Neodymium isotope ratios for iron-manganese crusts and manganese nodules of the Pacific Ocean

Iron-manganese crusts were chosen from existing collections in order to cover as wide an area and depth range as possible. Sampling was concentrated in the Central Pacific seamount provinces where crusts are most commonly found coating lithic substrates. Two Mn nodules from similar areas were also sampled for comparison. Sub-samples were taken for isotopic analysis from known depths within individual crusts and nodules either by use of a stainless steel dental drill or by chipping away surface oxide layers. After grinding in an agate pestle and mortar, authigenic Fe-Mn oxides were leached with warm 25N HCl Solutions were evaporated to dryness and Nd isolated and analysed isotopically. All ratios were normalized to a 143Nd/144Nd ratio of 0.7219, and repeated analyses of the La Jolla standard gave an average value of 0.511847 ± 21 (unweighted).