Formation age, geochemical characteristics of the Ninggang granite body in Jiangxi Province and its tectonic significance

The Ninggang granite body, located at the juncture of Hunan and Jiangxi provinces, is an important member of the Caledonian granite zone with south-north trend. It is mainly composed of monzogranite. LA-ICPMS U-Pb dating of zircons yields an age suggesting that it was formed in the Caledonian magmatism event. Although Ninggang granite body exhibit obvious of 433.8 +/- 2.2 Ma, variation of, SiO2 contents (67. 46% similar to 74. 85%), their ACNK values are all bigger than 1.1, potassium larger than sodium(K2O/Na2O = 1.36 similar to 2. 37) CaO/Na2O ratios larger than 0.3 and enrichment of Rb. Th and Cs, depletion of Nb, Ta, Ba and Sr, strong REE fractionation LREE/HREE = 5. 8 similar to 12.2) and relative obvious Fit depletion (delta Eu = 0. 28 similar to 0. 61). They also have lower epsilon(Nd)(l) values (-9. 3 similar to-8. 6), higher (Sr-87/Sr-86), ratios (0. 71172 similar to 0. 71937) and old Nd model ages (1838 similar to 1909Ma). These geochemical characteristics indicate that the Ninggang granite body belonged to crust sourced type of granite and were derived from the partial melting of psammitic; rock Under an extensional tectonic setting which is caused by continent-continent collision between remnant Cathaysia fragments and Yangtze Mock.