Print Icon Beach Sand and Offshore Investigations

The mainland of Indian sub-continent is endowed with a vast coastline over 6,000km along its nine (9) maritime coastal states. It hosts a number of multi-mineral shoreline placer deposits occurring as beach and dune sand, inland sand bodies/palaeo beach ridges and teris/red sediments. Favorable geological and geomorphological conditions coupled with tropical to sub-tropical climate and intricate drainage pattern have resulted in formation of these placer deposits of varied dimensions and concentrations. The heavy mineral suite in these placer deposits essentially comprises ilmenite, rutile, leucoxene, monazite, zircon, garnet, sillimanite, kyanite, pyroxene, amphibole, magnetite, xenotime, apatite, sphene, staurolite, tourmaline etc. in various proportions. Among these, seven (7) economically important minerals viz. ilmenite, rutile, leucoxene, monazite, zircon, garnet and sillimanite are popularly designated as Beach Sand Minerals (BSM). The uses of these minerals in both atomic energy and other industries are:

Ilmenite, Rutile and Leucoxene: These are the source mineral for titanium. It is mainly used as titanium pigment, structural material for nuclear reactor, desalination plant, welding rod flux, aircrafts, titanium metal production

Zircon: Zircalloys as cladding material for nuclear fuel, opacifier/ pigments for ceramics, refractories, jewelries, zirconium metal production

Monazite: Chief source for thorium and REEs. Thorium is envisaged to be used as fuel in 3rd stage of nuclear power programme and REE has multifaceted use in hi-tech applications.

Garnet: Abrasives, water filtration industries and decorative (artificial) building stones.

Sillimanite: Refractories

The Beach Sand and Offshore Investigations (BSOI) Group is entrusted with the exploration and evaluation of BSMs associated with shoreline placer deposits confined to East and West coasts of India in general as well as inland sand bodies (palaeo-beach ridges), inland alluvium and red sediments/teri sands along East coast in particular. The methodology for sampling of sand column in exploration for beach placer deposits has evolved from hand auger to Conrad Bunka and Dormer drill units and is carried out in two stages viz. (i) sampling of dry zone and (ii) sampling of wet zone. In the first stage, hand-auger is generally used to sample the dry zone i.e. above the water table. Subsequently, wet zone i.e. below the water table is sampled using varied drill units viz. Conrad Bunka, Vibro-corer or Dormer drills. The depth of sampling using these manual /semi-mechanised drill units varies from 7m - 12m in general and occasionally goes up to 15m. Recently, exploration in deeper levels (up to 50m) by ‘Sonic’ drilling in Chavara deposit, Kerala and Brahmagiri deposit, Odisha have indicated sizeable augmentation of heavy mineral resources. In view of this, future efforts are being directed towards exploring deeper parts of BSM deposits along East coast of India.

Extensive exploration over last six and a half decades has led to identification of a number of medium to high grade deposits that are being commercially exploited by Indian Rare Earths Limited (IREL), Kerala Mines and Metals Ltd (KMML) and privates companies in the states of Tamil Nadu, Kerala, Odisha and Andhra Pradesh. The Directorate has so far established 1,231.95mt of economic heavy minerals as on May, 2020 that has put the country in reckoning as far as world's thorium, zirconium, titanium and rare earths resource base is concerned. Individual resources of economic heavy minerals in order of abundance are 687.57mt of ilmenite (includes leucoxene), 264.92mt of sillimanite, 195.46mt of garnet, 34.70mt of rutile, 36.56mt of zircon and 12.73mt of monazite. These resources have been estimated in the states of Andhra Pradesh, Odisha, Tamil Nadu, Kerala, Maharashtra, Gujarat and West Bengal. However, the states of Andhra Pradesh, Odisha, Tamil Nadu and Kerala altogether contribute more than 98% to the total economic heavy minerals resource inventory of the country with meagre amount from rest of the states.

Beach and dune complexes of East Coast (a,b), Teri sands of TN (c) and Red sediments of AP (d)
Sampling of Sand column by Hand Auger (a), Dormer drill (b) and Sonic drill (c)
HM layering along Ganjam Coast, Odisha (a) and Surface HM concentration around Mandapam area, TN (b)

 

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