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Mineralogical characterization of individual growth structures of Mn-nodules with different Ni+Cu content from the central Pacific Ocean

Anna V. Wegorzewski, Thomas Kuhn, Reiner Dohrmann, Richert Wirth and Sylvain Grangeon
Mineralogical characterization of individual growth structures of Mn-nodules with different Ni+Cu content from the central Pacific Ocean
American Mineralogist (December 2015) 100 (11-12): 2497-2508

Abstract

The mineralogy of manganese nodules from the German license area in the eastern Clarion and Clipperton Zone (CCZ) of the central Pacific Ocean was studied using X-ray diffraction. Their individual nanometer to micrometer thick genetically different (hydrogenetic/diagenetic) layer growth structures were investigated using high-resolution transmission electron microscopy. Relationships between the mineral phases and metal content (e.g., Ni+Cu) were assessed with electron microprobe analyzer. The main manganese phase detected in nodules of this study was vernadite, a nanocrystalline and turbostratic phyllomanganate with hexagonal layer symmetry. In layer growth structures of hydrogenetic origin, Fe-vernadite dominates. Layer growth structures of suboxic-diagenetic origin contain three vernadite forms, which are the main Ni and Cu carriers. These Mn-phases were identified on the basis of their structural layer-to-layer distances (7 and 10 Aa) and on their capacity to retain these distances when heated. The first form is 7 Aa vernadite, which is minor component of the nodules. The second is a thermally unstable approximately 10 Aa vernadite collapsing between room temperature and 100 degrees C, and the third is a thermally stable approximately 10 Aa vernadite collapsing between 100 and 300 degrees C. Todorokite was neither detected in bulk nodules nor in any of the individual suboxic-diagenetic growth structures. Because the mineralogical composition of the nodule is quite homogeneous (only different vernadite-types), it is suggested that the content of Ni and Cu in the individual growth structures is controlled by their availability in the environment during individual growth phases. A profile through a CCZ nodule revealed that the thermal stability of the vernadites change from younger (thermally unstable vernadites, collapsing <100 degrees C) to older growth structures (thermally stable 10 Aa vernadites, collapsing >100 degrees C) of the nodule accompanied with changes in type and amount of interlayer cations (e.g., Mg, Na, Ca, K). The stability of the vernadites is probably due to re-organization and incorporation of metals within the interlayer of the crystal structure.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 100
Serial Issue: 11-12
Title: Mineralogical characterization of individual growth structures of Mn-nodules with different Ni+Cu content from the central Pacific Ocean
Affiliation: Federal Institute for Geosciences and Natural Resources, Hanover, Germany
Pages: 2497-2508
Published: 201512
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 77
Accession Number: 2016-007438
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: State Authority of Mining, Energy and Geology, DEU, GermanyGerman Research Centre for Geosciences, DEU, GermanyBRGM, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201604
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