Mid-Neoproterozoic mafic rocks in the western Jiangnan orogen, South China: Intracontinental rifting or subduction?

• Published in: Journal of Asian Earth Sciences
• Main Authors: Wan, Le, Zeng, Zuoxun, Asimow, Paul D., Zeng, Zhihui, Peng, Lianhong, Xu, Daliang, Wei, Yunxu, Liu, Wei, Lu, Chengdong, Chang, Wenqi
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2019
• Subjects: South China Block; Mid-Neoproterozoic; Mafic rocks; Western Jiangnan orogen; Subduction-related magmatism; Intracontinental rifting; East Antarctica; Antarc*; Antarctica; Ocean Island
• Online Access: https://doi.org/10.1016/j.jseaes.2019.104039

Widely distributed Meso- to Neoproterozoic igneous rocks record the evolution of the Jiangnan orogen. We present integrated geochemical and geochronological data for basalts from the Gaoqiao area, northwestern Hunan Province. U-Pb dating of zircons indicates that the formation of Gaoqiao basalts occurred in the Neoproterozoic, no earlier than 757 ± 16 Ma. Like the contemporaneous mafic rocks in neighboring areas, the Gaoqiao basalts show trace element characteristics suggesting derivation from a source similar to ocean-island basalts (OIBs), including strong enrichment in large-ion lithophile elements (LILEs), high-field strength elements (HFSEs) and TiO_2, and high Ti/Y ratios. Placed in a regional tectonic context, however, the Gaoqiao suite is most consistent with an intracontinental rift model and offers no support to the idea of ongoing subduction in middle-late Mid-Neoproterozoic time in the western Jiangnan orogen. Despite the coincidence between the age of this rift and the separation of East Antarctica-Australia from Laurentia, we argue that the rift recorded in the South China Block (SCB) was an independent and probably unrelated event during the break-up of the Rodinia supercontinent. © 2019 Elsevier Ltd. Received 29 March 2019, Revised 15 September 2019, Accepted 22 September 2019, Available online 23 September 2019.