Radionuclide analysis on nodules from MANOP Site

Manganese nodules and bottom waters have 230Th/232Th activity ratios considerably higher than other phases at this site suggesting that sea water is the likely source of Th for the nodules. Similar 230Th/232Th activity ratios in nodule tops and bottoms and in certain cases departure from expected 226Ra/230Th activity ratios in nodule tops and bottoms indicate that the nodules rotate every one to ten thousand years.

The micro nodules have diffusion coefficients of Ra similar to macro nodule bottoms. I suggest that they may act as a carrier phase for transporting metals through oxic sediments to nodules.