Serpentinite-derived slab fluids control the oxidation state of the subarc mantle

Zhang, Yuxiang; Gazel, Esteban; Gaetani, G. A.; Klein, Frieder

doi:10.1126/sciadv.abj2515

Cited by 34 publications

(11 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, owing to the strong oxidizing capacity of sulfate (Benard et al., 2018; Debret & Sverjensky, 2017; Evans & Tomkins, 2011), the release of sulfate‐rich fluids during serpentinite dehydration and their subsequent infiltration into the overlying mantle wedge may be essential for the oxidation of the sub‐arc mantle. In this context, primitive arc magmas in warm subduction zones are likely less oxidized overall than those in cold subduction zones (Zhang, Gazel, et al., 2021).…”

Section: Discussionmentioning

confidence: 99%

“…Arc magmas from cold subduction zones in the western Pacific are systematically enriched in Cu at intermediate MgO concentrations, indicating that their primitive magmas were initially sulfide undersaturated (Chiaradia, 2014; Jenner et al., 2010; Lee et al., 2012) and likely oxidized (Kelley & Cottrell, 2009; Zhang, Gazel, et al., 2021). Moreover, these arc magmas are characterized by high B/Nb ratios and heavy B isotopic compositions, suggesting that serpentinite‐derived fluids affected their mantle sources (De Hoog & Savov, 2018; Zhang, Gazel, et al., 2021), which may control their oxidized nature (Zhang, Gazel, et al., 2021). These characteristics make western Pacific subduction zones ideal for investigating whether the dehydration of subducted serpentinite releases oxidized sulfate‐rich fluids into the sub‐arc mantle.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Heavy Copper Isotopes in Arc‐Related Lavas From Cold Subduction Zones Uncover a Sub‐Arc Mantle Metasomatized by Serpentinite‐Derived Sulfate‐Rich Fluids

Chen

Tamehe

et al. 2022

JGR Solid Earth

Self Cite

View full text Add to dashboard Cite

Serpentinite dehydration during subduction releases fluids into the sub‐arc mantle, yet the oxidizing capability of these fluids remains controversial. Here, redox‐sensitive Cu isotopes and in situ S isotopes of magmatic sulfides in fresh lavas from three subduction zones in the western Pacific were analyzed to determine the speciation of multi‐valence elements in the serpentinite‐derived fluids. Notably, the basaltic lavas from the Mariana Arc, eastern Manus Basin, and southern Okinawa Trough have isotopically heavy Cu (δ65Cu = +0.26 to +0.67‰) compared to the mantle‐like δ65Cu values of the middle Okinawa Trough and Mariana Trough basalts (+0.11 to +0.14‰). In addition, positive correlations between δ65Cu and slab fluid indicators (e.g., B/Nb, Ba/Th, and Ba/La) combined with positive δ34S values (∼+4‰) of magmatic sulfides in the Mariana Arc lavas, suggest that fluids with isotopically heavy Cu and S metasomatized their mantle sources. Theoretically, the normalCnormalu2+−normalSnormalO42– ${\mathrm{C}\mathrm{u}}^{2+}-{\mathrm{S}\mathrm{O}}_{4}^{2\mbox{--}}$ bearing fluids released by serpentinite dehydration have extremely heavy Cu and S isotope compositions. Consequently, the sulfate‐rich fluids infiltration into the sub‐arc mantle produces heavy Cu and S isotopes in arc‐related magmas. Comparatively, sulfate‐rich fluids are absent at back‐arc depths due to the complete breakdown of serpentine minerals during the early stages of subduction, which results in the mid‐ocean ridge basalts‐like δ65Cu and δ34S values (∼−1‰) observed in the middle Okinawa Trough and Mariana Trough basalts. Therefore, heavy Cu isotopes in arc‐related magmas uncover that the sub‐arc mantle was metasomatized by serpentinite‐derived sulfate‐rich (oxidizing) fluids, which accounts for the oxidized nature of arc magmas in cold subduction zones.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heavy Copper Isotopes in Arc‐Related Lavas From Cold Subduction Zones Uncover a Sub‐Arc Mantle Metasomatized by Serpentinite‐Derived Sulfate‐Rich Fluids

Chen

Tamehe

et al. 2022

JGR Solid Earth

Self Cite

View full text Add to dashboard Cite

show abstract

“…The increasingly hydrous nature of magmas produced at NLV correlate with a sustained increase in oxygen fugacity (Figure 8). This association of fluid signature and oxidation state of magmas has been observed in regional comparisons among arcs through different proxies and approximations (Kelley and Cottrell, 2009;Evans et al, 2012;Zhang et al, 2021), although there is little consensus on the nature of the processes that link hydrous fluids to oxidation state. Proposed mechanisms range from direct supply of Fe 3+ and other oxidizing agents from the oceanic crust and sediments to the asthenospheric mantle (Mungall, 2002), to H 2 O dissociation into O 2 and H + , with either degassing or capture of the latter into mineral phases, to preferential removal of Fe 2+ by fractionating phases.…”

