Incompatible element-rich fluids released by antigorite breakdown in deeply subducted mantle

doi:10.1016/S0012-821X(01)00457-5

Earth and Planetary Science Letters

Volume 192, Issue 3, 30 October 2001, Pages 457-470

https://doi.org/10.1016/S0012-821X(01)00457-5 Get rights and content

Abstract

We present first trace element analyses of the fluid produced during breakdown of antigorite serpentine, a major dehydration reaction occurring at depth within subducting oceanic plates. Microinclusions filled with crystals+ aqueous liquid are disseminated within olivine and orthopyroxene grown at pressures and temperatures beyond the stability field of antigorite. Despite hydrogen loss and significant major element changes that have affected the analyzed inclusions, their trace element composition still reflects characteristics of the subduction fluid released during serpentinite dehydration. The fluid is enriched in incompatible elements indicating either (1) interaction with fluids derived from crustal slab components, or (2) dehydration of altered (serpentinized) oceanic mantle previously enriched in incompatible elements. Several features of the analyzed fluid+mineral inclusions (high Pb/Th, Pb/U and Pb/Ce) are in agreement with available experimental work, as well as with the geochemical signatures of most arc lavas and of several ocean island basalt mantle sources. The trace element patterns of the fluid+mineral inclusions do not display relative enrichment in large ion lithophile elements compared to high field strength elements, thus suggesting that the latter elements may become soluble in natural subduction fluids.

Introduction

Recent research on subduction zone metamorphism has concentrated on the nature and composition of fluids evolved during burial and heating of downgoing plates. Aqueous fluids are incorporated in the oceanic lithosphere during hydrothermal circulation at ridge settings and flux the mantle above subduction zones, to create arc volcanism at convergent plate margins. Release of fluids from a descending slab is accompanied by cycling of crustal components into a hydrous fluid and/or a melt phase, the migration of which into the overlying mantle induces metasomatism and partial melting [1]. Uncertainties concern the nature and composition of fluid agents released during subduction because of the paucity of deep natural rocks and fluids available for analysis. Constraints on the nature of fluids liberated in the deep mantle by subduction are placed by several experimental investigations at high pressures and temperatures [2], [3], [4], [5], and by studies of fluid inclusions in high to ultrahigh pressure rocks and in mantle xenoliths [6], [7], [8], [9]. These indicate that mineral solubility in fluids increases with pressure, and that interactions between released fluid and host rocks can lead to formation of fluids loaded with dissolved rock components [10], [11].

The trace element composition of fluids released at depth in subduction zones has been indirectly estimated by comparing primitive arc lavas with mid ocean ridge basalts (MORB), as well as by means of experimental studies of fluid–solid partitioning of trace elements at pressure–temperature conditions of the upper mantle [12], [13], [14], [15], [16], [17], [18], [19]. These studies indicate that the agents fertilizing the mantle sources of arc magmas are characterized by an enrichment in large ion lithophile elements (LILE: Cs, Rb, Ba, Pb, U, Th, Sr) and light rare earth elements (LREE: La, Ce, Nd) with respect to high field strength elements (HFSE: Ti, Nb). Pb is more readily transported by such fluids than U and Th [17], [19]: dehydration processes in the slab may thus produce large increases in U/Pb and Th/Pb of the residual subducting lithosphere, and may explain the low Ce/Pb ratios characteristic of arc magmas [20]. Since the fluids released during subduction experienced complex flow pathways into the mantle, it is yet unclear to what extent their LILE-enriched chemical signature is caused by dehydration of the slab, or by interaction of released fluids/melts with the mantle wedge [16], [21], [22]. However, direct trace element analyses of deep natural subduction fluids in high to ultrahigh pressure rocks are not available yet, and would be of considerable relevance to shed light on the above uncertainties. In this frame, subduction of hydrated, serpentinized oceanic mantle is an important variable [23], because breakdown of antigorite serpentine to olivine+orthopyroxene+water delivers 10–13 wt% bulk H₂O down to depths of 200 km. Antigorite breakdown therefore produces the largest amount of subduction fluids [24], the main features and compositions of which are yet unexplored. Here we report a textural and analytical study of primary fluid+mineral inclusions within olivine+orthopyroxene rocks from Cerro del Almirez (Betic Cordillera, SE Spain) which derive from subduction zone breakdown of antigorite serpentine. We show that these inclusions represent remnants of the metamorphic fluid phase evolved at antigorite breakdown, and we document that this fluid phase had high contents of incompatible elements.

