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Author Wang, Xiao hong ♦ Gan, Lu ♦ Müller, Werner E. G.
Source SpringerLink
Content type Text
Publisher SP Higher Education Press
File Format PDF
Copyright Year ©2009
Language English
Subject Domain (in DDC) Technology ♦ Engineering & allied operations
Subject Keyword polymetallic nodules ♦ ferromanganese crusts ♦ bacteria ♦ coccolithophores ♦ microorganisms ♦ biomineralization ♦ biogenic materials ♦ Materials Science
Abstract The ocean hosts inorganic raw materials to a magnitude, which surpasses the resources of these materials available on land. Those mineral resources include industrial minerals, metalliferous oxides, hydrothermal metalliferous sulfides, and dissolved minerals. Hence, a significant source of minerals for sustainable recovery in the future may be ocean waters. Among of those mineral resources, there are two kinds of very important minerals which are consolidated on the seabeds of ocean basins in polymetallic nodules and on the surface of seamounts in polymetallic crusts. Until now, the (bio)- chemical processes that result in the formation of metal deposits in the form of nodules or crusts are not understood. In the present review, we concentrate on the (potential) biogenic origin of nodule and crust formation.We studied polymetallic/ferromanganese nodules that had been collected from the Clarion-Clipperton Zone in the Eastern Pacific Ocean, by high-resolution scanning electron microscopy (HR-SEM) to search for microorganisms. The nodules are made up of small-sized micronodules, 100 to 450 μm in size, which are bound/glued together by an interstitial whitish material. In these micronodules, dense accumulations of microorganisms/bacteria can be visualized that display only two morphotypes: (i) round-shaped cocci and (ii) elongated rods. The microorganisms are decorated on their surfaces with S-layers, which are indicative for bacteria. Moreover, the data suggest that these S-layers are the crystallization seeds for the mineralization process. We conclude that the mineral material of the nodule has a biogenic origin and propose consequently the view that mineralization in nodules is caused by biologically controlled mineralization processes.In a second series of investigations, first evidence for a biogenic origin of ferromanganese crusts formation is given. Crusts were obtained from the Magellan seamounts and analyzed for their chemical composition using the EDX technique. Again, special emphasis had been put on the (potential) biogenic origin of the mineral deposition in these ferromanganese crusts. We could demonstrate by HR-SEM that, in those deposits, vast amounts of coccoliths (calcareous unicellular algae) exist. Surprisingly, the coccoliths are composed of Mn besides Ca and C, as analyzed by EDX. This result could be further substantiated by EDX mappings. We propose that initiation of crust formation involves the dissolution of calcite from the coccoliths, resulting in an oxidation of Mn$^{2+}$ to Mn$^{4+}$ and subsequent precipitation of Mn$^{4+}$O$_{2}$. Following this scheme, it can be assumed that crust formation may serve as an example for a biologically induced mineralization process.
ISSN 16737377
Age Range 18 to 22 years ♦ above 22 year
Educational Use Research
Education Level UG and PG
Learning Resource Type Article
Publisher Date 2009-04-04
Publisher Institution Chinese Universities
Publisher Place Heidelberg
e-ISSN 16737482
Journal Frontiers of Materials Science in China
Volume Number 3
Issue Number 2
Page Count 15
Starting Page 109
Ending Page 123

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Source: SpringerLink