Magnetic Properties of Iron in Soil Iron Oxides and Clay Minerals

Coey, J. M. D.

doi:10.1007/978-94-009-4007-9_14

Cited by 64 publications

(59 citation statements)

References 49 publications

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“…Note that the 6C1 fit is improved with the two-site model; the 5C1-4 and 3C1 spectra, not shown, are very similar. However, the model fails to fit the background for 2C1, suggesting a contribution from a weak magnetic component with transition temperature near 300 K. The results of the fits to the 300 K spectra of the seven "surface" samples are presented in Table 4, along with reported parameter values for fertihydrite (formula varies, e.g.,-FesHO8.4H20 [Murad, 1988] or 5Fe203.9H20 [Coey, 1988] The situation regarding the 2C1 and 3C1 samples is less clear. While the 300 K data are consistent with ferrihydrite, no associated magnetic transition is observed down to 13 K. The fit results (Table 6), including the low-temperature data, demonstrate that the weak magnetic component seen at 300 K in the 2C1 spectrum is due to goethite, which is often found associated with ferrihydrite in watery environments [Schwertmann, 1988].…”

Section: Primary Precipitates ("Surface" Samples)mentioning

confidence: 98%

A Mössbauer investigation of iron‐rich terrestrial hydrothermal vent systems: Lessons for Mars exploration

Wade¹,

Agresti²,

Wdowiak³

et al. 1999

J. Geophys. Res.

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Abstract. Hydrothermal spring systems may well have been present on early Mars and could have served as a habitat for primitive life. The integrated instrument suite of the Athena Rover has, as a component on the robotic arm, a M6ssbauer spectrometer. In the context of future Mars exploration we present results of M6ssbauer analysis of a suite of samples from an iron-rich thermal spring in the Chocolate Pots area of Yellowstone National Park (YNP) and from Obsidian Pool (YNP) and Manitou Springs, Colorado. We have found that M6ss-bauer spectroscopy can discriminate among the iron-bearing minerals in our samples. Those near the vent and on the surface are identified as ferrihydrite, an amorphous ferric mineraloid. Subsurface samples, collected from cores, which are likely to have undergone inorganic and/or biologically mediated alteration (diagenesis), exhibit spectral signatures that include nontronite (a smectite clay), hematite (ot-Fe203), small-particle/nanophase goethite FeOOH), and siderite (FeCO3). We find for iron minerals that M6ssbauer spectroscopy is at least as efficient in identification as X-ray diffraction. This observation is important from an exploration standpoint. As a planetary surface instrument, M6ssbauer spectroscopy can yield high-quality spectral data without sample preparation (backscatter mode). We have also used field emission scanning electron microscopy (FESEM), in conjunction with energydispersive X ray (EDX) fluorescence spectroscopy, to characterize the microbiological component of surface sinters and the relation between the microbiological and the mineralogical framework. Evidence is presented that the minerals found in these deposits can have multibillion-year residence times and thus may have survived their possible production in a putative early Martian hot spring up to the present day. Examples include the nanophase property and the M6ssbauer signature for siderite, which has been identified in a 2.09-billion-year old hematite-rich chert stromatolite. Our research demonstrates that in situ M6ssbauer spectroscopy can help determine whether hydrothermal mineral deposits exist on Mars, which is significant for exobiology because of the issue of whether that world ever had conditions conducive to the origin of life. As a useful tool for selection of samples suitable for transport to Earth, M6ssbauer spectroscopy will not only serve geological interests but will also have potential for exopaleontology.

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Section: Primary Precipitates ("Surface" Samples)mentioning

confidence: 98%

A Mössbauer investigation of iron‐rich terrestrial hydrothermal vent systems: Lessons for Mars exploration

Wade¹,

Agresti²,

Wdowiak³

et al. 1999

J. Geophys. Res.

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“…Goethite (αFeOOH) is widely distributed in soils, rocks, sediments, and ores [1,2], and it can be a source material for catalysts [3], magnetic materials [4], and in iron production [5]. In the past few decades, the thermal decomposition of goethite into hematite has been reported from various viewpoints, including kinetics analysis [6], spectroscopy [7,8], diffractometry [9,10], and electron microscopy [11].…”

Section: Introductionmentioning

confidence: 99%

Twin formation in hematite during dehydration of goethite

et al. 2016

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Twin formation in hematite during dehydration was investigated using X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy (TEM).When synthetic goethite was heated at different temperatures between 100 and 800 °C, a phase transformation occurred at temperatures above 250 °C. The electron diffraction patterns showed that the single-crystalline goethite with a growth direction of [001] G was transformed into hematite with a growth direction of [100] H . Two non-equivalent structures emerged in hematite after dehydration, with twin boundaries at the interface between the two variants. As the temperature was increased, crystal growth occurred. At 800 °C, the majority of the twin boundaries disappeared; however, some hematite particles remained in the twinned variant. The electron diffraction patterns and high-resolution TEM observations indicated that the twin boundaries consisted of crystallographically equivalent prismatic (100), (010), and (11 � 0) planes. According to the total energy calculations based on spin-polarized density functional theory, the twin boundary of prismatic (100) screw had small interfacial energy (0.24 J/m 2 ). Owing to this low interfacial energy, the prismatic (100) screw interface remained after higher-temperature treatment at 800 °C.

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“…In the lepidocrocite structure, ferric iron is coordinated in edge-shared octahedra, which form layers within [001] linked by hydrogen bridges [Ewing, 1935]. Information on magnetic properties has been largely obtained from Mössbauer spectroscopy [Coey, 1988]. Mössbauer studies show magnetic ordering between 73 and 77 K for well-crystalline lepidocrocite and complete ordering by 4.2 K [Johnson, 1969;Murad and Schwertman, 1984].…”

Section: Introductionmentioning

confidence: 99%

Low‐temperature magnetic properties of lepidocrocite

et al. 2002

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The magnetic properties of synthetic lepidocrocite (γ‐FeOOH) were investigated between 5 and 300 K. The purity of the samples was verified by X‐ray diffraction and Mössbauer spectra at room temperature. The lepidocrocite is paramagnetic at room temperature with a low field susceptibility of 57.8 × 10−8 m3 kg−1. It undergoes magnetic ordering at low temperature and a peak in in‐phase susceptibility occurs around 52 K, where it is antiferromagnetic. Thermal demagnetization of low‐temperature remanence after cooling in zero field and in a 2.5‐T field display a large loss in remanence from 5 to 30 K. Hysteresis loops are open and symmetric about the origin below 50 K; the remanent magnetization probably arises from a defect magnetic moment. The field‐cooled hysteresis loop at 5 K is shifted along the field axis, which implies an exchange bias between antiferromagnetic and ferrimagnetic alignment in the lepidocrocite.

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Magnetic Properties of Iron in Soil Iron Oxides and Clay Minerals

Cited by 64 publications

References 49 publications

A Mössbauer investigation of iron‐rich terrestrial hydrothermal vent systems: Lessons for Mars exploration

A Mössbauer investigation of iron‐rich terrestrial hydrothermal vent systems: Lessons for Mars exploration

Twin formation in hematite during dehydration of goethite

Low‐temperature magnetic properties of lepidocrocite

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