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Ultrafine-grained magnetite in deep-sea sediments: Possible bacterial magnetofossils
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A new extraction technique now permits ultrafine magnetite crystals to be separated from a variety of deep-sea sediments as mentioned in this paper, revealing the presence of several distinct crystal types, some of which closely resemble those formed by the magnetotactic bacteria.Abstract:
A new extraction technique now permits ultrafine magnetite crystals to be separated from a variety of deep-sea sediments. Morphologic characterization of these particles with transmission electron microscopy reveals the presence of several distinct crystal types, some of which closely resemble those formed by the magnetotactic bacteria. The apparently biogenic magnetite particles are of single-domain size and dominate the population in calcareous deep-sea sediments. Bacterially precipitated magnetite may therefore be a major source of the stable magnetic remanence in some marine sediments. These objects possibly constitute the smallest mineral fossils yet recovered from the sedimentary record.read more
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Search for past life on Mars: possible relic biogenic activity in martian meteorite ALH84001.
David S. McKay,Everett K. Gibson,Kathie L. Thomas-Keprta,Hojatollah Vali,Christopher S. Romanek,Simon J. Clemett,Xavier D. F. Chillier,C. R. Maechling,Richard N. Zare +8 more
TL;DR: High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and iron sulfides.
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Rock magnetism of Late Neogene and Pleistocene deep-sea sediments: Relationship to sediment source, diagenetic processes, and sediment lithology
TL;DR: This article examined the ability of the rock magnetic properties to differentiate the sediments according to factors such as lithology, geographical area, and the dominant mode of terrigenous sedimentation, which at these sites is via ice-rafting, via bottom currents, or via eolian processes.
Journal ArticleDOI
Dissolution and pyritization of magnetite in anoxie marine sediments
TL;DR: In this article, the rate of magnetite dissolution is proportional to the concentration of dissolved pore water sulfide and the surface area of the magnetite in anoxic marine sediments.
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Rock magnetic criteria for the detection of biogenic magnetite
TL;DR: In this paper, a combination of room temperature coercivity analysis and low temperature remanence measurements provided a characteristic magnetic signature for intact chains of single domain (SD) particles of magnetite from magnetotactic and dissimilatory iron-reducing bacteria.
References
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Iron Oxide Removal from Soils and Clays by a Dithionite-Citrate System Buffered with Sodium Bicarbonate
TL;DR: In this article, the bicarbonate-buffered Na2S2O4-citrate system was used for removing free iron oxides from latosolic soils, and the least destructive of iron silicate clays.
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Minerals formed by organisms
TL;DR: Biogenic minerals commonly have attributes which distinguish them from their inorganic counterparts, and they fulfill important biological functions.
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Theoretical single-domain grain size range in magnetite and titanomagnetite
TL;DR: In this paper, a theoretical model of single-domain (SD) grain sizes is applied to magnetite and titanomagnetite, where transition to a two-domain configuration takes place at the SD threshold d0.
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Depositional and postdepositional processes in the magnetization of sediments
TL;DR: The authors surveys 40 years of research on the processes by which a sediment acquires a detrital remanent magnetization (DRM), which can be divided into two types: depositional processes, which arise from interactions between the magnetic carriers and the substrate at the sediment/water interface, and postdepositional processes arising from the mobility of magnetic carriers within fluidfilled voids in the sediment.