Research On Changle-Zaoan Tectonic Zone (North Segment) In The Fujian Coastal Region

Changle-zaoan structural zone is located in the coastal area of Fujian province,in which strong earthquake occurred in geological history.But the development of this zone is still unsettled.Fujian coastal area is the frontier of China's economic development,and the starting point for the implementation of the marine strategy.This study focused on the northern part of the Changle-zaoan structural zone(from Fuzhou to Tupian),systematicly investigating the tectonic deformation,measuring the schistositilization strata attitude of the northern zone.And we collected the relevant samples.Based on the analysis of field data,the analysis and testing of samples,combined with regional geological data and previous research results,we studied the tectonic deformation characteristics,tectonic chronology,tectonic stress Field and tectonic evolution systematically.The tectonic deformation characteristics of the Changle-Zhao'an tectonic zone are mainly characterized by strong structural schistosity zones with tens of kilometers wide;the related rocks generally exhibit different degrees of microstructure deformation characteristics;Indicating that the main structure is mainly composed of the deformation structure and weak dynamic metamorphic rocks.Along the structure schistosity zone with the development of roughly the same period of the basic dyke group;and in this area found Pseudotachylite for the first time.The tectonic zone is weaker in the New tectonic period.The surface of the tectonic zone is weak and the surface is not large,the activity and the displacement is not obvious.The activity of the strong earthquakes is not high;it is not a deep fault zone.The Chronology study of the structural zone shows that the deformation of the main structure(the northward structural schistosity)is in the same period with the Mesozoic mid-late magmatic activity and metamorphism.The formation process can be divided into three stages:(1)Middle Jurassic and early in Late Jurassic(2)Late Jurassic and Early Cretaceous(3)Early Late Cretaceous,the most important stages of which were Late Jurassic and Early Cretaceous.In this paper,12 ages of the Paleoproterozoic and Mesoproterozoic(1400 ~ 2500Ma),5 Neoproterozoic ages(800 ~ 1400Ma)and 4 years of age are found in the Zircon dating of the early Cretaceous basement dyke group.(250 ~ 400Ma).They may reflect the information of the original rocks in different ages of the deep basins.It is presumed that there may be "Huaxia ancient land" base and the Caledonian fold belt and Late Paleozoic sedimentary caprock.According to the statistical analysis of the "structural schistosity zone" two paleo-tectonic stress fields can be divided into two main tectonic stress fields,which mainly correspond to the developmental stages of the north-east and north-west tectonic plates.The former main compressive stress direction is southeast-northwest.Which is the main tectonic formation period of the Late Jurassic to Early Cretaceous.The later main compressive stress direction is southwest-northeast,mainly in the Late Cretaceous.