Petrogenesis and tectonic implications of Paleoproterozoic mafic dikes in the southeastern North China Craton

Mafic dikes in cratonic regions record extensional tectonic processes within the continental lithosphere and thus provide key insights into mantle−crust interaction and deep-mantle geodynamics at regional to global scales. The tectonic setting of the Jiao-Liao-Ji belt in the eastern North China Craton remains debated due to multistage Precambrian overprinting, but resolving this issue is critical for reconstructing the North China Craton’s Precambrian evolution and its role in the Columbia supercontinent. Here, we report new laser ablation−inductively coupled plasma−mass spectrometry (LA-ICP-MS) U-Pb ages of 1.86−1.82 Ga (zircon) and 1.89−1.86 Ga (titanite), together with geochemical data, for mafic dikes intruding Neoarchean−Paleoproterozoic strata of the Jiaodong Terrane in the southern Jiao-Liao-Ji belt. The dikes display moderate light rare earth element enrichment, low Nb/La ratios, and variable εNd(t) values (−8.99 to +5.89). Based on trace-element systematics and intrusion ages, the dikes can be divided into two groups. Group I dikes (ca. 1.86 Ga) show higher Mg# and Nb/La ratios, lower Th/Nb and (La/Yb)N values, and more positive εNd(t) values (up to +5.89) than Group II dikes (ca. 1.82 Ga). Both groups were derived from a metasomatized subcontinental lithospheric mantle (SCLM), but their contrasting geochemical signatures reflect preexisting mantle heterogeneity, involving both depleted and enriched SCLM domains and variable melting degrees. Together with coeval A-type granites, alkaline rocks, and associated carbonate-clastic assemblages, the mafic dikes point to an intracontinental rift setting. These results suggest that the Jiao-Liao-Ji belt underwent intracontinental extension during the Paleoproterozoic, likely linked to the collapse of the Trans−North China orogen and the initial breakup of the Columbia supercontinent.