Petrogenesis and tectonic significance of the Paleoproterozoic Chibaisong meta-mafic rocks in the northeastern Jiao-Liao-Ji Belt

The Jiao-Liao-Ji Belt within the North China Craton had undergone a complex tectonic evolution, marked by extensive Paleoproterozoic magmatism that produced a diverse range of mafic to felsic magmatic rocks. These events provide valuable geological records for understanding the tectonic evolution of the Jiao-Liao-Ji Belt. This study focuses on the Paleoproterozoic Chibaisong meta-gabbro in southern Jilin, investigating the source of mafic magma, petrogenesis, and tectonic setting through systematic petrological analysis, zircon U-Pb dating, and geochemical studies. The findings contribute to constraining the dynamic mechanisms of Paleoproterozoic extensional rifting in the Jiao-Liao-Ji orogenic belt. Geochemical data indicate that the samples exhibit low SiO₂(47.99–50.66 wt.%), TiO₂(0.75–3.20 wt.%), Nb(3.22–8.09 ppm), and Ta(0.22–0.51 ppm) contents, along with high TFeO₃(11.97–15.82 wt.%) and MgO(5.67–12.66 wt.%) concentrations. They also show low Nb/La ratios and high (Th/Nb)_N values, consistent with the geochemical characteristics of tholeiitic basalts. The samples display low total rare earth element concentrations, weak or absent Eu anomalies, slight enrichment in light rare earth elements, relatively flat heavy rare earth element patterns, and depletion in Nb, Ta, and Ti. The meta-gabbro from southern Jilin exhibits geochemical similarities to Paleoproterozoic metamafic rocks from other regions of the Jiao-Liao-Ji Belt, resembling enriched mid-ocean ridge basalts (E-MORB) with Nb, Ta, and Ti depletion. Integration of previous studies and geochemical data suggests that the 2.16-2.10 Ga metamafic rocks in the Jiao-Liao-Ji Belt experienced contamination by older crustal material. These results indicate that the 2.16-2.10 Ga metamafic rocks are unlikely to be associated with island arc, continental arc, or mid-ocean ridge settings. Instead, they are more likely related to intraplate magmatism associated with continental rifting