Unusual  δ 56 Fe values in Samoan rejuvenated lavas generated in the mantle

Konter, J. G.; Pietruszka, A. J.; Hanan, B. B.; Finlayson, Valerie; Craddock, Paul R.; Jackson, Matthew G.; Dauphas, N.

doi:10.1016/j.epsl.2016.06.029

Cited by 74 publications

(84 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…6). In addition, our results are in accordance with the unusual heavy δ 56 Fe values (up to +0.34‰) recently determined in Samoan differentiated lavas (Konter et al 2016) (Fig. 6) Konter et al 2016).…”

Section: Fe Isotope Fractionation During Retrograde Greenschist Faciessupporting

confidence: 80%

“…In addition, our results are in accordance with the unusual heavy δ 56 Fe values (up to +0.34‰) recently determined in Samoan differentiated lavas (Konter et al 2016) (Fig. 6) Konter et al 2016). Enrichment in the heavy Fe isotopes in Samoan lavas was interpreted to be the result of a metasomatised mantle source or of a pyroxenite component in the source (Konter et al 2016).…”

Section: Fe Isotope Fractionation During Retrograde Greenschist Faciessupporting

confidence: 78%

“…6) Konter et al 2016). Enrichment in the heavy Fe isotopes in Samoan lavas was interpreted to be the result of a metasomatised mantle source or of a pyroxenite component in the source (Konter et al 2016). By analogy, the heavy δ 56 Fe values measured in the metabasites of the Ile de Groix suggest that they derive from an unusual heavy-Fe enriched mantle source.…”

Section: Fe Isotope Fractionation During Retrograde Greenschist Faciesmentioning

confidence: 99%

“…5a, b; Electronic Appendix, Fig. A1) Schuessler et al 2009;Craddock and Dauphas 2011;Konter et al 2016), or in island arc basalts and lavas (IAB, IAL) (−0.04 to +0.15‰; Dauphas et al 2009;Nebel et al 2015) (Fig. 6).…”

Section: Fe Isotope Fractionation During Retrograde Greenschist Faciesmentioning

confidence: 99%

“…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]. This difference indicates Fe isotope fractionation during mantle partial melting and magma differentiation (Teng et al 2013).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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

Korh

Luais

Deloule

et al. 2017

Contrib Mineral Petrol

View full text Add to dashboard Cite

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

show abstract

Section: Fe Isotope Fractionation During Retrograde Greenschist Faciessupporting

confidence: 80%

Section: Fe Isotope Fractionation During Retrograde Greenschist Faciessupporting

confidence: 78%

Section: Fe Isotope Fractionation During Retrograde Greenschist Faciesmentioning

confidence: 99%

Section: Fe Isotope Fractionation During Retrograde Greenschist Faciesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Korh

Luais

Deloule

et al. 2017

Contrib Mineral Petrol

View full text Add to dashboard Cite

show abstract

The behavior of iron and zinc stable isotopes accompanying the subduction of mafic oceanic crust: A case study from Western Alpine ophiolites

Inglis

Debret

Burton

et al. 2017

Geochem Geophys Geosyst

View full text Add to dashboard Cite

Arc lavas display elevated Fe 31 /RFe ratios relative to MORB. One mechanism to explain this is the mobilization and transfer of oxidized or oxidizing components from the subducting slab to the mantle wedge. Here we use iron and zinc isotopes, which are fractionated upon complexation by sulfide, chloride, and carbonate ligands, to remark on the chemistry and oxidation state of fluids released during prograde metamorphism of subducted oceanic crust. We present data for metagabbros and metabasalts from the Chenaillet massif, Queyras complex, and the Zermatt-Saas ophiolite (Western European Alps), which have been metamorphosed at typical subduction zone P-T conditions and preserve their prograde metamorphic history. There is no systematic, detectable fractionation of either Fe or Zn isotopes across metamorphic facies, rather the isotope composition of the eclogites overlaps with published data for MORB. The lack of resolvable Fe isotope fractionation with increasing prograde metamorphism likely reflects the mass balance of the system, and in this scenario Fe mobility is not traceable with Fe isotopes. Given that Zn isotopes are fractionated by S-bearing and C-bearing fluids, this suggests that relatively small amounts of Zn are mobilized from the mafic lithologies in within these types of dehydration fluids. Conversely, metagabbros from the Queyras that are in proximity to metasediments display a significant Fe isotope fractionation. The covariation of d 56 Fe of these samples with selected fluid mobile elements suggests the infiltration of sediment derived fluids with an isotopically light signature during subduction.

show abstract

The Role of Redox Processes in Determining the Iron Isotope Compositions of Minerals, Melts, and Fluids

Sossi¹,

Debret²

2021

Geophysical Monograph Series

View full text Add to dashboard Cite

Stable isotope fractionation is a response to the minimisation of free energy associated with differences in vibrational frequencies during substitution of isotopic masses between two phases. Site properties are dictated by the bonding environment of iron, and influence its 'force constant', a descriptor for bond strength. Because iron readily transitions between its ferrous (Fe 2+ ) and ferric (Fe 3+ ) state over the oxygen fugacities (fO 2 ) of terrestrial magmas, redox processes are presumed to control iron isotope fractionation. In fact, both co-ordination and redox state are key to interpreting iron isotope variations in high-temperature, high-pressure geological systems. Determinations of iron force constants by experimental, theoretical and spectroscopic means in minerals, melts and fluids are reviewed, emphasising the effect of composition in influencing isotopic fractionation. Within this framework, the application of numerical models of partial melting to iron isotope variations in oceanic basalts and subduction-zone (or arc) magmas has shed light on their genesis. The influence of melt composition, mineral mode and fluid exsolution in producing iron isotope fractionation in evolving magmas is explored. Iron isotopic signatures in magmatic rocks are linked to that of their sources, and are influenced by the iron isotopic evolution of subducting slabs and transfer of fluids to the mantle wedge. 2.0. Principles and nomenclature Ratios of two isotopes, n and d of an element, E, are generally expressed relative to their ratio in a standard in delta notation, which is given by:(1) 𝛿 𝑛/𝑑 𝐸 = ( ( 𝑛 𝐸/ 𝑑 𝐸) 𝑠𝑎𝑚𝑝𝑙𝑒

show abstract

Unusual δ 56 Fe values in Samoan rejuvenated lavas generated in the mantle

Cited by 74 publications

References 51 publications

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

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

The behavior of iron and zinc stable isotopes accompanying the subduction of mafic oceanic crust: A case study from Western Alpine ophiolites

The Role of Redox Processes in Determining the Iron Isotope Compositions of Minerals, Melts, and Fluids

Contact Info

Product

Resources

About