1980 - National Institute of Oceanography

In the Ratnagiri, Mirya and Kalbadevi bays, the reserves of ilmenite upto
a depth of 1 m were inferred to be 2 million tonnes. With the thickness of sand
indicated by seismic records to be 21 m and with their probable extension upto the depths
of 15 to 17 m, the total reserves in the other 13 bays may be many times greater. The
extensive data collected during these surveys are being analysed and processed.
The other organisations which collaborated in this project were the Oil &
Natural Gas Commission, Geological Survey of India, National Geophysical Research
Institute, Regional Research Laboratory (Bhubaneshwar), Physical Research Laboratory
and the Birbal Sahni Institute of Paleobotany.
3.3.2 Regional geology and manganese nodule deposits in the Arabian Sea and Central
Basin of the Indian Ocean
Necessary equipment such as Free Fall Grab, Boomerang grab, Radio marker,
Underwater camera and Direction finder etc. for sampling and photographing the
manganese nodules have been procured. The deep sea grabs and dredges have been
designed and fabricated. A double beam atomic absorption spectrophotometer is
being installed for the analyses of the samples. Based on the analyses of the data
collected earlier, a cruise plan has been finalised.
3 33 Geochemistry of the sediments of the continental margins of India
Geochemical studies were continued on the sediment samples collected from
the western continental margin between Ratnagiri and Mangalore, Mangalore and
Cochin and from the eastern shelf between Ganges and Calimere Point. The findings
of these studies are briefly given below.
1. Western continental margin
(a) Ratnagiri-Mangalore: In the bulk samples Si, Al, K, Na. Mg, Fe, Mn,
Li, Cu, Co, Ni and Zn decrease while Ca and Sr increase as we move away
from the coast but phosphorus does not show any distinct trend. The distribution
of the elements in the HCl soluble leaches clearly indicates that the major portion
of these elements is held in the clays. This is also confirmed by the strong correlation
between Al and Fe, K, Na, and Mg. Negligible amounts of elements in the
acetic acid leaches indicate that the adsorption by clay minerals and the Carbonate
phase are not the significant factors for the fixation of the elements in these sediments.
SiO2 content in these sediments is significantly less than the other nearshore
sediments. This is mainly contributed by detrital quartz as indicated by the lack of
correlation between Al and Si.
The outer shelf sediments are carbonate rich (75%) and biogenous while in
contrast to the outer shelf, carbonate sediments in the northern part of the study
area is oolitic in nature. Similarly, phosphorus in this area is associated with
organic matter as indicated by the strong correlation between P2O5 and organic
matter while in the northwestern region it is associated with carbonates.
(b) Mangalore-Cochin: The concentration of Al, Mn, Cu and Zn in the bulk.
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