Statistical properties of distribution of manganese nodules in Indian and Pacific oceans and their applications in assessing commonality levels and in exploration planning

Abstract

This chapter presents results of analysis of available statistical data on distribution of manganese (polymetallic) nodules on the seafloor of Indian and Pacific Oceans. It is concluded that the nodule fields of varying sizes within each of the two oceans share common distribution patterns. More importantly, the study brings out striking similarity between the distribution characteristics of nodule fields in the two oceans in terms of coefficients of variation of nodule abundance, variographic parameters including similar but high level of nugget coefficients and the unimodal lognormal frequency distribution of abundance values. The computations of estimation variances for study areas in Indian and Pacific Oceans establish the constancy of the product of variance of error and the area of nodule field under given conditions. Finally, since nodule abundance forms the governing parameter for exploration planning as brought out by the data, estimation variances for selected sizes of nodule fields have been computed for varying sampling grids for both the oceans. It is concluded that a given sampling grid of say, 0.15° over a given size of nodule field of 75,000 km2, produces an identical estimation error of less than ±10% of the respective mean abundance values in Indian as well as Pacific Oceans.