Head, Department of Applied Geology
University of Madras, Guindy Campus
K K Sharma, S G D Sridhar, R Krishnamoorthy, N Rajeshwara Rao and S A Barathi Manigandan
Department of Applied Geology, University of Madras, Guindy Campus, Chennai, India
India possesses a vast coastal tract of about 7500 km and has large reserves of beach sand minerals, such as ilmenite, rutile, leucoxene, zircon, monazite, sillimanite and garnet. The aim of this study is to map the coastal landforms using multispectral remote sensing data to demarcate the suitable zones for placer mineral exploration through field survey
The earth’s surface material is a product of interaction between three distinct variables: (1) the nature of the underlying rocks, (2) the internal movements of the earth as expressed in the tectonic regime and, (3) the external processes acting on the surface that are mainly controlled by climate. Hence, a thorough geomorphological investigation is essential to an understanding on placer minerals occurrence at all scales (Sutherland, 1985; Rajamanickam et al., 1997). The coastal areas are very particular in the field of placer mineral exploration due to the occurrence of littoral placers. India possesses a vast coastal tract of about 7,500 km and has large reserves of beach sand minerals, such as ilmenite, rutile, leucoxene, zircon, monazite, sillimanite and garnet. These deposits are mostly located in the coastal stretches of Peninsular India, with the exception of few inland placer deposits and teri sands.
The coastline of Tamil Nadu is about 975 km out of which 915 km falls in the east coast and another 60 km falls on the southwestern coast of India. Detailed (60 km) and reconnaissance surveys (519 km) were carried out over a coastal length of 579 km. Still 396 km are yet to be surveyed. Studies on the beach and dune heavy mineral deposits by close-grid sampling in the 508 km long coastal stretch of central and southern Tamil Nadu, reveals high concentration of heavy minerals, most commonly from the surface down to a depth of several metres (Mohan and Rajamanickam, 2000).
The present study is focused to a stretch of about 60 km length coastal zone starting from Kovalam to Palar river mouth along South Chennai coast. The aim of this study is to map the coastal landforms using multispectral remote sensing data to demarcate the suitable zones for placer mineral exploration through field survey. To achieve this study aim the following objectives were adopted.
- Mapping the geomorphological features from multispectral remote sensing data by incorporating the base map details derived from Survey of India topographical maps and validation by ground truth
- Demarcation of favourable sampling points for collecting samples where heavy minerals are enriched with the help of geomorphological map
- Collection of samples in grid pattern from the favourable locations for sedimentological and geochemical analysis
Primarily based on the tonal characteristics of IRS LISS-III imagery upto Level-III coastal geomorphological categories on 1:50,000 scale were demarcated and these details have been transferred to the base map prepared using the SOI topographical maps and the nearshore bathymetry details from the NH charts. The important geomorphic features like beach sand / dunes, stabilized dunes, back waters, tidal flats, coastal wetlands, river channels etc were demarcated and the potential zones containing suitable coastal landforms for littoral placer minerals are shown in Figures 1-3.
Fig 1 LISS-III FCC shows the Muttukadu Creek and its surroundings landforms
Fig 2 LISS-III FCC shows the Mahabalipuram Coast and its surroundings
Fig 3 LISS-III FCC shows the Palar river mouth and its surroundings