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摘要
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=4.37-5.19wt.%) and have overall oceanic island basalt-like trace element patterns, without negative Nb-Ta anomalies. In addition, they are characterized by lower La/Nb (<1.5) and La/Ta (<22), and higher Ce/Pb (>15) and Nb/U (>30) ratios, indicating an origin in the asthenospheric mantle. The relatively lower Nd-143/Nd-144 (0.512632-0.512648) and Pb-206/Pb-204 (18.20-18.22), but intermediate Sr-87/Sr-86 (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 (2.01-2.09wt.%) and high Cr concentrations (>240ppm) suggest interaction between asthenosphere-derived melts and metasomatized lithospheric mantle. Petrological modelling suggests that the diabases were generated from a low degree (~3-5%) of partial melting of lherzolite with ~2-3% garnet. Jiangxi diabase was generated in a within-plate extensional regime, probably related to the far effect of the Himalaya-Tibetan orogen.
- 出版日期2014-12-10
- 单位南京地质矿产研究所; 合肥工业大学
