Systematic iron isotope variations in mantle rocks and minerals: The effects of partial melting and oxygen fugacity

Williams, Helen M.; Peslier, A. H.; McCammon, Catherine; Halliday, Alex N.; Levasseur, S.; Teutsch, Nadya; Burg, Jean‐Pierre

doi:10.1016/j.epsl.2005.04.020

Cited by 218 publications

(153 citation statements)

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“…The strong enrichment of Fe in the topsoil of soils influenced by high groundwater tables is a typical feature of Pleistocene sandy fluvial lowlands and has been observed in many corresponding landscapes of Central and Northern Europe, e.g., Belgium (Stoops 1983), Germany (Schlichting 1965), Denmark (Breuning-Madsen et al 2000), and Poland (Kaczorek and Sommer 2003), but Poitrasson et al (2004) for δ 57 Fe, Weyer et al (2005) for δ 56 Fe, and Williams et al (2005) for δ 57 Fe, respectively f In-house salt standard of the ETH Zürich, Switzerland; values in brackets given by Teutsch et al (2009) andFehr et al (2008), respectively also in North America (Crerar et al 1979). Petrogleyic horizons of such soils largely consist of Fe (~200 tõ 500 g kg −1 ) that is predominantly occurring as oxidic Fe, i.e., most of the total Fe can be extracted by Fe d .…”

Section: Field Observationsmentioning

confidence: 98%

Iron oxide mineralogy and stable iron isotope composition in a Gleysol with petrogleyic properties

et al. 2011

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Purpose Properties of Fe oxides are poorly understood in soils with fluctuating water tables and variable redox conditions. The objective of this research was to (a) characterize the mineralogical composition of Fe oxides and (b) determine the relationship to the stable Fe isotope ratio in a soil with temporally and spatially sharp redox gradients. Materials and methodsThe lowland Gleysol (Petrogleyic) is in Northwest Germany and consists of oximorphic soil horizons (Ah 0-15, Bg 15-35, and CrBg 35-70 cm) developed from Holocene fluvial loam overlaying glaciofluvial sand with reductomorphic properties (2Cr horizon, +70 cm). Field measurements during the course of 28 months included the monitoring of groundwater table, soil redox potential, and analysis of the soil solutions. Solid Fe phases were studied by room temperature and cryogenic 57 Fe Mössbauer spectroscopy, and stable Fe isotope compositions by multiple collector inductively coupled plasma mass spectrometry. Results and discussion The groundwater table ranged from −83 cm below to +8 cm above soil surface (median −27 cm). Permanent reducing conditions occurred in the 2Cr horizon with dissolved Fe concentrations of 44.8 mg L −1 (median). The duration of oxidizing conditions increased in the order CrBg < Bg < Ah. Total Fe increased from 50 (Ah) over 316 (Bg) up to 412 g kg −1 (CrBg) and was lowest in the 2Cr horizon (7 g kg −1 ). Ferrihydrite (51% of total Fe) was dominant over goethite (24%) in the Ah horizon. Conversely, nanogoethite dominated both the Bg (94%) and CrBg (86%) horizons. Iron in siderite amounted to 7% in the CrBg horizon. Iron isotope compositions yielded a range of δ 57 Fe values from +0.29‰ (Ah horizon) to −0.30‰ (Bg horizon). In contrast to the overlying CrBg (δ 57 Fe=−0.19‰) and Bg horizons, the 2Cr horizon is characterized by a relatively high δ 57 Fe value of +0.22‰. Conclusions Lasting water saturation and frequent reducing conditions lead to the enrichment of goethite in subsoil. Once formed, goethite remains stable compared to ferrihydrite because it is less available for microbial mediated reductive dissolution. High δ 57 Fe values in the topsoil primary result from fast ferrihydrite precipitation during aeration immediately after reducing conditions. In contrast,

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Section: Field Observationsmentioning

confidence: 98%

Iron oxide mineralogy and stable iron isotope composition in a Gleysol with petrogleyic properties

et al. 2011

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“…Metasomatism and/or metamorphic/hydrothermal alterations are additional processes that can modify the Fe isotope composition of mantle material (Williams et al 2005;Weyer and Ionov 2007;Dziony et al 2014).…”

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Isotope Fractionation Processes of Selected Elements