Section snippets

Petrologic outline of olivine-orthopyroxene rocks at Cerro del Almirez

The high pressure transition from antigorite serpentinite to enstatite-olivine rock has been mapped at Cerro del Almirez [25], in ultramafic rocks closely associated with eclogites and metarodingites, and interlayered with metapelites, metaevaporites, marbles and graphite-bearing micaschists [26], [27], [28]. In the ultramafic rocks, subduction zone metamorphism overprints previous stages of oceanic hydration and alteration [25], [26]. Ultramafites at Cerro del Almirez consist mainly of two

Fluid inclusion petrography

The metamorphic olivines of both serpentinite and spinifex-like rocks contain fluid and fluid+mineral inclusions respectively. The metamorphic olivine (X_Mg=0.93) and diopside of serpentinites locally contain primary to pseudosecondary two-phase (liquid+vapor) aqueous inclusions (Fig. 1A). These inclusions are confined to the antigorite serpentinites and are absent in the spinifex-like olivine: they are generally very small (5–10 μm) and occur either as isolated inclusions, or as core clusters

Analytical methods

Microthermometry of liquid+vapor inclusions in serpentinites was performed using a Linkam THMSG 600 heating–freezing stage calibrated on the melting point of pure CO₂ (−56.6°C) and H₂O (0.0°C), and on the critical point of pure water (371.4°C) in synthetic fluid inclusions. Error range is ±0.2°C for low-temperature measurements, and ±1.0°C at high temperature; heating rates were constantly kept at 0.1°C s⁻¹.

Scanning electron microscopy and analyses of solid phases in fluid+mineral inclusions in

Early aqueous inclusions

Microthermometry was performed on the aqueous liquid+vapor inclusions hosted in olivine and diopside from serpentinites (Table 1). Inclusions display initial melting temperatures between −23 and −43.4°C, indicating presence of NaCl, MgCl₂ and CaCl₂ as main chloride species. Final melting temperatures between −3.2 and −11.6°C indicate moderate fluid salinities of 5.2–15.57 wt% chloride concentrations, here expressed as NaCl equivalents [34]. Total fluid inclusion homogenization always occurred

The fluid produced at antigorite breakdown

Two fluid populations were trapped by the Almirez ultramafic rocks: (1) early H₂O-rich inclusions in serpentinites, dissolving up to 15 wt% chloride components and related to prograde subduction metamorphism in the antigorite stability field; (2) a later inclusion generation containing aqueous fluid+crystals in spinifex-like olivine derived from antigorite breakdown at peak pressure and temperature. Although early aqueous inclusions were involved in late-stage density readjustments, it appears

Supplementary data

Acknowledgements

This research has been supported by grants from the Italian MURST to the project ‘Mineral reactions and chemical exchanges induced by fluid and melt migration through the Mantle’ to G.B. Piccardo and R.V., from the Schweizerischer Nationalfonds No. 20-056867.99 to V.T. M.T.G.-P. and V.L.-S.V. acknowledge support by Project BTE2000-1489 and Grupo RNM-0145 (Junta de Andalucı́a). Constructive reviews by O. Navon, C. Manning and T. Elliott have considerably improved the paper. We thank A. Stucky

References (51)

