西南天山乌什北山地区逆冲推覆构造的识别及大地构造意义

合理厘定西南天山构造属性,不仅对天山大地构造单元的准确划分具有重要科学意义,而且对中亚造山带的古生代构造演化也至关重要。通过对西南天山乌什北山地区的地质填图和构造解析,识别出5期构造变形,包括2期逆冲推覆构造。对主期逆冲推覆构造进行几何学、运动学研究表明,该逆冲推覆构造在空间上具有由北向南逆冲的运动学指向,并由北向南表现出由逆冲推覆构造的根带向前锋带变化的构造样式。根据逆冲推覆构造的物质组成及变形样式,认为西南天山乌什北山一带应属于塔里木板块北缘逆冲推覆构造带,从而为区域构造单元划分及西南天山晚古生代以来的构造演化过程提供构造变形方面的依据。

THE RECOGNITION OF THRUST NAPPE STRUCTURE AND ITS TECTONIC SIGNIFICANCE IN BEISHAN AREA, WUSHI COUNTY, SOUTHWESTERN TIANSHAN

Reasonably defining the tectonic attributes of Sorthwestern Tianshan not only has important scientific significance and practical value to the accurate division of Tianshan tectonic units, but also plays an importantrule in revealing the tectonic evolution during Paleozoic in Central Asian orogenic belt. Based on geological mapping and field structure analysis in Beishan area,Wushi County, Southwestern Tianshan, 5-phase deformation is recognized, including 2-phase thrust structures. The geometry and kinematics studies of the main thrust nappe structure prove that the thrust nappe structure yield with N-S direction. The structural deformation style of the thrust nappe can be established, and it presents root zone to front zone of nappe from north to south. According to the material composition and deformation features of thrust nappe structure, we think that Beishan area should be classified into the thrust nappe structure in north margin of Trim Plate in Paleozoic. It may provide deformational information for understanding the regional tectonic units division as well as the tectonic evolution in Southwestern Tianshan since Neopaleozoic.