Petrography of ferrosyenites from the Cuddapah intrusive Province, Peninsular India

: The paper deals with the petrographic details of the subalkaline ferrosyenites which are emplaced in the Cuddapah intrusive province (CIP) of peninsular India. These leucocratic rare rock types (colour index ranges 7 to 19 vol%) are found emplaced at Gundlapalle and Gokanakonda in the Guntur district and at Uppalapadu in the Prakasam district of Andhra Pradesh. All the ferrosyenites show equigranular, hypidiomorphic texture but mineralogically they are different, even though they are uniformly subalkaline in character. Ferrohedenbergite and its altered product called nontronite are found in Gundlapalle ferrosyenite, but fayalite along with clinopyroxene are found in Gokanakonda and Uppalapadu ferrosyenite. Again, at Gokanakonda, a second type of ferrosyenite is found with fayalite along with quartz.