Extremely Iron-Rich Olivines from Ferrosyenites of the Prakasam District, Andhra Pradesh with Petrogenetic Comments

Though fayalite + quartz association is common in a variety of rocks, it is extremely rare with orthopyroxene and virtually non~existent with orthopyroxene + garnet. Hence the fayalite-ferrosilite-ferrohedenbergite( almandine-rich)garnet-quartz-bearing ferrosyenites in the Prakasam district (A.P.) are deemed as singularly exceptional and amazingly unique (Leelanandam, 1993a). The main purpose of this communication is to present electron microprobe analyses of the extremely iron-rich olivines (Fa_97.29 - Fa_99.78) from these unusual rocks and to comment on the relevant petrogenetic implications.