Ferrosyenites from the Cuddapah Intrusive Province (CIP) of Peninsular India

Ferrosyenites, which are unique rock types, are emplaced in Cuddapah intrusive province of peninsular India. These rare rock types are found to emplace at Gundlapalle and Gokanakonda in the Guntur District and at Uppalapadu in the Prakasam District of Andhra Pradesh. These syenites show considerable variation in mineralogical and geochemical composition. For an example the Gundlapalle syenites are devoid of olivine whereas in the other plutons olivine is essentially present with or without quartz. Normatively, these syenites are characterised by quartz, hypersthene or quartz+hypersthene combination. There are no indications of alkaline character in these rocks. As the name of these rocks indicates Mg is found to depleted whereas Fe+2 is enriched due to the presence of ferrohedenbergite and fayalite. The rocks are derived from anhydrous gabbroic magma which is evidenced by the absence of hydrous ferromagnesium minerals and the magma is subjected to closed system fractionation. The ferrosyenite from Uppalapadu alkaline complex is dated by U-Pb Zircon as 1352 Ma.