Baddeleyite dating of a 2.34 Ga mafic dyke in the Western Shandong Province, North China Craton, and its tectonic implications

The mantle-derived magmatism of the early Paleoproterozoic is crucial to explore the tectonic environment of the Paleoproterozoic magmatic slowdown (∼2450–2200 Ma) of the North China Craton. The Wolongyu mafic dyke is exposed in the Taishan area, Western Shandong Province, eastern block of the North China Craton. This mafic dyke is meta-dolerite and has undergone greenschist facies metamorphism. SHRIMP baddeleyite and LA-ICP-MS zircon UPb dating revealed that the magmatic precursors of this dyke formed at 2344 ± 8 Ma and intruded into ∼2.5 Ga monzogranite. The Wolongyu mafic dyke is characterized by relatively flat patterns with light rare-earth element enrichment, slightly negative Eu anomalies (δEu = 0.86–0.98), and obvious Nb and Ta negative anomalies. The petrogenesis indicates that the Wolongyu mafic dyke is dominated by fractional crystallization of plagioclase and clinopyroxene with limited crustal contamination. Its geochemical features and εNd (t) values (1.07–1.83) are consistent with ∼1.8 Ga mafic dykes in the Western Shandong Province, indicating that these dykes were derived from partial melting of the metasomatized subcontinental lithospheric mantle. The Wolongyu mafic dyke was inferred to be in a plumb-triggered intra-continental extensional rifting environment in the eastern North China Craton during ∼2.3 Ga.