T. Andersen et al.
N₂ and CO₂ in deep crustal fluids: evidence from the Caledonides of Norway
Chem. Geol.
(1993)
M. Scambelluri et al.
Deep fluids in subduction zones
Lithos
(2001)
M.T. McCulloch et al.
Geochemical and geodynamical constraints on subduction zone magmatism
Earth Planet. Sci. Lett.
(1991)
E. Stolper et al.
The role of water in the petrogenesis of Mariana through magmas
Earth Planet. Sci. Lett.
(1994)
Y. Tatsumi et al.
Chemical characteristics of fluid phase released in from a subducted lithosphere and origin of arc magmas: Evidence from high-pressure experiments and natural rocks
J. Volcanol. Geotherm. Res.
(1986)
J.M. Brenan et al.
Mineral-aqueous fluid partitioning of trace elements at 900°C and 2.0 GPa: Constraints on the trace element chemistry of mantle and deep crustal fluids
Geochim. Cosmochim. Acta
(1995)
R. Stalder et al.
Mineral-aqueous fluid partitioning of trace elements at 900–1200°C and 3.0–5.7 GPa: New experimental data for garnet, clinopyroxene, and rutile, and implications for mantle metasomatism
Geochim. Cosmochim. Acta
(1998)
T. Kogiso et al.
Trace element transport during dehydration processes in the subducted oceanic crust: 1. Experiments and implications for the origin of ocean island basalts
Earth Planet. Sci. Lett.
(1997)
E. Puga et al.
Petrology and metamorphic evolution of ultramafic rocks and dolerite dykes of the Betic Ophiolitic Association (Mulhacén Complex, SE Spain): Evidence of eo-Alpine subduction following and ocean-floor metasomatic process
Lithos
(1999)
R.P. Taylor et al.
In situ trace-element analysis of individual silicate melt inclusions by laser ablation microprobe–inductively coupled plasma–mass spectrometry (LAM–ICP–MS)
Geochim. Cosmochim. Acta
(1997)

M.E. Schneider et al.

Fluids in equilibrium with peridotite minerals: Implications for mantle metasomatism

Geochim. Cosmochim. Acta

(1986)

J.A. Mavrogenes et al.

Hydrogen movement into and out of fluid inclusions in quartz: Experimental evidence and geologic implications

Geochim. Cosmochim. Acta

(1994)

J. Hermann et al.

Experimental constraints on high pressure melting in subducted crust

Earth Planet. Sci. Lett.

(2001)

P. Philippot et al.

Chlorine cycling in the subducted oceanic lithosphere

Earth Planet. Sci. Lett.

(1998)

E. Bonatti et al.

Equatorial Mid-Atlantic Ridge: petrologic and Sr isotopic evidence for alpine-type rock assemblage

Earth Planet. Sci. Lett.

(1970)

D.A. Ionov et al.

Nb–Ta-rich mantle amphiboles and micas: Implications for subduction-related metasomatic trace element fractionations

Earth Planet. Sci. Lett.

(1995)

M. Tiepolo et al.

Nb and Ta incorporation and fractionation in titanian pargasite and kearsutite: crystal-chemical constraints and implications for natural systems

Earth Planet. Sci. Lett.

(2000)

Y. Tatsumi

Migration of fluid phases and genesis of basalt magmas in subduction zones

J. Geophys. Res.

(1989)

A.L. Boettcher et al.

Phase relations in the system NaAlSiO₄–SiO₂–H₂O

Am. J. Sci.

(1969)

I.D. Ryabchikov et al.

Experimental evidence at high pressure for potassic metasomatism in the mantle of the Earth

Am. Mineral.

(1980)

C.E. Manning, Effect of sediments on aqueous silica transport in subduction zones, in: G.E. Bebout, D.W. Scholl, S.H....

K.H. Bureau et al.

Complete miscibility between silicate melts and hydrous fluids in the upper mantle: experimental evidence and geochemical implications

Earth Planet. Sci. Lett.

(1999)

P. Philippot et al.

Trace element-rich brines in eclogitic veins: implications for fluid composition and transport during subduction

Contrib. Mineral. Petrol.

