Geochronology, Geochemistry And Petrogenesis Of The Granitoids In The Sanming-ganzhou Area, South China

There are a lot of late Early Paleozoic granites and late Jurassic granites in theSouth China. Their petrogenesis and tectonic setting is still controversial. This paperreports the results of petrology, zircon U-Pb geochronology, zircon trace elements andHf isotope geochemistry, as well as whole rock major and trace element geochemistryof the granites in the Sanming-Ganzhou region, south China, in order to provide newinformation of the geochamical features, petrogenesis, tectonic settings, and theirimplications on crustal evolution during the Silurian to late Jurassic in the SouthChina block.The samples are from Ninghua pluton, Huitong pluton, Epo pluton and Jiangbeipluton. The rocks types are mainly biotite granite, granodiorite, two-mica granite anddiorite enclaves. Zircon U-Pb dating results indicate that the ages of the Ninghuapluton is ca.443Ma. The Epo pluton crystallized at the age of ca.422Ma and theJiangbei pluton crystallized at the age of ca.155Ma. The age of the dioritic enclavefrom the Huitong pluton is coeval with the host granitoid (ca.425Ma).The geochemical characteristics of the granites of late Early Paleozoic, arebelonging to peraluminous to strongly peraluminous, calc-alkaline to high-Kcalc-alkaline series. They are enriched in LREE, and depleted in HREE, withsignificant Eu negative anomaly. They are rich in Rb, Th, U, K, and depleted in Ba, Sr,Nb, P, Ti. The rocks show negative εHf(t) and old Hf crustal model age. Their εHf(t)value vaties in a large range and the granite zircon saturation temperature is relativelyhigher, which indicating that there may be mantle materical participation in the sourceregions. The petrogenesis of the dioritic enclaves and the host granitoid is probablyrelated to magma mixing. The granite samples show S-type granite affinities.The late Jurassic granites are peralumious high-K calc-alkaline series, anddepleted in MREE, with medium Eu negative anomaly. They are enriched in Rb, Th,U, K, Pb, depleted in Nb, Ta, P, Ti, Ba, Sr. They belong to I-type granites. The zirconHf isotope data show that the samples have negative εHf(t) values and old crustalmodel age.The Silurian granites and enclaves may be formed in the postcollisionalexetensional environment, with the lithosphere thining and mantle material upwelling.The late Jurassic granite formed in the intraplate extensional environment.