Mid-Neoproterozoic magmatism in the northern margin of the Yangtze Block, South China: Implications for transition from subduction to post-collision

Abstract The South Qinling Belt was located in the northernmost domain of the Yangtze Block during Neoproterozoic, and witnessed extensive magmatism in its southern part ( 800 Ma). The mechanism and implications of the contrasting magmatism on the southern and northern sectors of this major orogenic belt remain unclear. Here we investigate a suite of magmatic intrusions along the Ningshan-Xianghe Fault that separates these two domains to gain insights into the Mid-Neoproterozoic tectonic processes in the northern segment of the Yangtze Block. LA-ICP-MS zircon U-Pb dating yields ages of ca. 851–783 Ma for the Precambrian stocks along the Ningshan-Xianghe Fault. Our result suggests that the ca. 851 ± 5 Ma Xiaolingguan diorite has an adakitic affinity, and was derived from the partial melting of thickened basaltic lower crust. The ca. 834 ± 4 Ma Yaolinghe diorite was formed through the recycling of Paleoproterozoic crustal materials in a syn-collisional setting. The ca. 783 ± 5 Ma Liangjiawan granite is inferred to have formed by partial melting of crustal high-K metabasaltic rocks in a post-collisional setting. This event may be attributed to a Mid-Neoproterozoic tectonic transition from subduction to collision and post-collision, which gave rise to syn- and post-collisional magmatism in the northern margin of the Yangtze Block.