(1991)

M. Scambelluri et al.

High salinity fluid inclusions formed from recycled seawater in deeply subducted alpine serpentinite

Earth Planet. Sci. Lett.

(1997)

O. Navon et al.

Mantle-derived fluids in diamond micro-inclusions

Nature

(1988)

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Serpentinite-derived components play an important role in chemical cycling in subduction zones. However, it is difficult to identify recycled serpentinite in subarc mantle due to the overprinting of other slab components, and how serpentinite contributes to arc magmatism is poorly understood. Here we report Mo and Mg isotopic compositions of Early Paleozoic Qushiang arc mafic rocks in the East Kunlun orogen. The Qushiang mafic rocks have variable δ⁹⁸Mo values of −0.50‰ to 0.78% and δ²⁶Mg values of −0.31‰ to −0.05‰. These features, combining with arc-type trace element distribution patterns, enriched SrNd isotopes, and variable zircon HfO isotopes, suggest the incorporation of different subducting components in their mantle source. Some mafic rocks show high δ⁹⁸Mo values together with low Mo/Ce ratios and enriched SrNd isotopes, suggesting the contribution of subducted sediment (SSD)-derived melts. Additionally, light Mo isotopes are also identified in mafic rocks, which are closely related to depleted SrNd isotopes. These features are mainly inherited from the subducted dehydrated altered oceanic crust (SAOC)-derived melts. More importantly, the coexisting and significantly high δ²⁶Mg and δ⁹⁸Mo values of these rocks could not be explained by the SSD or SAOC components, but require serpentinite components in the subarc mantle source. Our study reveals that combined Mo and Mg isotopic studies are potential tools for tracing serpentinite recycling, and provides new insight into the mechanisms by which different subducting components contribute to arc magmatism.
Magnesium isotopic fractionation during post-serpentinization alteration: Implications for arc and oceanic Mg cycles
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In recent years, numerous geodynamic studies have concentrated on serpentinites and the serpentinization processes that occur within subduction zones. However, as an important host phase for Mg, whether Mg isotopic fractionation occurs during peridotite serpentinization is still unclear. In our study, we conducted high-precision Mg isotope analyses on serpentinized peridotites and forearc serpentinites from the Mariana subduction zone. Except for one sample affected by strong late weathering with clay formation, which had an anomalously high δ²⁶Mg value (0.01 ± 0.04‰), the moderately serpentinized peridotites (−0.24 ± 0.04‰, 2SD, n = 3) and deep (>40 mbsf) serpentinites (−0.24 ± 0.02‰, 2SD, n = 3) have Mg isotopic compositions consistent with mantle peridotites (−0.25 ± 0.04‰). Shallow serpentinites display slightly higher δ²⁶Mg values (−0.19 ± 0.04‰, 2SD, n = 15) than mantle peridotites, and these values tend to increase toward the seafloor. These high δ²⁶Mg values of forearc serpentinites cannot be attributed to serpentinizing fluid metasomatism and mantle wedge serpentinization processes, while post-serpentinization alteration involving brucite dissolution played a dominant role. Rayleigh fractionation simulations suggest that the heavy Mg isotopes are preferentially allocated to serpentinites during the post-serpentinization alteration process, where the calculated ∆²⁶Mg_{brucite-fluid} varies from 0.1‰ to 0.8‰. This study deduces that the process of serpentinite dehydration in the subarc mantle cannot significantly change the Mg isotopic composition of arc lavas because serpentinite itself has a mantle-like Mg isotopic composition. Moreover, the fluids released by the brucite dissolution process have a low δ²⁶Mg value, making an important contribution to the Mg budget of modern ocean seawater.
Did the Troodos ophiolite of Cyprus form during subduction inception?
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Understanding whether ophiolites formed during subduction inception or above long-lived subduction zones poses an outstanding challenge as modern examples of incipient subduction zones are rare. It is generally agreed that the Troodos ophiolite of Cyprus was formed at a spreading center above a subduction zone within the closing Neo-Tethys Ocean during the Late Cretaceous; beyond this, however, details of its geodynamic origin have been widely debated. To explore this problem, we examine further the analogy previously made between the Troodos ophiolite and the Mariana fore-arc, by here comparing extrusive rocks from the Troodos ophiolite to Pliocene-aged basalts from the southeastern Mariana fore-arc rifts (SEMFR), which formed by near-trench spreading above a highly dehydrating, mature subducted slab. The SEMFR basaltic glasses and olivine-hosted melt inclusions possess the highest markers of water-rich, slab-fluids (Rb/Th, Cs/Th, H₂O/Ce, Ba/Th) of any worldwide arc magmas, a signature that may be