塔里木克拉通盆地中部走滑断裂形成与发育机制

Origin and growth mechanisms of strike-slip faults in the central Tarim cratonic basin,NW China

通过断裂构造解析和年代学研究,探讨塔里木克拉通盆地内走滑断裂形成与发育机制。结果表明:①走滑断裂发育具有多期性与分段性,同断裂期裂缝方解石胶结物U-Pb定年与地震解析限定走滑断裂形成时间为中奥陶世末(距今460 Ma);②走滑断裂形成受控于原特提斯洋闭合产生的近南北向远程挤压应力场;③基底结构与构造岩相差异等影响走滑断裂带的南北分区;④在先期安德森破裂的基础上,走滑断裂以连接生长为主,并伴随断裂尾端扩张与相互作用等非安德森破裂机制生长;⑤塔北共轭走滑断裂通过相继滑动机制调节相互截切部位的变形,并通过叠覆区的强烈局化作用调节主要位移与变形,塔中走滑断裂尾端窄深地堑与逆冲带走滑段积聚了更多的走滑变形与应变量。综合分析,塔里木克拉通盆地内走滑断裂通过连接生长为主的多种非安德森破裂机制形成不断连接加长的“小位移”长断裂,并受控于区域与局部应力场、先存基底构造与岩相差异,造成了走滑断裂的多样性。

Through fault structure analysis and chronology study,we discuss the origin and growth mechanisms of strike-slip faults in the Tarim Basin.(1)Multiple stages strike-slip faults with inherited growth were developed in the central Tarim cratonic basin.The faults initiation age is constrained at the end of Middle Ordovician of about 460 Ma ago according to U-Pb dating of the fault cements and seismic interpretation.(2)The formation of the strike-slip faults were controlled by the near N-S direction stress field caused by far-field compression of the closing of the Proto-Tethys Ocean.(3)The faults localization and characteristics were influenced by the pre-existing structures of the NE trending weakening zones in the basement and tectonic lithofacies from south to north.(4)Following the fault initiation under the Andersonian mechanism,the strike-slip fault growth was dominantly fault linkage,associated with fault tip propagation and interaction of non-Andersonian mechanisms.(5)Sequential slip accommodated deformation in the conjugate strike-slip fault interaction zones,strong localization of the main displacement and deformation occurred in the overlap zones in the northern Tarim,while the fault tips,particularly of narrow-deep grabens,and strike-slip segments in thrust zones accumulated more deformation and strain in the Central uplift.In conclusion,non-Andersonian mechanisms,dominantly fault linkage and interaction,resulted in the small displacement but long intraplate strike-slip fault system in the central Tarim basin.The regional and localized field stress,and pre-existing structures and lithofacies difference had strong impacts on the diversity of the strike-slip faults in the Tarim cratonic basin.