Petrogenesis and tectonic setting of late Paleoproterozoic diorites in the Trans-North China Orogen

Abstract. The Xiong’er volcanic rocks and mafic dike swarms mark a significant magmatic event after the amalgamation of the North China Craton (NCC) in the Paleoproterozoic, yet their tectonic origins remain controversial. Several Paleoproterozoic diorite intrusions have received widespread attention recently. Their genesis and geological significance are crucial for understanding the evolution of the NCC. In this study, we report zircon U-Pb ages and geochemical data of the Jiguanshan diorite. The diorites in the Trans-North China Orogen, including the Jiguanshan diorite, have comparable element and isotopic geochemical characteristics. The weighted mean average of initial ⁸⁷Sr/⁸⁶Sr and ε_Nd(t) values is 0.7052 ±0.0003 and -6.5 ±0.2, respectively. The initial Pb isotope compositions of these diorite samples do not show significant enrichment of radiogenic lead. In terms of Sr-Nd-Pb isotope compositions and Nb/Ta, Ba/Th, and Sr/Th ratios, these diorites differ from the Xiong’er volcanic rocks and mafic dike swarms. Our results suggest that these diorites originated from the basaltic lower crust, rather than from the enriched subcontinental lithospheric mantle. Whole-rock and zircon trace element geological tectonic diagrams indicate that the diorites formed in a rift environment. These diorites mark a crustal-origin rock shift from orogenic-related magmatism to intraplate magmatism during the post-collisional extensional stage.