consistent with efficient slab dehydration within ∼90–100 km from the trench. Troodos ophiolite lavas, which have preserved fresh glasses, recorded similar, elevated slab-fluid markers to those of the SEMFR glasses. Although geodynamic comparisons cannot be direct, we nevertheless propose that the chemical similarities in these slab-fluid markers support the formation of the Troodos ophiolite above a highly dehydrating, shallow subducted plate in a near-trench setting. Unlike the southern Marianas, lack of juvenile arc volcanism and associated volcaniclastics, but presence of an extensive boninitic sheeted dyke complex with associated extrusive section, demonstrates that Troodos presumably developed by organized seafloor spreading in a near-trench setting, immediately following subduction inception of the Neo-Tethyan plate. As such, the chemical similarities between the SEMFR magmas and the Troodos ophiolite can only be used to provide constraints upon the geodynamic and the petrogenetic conditions of magma formation. Hence, deciphering precisely the original setting of ophiolites requires us to integrate thoroughly accurate geology and petrographic descriptions, along with comparison with modern analogues of infant subduction zones.
Barium isotope behavior during interaction between serpentinite-derived fluids and metamorphic rocks in the continental subduction zone
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Serpentinites in subduction zones are important fluid reservoirs for crust-mantle interaction and arc magma formation. The serpentinite-derived fluids can carry fluid-mobile elements such as Ba and potentially affect the geochemical composition of the metamorphic rocks in the subduction zones. However, the Ba isotope behavior during interaction between serpentinite-derived fluids and metamorphic rocks is still poorly understood. The whiteschists of the Dora-Maira Massif in the Western Alps have experienced fluid infiltration by serpentinite-derived fluids during deep subduction. Here we report the Ba isotope data of the whiteschist and its protolith metagranite to investigate the Ba isotope behavior during fluid-rock interaction. The metagranites, which have experienced ultrahigh-pressure metamorphism, have a small variation of δ¹³⁸Ba (−0.25 to 0.26‰), while the whiteschists display a large Ba isotope variation from −0.99‰ to 0.48‰. Such a large variation in whiteschists cannot be explained by chemical weathering, protolith heterogeneity, or kinetic effects. Instead, considering the negative correlations of δ¹³⁸Ba with Ba and other fluid-mobile elements (e.g., Sr, Cs, Zn, and Cu) and the geochemical composition features of serpentinite-derived fluids, the large Ba isotope variation in whiteschists is inferred to be induced by the interaction between serpentinite-derived fluid and metagranite during intense fluid infiltration. This is consistent with the observation that the whiteschists with low Ba contents tend to exhibit heavier Mg-Fe isotope compositions but lighter Li isotope compositions, which indicates that the related fluids were derived from the dehydration of mantle wedge serpentinite. The fluid infiltrating process is well explained by a numerical model with high fluid-rock ratios of 4 to 12. Our modeling further suggests that serpentinite-derived fluid has a distinctly higher δ¹³⁸Ba value than the depleted upper mantle. During fluid-rock interaction, heavy Ba isotopes prefer to be infiltrated into fluids with an apparent fractionation factor (Δ¹³⁸Ba_rock-fluid) of mostly −0.5‰ to −0.1‰ but can be down to −0.8‰ to −0.7‰ required for a few samples. A two-stage dehydration and metasomatism model at different depths can well explain the formation of Dora-Maira whiteschists. Whereas the Ba isotope composition of mantle wedge serpentinite is mainly dictated by crust-derived fluids from the subducting slab, an interaction between the serpentinite-derived fluids and the metagranite protolith resulted in a large Ba isotope variation of whiteschists. In case of a general involvement of serpentinites in subduction zones, serpentinite-derived fluids would significantly affect the Ba isotope compositions of subarc mantle peridotites and also arc lavas.
Epitactic magnetite growth in fluid inclusions as driving force for olivine oxidation coupled with hydrogen production at high pressure
2023, Chemical Geology
