Accumation rates of manganese in manganese nodules using differential 230Th-231Pa activities

The manganese content of 7 manganese nodules was determined by neutron activation. The decrease of unsupported 231Pa and 230Th in the outer few tenths of millimeters was used to evaluate Mn accumulation. Because CaCO3 is a Mn-free diluent, the Mn concentration results and the nodules accumulation rate results are given on a carbonate-free basis. Nodule densities were assumed to be 2.5 g/cm³. The Mn accumulation rates are calculated per unit cross sectional area of the nodule rather than per unit surface area.