Petrogenesis and mantle source characteristics of Cenozoic alkaline diabase, Jiangxi Province, southeastern China

Major element, trace element, and Sr–Nd–Pb isotopic compositions of Cenozoic diabase in southeastern China provide insights into the nature of their mantle sources and processes. The diabases are alkaline in lithochemistry (Na2O + K2O = 4.37–5.19 wt.%) and have overall oceanic island basalt-like trace element patterns, without negative Nb–Ta anomalies. In addition, they are characterized by lower La/Nb ( 15) and Nb/U (>30) ratios, indicating an origin in the asthenospheric mantle. The relatively lower 143Nd/144Nd (0.512632–0.512648) and 206Pb/204Pb (18.20–18.22), but intermediate 87Sr/86Sr (0.7061–0.7063) ratios of the diabases are similar to enriched mantle type 1, suggesting crustal contamination or mixing with metasomatized lithsopheric mantle. However, the low Th and U contents and lack of correlations of Nd isotope compositions and MgO preclude significant crustal contamination. Alternatively, the moderate TiO2 contents (2.01–2.09 wt.%) and high Cr concentrati...