A multidisciplinary study on the emplacement mechanism of the Qingyang–Jiuhua Massif in Southeast China and its tectonic bearings. Part I: Structural geology, AMS and paleomagnetism

摘要: During the Cretaceous, South China Block (SCB) experienced a widely distributed extensional event including numerous plutons emplacement and basin opening. Investigations on tectonic regime coeval with pluton emplacement, mechanism of remain relatively rare in SCB. In order to address these questions, multidisciplinary approach, field structural petrographic observations, anisotropy magnetic susceptibility (AMS) paleomagnetic analyses, was carried out Qingyang-Jiuhua granitic massif which intrudes into Lower Yangtze fold belt northeastern part The is composed granodioritic Qingyang monzogranitic Jiuhua dated by zircon U-Pb method at ca. 142 Ma, 131 respectively. Our observations show that intrusion does not modify strike. A weak ductile deformation country rocks granitoid can be only observed boundary zone limited contact metamorphism. aureole massif, foliation follows contour, mineral lineation rare. When present, it exhibits down-dip attitude. Field microstructural indicate isotropic magmatic textures most parts massif. AMS analysis 93 sites reveals values for degree (PJ 0) measured samples. Two principal patterns are identified: horizontal foliations center plutons, vertical boundaries. Magnetic strike largely scattered, weakly inclined scale entire investigations (a) younger did produce remagnetization older pluton, (b) no relative movement between two (c) experience any important respect China, considering uncertainties. Integrating newly obtained results previous our study favors permissive i.e. magma an opening space controlled NW-SE brittle stretching upper crust, agreement regional framework