Integrated Geochemical and Morphological Data Provide Insights into the Genesis of Ferromanganese Nodules
AbstractFerromanganese nodules grow by precipitation of metals from seawater and/or sediment pore water. The formation of different genetic types depends on the composition and redox conditions of the water and upper sediment layers, water depth, and primary productivity in surface waters. Many characteristics of nodules have been used to investigate their genesis. In this paper, we compare nodules from different environments using Computed Tomography, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy, and Micro X-ray Fluorescence data to better understand how geochemical differences are linked to different morphological features. We use representative samples of purely hydrogenetic nodules and mixed-type nodules with various proportions of hydrogenetic and diagenetic growth laminae. Our results show a micrometric alternation between high-absorbance massive Mn-enriched (Mn/Fe up to 40) laminae and low-absorbance dendritic Mn-depleted (Mn/Fe about 1) laminae in mixed-type nodules, suggesting the rhythmic alternation of hydrogenetic oxic conditions and suboxic diagenetic input. This micro-rhythmic alternation is absent in purely hydrogenetic nodules, which are homogenous both chemically and morphologically. A conceptual model is proposed to account for these geochemical and morphological differences in terms of the vertical migration of the oxic-suboxic front relative to the base of the nodules. View Full-Text
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Description: Video S1: three-dimensional computed tomography of sample JC120-104B; Video S2: three-dimensional computed tomography of sample SS4-280; Video S3: three-dimensional computed tomography of sample SK35-26; Video S4: three-dimensional computed tomography of sample RGR.
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Benites, M.; Millo, C.; Hein, J.; Nath, B.N.; Murton, B.; Galante, D.; Jovane, L. Integrated Geochemical and Morphological Data Provide Insights into the Genesis of Ferromanganese Nodules. Minerals 2018, 8, 488.
Benites M, Millo C, Hein J, Nath BN, Murton B, Galante D, Jovane L. Integrated Geochemical and Morphological Data Provide Insights into the Genesis of Ferromanganese Nodules. Minerals. 2018; 8(11):488.Chicago/Turabian Style
Benites, Mariana; Millo, Christian; Hein, James; Nath, Bejugam N.; Murton, Bramley; Galante, Douglas; Jovane, Luigi. 2018. "Integrated Geochemical and Morphological Data Provide Insights into the Genesis of Ferromanganese Nodules." Minerals 8, no. 11: 488.
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