Enrichment of REEs in polymetallic nodules and crusts and its potential for exploitation

Polymetallic nodules and crusts are two of the most important mineral deposits in the ocean. They are rich in rare earth elements (REEs), iron, manganese, copper, cobalt, nickel, and other useful metals. This paper discussed the analysis of 25 nodule and crust samples collected from the South China Sea, the Pacific, Atlantic, and Indian Oceans. The samples were analyzed for REE content by ICP-MS/AES. The average REE concentration was found to be 1096.96×10−6 in the nodules and 1623.88×10−6 in the crusts. Both of these values are much higher than those recorded in Earth's dry-land crust and sedimentary rocks. This REE enrichment is mainly controlled by the absorption of ferromanganese oxides and clay minerals in the nodules and crusts and the high levels of REEs in seawater and sediments. High cerium enrichment in the nodules and crusts may lead to more effective exploitation of REEs in the future.