Influence of bathymetry in manganese nodule pilot mine site selection: A case study from the Central Indian Basin

Abstract

Although manganese nodules are observed in all world oceans, known reserves cannot be only criterion in future mine sites selection and sizing. Detailed and accurate depth data is another major prerequisite. With the advent of multibeam swath mapping systems, the knowledge of the complexitites of the seafloor had increased many fold. Use of the high resolution bathymetric data in pilot mine site selection is discussed here. About 23,000 km sup(2) of detailed multibeam-Hydrosweep data from the Central Indian Basin is presented here. Average depth is 5150 m. This area is comparatively flat-except for the large seamount of height 1200 m which appears on the northernmost part of the area. Also, there are two small abyssal hills in the center of the area. Average nodule abundance in the study area is 5.5 kg/m sup(2). Seafloor slope angles calculated from the water depth date reveal that, the area has predominantly gentle slopes. However, the regions of seamount and abyssal hills show higher slopes- up to 40 degrees . The aras of steep slope are unlikely to be approachable for the future mining system. The slope angle data can be used to actually plan tracks for the mining equipment to optimise recovery. Based onthe relief characteristics and manganese nodule abundances data, about 90% of the study ara can be demarcated for mining