Chemical composition of ferromanganese crusts dredged from the Marshall Islands

In 1984, the U.S. Geological Survey (USGS) conducted a reconnaissance cruise L9-84-CP aboard the R/V S.P. LEE along the northern Ratak Ridge, Marshall Islands and retrieved ferromanganese crusts (Mn crusts) on the submarine slopes of seamounts. Most of the Mn-crust samples collected on this cruise had average thicknesses less than the 4-cm minimum considered necessary for economic exploitation. However Mn crusts greater than 4-cm-thick were collected on Erikub Seamount (D6), Bikar Guyot (D15), and Ratak Guyot (D18), with an extremely thick 10.0 cm crust recovered from Ratak Guyot. The samples were sectionned and geochemical analyses were separately conducted on separate layers identified in those crusts. Major and minor elements were determined by Induction Coupled Plasma Emission Spectroscopy on samples dried at 110°C. Pt, Pd, and Rh were determined by fire assay.