Patterns of spatial distribution of elements in phosphate-free Fe–Mn Pacific nodule

The distributions of ore elements (Mn, Fe) and 20 chemical “trace” elements in a ferromanganese nodule from underwater Magellan mountains (Pacific Ocean) have been studied with scanning X-ray fluorescence analysis using synchrotron radiation (XRF-SR) with the scanning step of 400 μm. The nodule is characterized by the low phosphorus content (less than 1.0%). The variability of concentrations of the most elements including Mn and Fe from periphery to the nodule center is less than 15%. For all points of a scanning profile, the positive Ceh/Ceh* anomaly is evident, the spread in values being in the range 1.14–1.85. The Fe/Mn-modulus and values of the Ceh/Ceh* anomaly have, as a whole, the negative correlation, however, their imperfect out-of-phase distributions allow one to assume three competing ways for supply Mn into a nodule: from hydrothermal waters, as well as from bulk ocean water and underlying bottom sediment.