| The Youjiang Basin on the southwestern margin of the Yangtze block is located at the intersection of the Paleo-Tethys tectonic domain and the Paleo-Pacific tectonic domain.Since its formation in the Hercynian-Indosinian,the Youjiang Basin has undergone multiple stages of structural deformation from the Indosinian,Yanshanian to the Himalayan period,forming a large number of domes.The nature of these domes is mainly complex anticline formed by the superposition of buckle fold structures.Predecessors have analyzed the geometry,kinematics and dynamics of some complex anticlines,and believed that the structural deformation of the Youjiang Basin can be roughly divided into three stages:EW-trending folds and thrust faults formed in the Indosinian,NW-trending folds and thrust faults in the early Yanshanian,and NE-trending transpressional strike-slip faults formed in the late Yanshanian.However,the main structural factors controlling the formation of the complex anticlines in the Youjiang Basin and the characteristics of its regional stress field are still unclear.In response to this problem,this paper investigated an NE-trending complex anticline-Leye complex anticline-located in the east of the Youjiang Basin,north of the Youjiang Fault and close to the Ziyun-Luodian-Duan Fault.Detailed structural analysis shows that the Leye complex anticline has undergone at least two phases of thrust fault and fold(D1 and D2)superimposition.And with the Youjiang Fault as the boundary,the tectonic lines on the north and south sides of the fault have significant difference:the complex anticlines to the south of the Youjiang Fault is generally EW-trending,while NE-trending complex anticlines occurs to north of the Youjiang Fault.The NE-trending folds to the north of the Youjiang Fault undergone D1 structural deformation,manifested as NE-trending thrust faults,NE-trending folds and associated cleavage,etc.According to the geological relationship,the D1 deformation occurred in P1-P2.The D1folding may be later than the?269±1.8 Ma diabase emplacement activity in this area.The emplacement of the diabase and the D1 folding may correspond to the earlier and later activities of the Dongwu movement in this area,respectively.The compressive stress field derived from the strike-slip movement of two regional faults in this period-the Ziyun-Luodian-Duan Fault and the Youjiang fault-may be contributed to the D1folding.The D2 folding is the result of the propagation of the Indosinian orogenic foreland fold-thrust belt from south to north.This study of the structural style and deformation sequence of the Leye complex anticline will help reconsider the manifestation and influence of the Dongwu movement in the Youjiang Basin,and perfect the information on the structural evolution of the Youjiang Basin. |
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