We disclose the crystallisation evolution of magnetite-bearing multiphase inclusions hosted in metamorphic olivine of harzburgites from the Cerro de Almirez (Betic Cordillera, Spain), which have been interpreted as final products of the trapping of the aqueous fluid produced by the subduction-zone dehydration of former serpentinites. The chemical exchange between inclusion fluid and olivine started soon after entrapment, at peak P-T conditions of 1.6–1.9 GPa and 650–700 °C, and continued during cooling along the retrograde path, with the coexistence of olivine and magnetite with orthopyroxene, chlorite, talc, antigorite and the destabilisation of olivine and antigorite into brucite and low-temperature chrysotile serpentine, as recognised by Raman analyses. Thermodynamic modelling and mass balance calculations demonstrate that the water component of fluid trapped in the inclusions of metamorphic olivine is expected to trigger the oxidation of the fayalite component in olivine, producing a mineral assemblage made of magnetite + orthopyroxene and molecular hydrogen, where the elemental redox processes are Fe²⁺ of olivine that oxidizes to Fe³⁺ and H⁺ of water that reduces to H₂. Probable H₂ trapped in the olivine host close to the inclusion wall has been detected by Raman spectroscopy. To corroborate its presence, we performed quantitative mass spectrometry analyses of the fluid phase trapped in the multiphase inclusions and of the olivine crystals hosting the inclusions, revealing that 1 kg of olivine matrix contains 6.2 ± 0.1 mmol of H₂. We identify two synergistic driving forces of the whole process, which has the peculiarity to produce molecular hydrogen at apparently oxidising conditions: i) the building up of an epitaxial interface between olivine and magnetite, and ii) the olivine ability to trap H₂ at high pressures. The olivine + H₂O system of these natural microreactors simulates a process of oxidation of the mantle olivine by water, with production of H₂ at pressure and fO₂ conditions (FMQ + 2) at which water reduction is considered an unlike mechanism.
Inheritance versus subduction-related δ<sup>11</sup>B signatures of eclogites: Insights from the Voltri Massif (Ligurian Western Alps, Italy)
2023, Chemical Geology
Trace element and isotopic compositions of exhumed high-pressure (P) mafic rocks are an important archive to investigate chemical processes in subduction zones. Here we report the B isotope (δ¹¹B) composition of eclogitic mafic rocks enclosed in high-P serpentinite from the Voltri Massif, Ligurian Alps (Italy). Combined with bulk δ¹⁸O values, ⁸⁷Sr/⁸⁶Sr ratios and trace element data, the δ¹¹B of eclogitic mafic rocks were investigated to test oceanic inheritance vs. subduction-related processes and to provide inferences on the timing of B uptake in eclogitic metagabbros.
Petrographic observations along with major and trace element data indicate that the eclogite facies mafic rocks derived from primitive Mg-Al-bearing gabbros (Erro-Tobbio eclogites) and differentiated Fe-Ti-bearing oxide gabbros (Vara eclogites). Metarodingite from Vara shares similar REE pattern to that of the Erro-Tobbio eclogites, suggesting a plagioclase-rich gabbroic protolith. The studied rocks show variable enrichments in fluids-mobile elements (e.g., Cs, Ba, Li, Sr; high Li/Y, B/Nb). Boron concentrations range between 2.3 and 7.6 ppm, with no significant differences among the different samples. Oxygen isotope compositions (1σ ± 0.1‰) for the Vara and the Erro-Tobbio eclogites range from +5.4 to +6.4‰ and from +3.1 to +5.3‰, respectively, whereas the ⁸⁷Sr/⁸⁶Sr ratios range between 0.7036 and 0.7042 for the Vara eclogites and from 0.7030 to 0.7034 for Erro-Tobbio metagabbros. The B isotope compositions for the Vara eclogites range between −3.2 to +0.9‰, which are in striking contrast with the positive δ¹¹B signatures of the Erro-Tobbio eclogitic metagabbros ranging from +4.3 to +8.9‰, the highest positive δ¹¹B signatures observed in eclogitic metagabbros so far. Metarodingite from Vara has a δ¹⁸O of +3.7‰ and ⁸⁷Sr/⁸⁶Sr of 0.7046 and a δ¹¹B value of +11.5‰.
We argue that the δ¹⁸O signatures and the ⁸⁷Sr/⁸⁶Sr ratios of metamafic rocks from the Voltri Unit mainly reflect inherited signatures from the seafloor, whereas subduction-related processes are mainly traced through δ¹¹B variations. Progressive B isotope fractionation due to dehydration processes during subduction is responsible for the dominantly negative δ¹¹B signatures of eclogites from the Vara area and elsewhere, whereas the positive δ¹¹B of the high-P metarodingite is compatible with an inherited oceanic signature, although interaction with fluids released by the surrounding serpentinites at peak conditions cannot be ruled out. We discuss three scenarios to explain the positive δ¹¹B imprint reported for the Erro-Tobbio eclogites: (i) inheritance of oceanic signatures, (ii) records of B isotope fractionation from an extreme ¹¹B-rich protolith, or (iii) interaction with ¹¹B-rich slab fluids derived from serpentinite hydration at high-P. Based on these scenarios, two potential implications of global relevance are presented: (1) the transfer of largely unmodified oceanic signatures up to eclogite facies conditions, and (2) the formation of newly (subduction-related) ¹¹B-rich reservoirs. We propose that the protolith composition of the mafic crust controls the development of hydrous phases at high-P thus enabling the preservation of high δ¹¹B signatures. This mechanism of chemical transfer may generate a ¹¹B-rich reservoir that, together with high-P serpentinites, may form positive δ¹¹B domains in the mantle.

