Evolutionary History and Dynamic Mechanism of Structures in Xiaoxiyang Coalfield,Western Fujian Province

In order to understand the evolutionary history and dynamic mechanism of thrusting nappe structural zone of western Fujian province,the characteristics of geometry and kinematics and dynamic mechanism of structure in Xiaoxiyang coalfield were studied by combining structural analysis with background analysis,which locates the front part of thrusting nappe structural zone.The results show that there are two basic structural types of decollement structure and thrusting nappe structure.The whole profile of coalfield is in the form of 仑 pattern,where the 人 represents the imbricate arrangement of multi-period thrusting nappes and the 匕 the reversed syncline and its decollement fault along with axial plane.At early triassic and middle Jurassic,Cathysia and Kula plates respectively underthrust beneath the Yangtze block and Cathysia block,which results in the regional compression and the uplift of Wuyishan mountain.By the pressure and gravity from northwestern,the bedding decollement structure and the formation of reversed syncline successively developed at the Indosinian epoch,and the thrusting nappe structure ultimately generated in the coalfield at early Yanshanian epoch.In late Yanshanian and Himalayan epoch,the well field suffered from the reformation and erosion and parts of structure were inversed under the regional tension environment.