ALMANDINE AND SPESSARTINE GARNETS FROM THE GIANT PLAGIOCLASE BASALTS OF DECCAN TRAPS, WESTERN GHATS, INDIA

Electron microprobe analysis of small (0.3 mm x 0.1 mm) and rare cryst als of almandine and spessartine garnets with subordinate amounts of o ther end member molecules such as pyrope, grossular and andradite is r eported for the first time from the giant plagioclase basalts of the K handala and Jawahar Formations of Deccan Traps from the Western Ghats. A high-pressure magmatic origin has been proposed consistent with the available mineralogy. The highly variable almandine content (41-81%), together with the wide variations noticed in the pyrope (3-40%) molec ule, is ascribed to iron enrichment of the host rocks and also to the possible mixing of such evolved compositions with primitive MgO-rich l iquids in the magma chamber, with or without possible mirror contamina tion from lower crustal metamorphic assemblages.