GEOLOGICAL IMPLICATIONS OF TECTONIC STRESS FIELD FORMED IN MAFIC DIKES IN SOUTHEASTERN FUJIAN
ZHANG Guishan 1,2 , WEN Hanjie1, HU Ruizhong1, QIU Yuzhuo1, YANG Guangshu1 and YU Wenxiu1 (1. Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou 550002, China; 2. The Graduate School of the Chinese Academy of Sciences, Beijing 100039, China)
The coastal area around Southeastern Fujian is located in the Changle-Nan'ao tectonic zone, where mafic dikes (swarms) were developed since late Mesozoic. To prove the popular view that the geometrical form and occurrence of mafic dikes should record the evolution of local stress field, a study was carried out on the mafic dikes from Chihu of Zhangpu and Haibian of Dongshan, and it was found that the Changle-Nan'ao tectonic belt might be a levorotatory ductile shear zone in the late Cretaceous, but was thereafter converted to the lefthanded fragile shear zone in the Paleocene; We believe that this was caused by the NW-trending subduction of the paleo-Pacific plate. Since late Cretaceous, the stress changes between shearing and tension in Southeastern Fujian, which indicates that the crustal extension is not continuous but proceeded by many stages; Through the low stress subduction of oceanic plate, crustal extension has dominated in Southeastern China.