The volcanic rocks of the Suxiong Formation are widely developed in the western margin of the Yangtze Plate,and their geochemical and chronological characteristics are of great significance for exploring the relationship between the volcanic rocks of the Suxiong Formation and uranium mineralization in this area.Collect rhyolite samples from the Suxiong Formation in Mianning area,Sichuan,and analyze their major,trace,and rare earth element compositions,as well as zir-con U-Pb-Lu-Hf isotope compositions,to study the rock type,magma source area,and tectonic evolution background of the Suxiong Formation rhyolite.The zircon U-Pb age of the Suxiong Formation rhyolite is(823.8±3.7)Ma(MSWD=3.4),indicating that it was formed in the early Neoproterozoic.Rhyolite has the characteristics of high Si(SiO2=70.14％～76.75％,average 74.19％),high alkali(K2O+Na2O=6.66％～7.67％,average 7.25％),low Al(Al2O3=11.36％～13.12％,average 12.10％),low Ca(CaO=0.26％～2.39％,average 1.08％),and low Mg(MgO=0.18％～0.74％,average 0.37％),and belongs to the peraluminous alkaline series rocks.Relatively enriched in Th,Rb,U,Zr,and Hf,and relatively deficient in Ba,P,Nb,Ti,Sr,it has the characteristics of relatively enriched light rare earth ele-ments,relatively deficient heavy rare earth elements,obvious negative anomalies in Eu,and a seagull shaped distribution of rare earth element distribution curves.It also has high values of 10 000 Ga/Al,Y/Nb,and zircon saturation tempera-ture,indicating that it belongs to A2 type rhyolite.The zircon Lu-Hf isotope composition of rhyolite indicates that it origi-nated from partial melting of newly accreted crust and was mixed with mantle material.It is believed that the volcanic rocks of the Suxiong Formation were formed in the extensional environment of the collision active continental margin in the early Neoproterozoic.During the tectonic evolution process,the subduction and retreat of the oceanic crust led to the upwelling of the enriched sodium asthenosphere,which promoted uranium enrichment.The volcanic rocks of the Suxiong Formation have good conditions for providing uranium sources.
Suxiong FormationA type granitezircon U-Pb ageLu-Hf isotopeuranium
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