Formation of the Neoproterozoic ophiolites in southern China: New constraints from trace element and PGE geochemistry and Os isotopes

Furthermore, gabbro and basalt from the SAO have N-MORB- or arc-like geochemical characteristics that reflect the incorporation of crustal materials into the mantle source, suggesting that this ophiolite formed in a continental marginal back-arc basin setting. In comparison, the less pronounced depletions in trace elements and PGEs, as well as the restricted 187Os/188Os isotopic compositions of NJO serpentinized peridotites, suggest that they formed in a fore-arc setting. The contrasting geochemical characteristics of the two ophiolite suites indicate that they were generated during distinct stages of convergence along the southeastern margin of the Yangtze Block. Our results show that ophiolite suites produced within a single orogenic cycle could preserve diverse geochemical characteristics, and may provide insights into the initiation and cessation of continental amalgamation.