Neoproterozoic (ca. 825 Ma) basaltic magmatism in the southeastern margin of the North China Craton and its implications for the configuration of Rodinia breakup

Abstract Whether or not the North China Craton (NCC) preserves a record of its presumed breakup from Rodinia during the Neoproterozoic remains obscure due to a lack of magmatic events. However, the discovery of Neoproterozoic (ca. 825 Ma) basaltic magmatism in the Haiyangsuo complex, which was a part of the NCC before being incorporated into the Sulu orogen during the Triassic, provides a crucial clue to this issue. Thus, a combined study of field relationships, petrography, mineral chemistry, whole-rock geochemistry, and zircon geochronology was conducted on the metabasites from the Haiyangsuo complex. Evidence suggest metabasites I and II evolved from the same parental magma. In addition, compared to metabasites II, they are likely closer in composition to their parental magma. A simple binary Sr-Nd isotope mixing model suggests that the parental magma incorporated considerable crustal components (10–20 vol%) to form whole-rock compositions of the metabasites II. Zircon domains from the metabasites with magmatic origins yield ages of ca. 826–825 Ma, recording the intrusion age of the basaltic magma. Felsic veins, on the boundaries between the metabasites and granitic gneisses, have similar εNd(t = 825 Ma) values of −22.4 to −20.7 with the granitic gneisses (−26.9 to −25.8). Relict magmatic zircon cores from the veins yield 207Pb/206Pb dates of 2744–2206 Ma, consistent with those of oscillatory-zoned zircon cores (ca. 2706–2224 Ma) from the country gneisses, whereas newly grown domains crystallized from melts yield ages of ca. 824–823 Ma and εHf(t = 825 Ma) values of −11.9 to −10.0, broadly consistent with those of the Neoproterozoic zircon domains from the metabasites. Therefore, we propose that the hydrous melt, released by basaltic magma during the late evolution stage, subsequently infiltrated the margin of the country gneisses, finally forming the felsic veins. Accordingly, these results provide further evidence for the ca. 825 Ma basaltic magmatism in the Haiyangsuo complex. This Neoproterozoic basaltic magmatism (ca. 830–820 Ma) along the southeastern margin of the NCC witnessed the initial separation of the NCC from the Rodinia supercontinent. This study provides crucial information on the NCC during the breakup of Rodinia and helps to reconstruct the paleogeography of the supercontinent.