Petrogenesis of Cenozoic Mafic Dykes From Jiaodong Peninsula, the South‐Eastern North China Craton: Implications for the Evolution of the Lithospheric Mantle

ABSTRACT The study on the genesis and tectonic setting of the Cenozoic mafic dykes in the Jiaodong Peninsula provides key constraints for revealing the deep geodynamic processes of the eastern North China Craton. This study employed a comprehensive approach, encompassing detailed zircon U–Pb dating, zircon Hf isotope analysis, whole‐rock major and trace element analysis, and Sr‐Nd isotope analysis on the Cenozoic mafic dykes in the Jiaodong Peninsula. Geochronology studies indicate that mafic dykes in Jiaodong formed between 45 and 21 million years ago. The Cenozoic Jiaodong mafic dykes exhibit enrichment in large‐ion lithophile elements and light rare earth elements, characterised by high ( 87 Sr/ 86 Sr) i ratios of 0.7098–0.7113 and low ε Nd ( t ) values of −18.8 to −17.6, indicating their source region as EM II‐type lithospheric mantle. These mafic dykes exhibit high Dy/Yb ratios (2.15–2.94), suggesting the magma formed by low degree of partial melting of amphibolite‐grade peridotite in the spinel‐garnet transition zone. The Cenozoic Jiaodong mafic dykes have Ba/Th ratios of 139–362 and Ba/La ratios of 22–33, indicating significant influence from subduction‐related fluid alteration on the mantle source region. Cenozoic mafic magmatic activity in the Jiaodong Peninsula is closely associated with the lithospheric extension and thinning triggered by the subduction and slab rollback of the Paleo‐Pacific Plate. This study confirms that the eastern North China Craton was tectonically active between 45 and 21 million years ago, with lithospheric thinning continuing into the early Cenozoic. This study presents new evidence on the timing and scope of the North China Craton's destruction and the multi‐phase subduction‐extension coupling mechanism.