Abstract
TThe Bt-Grt gneiss from the Akarui Point, Lützow-Holm Complex, East Antarctica is mainly composed of Grt, Bt, Sil, alkali-feldspar, Qtz and Pl. The alkali-feldspar with obvious perthite texture is abundant in the rock matrix. The formation temperature of the alkali-feldspar is estimated to be above 825°C by ternary feldspar thermometry (Fuhrman & Lindsley, 1988) utilizing the recalculated integrated single-phase alkali-feldspar composition. This temperature is nearly the same with the highest temperature estimated in the Akarui Point. In alkali-feldspars next to biotite or garnet aggregating with biotite, domains with perthitic texture adjoining anti-perthitic texture are often found within single alkali-feldspar crystal. At the contact between alkali-feldspar and biotite, it is often observed that serrate projections of biotite are developed against alkali-feldspar every 3-5um. The projections are selectively developed next to orthoclase. These projections of biotite are not developed next to albite lamellas. We consider that these textures were formed as the biotite grew by consuming potash in alkali-feldspar when H2O fluid infiltrated locally into the rock matrix.
