The Marine and Coastal Surveys Division of the Geological Survey of India (GSI), which has surveyed the territorial waters off Kerala since 1985 has found substantial deposits of construction grade sand, which can address the perennial shortage of construction sand in the State.
The deposits, estimated at around 750 million tonnes, can last for nearly 25 years at the present requirement of 30 million tonnes for construction purposes a year in Kerala, said C.V. Gopalan, Director, GSI, Mangaluru.
He added that the Government of India, which was exploring the potential of sea resources, would make an elaborate impact assessment before mining is undertaken.
He was making a presentation on ‘Offshore sand resources of Kerala - An alternative sand crisis’ recently at the Diamond Jubilee Annual Convention of the Indian Geophysical Union here. The presentation consisted of findings by a team of GSI scientists comprising Dr. Gopalan, N.M. Shareef, A.C. Dinesh, C. Jayaprakash, S.V. Hegde, N. Maran, and K.K. Bhat.
The presentation said a sizeable amount of construction grade sand resources were reported from several areas off Ponnani, Chavakkad, Kochi, Alappuzha and Kollam at water depth varying from 22 metres to 45 metres.
The team found that the recovered sand was of good quality and grade where sand percentages in the sediment recovered material varied from 80 to 96. The clay content in the sediment varied from 4% to 20%. The sand includes fine, medium and coarse grains.
The silica sand is mixed with clay and carbonaceous matter/peat. The vibro-core samples were collected onboard vessel Samudra Shaudhikama and core lengths varied.
The explorations revealed that sand in these deposits were of riverine origin, which were angular and modified to rounded to sub-rounded by marine activities. Sand can be extracted and used for construction purposes after removing excess salt content (below 0.075%) by repeated washing. The sand thus obtained “can provide an alternative source to meet the construction material crisis faced by Kerala,” the presentation said.
The source of the sandbodies is traced to the hinterlands of Western Ghats consisting of Charnockites, Khondalites, Gneisses, and Migmatites. The sand also contains heavy minerals in traces like ilmenite, monazites, rutile, zircon, garnet, and sillimanites, the presentation added.
