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G. N. Baturin 《Doklady Earth Sciences》2006,407(1):330-334
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Morphology, microstructure, and chemical composition of the nodular fraction of phosphatic sand from the outer Namibia shelf are considered. The nodules are divided into three varieties: concretions, phosphatic casts of shells pelecipod and gastropod, and phosphatized sea lion coprolites. A part of nodules shows massive homogeneous structure, whereas other nodules contain sand-size phosphatic grains derived from the host phosphatic sand. All nodules display the same spectrum of microstructures, including colloform, granular-globular, and crystallomorphic ones. The crystallomorphic nodules are composed of scattered and aggregated crystallites of isometric, rod-shaped, and dumbbell-shaped forms, as well as crystallized shells on grains incorporated into nodules. Phosphatized remains of diatoms, foraminifers, and embryonic gastropods, as well as vermicular and filamentous bacterial forms occur among biogenic components of the nodules. Framboidal pyrite is present in all nodules. In terms of phosphate microstructure, character of organic remains, and chemical composition, the nodules are similar to phosphate grains of the host sand, recent phosphorites from the inner Namibia shelf, and some ancient phosphorites. 相似文献
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The mineral and chemical compositions of a set of crust samples collected from the North, Central and South Atlantic were
examined by means of analytical electron microscopy and ICP-MS, chemical, and microchemical elemental analysis. The dominant
mineral phases of the crusts are vernadite, asbolane, and goethite, with minor ferrihydrite, and rare hematite and feroxyhyte.
The samples show wide variability in major and trace elements; however, their characteristic geochemical signatures indicate
hydrogenetic origin. A comparison between the compositions of oceanic hydrogenetic and hydrothermal crusts and metalliferous
hydrothermal sediments from different ocean areas suggests that the geochemical approach may be insufficient in some cases
and fail to identify a hydrothermal input in ferromanganese crusts of a mixed composition. 相似文献
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Doklady Earth Sciences - The relation of nonferrous metals and other elements to the main mineral phases in iron–manganese ore is a matter of interest in theoretical and practical terms and... 相似文献
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The geochemical study of the suspended matter in the waters of the Amazon River and its tributaries revealed that the chemical composition of this material ranges widely; however, generally, it is similar to the average composition of the suspended matter in the rivers and clayey sedimentary rocks around the world. Against this background, an essential regional Hg enrichment due to the anthropogenic factor is distinguished. The suspensions from the so-called clear waters from the tributaries of the Amazon River—Xingu and Trombetas—demonstrate the local enrichment in Pb, Sn, Zn, and organic carbon indicating the ore mineralization of the drainage basin, and points to the presence of metal-organic complexes. 相似文献
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Solar System Research - A method has been developed for detecting impact orbits of asteroids in the confidence ellipsoid of the initial parameters of motion. The method consists in conditionally... 相似文献
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The elemental composition of ferromanganese sedimentary structures from the bottom of Lake Baikal represented by nodules and
crusts, as well as the enclosing sediments, have been studied by the atomic absorption, chemical, and ICP-MS methods. It is
established that the contents of the rock-forming and accompanying elements in them are highly variable. In this connection,
the examined samples are divided in two groups differing by their Mn/Fe values. In most of the samples, they range from 0.01
to 0.1, although some of the ferromanganese structures or their parts are substantially enriched in manganese. The contents
of most of the rare and dispersed elements in the ferromanganese structures are usually at the background level, although
the samples maximally enriched in iron or manganese are characterized by relatively high copper, nickel, cobalt, vanadium,
zinc, and molybdenum concentrations. 相似文献