Geological and Geophysical Exploration for offshore Ilmenite placers off the Konkan Coast, Maharashtra, India

Abstract

Detailed offshore surveys (Sextants and microwave position fixing system) of a 130 km long strip along the Konkan Coast (1889 km echosounding, 895 lkm of shallow seismic and 1228 l/km of magnetics followed by 1117 grab and 66 piston-gravity core samples). The onshore sediments of these bays contain heavy mineral placers which in most cases extend offshore also. The seabed in most of the bays is marked by even topography and the nearshore sand covered areas are marked by steep gradient and the offshore clay covered areas by gentle gradients. The seabed in the bays down to a water depth of 9 to 12 m is largely covered by sand beyond which the sands are covered by clays. The surficial sands in these bays cover an area of 96 km2 and contain upto 91% heavy minerals and 64% of ilmenite. The dual frequency echograms, seismic profiles and short cores confirm the extension of the heavy mineral rich sands below the clays. The thickness of the heavy mineral rich sands ranges from 2 to 10 m and these cover total area of 436 km2. The offshore reserves and ilmenite are estimated to be about 12.5 million tons whereas estimates based on the 2 to 10 m thickness and spread of ilmenite bearing sands over an area of 436 km2, total reserves appears to be very large