The strategy for refined exploration, carried out through ORV Sagar Kanya, has been to progressively reduce the sampling interval from 100 to 25 km and to generate accurate bathymetric maps of the mine site area, leading to better visualisation of the sea-bed topography from where these nodules will have to be mined, as well as more reliable estimates of their reserves in the Pioneer area allotted to India. High resolution bathymetric maps of over half of this area have already been made using the sophisticated hydrosweep equipment recently fitted on ORV Sagar Kanya.

Analysis of samples

Samples collected during the earlier cruises were analysed by scientists of the National Institute of Oceanography, Goa. Their chemical analysis indicated that average moisture content of the nodules recovered from the Pioneer area is 20% (range 16-25;%). The Mn content in these nodules varied between 15 and 34% and Fe content between 2 and 16%. The higher concentration of Mn, Cu and Ni in nodules as associated with siliceous sedimentary environment while reverse was true in red clay sediments.

Detailed studies of internal structure of nodules indicated close relation between Fe-Mn oxyhydroxide precipitation and global palaeo oceanographic conditions.

Geochemical studies of sediment samples from nodules bearing environment revealed five important sources for its content of major and minor elements.

Regional geochemical study of nodules showed a marked difference in composition between those from subequatorial part and basinal areas.

Studies on physical properties of nodules revealed that Indian Ocean nodules are anisotropic and found to be denser, porous, and display faster P-wave velocity in comparison to those from Atlantic and Pacific Oceans.

A programme for digitisation of sea-bed photographs to compute coverage and abundance of polymetallic nodules was developed.