Abstract:

In this study, we present detailed LA-ICP-MS zircon U-Pb chronology, major and trace elements, and Sr-Nd-Hf isotopic
data for the Xinfengjie pluton in central Jiangxi province, and discuss its petrogenesis and tectonic implications. Our results show
that the Xinfengjie granites are composed of two-mica granites and biotite granites, both of which were formed in late Jurassic (ca.
148 Ma). The two-mica granites have SiO2 contents of 75.71~78.36%. They are weakly peraluminous to strongly peraluminous rocks,
and belong to high-K calc-alkaline series. Their Mg# vary from 0.26 to 0.34, and they have low Ga/Al ratios (mostly < 2.6×10-4) and low
Zr+Nb+Ce+Y contents (<350×10-6). They have whole-rack εNd(t) of -10~-8.2, and zircon in-situ εHf(t) of -15.7~-9.4. The biotite
granites have SiO2 contents of 71.25~74.41% . They are metaluminous to weakly peraluminous rocks, and also belong to high-Kcalc-alkaline series. Their Mg# vary from 0.32 to 0.37, and they also have low Ga/Al ratios (mostly < 2.6×10-4) and low Zr+Nb+Ce+Y
contents (<350×10-6). They have initial 87Sr/86Sr ratios of 0.7136~0.7153, εNd(t) of -10.0~-8.9, and zircon in-situ εHf(t ) of -16.5~-10.9.
Through our comprehensive research, we consider that the two-mica granites show characteristics of S-type granites, and were formed at
lower temperature by partial melting of meta-pelite in the lower crust, while the biotite granites exhibit I-type affinity, and were formed
at higher temperature by partial melting of felsic rocks in the lower crust. This pluton emplaced in a continental-arc tectonic regime
which was induced by the subduction of the paleo-pacific plate.

Key words: Xinfengjie granites, Central Jiangxi province, LA-ICP-MS zircon U-Pb age, Sr-Nd-Hf isotopes, S- and I-type granites