Mid-Mesoproterozoic mafic magmatism (ca. 1.38 Ga) in the northern Yangtze Craton, China: A geological response to the Columbia supercontinent breakup

Mid-Mesoproterozoic rifting and magmatic events associated with the breakup of the Columbia supercontinent—particularly along the northern margin of the Yangtze Craton—remain poorly studied. This study presents new results from detailed geological mapping, petrography, U-Pb zircon geochronology, whole-rock Sr-Nd-Pb and zircon Hf isotope analyses, and geochemical investigations of newly identified mid-Mesoproterozoic garnet-plagioclase amphibolites in the Susong complex, part of the Dabie Orogenic Belt in central China. U-Pb zircon dating yields ages of ca. 1.38 Ga, and zircon morphology together with geochemical indicators (e.g., Th/U ratios) confirm a magmatic origin. The meta-mafic rocks show high Zr/Hf and low Th/Nb ratios, consistent with a within-plate tectonic setting, and display affinities with ocean-island basalts. Their εNd(t) values (−6 to +7) and zircon εHf(t) values (−13.5 to +7.4) are widely scattered, and one-stage TDM ages for both Nd and Hf cluster at ca. 1.3 Ga, indicating that melt extraction and source differentiation were broadly similar in age. The presence of older model ages (ca. 2.5−2.0 Ga) further reflects the incorporation of ancient crustal or lithospheric fragments into an enriched mantle domain modified by a plume or asthenospheric upwelling. This newly recognized mafic magmatism, together with previously documented coeval felsic magmatism, records a bimodal signature along the Yangtze Craton margin during this period. The results provide new constraints on intracontinental rifting processes and mantle dynamics during the final breakup of the Columbia supercontinent and refine the geodynamic framework of the Mesoproterozoic evolution of the Yangtze Craton.