A step-by-step relinquishment method for cobalt-rich crusts: a case study on Caiqi Guyot, Pacific Ocean

For cobalt-rich crusts in a contract area, the regular-shaped cells for relinquishment are obviously different from the natural ore distribution, and this brings challenges in evaluating the resources within them. Based on survey data in the China Ocean Mineral Resources Research and Development Association (COMRA) contract area, this study analyzed factors that could influence the relinquishment of cobalt-rich crusts. According to the guidelines of the International Seabed Authority, each original block of the COMRA contract area was subdivided into 16 cells. The contract areas were then divided into orebodies, unclear areas, and non-resource areas based on the distribution of the orebodies. Then, these attributions were assigned to the cells and the resources inside each cell were evaluated and identified, according to resource quantity, as resource cells, unclear cells, and non-resource cells. Finally, relinquishment was assessed by a step-by-step method in the following priority order: non-resource cells, unclear cells, and resource cells. This method was applied to the Caiqi Guyot (a guyot in the COMRA contract area) as a case study. The results show that the proposed method is suitable for the relinquishment of cobalt-rich crusts in the COMRA contract area and can also be applied to other contract areas worldwide.