Differential lithospheric evolution during craton destruction: Insights from Mesozoic mafic magmatic suites with transitional features in the North China Craton

Abstract

During the Mesozoic, the North China Craton (NCC) especially the eastern part underwent significant destruction of its cratonic roots. During ∼125–120 Ma, the source of magmatism shifted from an ancient enriched lithospheric mantle to a juvenile depleted asthenospheric mantle. While this geochemical change is clear in the eastern NCC, it is unclear whether a similar shift occurred in the central NCC or if the lithospheric evolution differed across the craton. Mafic magmatic suites are key to understanding the evolution of cratonic lithospheric mantle, especially by analyzing their geochemical and isotopic transitions. This study examines the Mesozoic Laiyuan ultramafic–mafic intrusions in central NCC, classified into gabbro, gabbroic diorite, and cumulate suites (pyroxenite and hornblendite). Zircon U-Pb dating indicates gabbroic rocks formed between 136–124 Ma and cumulated between 130–129 Ma. These rocks also display similar isotopic signatures, including zircon Hf isotopes ranging from −24.9 to −7.8 and −28.3 to −15.9, (87Sr/86Sr)i ratios from 0.705945 to 0.706335 and 0.705692 to 0.706038, and εNd(t) values from −16.1 to −12.8 and −15.8 to −12.5, respectively. Geochemical and isotopic data suggest an enriched lithospheric mantle source influenced by subduction-related metasomatism with minimal crustal contamination. The gabbroic and ultramafic layers represent residual melts and cumulates from a common source, respectively. Geochemical data reveal a transition in the mantle source from ultramafic-mafic intrusions (∼140–124 Ma) to dolerite (∼125–117 Ma) and lamprophyre (∼115–110 Ma), indicating lithospheric thinning and asthenosphere upwelling. This gradual transition in the central NCC contrasts with the rapid change in the eastern NCC, reflecting different lithospheric evolution processes: thermo-mechanical erosion in the central NCC and lithospheric delamination in the eastern NCC. These findings highlight diverse mechanisms of cratonic destruction across the NCC.