B, Sr and Pb isotope geochemistry of high-pressure Alpine metaperidotites monitors fluid-mediated element recycling during serpentinite dehydration in subduction mélange (Cima di Gagnone, Swiss Central Alps)

Cannaò, Enrico; Agostini, Samuele; Scambelluri, Marco; Tonarini, S.; Godard, Marguerite

doi:10.1016/j.gca.2015.04.024

Cited by 62 publications

(65 citation statements)

References 99 publications

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“…Positive anomalies in As, Sb, Be, B, elevated contents in radiogenic Sr and Pb, low δ 11 B characterizing bulk rocks and high-pressure minerals, point to element transfer from paragneiss to the serpentinized peridotite protoliths during subduction burial (Scambelluri et al, 2014;Cannaò et al, 2015). These geochemical characteristics identify Gagnone as a prime example of mantle rocks recording fluid-mediated element exchange with metasediments in plate-interface subduction melanges.…”

Section: Discussionmentioning

confidence: 96%

“…The high concentration of such fluid-mobile elements measured in the Gagnone bulk rocks, in the fluid-related inclusions and in the high-pressure minerals fits the above interpretation. Our trace element data (together with radiogenic Pb and Sr; Cannaò et al, 2015) thus offer a record of 'fluid-transported' elements from the country paraschist into the melanged ultramafic bodies, elements that may be delivered later to subarc fluids.…”

Section: Relevance For Trace Element Cycling Along the Subduction Intmentioning

confidence: 91%

“…1D). Equilibration of ultrabasic lenses with sediment-derived fluids is also suggested by their high contents of radiogenic Sr and Pb isotopes ( 87 Sr/ 86 Sr and 206 Pb/ 204 Pb ratios of 0.71244 and 18.837, respectively; Cannaò et al, 2015), which approach the composition of associated paragneisses. Enrichments in the above fluid-mobile elements are common to all eclogitic minerals, indicating that open-system subduction metamorphism predated eclogite-facies dehydration of the ultrabasic lenses.…”

Section: Geologic and Petrologic Backgroundmentioning

confidence: 99%

“…Exchange with surrounding sedimentary rocks can cause serpentinite enrichment in specific tracers like As, Be, Sb, B, radiogenic Sr, Pb and isotopically light B (Hattori and Guillot, 2003;Marchesi et al, 2013;Harvey et al, 2014;Scambelluri et al, 2014;Angiboust et al, 2014;Lafay et al, 2013;Cannaò et al, 2015). Element addition to serpentinite may occur during prograde burial (Deschamps et al, 2011;Scambelluri et al, 2014), or during fluid channeling along shear zones in subducting slabs (Angiboust et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Fluid-related inclusions in Alpine high-pressure peridotite reveal trace element recycling during subduction-zone dehydration of serpentinized mantle (Cima di Gagnone, Swiss Alps)

Scambelluri

Pettke

Cannaò

2015

Earth and Planetary Science Letters

108

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Available online xxxx Editor: T.A. Mather Keywords: serpentinized mantle garnet peridotite chlorite harzburgite polyphase inclusions subduction fluids fluid-mobile elementsSerpentinites release at sub-arc depths volatiles and several fluid-mobile trace elements found in arc magmas. Constraining element uptake in these rocks and defining the trace element composition of fluids released upon serpentinite dehydration can improve our understanding of mass transfer across subduction zones and to volcanic arcs. The eclogite-facies garnet metaperidotite and chlorite harzburgite bodies embedded in paragneiss of the subduction melange from Cima di Gagnone derive from serpentinized peridotite protoliths and are unique examples of ultramafic rocks that experienced subduction metasomatism and devolatilization. In these rocks, metamorphic olivine and garnet trap polyphase inclusions representing the fluid released during high-pressure breakdown of antigorite and chlorite. Combining major element mapping and laser-ablation ICP-MS bulk inclusion analysis, we characterize the mineral content of polyphase inclusions and quantify the fluid composition. Silicates, Cl-bearing phases, sulphides, carbonates, and oxides document post-entrapment mineral growth in the inclusions starting immediately after fluid entrapment. Compositional data reveal the presence of two different fluid types. The first (type A) records a fluid prominently enriched in fluid-mobile elements, with Cl, Cs, Pb, As, Sb concentrations up to 10 3 PM (primitive mantle), ∼10 2 PM Tl, Ba, while Rb, B, Sr, Li, U concentrations are of the order of 10 1 PM, and alkalis are ∼2 PM. The second fluid (type B) has considerably lower fluid-mobile element enrichments, but its enrichment patterns are comparable to type A fluid. Our data reveal multistage fluid uptake in these peridotite bodies, including selective element enrichment during seafloor alteration, followed by fluid-rock interaction along with subduction metamorphism in the plate interface melange. Here, infiltration of sediment-equilibrated fluid produced significant enrichment of the serpentinites in As, Sb, B, Pb, an enriched trace element pattern that was then transferred to the fluid released at greater depth upon serpentine dehydration (type A fluid). The type B fluid hosted by garnet may record the composition of the chlorite breakdown fluid released at even greater depth. The Gagnone study-case demonstrates that serpentinized peridotites acquire water and fluid-mobile elements during ocean floor hydration and through exchange with sediment-equilibrated fluids in the early subduction stages. Subsequent antigorite devolatilization at subarc depths delivers aqueous fluids to the mantle wedge that can be prominently enriched in sediment-derived components, potentially triggering arc magmatism without the need of concomitant dehydration/melting of metasediments or altered oceanic crust.

