Restart of Subduction Processes in the Xiong’ershan Area of Southern North China Craton: Evidence from Low δ¹⁸O K-Rich Rocks during the Paleoproterozoic

Abstract The Paleoproterozoic supercontinent cycle likely began with a mountain-building event around 2.1 Ga, following a global tectono-magmatic lull occurred around 2.3 Ga, during which there was a notable decrease in magmatic activity. The nature of tectonic activity between 2.2 and 2.1 Ga remains unclear. This paper focuses on the discovery of low δ¹⁸O zircon-bearing potassic magmatic rocks in the Taihua Complex on the southern margin of the North China Craton (NCC). Through zircon U-Pb dating, Hf-O isotopic analyzes, whole-rock major and trace elements, as well as apatite Sr-Nd isotopic studies, we have constructed a model for the related geological evolution. Zircon U-Pb dating results clearly indicate active magmatism around 2.2–2.1 Ga, including granites at ~2.13 Ga, quartz monzodiorites at 2.16–2.12 Ga, and mafic cumulate rocks at 2.19 Ga. These potassic rocks show high K2O content, ranging from 0.95 wt.% to 7.00 wt.%, with a mean value of 3.95 wt.%, K2O/Na2O ratios, varying from 0.44 to 3.40, with a mean value of 1.24. These characteristics suggest contemporaneous formation of various mafic to intermediate-felsic rock types during the same period. The quartz monzodiorites and regionally distributed mafic dikes/intrusions show a variation in major element compositions, with trace element patterns characteristic of island arc settings, and consistent zircon Hf isotopic and apatite Sr-Nd isotopic characteristics, indicating a common origin in continental arc magmatic system. The 2.2–2.1 Ga granites possibly formed from partial melting of metasedimentary rocks. The zircon Hf-O isotopic features suggest that high-temperature hydrothermal activity induced by mantle upwelling may have played an important role. The zircon δ¹⁸O values from magmatic events during this period show a wide range (1.7, 5.7‰), but most are close to mantle values, further supporting the involvement of mantle-derived mafic magma processes. These findings provide important insights into the Precambrian tectonic evolution following a global tectono-magmatic lull.