Section: Origin Of Mafic Magmasmentioning

confidence: 91%

Magma and Mineral Composition Response to Increasing Slab-Derived Fluid Flux: Nevado de Longaví Volcano, Southern Chilean Andes

et al. 2022

View full text Add to dashboard Cite

Nevado de Longaví volcano (NLV), in the Southern-Central Chilean Andes, has erupted during the Holocene magmas with compositions that are in several ways atypical for the region. These characteristics include elevated La/Yb ratios in evolved magmas, in an area of only moderately thick crust, coupled with low concentrations of K, Th, and other incompatible elements and elevated ratios of fluid-mobile (B, Cs, Li, Sb) to fluid-immobile elements. Samples have an unusual mafic mineralogy dominated by amphibole. The petrology of the Holocene products of NLV have been related to the influence of an oceanic transform fault (Mocha Fracture Zone; MFZ) that supplies the mantle wedge with unusually high amounts of fluids via dehydration of serpentinite bodies hosted by the subducted oceanic lithosphere. Because the trace of this transform fault is oblique to the convergence vector, its position along the arc has varied through time, as has the magnitude of its influence on the nature of the magmas erupted at NLV. The whole-rock and mineral chemistry of volcanic products from NLV, tied to a simplified stratigraphy, documents the secular changes in the magmatic system as the oceanic fault approached its current position. Magmas erupted ∼1–0.6 Ma are relatively low in water (as inferred from mineralogy and chemical proxies) and reduced (NNO-1 to NNO+0.5), and are similar to compositions found in neighboring volcanoes. From 0.25 Ma to the present, magmas are water-rich and oxidized (NNO-0.5 to NNO+1.7). In the intervening 0.6–0.25 Ma, mafic magmatism acquired a transient crustal component, which we identify as subducted sediment melts, on the basis of radiogenic isotopes and Pb, Th, and U abundances. Fluids released from serpentinite in the fracture zone were rich in Li, B, Sb, Cs and Ba, but not in K, Th, U and Sr. The fluid addition led to enhanced melting, particularly hydrous magmas that stabilized amphibole early during fractionation, higher oxygen fugacities, and distinctive chemical compositions.

show abstract

“…However, there is a continuing debate on whether the redox state of fluid speciation is oxidized or reduced. Most previous studies on fluid inclusions in highpressure (HP) metamorphic rocks, experiments, isotope evidence, and thermodynamic calculations suggested that the slab-derived fluids are highly oxidized (Scambelluri and Philippot, 2001;Frezzotti et al, 2011;Frezzotti and Ferrando, 2015;Pons et al, 2016;Rielli et al, 2017;Gerrits et al, 2019;Walters et al, 2020a;Iacovino et al, 2020;Maurice et al, 2020;Zhang et al, 2021;Ague et al, 2022), whereas some argued for rather reduced fluids (Song et al, 2009;Frezzotti and Ferrando, 2015;Brovarone et al, 2017;Tao et al, 2018;Chen et al, 2019;Piccoli et al, 2019;. As a result, the redox state of slab-derived fluids is proposed to have a broad fO 2 range varying from △FMQ+5 to △FMQ-4 (e.g., Evans and Powell, 2015;Debret and Sverjensky, 2017;Piccoli et al, 2019;Walters et al, 2020b;Wang et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Redox species and oxygen fugacity of slab-derived fluids: Implications for mantle oxidation and deep carbon-sulfur cycling

Chen

et al. 2022

Front. Earth Sci.

View full text Add to dashboard Cite

The generation and migration of slab-derived fluids modulate subduction zone seismicity, arc magmatism, and deep volatile cycling. However, the redox species and oxygen fugacity (fO2) (hereafter expressed as log units relative to the fayalite–magnetite–quartz buffer, △FMQ) of slab-derived fluids are highly debated. Here we conducted phase equilibria modeling on altered oceanic crust (AOC) and serpentinites along typical subduction geotherms in the C-S-bearing system over a pressure range of 0.5–6 GPa. With the averaged compositions of AOC and serpentinite, our calculated results show that oxidized carbon-sulfur species dominate slab-derived fluids during slab subduction. As a result, slab-derived fluids are highly oxidized and at or above the typical △FMQ values of arc magmas at forearc to subarc depths. The predicted oxidized carbon and sulfur species are compatible with natural observations in fluid inclusions from many oceanic HP metamorphic rocks. More importantly, it is revealed that, the redox state of slab-derived fluids is primarily controlled by the redox budget (RB) of the slab prior to subduction. Subduction-zone thermal structure, however, only exerts a minor influence on the slab-derived fluid fO2, which is supported by the similar fO2 ranges in arc lavas from cold and hot subduction zones. Our models further show that, if an open system is assumed, most of carbon (>70%) and sulfur (>50%) in cold subducted AOC and serpentinite would be lost at subarc depths. Small amounts of carbon and sulfur could be transported into the deeper mantle via closed-system subduction and open-system cold subduction, supplying the source materials for volatile-rich intraplate magmas and superdeep diamonds.

show abstract

Serpentinite-derived slab fluids control the oxidation state of the subarc mantle

Cited by 34 publications

References 71 publications

Heavy Copper Isotopes in Arc‐Related Lavas From Cold Subduction Zones Uncover a Sub‐Arc Mantle Metasomatized by Serpentinite‐Derived Sulfate‐Rich Fluids

Heavy Copper Isotopes in Arc‐Related Lavas From Cold Subduction Zones Uncover a Sub‐Arc Mantle Metasomatized by Serpentinite‐Derived Sulfate‐Rich Fluids

Magma and Mineral Composition Response to Increasing Slab-Derived Fluid Flux: Nevado de Longaví Volcano, Southern Chilean Andes

Redox species and oxygen fugacity of slab-derived fluids: Implications for mantle oxidation and deep carbon-sulfur cycling

Contact Info

Product

Resources

About