Bulk Polymetallic Nodule Collection in Central Indian Basin- Implications of Acoustic Survey Technologies for Site Selection and Innovations to Maximize Nodule Recovery

摘要

The task of collecting polymetallic nodules in bulk quantities for metallurgical process studies has been assigned to National Centre for Antarctic and Ocean Research (NCAOR), Goa. NCAOR is normally given a target to collect 20 to 40 tonnes of nodules every year for metallurgical studies. For achieving this task, using minimum ship time, acoustic geophysical techniques have been used for identifying areas of high nodule concentration and safe areas for deepsea dredging operations by using a nodule mining dredge. The acoustic geophysical techniques such as Multibeam Swath Bathymetric Echosounding (MBES) “Hydrosweep-DS2” and Shallow Acoustic Seismic Sub- Bottom Profiling (SBP) “Parasound”, have been used for identifying the areas of high and low nodule concentrations and thereby maximizing the opportunities of recovery of nodules with each dredgehaul. Mapping using MBES provided realistic imaging of the bottom topography for selection of suitable dredging locations and SBP provided fairly good estimates of nodule concentration on the seafloor. Also various mechanical and design improvisations in the dredges, based on past experience of operations, have been made to maximize recovery of polymetallic nodules.