Shuitou Pluton in southern Jiangxi is traditionally considered to be Caledonian granite,and its genesis is still unclear.The biotite granite of Shuitou pluton is taken as the research object,and petrology,zircon U-Pb chronology,monazite U-Pb chronology and zircon Hf isotope are studied.The results show that the LA-ICP-MS zircon and monazite U-Pb weighted average ages are(151.6±1.80)Ma and(145.3±1.20)Ma.Geochemistry shows that Shuitou pluton is rich in silicon and alkali,with SiO2 content of 72.85%-76.14%and total alkali(K2O+Na2O)content of 7.98%-8.39%.It is enriched in elements such as Rb,Th,U,and Nd,and depleted in elements such as Ba,Nb,Sr,P,and Ti.LREE is relatively enriched((La/Yb)N=2.20-9.38),with obvious negative Eu anomaly(δEu=0.11-0.40).The zircon εHf(t)values range from-6.78 to 10.04,and the two-stage model age(TDM2)ranges from 1832 Ma to 1633 Ma.which is the product of partial melting of the lower crust in Mesoproterozoic.In conclusion,the Shuitou pluton is a highly differentiated type I granite,formed during Late Jurassic magmatic activity,originating from partial melting of the lower crust in the mid-Proterozoic era.It formed in a post-arc extensional tectonic environment and is related to magma intrusion along the Zhenhe-Dapu deep fault.
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