Geophysical and Geological Exploration of Cobalt-rich Ferromanganese Crusts: An Attempt of Small-Scale Mapping on a Micronesian Seamount

Abstract

Ferromanganese crusts in the Pacific Ocean are potential economic resources of cobalt, nickel and platinum. Previous shipboard geological and geophysical exploration has been directed towards innovation in effective methods of mapping the abundance and grade of manganese nodules on the seafloor for evaluation and mine site selection. However, any simple techniques have not been valid for complicated and variable nature of the crusts and topography. This study attempts to establish a distribution pattern of ferromanganese deposits on a Micronesian seamount using conventional narrow-beam and SSS mapping, dredge sampling Cand TV/camera monitoring with a geological interpretation. We tried to correlate acoustic remote sensing data with the surface geology, and decipher the regional-scale distribution of crusts in relation to large-scale mass wasting that took place in the early Miocene or before. The general distribution pattern of crusts over the surface of the seamount indicates that only about 40% of the apparent “acoustic outcrop” represents actual ferromanganese crust coverage. The combined method outlined here is the most useful in evaluating ferromanganese deposits, prior to possible hi-tech fine-scale mapping using submersibles, ROV and AUV.

Keywords:

• exploration
• ferromanganese crust
• metal resource
• micronesia
• Northwest Pacific seamount

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Erratum

The authors thank MMAJ (now merged into Japan Oil, Gas and Metal Resources Corporation) and DORD (Deep Ocean Resource Development Co. Ltd.) for their cooperation during shipboard exploration. Also, Drs. G.P. Glasby and D.S. Cronan for their detailed review of the paper.