Heterogeneous distribution of bulk chemical compositions and occurrence of meso-perthitic feldspars in felsic gneisses from Mt.Riiser-Larsen, East Antarctica

Abstract

Elemental mappings of felsic gneiss from Mt.Riiser-Larsen were obtained by using X-ray Fluorescence microscope and wave dispersive X-ray diffractometor, to reveal the heterogeneity chamical compositions of the gneiss and feldspars (Tfs) in the gneiss. In the results, the gneiss were clasified into 4 parts according to mineral assemblages; (a)oligoclase part (b)Tfs part, continuously-varied bulk chemical compositions (c)Or-rich Tfs part (d)myrmekite-like texture part that is composed of oligoclase and quartz. The occurrence of these 4 parts and heterogeneity of the gneiss are able to be explained reasonably by partial melting on ultra high temperature metamorphism and following crystal fractionation of feldspar.