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Incompatible element-rich fluids released by antigorite breakdown in deeply subducted mantle

Abstract

Introduction

Section snippets

Petrologic outline of olivine-orthopyroxene rocks at Cerro del Almirez

Fluid inclusion petrography

Analytical methods

Early aqueous inclusions

The fluid produced at antigorite breakdown

Supplementary data

Acknowledgements

Chem. Geol.

Lithos

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

J. Volcanol. Geotherm. Res.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Lithos

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Migration of fluid phases and genesis of basalt magmas in subduction zones

J. Geophys. Res.

Phase relations in the system NaAlSiO4–SiO2–H2O

Am. J. Sci.

Experimental evidence at high pressure for potassic metasomatism in the mantle of the Earth

Am. Mineral.

Complete miscibility between silicate melts and hydrous fluids in the upper mantle: experimental evidence and geochemical implications

Earth Planet. Sci. Lett.

Trace element-rich brines in eclogitic veins: implications for fluid composition and transport during subduction

Contrib. Mineral. Petrol.

High salinity fluid inclusions formed from recycled seawater in deeply subducted alpine serpentinite

Earth Planet. Sci. Lett.

Mantle-derived fluids in diamond micro-inclusions

Nature

Phase relations in the system NaAlSiO₄–SiO₂–H₂O