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Section: Discussionmentioning

confidence: 96%

Section: Relevance For Trace Element Cycling Along the Subduction Intmentioning

confidence: 91%

Section: Geologic and Petrologic Backgroundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fluid-related inclusions in Alpine high-pressure peridotite reveal trace element recycling during subduction-zone dehydration of serpentinized mantle (Cima di Gagnone, Swiss Alps)

Scambelluri

Pettke

Cannaò

2015

Earth and Planetary Science Letters

108

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“…Orange stars represent the estimated stability conditions of different rodingites and metarodingites in literature that are shown for comparison. 1: Cima di Gagnone (Cannaò, Agostini, Scambelluri, Tonarini, & Godard, ; Evans & Trommsdorff, ; Evans et al., ), 2: Zermat Saas (Barnicoat & Fry, ; Ferrando et al., ; Li et al., ; Zanoni et al., ), 3: Meliatic Bôrka Nappe (Li, Putiš, Yang, Koppa, & Dyda, ), 4: Kamuikotan Tectonic Belt (Banno, ; Katoh & Niida, ), 5: Tianshan (Li et al., ), 6: Cape San Martín (Franciscan Complex; Coleman, ; Ernst, ; Terabayashi & Maruyama, ), 7: Val Malenco (Berger & Bousquet, ; Puschnig, ), 8 and 11: JM Asbestos mine (Normand & Williams‐Jones, ), 9: Abitibi belt (Schandl et al., ), 10: Bou Azzer (Leblanc & Lbouabi, ), 12: Appalachian Piedmont (Mittwede & Schandl, ), 13: Cassiar (O'Hanley et al.,), 14 and 15: Mid Atlantic ridge (Frost et al., ; Honnorez & Kirst, ), 16: Paddy‐Go‐Easy Pass (Frost, )…”

Section: Discussionmentioning

confidence: 99%

High‐P metamorphism of rodingites during serpentinite dehydration (Cerro del Almirez, Southern Spain): Implications for the redox state in subduction zones

Laborda-López

Sánchez‐Vizcaíno

Marchesi

et al. 2018

Journal Metamorphic Geology

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The transition between antigorite‐serpentinite and chlorite‐harzburgite at Cerro del Almirez (Betic Cordillera, Southern Spain) exceptionally marks in the field the front of antigorite breakdown at high pressure (~16–19 kbar) and temperature (~650°C) in a paleosubducted serpentinite. These ultramafic lithologies enclose three types of metarodingite boudins of variable size surrounded by metasomatic reaction rims. Type 1 Grandite‐metarodingite (garnet+chlorite+diopside+titanite±magnetite±ilmenite) mainly crops out in the antigorite‐serpentinite domain and has three generations of garnet. Grossular‐rich Grt‐1 formed during rodingitization at the seafloor (<2 kbar, ~150–325°C, ~FMQ buffer). During subduction, the alternating growth of Grt‐2b (richer in andradite and pyralspite components than Grt‐1) and Grt‐3 (very rich in andradite component) reflects the change from internally buffered metamorphic conditions (>10 kbar, ~350–650°C, ~FMQ buffer) to influx events of oxidizing fluids (fO2 ~HM buffer) released by brucite breakdown in the host antigorite‐serpentinite. Type 2 Epidote‐metarodingite (epidote+diopside+titanite±garnet) derives from Type 1 and is the most abundant metarodingite type enclosed in dehydrated chlorite‐harzburgite. Type 2 formed by increasing μSiO2 (from −884 to −860 kJ/mol) and decreasing μCaO (from −708 to −725 kJ/mol) triggered by the flux of high amounts of oxidizing fluids during the high‐P antigorite breakdown in serpentinite. The growth of Grt‐4, with low‐grandite and high‐pyralspite components, in Type 2 metarodingite accounts for progressive reequilibration of garnet with changing intensive variables. Type 3 Pyralspite‐metarodingite (garnet+epidote+amphibole+chlorite±diopside+rutile) crops out in the chlorite‐harzburgite domain and formed at peak metamorphic conditions (16–19 kbar, 660–684°C) from Type 2 metarodingite. This transformation caused the growth of a last generation of pyralspite‐rich garnet (Grt‐5) and the recrystallization of diopside into tremolitic amphibole at decreasing fO2 and μCaO (from −726 to −735 kJ/mol) and increasing μMgO (from −630 to −626 kJ/mol) due to chemical mixing between the metarodingite and the reaction rims. The different bulk Fe3+/FeTotal ratios of antigorite‐serpentinite and chlorite‐harzburgite, and of the three metarodingite types, reflect the highly heterogeneous oxidation state of the subducting slab and likely point to the transfer of localized oxidized reservoirs, such as metarodingites, into the deep mantle.

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The Behavior of Halogens During Subduction-Zone Processes

Barnes

Manning

Scambelluri

et al. 2018

Springer Geochemistry

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B, Sr and Pb isotope geochemistry of high-pressure Alpine metaperidotites monitors fluid-mediated element recycling during serpentinite dehydration in subduction mélange (Cima di Gagnone, Swiss Central Alps)

Cited by 62 publications

References 99 publications

Fluid-related inclusions in Alpine high-pressure peridotite reveal trace element recycling during subduction-zone dehydration of serpentinized mantle (Cima di Gagnone, Swiss Alps)

Fluid-related inclusions in Alpine high-pressure peridotite reveal trace element recycling during subduction-zone dehydration of serpentinized mantle (Cima di Gagnone, Swiss Alps)

High‐P metamorphism of rodingites during serpentinite dehydration (Cerro del Almirez, Southern Spain): Implications for the redox state in subduction zones

The Behavior of Halogens During Subduction-Zone Processes

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