Low‐temperature magnetic properties of pelagic sediments (Ocean Drilling Program Site 805C): Tracers of maghemitization and magnetic mineral reduction

Смирнов, А. В.; Tarduno, J. A.

doi:10.1029/2000jb900140

Cited by 95 publications

(126 citation statements)

References 53 publications

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“…In contrast, CIE samples exhibit a weak Verwey transition (T v ) depressed $20 K, which suggests the presence of nonstoichiometric SD magnetite. The lowtemperature remanence behavior of CIE samples is typical of a mixture of detrital and biogenic magnetite [Moskowitz et al, 1993;Smirnov and Tarduno, 2000;Weiss et al, 2004], an interpretation supported by our TEM results (Figures 4a and 4c). Moreover, Moskowitz et al [1993] suggest that dZFC and dFC can indicate the presence of biogenic magnetic and discriminate it from detrital or other authigenic forms in bulk sediment samples [see also Weiss et al, 2004].…”

Section: Pa4104supporting

confidence: 76%

A biogenic origin for anomalous fine‐grained magnetic material at the Paleocene‐Eocene boundary at Wilson Lake, New Jersey

Lippert

Zachos

2007

Paleoceanography

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[1] The Paleocene-Eocene Thermal Maximum, which occurred $55.5 Ma, was caused by a massive release of carbon, as indicated by an $3% negative carbon isotope excursion recorded in the marine, atmospheric, and terrestrial reservoirs. One suggested source for the carbon, a cometary impactor, is based on the sudden appearance and high concentration of single-domain (SD) magnetite in Paleocene-Eocene (P-E) boundary cores from the North Atlantic continental margin. We evaluate the potential sources of SD magnetite at the P-E boundary by presenting new magnetic hysteresis, low-temperature magnetic remanence, and transmission electron microscopy data from the North Atlantic coastal ocean. Our results show a similar increase in SD material but demonstrate that the magnetic material has a biogenic origin. These findings indicate that the high concentrations of SD magnetite immediately above the P-E boundary are the result of unusual accumulations and/or preservation of magnetotactic bacteria. Such bacteria typically occupy the oxic-anoxic transition zone near the sediment-water interface or in the water column. The high abundances of SD magnetite in sediments from across the shelf may be an artifact of nonsteady state redox conditions and exceptional preservation of SD magnetite. It may also indicate that the oxic-anoxic redox boundary shifted into the water column. The latter explanation implies transient eutrophy of the coastal ocean in this region, most likely due to seasonally enhanced runoff, and increased stratification and nutrient loading.

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Section: Pa4104supporting

confidence: 76%

A biogenic origin for anomalous fine‐grained magnetic material at the Paleocene‐Eocene boundary at Wilson Lake, New Jersey

Lippert

Zachos

2007

Paleoceanography

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“…54 Nonetheless, FeO domains can be shown to form kinetically as interim phases at interfaces from oxidation to hematite or reduction to magnetite. 43 It has been found that FeO can exist in three crystal structures, namely B1 (NaCl structure, ), B2 (CsCl structure, ), and B8 (NiAs, P6 3 mc), 55 56 All this suggests that in fact gradations of oxygen stoichiometry are expected for iron oxide core-shell particles.…”

Section: Results and Discussion A Structural Characterizationmentioning

confidence: 99%

Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of interface on stability of magnetic properties

McCloy

Jiang

Droubay

et al. 2013

Journal of Applied Physics

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A cluster deposition method was used to produce films of loosely aggregated nanoclusters (NC) of Fe core-Fe 3 O 4 shell or fully oxidized Fe 3 O 4 . Films of these NC on Si(100) or MgO(100)/Fe 3 O 4 (100) were irradiated to 10 16 Si 2+ /cm 2 near room temperature using an ion accelerator. Ion irradiation creates structural change in the NC film with corresponding chemical and magnetic changes which depend on the initial oxidation state of the cluster. Films were characterized using magnetometry (hysteresis, first order reversal curves), microscopy (transmission electron, helium ion), and x-ray diffraction. In all cases, the particle sizes increased due to ion irradiation, and when a core of Fe is present, irradiation reduces the oxide shells to lower valent Fe species. These results show that ion irradiated behavior of the nanocluster films depends strongly on the initial nanostructure and chemistry, but in general saturation magnetization decreases slightly.

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“…The offsets were more noticeable for the HM sample group. Large FC-ZFC offsets are typically seen for goethite [Guyodo et al, 2006, Carter-Stiglitz et al, 2006, and much smaller ones in multidomain (> 1 μm), partially oxidized, magnetite [Smirnov and Tarduno, 2000]. Both phases probably contribute to the FC/ZFC behavior, but because of the very large differences in the intrinsic saturation magnetization between magnetite/maghemite and goethite, the former dominates in these series of measurements.…”

Section: Low-temperature Magnetic Properties: Fc Zfc and Rtsirmmentioning

confidence: 99%

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

et al. 2016

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Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth's most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellowreddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002-0.57 wt. %) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM<0.1m. For all examined samples, the average iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4 % in magnetite, and 65% in ferric silicates. Structural iron in clay minerals may account for much of the iron in the ferric silicates. We estimate that the mean ferric oxides flux exported from the Bodélé Depression is 0.9 Tg/yr with greater than 50% exported as ferric oxide nanoparticles (<0.1m). The high surface-to-volume ratios of ferric oxide nanoparticles once entrained into dust plumes may facilitate increased atmospheric chemical and physical processing and affect iron solubility and bioavailability to marine and terrestrial ecosystems.

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Low‐temperature magnetic properties of pelagic sediments (Ocean Drilling Program Site 805C): Tracers of maghemitization and magnetic mineral reduction

Cited by 95 publications

References 53 publications

A biogenic origin for anomalous fine‐grained magnetic material at the Paleocene‐Eocene boundary at Wilson Lake, New Jersey

A biogenic origin for anomalous fine‐grained magnetic material at the Paleocene‐Eocene boundary at Wilson Lake, New Jersey

Ion irradiation of Fe-Fe oxide core-shell nanocluster films: Effect of interface on stability of magnetic properties

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

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