Neoproterozoic granitoid in northwest Sulu and its bearing on the North China‐South China Blocks boundary in east China

Abstract

Middle Neoproterozoic granitoid rocks are found in the Wulian region that is located in the northwestern part of the Sulu orogen and is approximately bounded by the Wulian‐Yantai fault in southeast. Zircon U‐Pb dating yields concordant ages of 738 ± 10 to 758 ± 5 Ma for three granites and one gabbro; hornblende Ar‐Ar dating on the gabbro gives consistent plateau and isochron ages of 719.1 ± 3.7 and 717.9 ± 7.2 Ma, respectively. This suggests that the Wulian granitoids correspond to bimodal magmatism during the mid‐Neoproterozoic in the northern margin of the South China Block in response to the breakup of Rodinia supercontinent. They were tectonic slices scraped off from the upper part of the South China Block during the Triassic continental subduction. This demonstrates that the suture location between the North China Block and the South China Block lies north of the Wulian and Penglai Groups rather than along the Wulian‐Yantai fault that marks the northern margin of ultrahigh pressure metamorphic belt.