Radiochemical data for a manganese nodule sample from the MN7601-PLEIADES campaign (R/V Melville)

Using radiochemical methods, the authors have measured the distribution of uranium, thorium, radium, polonium and protactinium isotopes from the top and bottom sides of the a manganese nodule from Station 20 of the PLEIADES Mn7601 campaign. This "apple" shaped nodule (6.5x3.0 cm) was laying on a bed of siliceous ooze (see illustrations). Successive thin layers of the nodule were carefully scraped from the surface of the measured area with a sharp surgical blade. All samples reduced to powder were air-dried at 110°C for at least two hours before analysis. The relative gross alpha activities from each layer were assayed by Alpha spectrometry using a thick-source counting in a scintillation counter.