Exploration of Deep Ocean Ferromanganese Nodule Fields Using Radon as a Tracer

Abstract

AbstractFerromanganese nodules (Fe‐Mn nodules) are considered as potential sources of in‐demand metals (such as manganese, cobalt, nickel, copper, and rare‐earth elements) that are used in high‐technology industries. The resource potential of Mn nodules in the world ocean remains uncertain due to technological and financial challenges. Here we propose an effective tracer: the natural radioactive radon isotope (222Rn) to assess the abundance of Fe‐Mn nodules on the sea floor. Significant linear relationships were observed between benthic excess 222Rn fluxes and concentrations with Fe‐Mn nodule occurrence and coverage on the global seafloor. Benthic excess 222Rn flux >107 dpm/m2/yr or bottom water 222Rn concentrations >2,000 dpm/m3 indicate the possibility of Fe‐Mn nodules occurrence at >80% and seabed coverage of >25%. Our results indicate radon, relatively easy to measure, could serve as a novel and efficient tool for targeting Fe‐Mn nodule resources in the global abyssal ocean.