High-field remanence properties of synthetic and natural submicrometre haematites and goethites: significance for environmental contexts

Maher, Barbara A.; Karloukovski, Vassil; Mutch, Thomas J.

doi:10.1016/j.epsl.2004.05.042

Cited by 76 publications

(65 citation statements)

References 24 publications

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“…Since magnetite and maghemite are usually completely saturated above 0.3 T, HIRM is a measure of the amount of high-coercivity, antiferromagnetic phases (hematite and goethite) and the S 300 -ratio is a measure of the relative amounts of low-coercivity (magnetite/maghemite) to highcoercivity (hematite/goethite) phases. However, since goethite is extremely hard to magnetize at room temperature in fields below 2.0 T (Maher et al, 2004;Rochette et al, 2005) it may contribute a negligible amount to HIRM or the S 300 -ratio value even though it may be the abundant phase. Furthermore, depending on particle sizes and cation impurity, the magnetic ordering temperature for goethite may be below room-temperature and thus be invisible to remanence measurements at room-temperature [Liu et al, 2006].…”

Section: Magnetic Methodsmentioning

confidence: 99%

“…This is consistent with the reflectance data for HM samples that showed that relative to goethite, hematite was the subordinate phase. A small fraction of hematite may also be partially demagnetized in 0.2 T AF during the first part of the Carter-Guyodo method, thereby underestimating the hematite contribution [Maher et al, 2004].…”

Section: Low-temperature Magnetic Properties: Goethite and Hematitementioning

confidence: 99%

“…It is not unusual for the Morin transition to be suppressed in natural hematite due to poor crystallinity, cation-substitution, or nanoparticle effects (Vandenberghe et al, 2001;Maher et al, 2004;Özdemir et al, 2008;Jiang et al, 2014).…”

Section: Low-temperature Magnetic Properties: Goethite and Hematitementioning

confidence: 99%

“…We also determined the type of ferric oxide mineral, whether primarily hematite (-Fe 2 O 3 ) or goethite (-FeOOH), which are the two most common forms in desert soils and surfaces (hereafter collectively referred to as iron oxides or ferric oxides), and which have different optical properties. Reflectance spectroscopy can be used to identify different ferric oxide minerals (e.g., Clark et al, 2007), as can certain magnetic methods (Maher et al, 2004;Guyodo et al, 2006;Carter-Stiglitz et al, 2006;Liu et al, 2006;Maher, 2011). Mössbauer spectroscopy was also employed to identify with high specificity various iron phases, including amounts of hematite and goethite as well as the fraction that occur as nanoparticles, in a sample.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Magnetic Methodsmentioning

confidence: 99%

Section: Low-temperature Magnetic Properties: Goethite and Hematitementioning

confidence: 99%

Section: Low-temperature Magnetic Properties: Goethite and Hematitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…Hematite abundances are typically inferred using HIRM or other properties aimed at isolating high-coercivity mineral signals (e.g., an alternating field-demagnetized IRM or IRM@AF) (Larrasoaña et al, 2003b(Larrasoaña et al, , 2006(Larrasoaña et al, , 2008Liu et al, 2012b). The maximum field that can be imparted in most laboratories for IRM acquisition is around 1 T, and the coercivity of goethite is typically larger than several (up to 57) T (Peters and Dekkers, 2003;Maher et al, 2004;Rochette et al, 2005;Maher, 2011). HIRM and IRM@AF are, therefore, practically unaffected by any goethite in sediments.…”

Section: Marine Sedimentsmentioning

confidence: 99%

Source-to-sink magnetic properties of NE Saharan dust in Eastern Mediterranean marine sediments: review and paleoenvironmental implications

et al. 2015

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Influence of seawater exchanges across the Bab-el-Mandeb Strait on sedimentation in the Southern Red Sea during the last 60 ka

et al. 2013

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[1] The location of core MD92-1008 close to the southern edge of the Red Sea is ideal to study the evolution of seawater exchanges with the Northern Indian Ocean through the Bab-el-Mandeb narrow strait. The present study was aimed at documenting the paleoceanographic evolution of this area over the past 60 ka using high-resolution magnetic, sedimentological, and geochemical indicators. Two modes of variability dominate the records: (i) long-term, glacial-interglacial variations and (ii) rapid, millennial scale variability (Dansgaard-Oeschger type) during the last glacial period. Changes in magnetic concentration were documented from natural and laboratory magnetizations after proper normalization. They are inversely correlated to the total organic carbon (TOC) content, pointing out the key role played by reductive dissolution of magnetite on the evolution of magnetic concentration. Based on the temporal evolution of TOC, CaCO 3 , and planktonic δ 13 C, we suggest that past changes in the organic matter content (i) were closely linked to glacio-eustatic variations which modulated long-term seawater exchanges and nutrient supplies to the Red Sea through the narrow Bab-el-Mandeb Strait and (ii) reflect millennial-scale changes in productivity driven by monsoon wind intensity which controlled the amount of nutrient-rich intermediate waters upwelled in the Gulf of Aden during the summer season and advected into the Southern Red Sea. The sea level rise following the onset of deglaciation generated a rapid flush of detrital material that was accumulated on the continental margins and on the previously emerged zones of the Bab-el-Mandeb area.

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High-field remanence properties of synthetic and natural submicrometre haematites and goethites: significance for environmental contexts

Cited by 76 publications

References 24 publications

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

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

Source-to-sink magnetic properties of NE Saharan dust in Eastern Mediterranean marine sediments: review and paleoenvironmental implications

Influence of seawater exchanges across the Bab-el-Mandeb Strait on sedimentation in the Southern Red Sea during the last 60 ka

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