Geochronology, Geochemistry And Petrogenesis Of The Fucheng Granite From Huichang Country Jiangxi Province

The Fucheng granites lies in Huichang country Gaizhou city Jiangxi province. It is a multiple times into the intrusive mass of granitic rock. The Fucheng granites are mainly composed of the subject middle-coarsed-grained two-mica granite and the complement fine-grained biotite monzonite granite. The rock have been studied for LA-ICP-MS zircon U-Pb ages, whole-rock elemental and Hf isotopic compositions to constrain their sources and tectonic settings. Combined with the petrographic and regional geological settings, the petrogenesis and tectonic settings of the rock mass have been discussed. And on the basis of the uranium geoChemical characteristics and Indosinian granites geoChemical characteristics of the rock, we have preliminarily determined the uranium producing capacity.LA-ICP-MS U-Pb dating results of zircons imply that the subject granite was emplaced at 227Ma and 218Ma showing that there was at least two times of Indosinian magmatic activities. The subject granite has high SiO2 contents(72.1～78.1%) A12O3 contents (10.4-13.3%) and high contents of alkalis(ALK=5.56～8.72%, K2O/Na2O=1.29～28.3), low abundances of calcium, magnesium. It has high Rb/Sr ratio and low K/Rb and Nb/Ta ratio. The A/CNK values of the subject granite vary from 0.99 to 1.62, and most of the values are more than 1.1. The rocks display low total REE contents (∑REE=87.7～300ppm) with strongly negative Eu anomalies, and enriched in LILEs such as Rb, Cs, K, Pb, and HFSEs such as Th, U, Ta, Zr and depeted in Ba, Sr, P, Ti. Overall, our integrated mineralogical and geoChemical features suggest that the Fucheng subject granite is S-type granites. Isotopically, their zircon Hf isotopes show large variations, with most of εHF(t) values varying between -4～-9, corresponding to two stage model age of 1.4～1.96Ga. And it shows that the source rock was the metamorphic rock which was rich in pelite by way of partial melting and then after the fractional crystallization, the Fucheng subject granite was formed in syn-collisional setting. The rock has higher U content, lower Th/U ratio, and the higher activity uranium leaching rate, showing that the rock mass has a certain uranium production potential.LA-ICP-MS U-Pb zircon ages for Fucheng complement granite is 219.1～221.5Ma, and the average is 220 Ma, indicating that this pluton was generated in Indosinian stage. Chemically, this pluton is weakly peraluminous to strongly peraluminous(A/CNK=1.03～1.26), and show high contents of silica (SiO2=71.7～78.2%) and alkalis (7.16～9.31%, K2O/Na2O=1.47～3.53), low abundances of calcium, magnesium. The rocks display low total REE contents (∑EE=66.0-204ppm) with strongly negative Eu anomalies, and enriched in LILEs such as Rb, Cs, K, Pb, and HFSEs such as Th, U, Ta, Zr and depeted in Ba, Sr, P, Ti. Overall, our integrated mineralogical and geoChemical features suggest that the Fucheng granites are S-type granites. Isotopically, their zircon Hf isotopes show large variations, with εHF(t) values varying between-2.29～-10.8, the average being -7.5, corresponding to two stage model age of 1.4～1.96Ga. And it shows that the source rock was the metamorphic rock which was rich in pelite by way of partial melting and then after the fractional crystallization, the Fucheng fine-grained granite was formed in syn-collisional setting. The rock has higher U content, lower Th/U ratio, and the higher activity uranium leaching rate, showing that The rock mass has a certain uranium production potential.