Sapphirine-Bearing Quartzite from the Eastern Ghats Granulite Terrain, Vizianagaram, India

Abstract

Sapphirine occurs in a quartzite in the Eastern Ghats granulite province near Vizianagaram, India. Sapphirine is developed at the contact of quartzite and spinel-magnetite-cordierite bands and occurs as small grains throughout the quartzite. Bulk chemical analyses of sapphirine-bearing rock suggest that the protolith was a quartzite with aluminous and ferruginous cements. The presence of monazite and rare earth element (REE) analyses also indicate a sedimentary origin. Textural relations indicate that spinel, sapphirine, hypersthene, and sillimanite formed in an early metamorphic event at very high temperature and elevated pressure. Low activity of water and high oxygen fugacities accompanied reactions forming these minerals. Later metamorphic reactions accompanied by higher activity of water produced cordierite and biotite. Mineralogic geothermometry also supports a multi-stage metamorphic history. Experimental evidence for temperatures of 850°C or more required to stabilize sapphirine and quartz indicates that some parts of the Eastern Ghats province are among the highest temperature metamorphic terrains which have been described, comparable to Napier Complex of Endeby Land, Antarctica and the Wilson Lake area of Labrador.