The Early Jurassic tectono-magmatic events in Southern Jiangxi and Northern Guangdong provinces, SE China: constraints from the SHRIMP zircon U-Pb dating

The Jurassic to Cretaceous magmatism in the South China Block (SCB) has important geological significance for its tectonic evolution, particularly, the tectonic regime change. We report here new SHRIMP zircon U-Pb ages, geochemical and Sr-Nd isotopic results from the Early Jurassic magmatic rocks in eastern Nanling region of southern Jiangxi and northern Guangdong provinces, SE China. The SHRIMP zircon U-Pb analyses yield consistent Early Jurassic ages of 193 ± 2. Ma for granodiorite and 196 ± 1. Ma for gabbro-diabase from the Hanhu complex of southern Jiangxi Province. Field observation indicates that the gabbro-diabase coexists with syenite in granodiorite, and that the mafic components infiltrate into the syenite. Combined with the SHRIMP zircon U-Pb ages of 196 ± 2. Ma for granites and 195 ± 1. Ma for gabbros of the Xialan complex of northern Guangdong province, these contemporary ages represent an earliest tectono-magmatic events during the Yanshanian orogeny. These results reveal that there are tectonic extension and the post-collisional and intraplate magmatism events at or before 196. Ma, in contrast to the wide believed quiescent stage (205-180. Ma) of magmatic activity in SE China. The confirmation of these tectono-magmatic events in the eastern Nanling area thus sheds new light on the quiescent stage of magmatic activity in SE China during 205-180. Ma and provides new constraints to understand the Early Jurassic tectonic evolution of SE China.