of the trending translation of the Sudong syncline was further verified.