Apatite-Magnetite Veins of Kasipatnam Hill, Visakhapatnam District, Andhra Pradesh

The Kasipatnam hill along the foot of the Eastern Ghats 60 km north-west of Vishakapatnam is largely made up of charnockites and associated rocks surrounded by khondalites constituting a domal structure. These are intruded by numerous dykes and veins made up mostly of apatite, magnetite and vermiculite with minor amounts of zircon, allanite, scapolite, actinolite and diopside. The mineralisation is structurally controlled, being restricted to shear joints and fractures cutting across the charnockitic rocks. The mode of occurrence, mineralogy, zoning, wall-rock alteration and paragenesis of the apatite-magnetite-vermiculite veins are described and their origin discussed. Possible affinity to carbonatite complexes is indicated.