" Soutenance de thèse en cotutelle internationale de Wei WEI. | Université d'Orléans

Université d'Orléans

Soutenance de thèse en cotutelle internationale de Wei WEI.

27/12/2013 - 10:00 - 27/12/2013 - 14:00

URL: http://www.univ-orleans.fr/actus/soutenances

Nom du contact: Etudes Doctorales

Courriel du contact: etudes.doctorales@univ-orleans.fr

Lieu: Université de l'Académie des Sciences de Chine

Titre : Characteristics of the Late Mesozoic tectonic evolution of the eastern part of the South China Block and geodynamic implications -multi-approach study on emplacement of Qingyang-Jiuhua, Hengshan and Fujian coastal granitic massifs and related tectonic structure.

Discipline : Sciences de la Terre et de l'Univers

Résumé :

The vast distribution and long duration of Late Mesozoic magmatism in the eastern part of South China presents a unique case in the world. This offers a natural laboratory to study the process of magmatisation, the emplacement mode of magma, the relationship between magmatism and tectonics, the geodynamic role on the magma emplacement and lithospheric evolution. Since 50’s, geoscientists have carried out numerous studies with remarkable scientific achievements. However, certain fundamental questions remain unsolved and/or are in hot debate. In order to make progress in these scientific issues, we have carried out in a multi-disciplinary study in Late Mesozoic Qingyang-Jiuhua massif, Hengshan massif and Fujian coastal zone, including field structural observation, micro-observation on thin section, U-Pb dating on monazite, AMS, paleomagnetism, gravity modeling and Amphibole-Total Al barometer. In the views of deformation in granitic massifs and their country rocks, mode and influence of regional tectonics on the emplacement, though each studied zone reveals its distinguished characteristics, they show some intrinsic and common relationships among them.  With our new results and integrating previous data, we discuss the tectonic context of emplacement of these Late Mesozoic magmatic massifs and geodynamic evolution of SCB in this thesis, and propose a 3-step geodynamic model: (1). during 145-130 Ma, the Paleo-Pacific plate subducted northwestwardly the Philippines micro-continent, approaching to SCB, important subduction-related arc volcanism was produced in the coastal areas of Zhejiang-Fujian-Guangdong, forming a back-arc extension tectonic system; (2). during 130-110 Ma, due to the collision between the Philippines micro-continent and SCB, the compressive tectonic structure was developed in the Changle-Na’ao coastal zone. However, the inland of the eastern part of SCB is still under NW-SE extensive tectonic regime; (3). during 100-90 Ma, a new subduction zone was developed in the SE flank of the Philippines micro-continent, the subducting slab attended beneath the Changle-Nan’ao tectonic belt, with the possible break-off of slab, the asthenospheric ascending makes the important emplacement of magmatic massif and dykes. The tectonics of the eastern part of SCB is characterized by a general extensive system in this period.