江南造山带的形成与演化:来自新元古代南桥辉绿岩的证据OA

The Jiangnan Orogen,situated on the southeastern margin of the Yangtze Block,represents the tectonic suture zone between the Yangtze Block and Cathaysia Block.The formation and evolution of this oro-genic belt remain significant research topics.This study presents LA-ICP-MS zircon U-Pb dating and petro-geo-chemical analyses of the Nanqiao diabase from the central Jiangnan Orogen,to investigate their petrogenesis and tectonic evolution implications.LA-ICP-MS zircon U-Pb dating indicates the Nanqiao diabase formed at ca.(839±7)Ma.The diabase exhibits low SiO2 content(48.4%-52.0%),relatively high MgO contents(6.96%-9.12%)and high Mg#values(70.3-79.1),and characteristic of tholeiitic series.Most samples demonstrate light rare earth element(LREE)depletion without significant Eu anomalies,while some samples display LREE enrichment with pronounced negative Eu anomalies.The rocks show enrichment in highly incompatible elements such as Rb and Th but depletion in moderately incompatible elements including Nb,Ta,Zr,Hf,and Ti.Geochemical analysis suggests that the Nanqiao diabase originated from decompression-induced upwelling of mantle material at rela-tively shallow depths(＜85 km),potentially associated with extension of a back-arc setting during subduction along the southeastern margin of the Yangtze Block.Integration with previous researches indicate a trench-arc-basin system developed along the southeastern margin of the Yangtze Block between 850 Ma and 820 Ma.The amalgamation between the Yangtze Block and the Cathaysia Block occurred at around 820-800 Ma.