一个可能的走滑冲起构造——以黔西南碧痕营穹窿为例

A Possible Pop-up Structure in Strike-slip Fault System——An Example from Bihenying Dome in Southwestern Guizhou Province

通过遥感影像解译及野外地质调查,对黔西南晴隆碧痕营穹窿的成因进行了较为系统的分析。研究表明,碧痕营穹窿严格受近东西向和北东向延伸的两组断层控制,穹窿轴向与北东向断层走向一致。控制穹窿发育的三条断层均为压纽性走滑断层,断层旁侧的R剪切指示断层为右行走滑。两组走滑断层连接构成的右行左阶限制性弯曲与断层的压扭性质吻合。穹窿的几何形态为不规则的长方形,与限制性弯曲带上的隆起或冲起构造的形态相似;穹窿核部与边界之间的地形高差较大（700~800 m）,且核部和翼部（四周）的岩层近于水平,缩短弯曲不明显,说明穹窿的形成不是以纵弯褶皱机制下的弯滑和弯流褶皱作用为主,主要成因可能是沿汇聚型走滑断层上盘的逆冲所致,即碧痕营穹窿极有可能是走滑断层系统中限制性弯曲上形成的一个走滑冲起构造。

The Bihenying dome is located at Southwestern Guizhou,through remote sensing image interpretation and field investigation of its causes for a more systematic analysis. This study shows that the dome is controlled by the EW and NE striking of two groups of fault strictly,and the dome axial is consistent with the NE trending fault. The development of dome is controlled by three faults that transpressional strike-slip fault,and the rightstepping R shears indicative of dextral displacement. The right lateral displacement and left stepping fold hinges of restraining bend link the two strike-slip faults. The structure is similar to the pattern of the transpressional strike-slip fault. The geometry of the dome is irregular rectangle,which is similar to the geometry of the uplift or pop-up structure above restraining bend zone,the core part of with boundary between has a greater elevation（700 ~ 800m）,and the core and limb of rock nearly horizontal,that is,shortening the bend is not obvious.Thus it indicates that the dome was not caused by the buckle folding mechanism including flexural-slip folding and flexural-flow folding,which may be the main attribute to the hanging wall of fault of thrusting along convergent strike-slip fault. The Bihenying dome is most likely to a pop-up structure formed by a strike-slip fault system for restraining bend.