Trace Element Partitioning in HP–LT Metamorphic Assemblages during Subduction-related Metamorphism, Ile de Groix, France: a Detailed LA-ICPMS Study

Korh, Afifé El; Schmidt, Susanne Theodora; Ulianov, Alexey; Potel, Sébastien

doi:10.1093/petrology/egp034

Cited by 87 publications

(97 citation statements)

References 58 publications

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“…The Fe isotope ratios are given in (El Korh et al 2009 (Fig. 3a-c), nor with the Fe 3+ /ΣFe and Fe/ Ti ratios (Fig.…”

Section: Resultsmentioning

confidence: 96%

“…1) (see Bosse et al 2002;Ballèvre et al 2003;El Korh et al 2013; and references therein). The metabasites correspond to former hydrothermally altered enriched mid-ocean ridge basalts (E-MORB), interlayered with pelitic micaschists (Bernard-Griffiths et al 1986;Bosse et al 2002;El Korh et al 2009. Because of the lack of ultrabasic and gabbroic rocks, the high-pressure rocks were interpreted as remnants of the uppermost part of an oceanic lithosphere or of basaltic lavas, emplaced during the Cambro-Ordovican rifting widely recognised along the northern Gondwana margin (El Korh et al 2012;von Raumer et al 2015).…”

Section: Geological Setting and Investigated Samplesmentioning

confidence: 99%

“…In eclogites, the peak pressure-temperature (P-T) conditions were estimated at 1.6-2.5 GPa and 500-600 °C (using pseudo-section phase diagrams) and correspond to the blueschist to eclogite facies transition, i.e. to a 60-70 km depth in a subduction zone with an intermediate thermal regime (El Korh et al 2009). In micaschists, the maximum peak P-T conditions were estimated to be 1.6-1.8 GPa, 450-500 °C using the NFMASH system (Bosse et al 2002).…”

Section: Geological Setting and Investigated Samplesmentioning

confidence: 99%

“…Blueschist facies rocks often contain pseudomorphs after lawsonite, composed of epidote, phengite, paragonite, actinolite, and albite (Ballèvre et al 2003). The different mineral assemblages between blueschists and eclogites result from slight differences in the composition of the protolith and/or small variations in temperature (50-75 °C) for the peak metamorphic conditions (El Korh et al 2009). Partial retrogression of eclogites and blueschists is evidenced by: (1) barroisite + albite symplectites replacing omphacite; (2) barroisite and actinolite overgrowths along glaucophane rims; (3) alteration of garnet to chlorite; and (4) replacement of rutile by titanite.…”

Section: Geological Setting and Investigated Samplesmentioning

confidence: 99%

“…1 Geological map of the Ile de Groix (after Audren et al 1993;Bosse et al 2002;El Korh et al 2013). *The beach "Plage des Grands Sables" periodically moves with the oceanic currents 12b and 25a), three eclogites (GR 21, 24a and 29) and five retrograde greenschists (GR 06a, 23 and 25b and albitic greenschists GROA 43 and 52) [for the detailed description of the samples see El Korh et al 2009Korh et al , 2011Korh et al , 2013 and Table 1]. …”

Section: Geological Setting and Investigated Samplesmentioning

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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“…The Fe isotope ratios are given in (El Korh et al 2009 (Fig. 3a-c), nor with the Fe 3+ /ΣFe and Fe/ Ti ratios (Fig.…”

Section: Resultsmentioning

confidence: 96%

Section: Geological Setting and Investigated Samplesmentioning

confidence: 99%

Section: Geological Setting and Investigated Samplesmentioning

confidence: 99%

Section: Geological Setting and Investigated Samplesmentioning

confidence: 99%

Section: Geological Setting and Investigated Samplesmentioning

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

Self Cite

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An Integrated Apatite Geochronology and Geochemistry Tool for Sedimentary Provenance Analysis

O’Sullivan

Chew

Morton

et al. 2018

Geochem Geophys Geosyst

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Sediment provenance studies utilizing detrital geochronology are often limited by source‐rock non‐uniqueness with respect to mineral age. Thus, the development of integrated techniques which permit identification of source rock age and lithology are highly desirable. In this case study from the southern Massif Central, France, we target modern‐river sediment from the river Tarn to assess the utility of combined U‐Pb and multiple trace‐element geochemical analysis of detrital apatite as a provenance tool. The study area was chosen because the sediment source areas chiefly comprise a relatively simple mix of medium‐ to low‐grade Variscan metasediments and late Variscan granitoids, which should yield detrital apatite readily distinguishable by age, trace‐element chemistry, or both. Based on comparison with previously published apatite trace‐element data from metasedimentary rocks and granitoids, pelitic apatite in the river Tarn detritus is primarily distinguished by high Sr/Mn, light rare‐earth element depletion (LREE) and low actinide contents, whereas granitic apatite is characterized by much lower Sr/Mn, and high LREE and actinide abundances. These source rock determinations are highly consistent with apatite trace‐element data from Tarn tributaries that drain either predominantly metapelitic or granitoid catchments. U‐Pb analysis of detrital rutile was also undertaken on those catchments for comparative purposes. As pelitic and granitic apatite can be readily distinguished, samples that have experienced downstream sediment mixing can then be comprehensively characterized. Using this method we identify a source lithology for nearly every analyzed apatite grain in the river sediment, even though 59% of the analyzed grains do not yield reliable U‐Pb ages.

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A data screening approach to confirming a target mineral is chlorite using EPMA and LA‐ICPMS data

Freij,

Gregory,

Liu

2023

Geoscience Data Journal

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Applying machine learning techniques to large datasets of in situ analyses has been proven to be a powerful tool in Earth Sciences. However, problems may arise when dealing with minerals such as chlorite, that exist as a solid solution rather than a single, stoichiometric ideal. It can be difficult to determine whether the variations in major element concentrations are due to compositional difference in the mineral of interest or due to sampling of the surrounding mineral phases in addition to the mineral of interest during the analyses. If the latter, interpretations of the results would be complicated, misled or even spurious. Here we present a method to identify chlorite based on the major and minor element content, from both LA‐ICPMS and EPMA data. Further we present a dataset of 3,317 analyses of chlorite and have shown that 7.4% of these analyses include significant quantities of non‐chlorite material.

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Trace Element Partitioning in HP–LT Metamorphic Assemblages during Subduction-related Metamorphism, Ile de Groix, France: a Detailed LA-ICPMS Study

Cited by 87 publications

References 58 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)

An Integrated Apatite Geochronology and Geochemistry Tool for Sedimentary Provenance Analysis

A data screening approach to confirming a target mineral is chlorite using EPMA and LA‐ICPMS data

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