Hoefs

2015

Stable Isotope Geochemistry

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“…Teng et al 2008Teng et al , 2013Schuessler et al 2009;Sossi et al 2012;Liu et al 2014); and/or (3) fluid-and melt-induced mantle metasomatism (Beard and Johnson 2004;Zhao et al 2010;Poitrasson et al 2013). Variations of oxygen fugacity and redox conditions in the mantle also play a role in Fe isotope fractionation, as they affect mantle melting processes (Williams et al 2004(Williams et al , 2005Dauphas et al 2009;Teng et al 2013). MORB [δ 56 Fe from 0.053 ± 0.015‰ at 95% confidence level (CL), to 0.176 ± 0.014 at 2σ standard error (2σ SE); Weyer and Ionov 2007;Craddock and Dauphas 2011;Sossi et al 2012;Nebel et al 2013;Teng et al 2013], back-arc basin basalts (BABB) [δ 56 Fe from 0.026 ± 0.022 to 0.096 ± 0.022‰ at 2σ SE; Teng et al 2013;Nebel et al 2013], as well as ocean island basalts (OIB) [δ 56 Fe from −0.011 ± 0.030‰ (95% CL) to +0.30 ± 0.028‰ (2σ SE); Weyer and Ionov 2007;Teng et al 2008Teng et al , 2013Schuessler et al 2009;Konter et al 2016], are isotopically heavier than mantle peridotites and xenoliths [δ 56 Fe = +0.014 ± 0.018‰ (95%CL), Weyer and Ionov 2007; +0.025 ± 0.025‰ (95%CL), Craddock et al 2013;δ 57 Fe = +0.05 ± 0.01‰ (2σ SE), corresponding to a δ 56 Fe value of c. 0.034 ± 0.01‰, Sossi et al 2016].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Williams et al 2005Williams et al , 2009Dauphas et al 2009;Sossi et al 2012Sossi et al , 2016Teng et al 2013 54 Fe) standard − 1] × 1000; with x = 56 or 57). In magmatic rocks, fractionation may result from: (1) variable degrees of partial melting (Williams et al 2005;Weyer and Ionov 2007;Dauphas et al 2009;Teng et al 2013); (2) fractional crystallisation (e.g. Teng et al 2008Teng et al , 2013Schuessler et al 2009;Sossi et al 2012;Liu et al 2014); and/or (3) fluid-and melt-induced mantle metasomatism (Beard and Johnson 2004;Zhao et al 2010;Poitrasson et al 2013).…”

Section: Introductionmentioning

confidence: 99%

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Iron isotope fractionation in subduction-related high-pressure metabasites (Ile de Groix, France)

Korh

Luais

Deloule

et al. 2017

Contrib Mineral Petrol

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1during metamorphism: newly-formed Fe-rich minerals allowed preserving bulk rock Fe compositions during metamorphic reactions and hampered any Fe isotope fractionation. Greenschists have δ 56 Fe values (+0.17 ± 0.01 to +0.27 ± 0.02‰) similar to high-pressure rocks. Hence, metasomatism related to fluids derived from the subducted hydrothermally altered metabasites might only have a limited effect on mantle Fe isotope composition under subsolidus conditions, owing to the large stability of Fe-rich minerals and low mobility of Fe. Subsequent melting of the heavy-Fe metabasites at deeper levels is expected to generate mantle Fe isotope heterogeneities.Keywords Fe isotopes · Metabasites · Subduction · HP-LT metamorphism · Blueschists · Eclogites · Greenschists · Basaltic protoliths IntroductionHigh-pressure/low-temperature (HP-LT) rocks are remnants of ancient subduction zones. They provide information on geochemical processes and deep fluid-rock interactions occurring at present-day active convergent margins. Fluid infiltration during high-and lowtemperature hydrothermal alteration of the oceanic crust at mid-ocean ridges and on the seafloor is responsible for the hydration of basic rocks and serpentinisation of the lithospheric mantle. During subduction, the hydrothermally altered oceanic crust dehydrates continuously and releases large amounts of H 2 O at a relatively shallow level in the subduction zone (50-80 km) (Schmidt and Poli 1998;Rüpke et al. 2004). Deserpentinisation of the lithospheric mantle occurs at deeper levels (100-200 km), where fluids are expected to be the source of arc melting (Ulmer and Abstract Characterisation of mass transfer during subduction is fundamental to understand the origin of compositional heterogeneities in the upper mantle. Fe isotopes were measured in high-pressure/low-temperature metabasites (blueschists, eclogites and retrograde greenschists) from the Ile de Groix (France), a Variscan high-pressure terrane, to determine if the subducted oceanic crust contributes to mantle Fe isotope heterogeneities. The metabasites have δ 56 Fe values of +0.16 to +0.33‰, which are heavier than typical values of MORB and OIB, indicating that their basaltic protolith derives from a heavy-Fe mantle source. The δ 56 Fe correlates well with Y/Nb and (La/Sm) PM ratios, which commonly fractionate during magmatic processes, highlighting variations in the magmatic protolith composition. In addition, the shift of δ 56 Fe by +0.06 to 0.10‰ compared to basalts may reflect hydrothermal alteration prior to subduction. The δ 56 Fe decrease from blueschists (+0.19 ± 0.03 to +0.33 ± 0.01‰) to eclogites (+0.16 ± 0.02 to +0.18 ± 0.03‰) reflects small variations in the protolith composition, rather than Fe fractionation

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Systematic iron isotope variations in mantle rocks and minerals: The effects of partial melting and oxygen fugacity

Cited by 218 publications

References 44 publications

Iron oxide mineralogy and stable iron isotope composition in a Gleysol with petrogleyic properties

Iron oxide mineralogy and stable iron isotope composition in a Gleysol with petrogleyic properties

Isotope Fractionation Processes of Selected Elements

Iron isotope fractionation in subduction-related high-pressure metabasites (Ile de Groix, France)

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