扬子西缘冕宁地区新元古代辉绿岩的岩石成因及其构造意义OA

Neoproterozoic mafic dyke swarms are key indicators for reconstructing the timing and dynamic processes of the Rodinia supercontinent breakup.Based on systematic analyses of zircon chronology,whole-rock geochemis-try,and zircon Lu-Hf isotopes,this study investigates the petrogenesis and geodynamic setting of a newly discov-ered diabase dyke swarm in the Mianning area on the western Yangtze Block,South China.LA-ICP-MS zircon U-Pb dating reveals that the Mianning diabase crystallized at 835.8±4 Ma,indicating its formation during the Neo-proterozoic.The diabase exhibits variable SiO2 content(45.2％to 48.0％)and MgO(6.82％to 8.15％)con-tents,as well as Mg#values(46～57),along with high Al2O3(14.00％～15.75％)content.The studied rocks display relatively flat rare earth element(REE)distribution patterns,with enrichment in Rb,Ba,and K,and de-pletion in Nb,Ta,Sr,and P.The studied rocks exhibit enriched zircon Lu-Hf isotopes[εHf(t)=-2.2 to 1.6].Petrogenetic analysis indicates that the Mianning diabase originated from low-degree partial melting of an enriched mantle wedge,with the mantle source having been modified by fluids derived from altered oceanic crust.The Neo-proterozoic Mianning diabase on the western Yangtze Block formed in an extensional continental arc setting,impl-ying that the western margin of the Yangtze Block may have been located at the periphery of the Rodinia superconti-nent during the Neoproterozoic era.