Zircon U-Pb geochronological and Hf isotopic constraints on petrogenesis of Tieshan and Jinshandian plutons in the southeastern Hubei Province
鄂东南地区与铁山和金山店铁矿有关的花岗质岩体锆石LA-ICP-MS年龄和Hf同位素组成及其地质意义

During the Late Mesozoic,extensive magmatism and associated ore deposits were developed in the Middle-Lower Yangtze River metallogenic belt,East China.As the Tieshan and Jinshandian quartz diorite in the southeastern Hubei Province examples,we performed in situ zircon U-Pb dating and Hf isotopic analyses on 5 samples.Twenty-six zircons in the quartz diorite from the Tieshan sample jls1-110 yield excellent concordant results with a weighted mean 206 Pb/ 238 U age of 138.9±0.96Ma(n=26,MSWD=0.82). Zircons from Tieshan sample jls3 yield excellent concordant results with a weighted mean 206 Pb/ 238 U age of 138.2±0.94Ma(n=24, MSWD=0.85).Zircons from Tieshan sample jls4 yield excellent concordant results with a weighted mean 206 Pb/238 U age of 131.0± 1.2Ma(n=11,MSWD=0.94).Zircons from Tieshan sample jls5 yield excellent concordant results with a weighted mean 206 Pb/238 U age of 118.9±1.2Ma(n=14,MSWD=1.20).Zircons from Jinshandian sample jsd yield excellent concordant results with a weighted mean2 06Pb/ 238 U age of 128.6±0.88Ma(n=22,MSWD=0.98).ε Hf (0)andε Hf (t)values of the Tieshan quartz diorite are minus.Hf model age of the first stage(t DM1 )is 1.33Ga and the age of the second stage(t DM2 )is 2.03Ga.ε Hf (0)andε Hf (t) values of the Jinshandina quartz diorite are minus.Hf model age of the first stage(t DM1 )is 1.03Ga and the age of the second stage (t DM2 )is 1.56Ga.Hf isotopic compositions from the Tieshan and Jinshandian quartz diorites show that maybe the curst-derived materials joined in the rock body forming supplement for the crust-derived magma of the Middle-Lower Yangtze River.Based on the datum of petrology,geochemistry and ore isotope ages,we can infer that the skarn type iron deposits of the Early Cretaceous in the southeastern Hubei Province formed on the environment of lithospheric extending and thinning.