The distribution of rare earth, precious metal and other trace elements in Recent and fossil deep-sea manganese nodules.

Abstract

Four deep-sea manganese nodules and one fossil nodule from Timor have been analysed for 45 elements (major elements, rare earths and precious metals) by X-ray fluorescence, spark source mass spectrometry and neutron activation analysis. Co-existing sediments from two nodule sites in the South western Pacific Basin have also been analysed. Differences in nodule composition are apparent, particularly for the Timor nodule. The trace metal compositions of this nodule, however, reveals it to be a typical deep-sea nodule, although some element redistribution has clearly taken place since exposure of the nodule on land. The distribution of a number of elements including Tl, Ir, Pd, Au and the rare earth elements between deep-sea nodules and their associated sediments appears to be dependent on a number of factors including the major element composition of the nodule (e.g. dilution by the silicate phase of the nodule), the differing stability of various element complexes in seawater, and the influence of differences in redox states on complex stability. Au and Si, on the other hand, are positively correlated in nodules and sediments possibly because they have a common source, either submarine detritus or basalt-seawater interaction. The rare earth contents of the sediments from the N.E. sector of the Southwestern Pacific Basin are high compared with previous determinations of rare earths in marine sediments and show no evidence of Ce depletion relative to La on a shale-normalised basis. These high contents reflect the well oxidised conditions and low sedimentation rates of this environment.

Critical metals in manganese nodules from the Cook Islands EEZ, abundances and distributions

“…Of those critical metals, Bi, Li, and Th have concentrations too low in CIs nodules to be of economic interest, but the other metals have been evaluated for economic potential (Tables 2, 3). In addition, Ti is higher in CIs nodules (average 1.28%) than in nodules found elsewhere (0.16%-0.42%; Hein and Koschinsky, 2014; see also Glasby et al, 1978) and Ti is also of economic interest. Finally, Sc, while occurring in the nodules only at the Earth's crustal average, may still be of economic interest because of its high global metal market price and the ease of extraction of metals from the ferromanganese (oxyhydr)oxide matrix .…”

The marine geochemistry of the rare earth elements

“…For example an observed anomaly in a nodule does not necessarily arise from the last process before sampling (i.e., nodule formation) but can also be the reflection of any previous processes. Anomalies of Ce may not solely be indicators of the redox conditions during nodule formation (GLASBY 1973;PIPER, 1974b), but may also reflect the anomaly pattern of the local sedimentation which occurred earlier (GLASBY et al, 1978;RANKIN &GLASBY, 1979). The aforementioned Eu depletions in seawater (ELDERFIELD &GREAVES, 1982) most likely do not result from marine chemistry, but from earlier fractionations during evolution of igneous rocks.…”

Characteristics and Origin of Sedimentary-Related Manganese Layers in Timor Island, Indonesia

“…Comprehensive geochemical data of manganese ores are tabulated in Table 1 and Table 2. (Rollinson, 1995), continental and oceanic (Jiancheng et al, 2006); Timor nodule (Glasby et al, 1978); Other data (Maynard, 2005). Note: Manganese ore of Tanganshan and Xiangtan in China is a Neoproterozoic Mn deposit with REE distribution and positive Ce anomaly implying a mixing of hydrothermal fluid and hydrogenous; ancient manganese deposits of Molango (Jurrasic) and Kalahari (Paleo-proterozoic) shows a similar REE distribution pattern with hydrothermal Pacific Mn which has a negative Ce anomaly due to hydrothermal fluid mixing with seawater; Hydrogenous Mn ore contains a highest REE and positive Ce anomaly; Timor Mn nodule shows a REE distribution pattern and positive Ce anomaly, which correspond to Pacific Mn nodule; (c) Various rock REE composition normalized by chondrite (Krauskopf and Bird, 1995).…”