Discussions On Features Of Mesozoic Thrust-fault Belts And Relationship Between Thrust-fault Belts And Magmatism In Southwestern Fujian And Adjacent Regions

Southwestern of Fujian and adjacent regions (SFAR) lie in the southeast of theSouth China Block (SCB). The stage of evolution in this area consists of basement inPre-Devonian, deformation of the basin in Late Paleozoic and complicated structuralevolution with strong magmatism since Mesozoic. Due to the strong tectonicdeformation caused by the plate movement of the East Asian lithosphere inChina and adjacent regions, a large scale of NE-NNE direction fold and thrust nappestructure has developed in the study area especially since the Middle Jurassic.To seek the spatial and temporal evolution regularity of the study area, weanalyzed the base type of the nappe structure and structural features on its features ofdeformation. We also discussed the forming age, thrusting displacement, features ofkinematics and dynamics.Then a model of the nappe structure could be proposed withthese conclusions:1. The nappe structure in SFAR located in the inside belt of Wuyishan uplift zone,the transportation belt between Wuyishan uplift zone and the study area geotectogene,the inside belt of the study area geotectogene and the east boundary belt of theSouthwestern Fujian geotectogene (SFG). These belts have different structures,components, directions and displacements.2. The decollement structure in SFAR is mainly formed in the Indosinian, whereasthe nappe structure formed in different periods, which are the early Mesozoic (the endof Indosinian), Middle Jurassic-Early Cretaceous (the early Yanshanian), and LateCretaceous (the late Yanshanian).3. According to a balanced cross-section analysis, regional stress field study, thecalculation of the thrust distance and the chronology of magma activities, it was ashallow nappe structure that happened during the Indosinian, then turned into amiddle–shallow one. There are four characters of the broad flat nappe structure insideSFG, including38%reduction of length, a direction from NW to SE, the napping distance less than105km of the broad flat nappe structure and ended at about142Maas conforming with the transforming age from compression to extension.4. A study on isotope chronology and petrol-geochemistry was undertaken withsamples form DatianGuangping-Tangquan napping body, LonggongShan–Jiufengqinapping body and the Mesozoic granite in adjacent regions. The late Mesozoicmagmatic intrusion related to nappe structure formed in150Ma±and130Ma±ingeneral. The magmatic action formed in the tectonic setting of compression toextension, which has spatial and temporal relationship with strong deformationdeveloping between late Jurassic to early Cretaceous in the east of the nappe structure.