COVARIANCE PLOTS OF TRACE ELEMENTS AND DISCUSSION ON A COMPOSITIONAL ZONATION OF MAGMA CHAMBERS FOR YANBEI VOLCANICINTRUSIVE COMPLEX IN JIANGXI PROVINCE
江西岩背火山-侵入杂岩的微量元素协变关系及其岩浆房成分分带形成机制的探讨

Taking the volvcanic-intrusive complex of Yanei Porphyry type tin depositarea as an example,according to the covariance plots of Sr, R. Zr,Hf,Nb in six different coordinates,the mechanisms of compositional zonation in magma chamber shave been discussed.The results suggest that the magma melts for first and second cycles both were formed by the colleectionla melting processes(acidic for first cycle;intermediate-acidic for second). A part of acidic magma for first cycle. which was not extruded onto the surface, might be crystallized in equilibrium state (non-ideal)at depth.leading to the enrichment in F, H2O and oreforming element. such as Sn, Nb.Ta ect. in the residual melt.