Geochronology, geochemistry, and tectonic implications of Jishou Cretaceous diabase, western Xuefengshan tectonic zone in South China

From the east of the Xuefengshan tectonic zone (XTZ) to the Pacific coast of the South China Block, there exist widespread Mesozoic magmatic rocks, which attract a great deal of attention for their forming mechanism and evolutional history. Among them, the Mesozoic Jishou diabase located at the west of the XTZ is reported in this study. Based on our geochronologic analysis, the diabase has a U–Pb age of 134 ± 2.3 Ma. The diabase belongs to calc‐alkaline series in a SiO 2 ‐K 2 O diagram and illustrates significant enrichment in light rare earth elements and flat heavy rare earth elements without obvious Eu anomalies. Meanwhile, the diabase has negative εHf(t) and εNd(t) values and higher radiogenic 87 Sr/ 86 Sr(t) ratios, suggestive of EM2‐like Sr‐Nd isotopic compositions. The diabase shows high variations in 207 Pb/ 204 Pb(t; 15.609–15.671), 206 Pb/ 204 Pb(t; 17.943–18.742), and 208 Pb/ 204 Pb(t; 38.268–39.302). It is suggested that the Jishou diabase may be generated from the lithospheric mantle in response to the decompression melting accompanied by lithospheric extension during Pacific subduction process. During the Early Cretaceous (145–120 Ma), the upwelling and melting of the mantle occurred under the XTZ, causing intraplate Jishou diabase magma. Subsequently, the significantly descending of the subducted Paleo‐Pacific slab led progressively eastward generation and migration of subduction‐related magmas, resulting in a widespread distribution of igneous rocks in the Cathaysia Block.