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Schwarzenbach EM, Dragovic B, Codillo EA, Streicher L, Scicchitano MR, Wiechert U, Klein F, Marschall HR, Scambelluri M. Mobilization of isotopically heavy sulfur during serpentinite subduction. SCIENCE ADVANCES 2024; 10:eadn0641. [PMID: 39110792 PMCID: PMC11305377 DOI: 10.1126/sciadv.adn0641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 06/28/2024] [Indexed: 08/10/2024]
Abstract
Primitive arc magmas are more oxidized and enriched in sulfur-34 (34S) compared to mid-ocean ridge basalts. These findings have been linked to the addition of slab-derived volatiles, particularly sulfate, to arc magmas. However, the oxidation state of sulfur in slab fluids and the mechanisms of sulfur transfer in the slab remain inconclusive. Juxtaposed serpentinite and eclogitic metagabbro from the Voltri Massif (Italy) provide evidence for sulfur mobilization and associated redox processes during infiltration of fluids. Using bulk rock and in situ δ34S measurements, combined with thermodynamic calculations, we document the transfer of bisulfide-dominated, 34S-enriched fluids in equilibrium with serpentinite into adjacent metagabbro. We argue that the process documented in this study is pervasive along the subduction interface and infer that subsequent melting of these reacted slab-mantle interface rocks could produce melts that display the characteristic oxygen fugacity and sulfur isotope signatures of arc magmas worldwide.
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Affiliation(s)
- Esther M. Schwarzenbach
- Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
- Department of Geosciences, University of Fribourg, Fribourg, Switzerland
| | - Besim Dragovic
- School of the Earth, Ocean & Environment, University of South Carolina, Columbia, SC, USA
| | - Emmanuel A. Codillo
- Massachusetts Institute of Technology-Woods Hole Oceanographic Institution Joint Program in Oceanography/Applied Ocean Science and Engineering, Woods Hole, MA, USA
- Earth and Planets Laboratory, Carnegie Institution for Science, Washington DC, USA
| | - Linus Streicher
- Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | | | - Uwe Wiechert
- Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany
| | - Frieder Klein
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Horst R. Marschall
- Institut für Geowissenschaften, Goethe Universität, Frankfurt am Main, Germany
| | - Marco Scambelluri
- Department of Earth, Environmental and Life Sciences, University of Genoa, Genoa, Italy
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2
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Holycross M, Cottrell E. Garnet crystallization does not drive oxidation at arcs. Science 2023; 380:506-509. [PMID: 37141374 DOI: 10.1126/science.ade3418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Arc magmas, the building blocks of continental crust, are depleted in total iron (Fe), have higher ratios of oxidized Fe to total Fe (Fe3+/∑Fe), and record higher oxygen fugacities (fO2's) compared with magmas erupted at mid-ocean ridges. Garnet crystallization could explain these observations if garnet removes substantial amounts of Fe2+, but not Fe3+, from magma, yet this model for continental crust generation has never been tested experimentally. Analysis of garnets and melts in laboratory experiments show that the compatibilities of Fe2+ and Fe3+ in garnet are of similar magnitudes. Our results indicate that fractional crystallization of garnet-bearing cumulates will remove 20% of total Fe from primary arc basalts but negligibly alter the Fe3+/∑Fe ratio and fO2 of the melt. Garnet crystallization is unlikely to be responsible for the relatively oxidized nature of basaltic arc magmas or the Fe-depletion trend observed in continental crust.
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Affiliation(s)
- Megan Holycross
- Cornell University, Ithaca, NY 14853, USA
- National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Elizabeth Cottrell
- National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
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3
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Decoupling of inorganic and organic carbon during slab mantle devolatilisation. Nat Commun 2022; 13:308. [PMID: 35031609 PMCID: PMC8760304 DOI: 10.1038/s41467-022-27970-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 12/10/2021] [Indexed: 11/25/2022] Open
Abstract
Serpentinites are an important sink for both inorganic and organic carbon, and their behavior during subduction is thought to play a fundamental role in the global cycling of carbon. Here we show that fluid-derived veins are preserved within the Zermatt-Saas ultra-high pressure serpentinites providing key evidence for carbonate mobility during serpentinite devolatilisation. We show through the O, C, and Sr isotope analyses of vein minerals and the host serpentinites that about 90% of the meta-serpentinite inorganic carbon is remobilized during slab devolatilisation. In contrast, graphite-like carbonaceous compounds remain trapped within the host rock as inclusions within metamorphic olivine while the bulk elemental and isotope composition of organic carbon remains relatively unchanged during the subduction process. This shows a decoupling behavior of carbon during serpentinite dehydration in subduction zones. This process will therefore facilitate the transfer of inorganic carbon to the mantle wedge and the preferential slab sequestration of organic carbon en route to the deep mantle. Hydrated mantle rocks store a significant amount of organic and inorganic carbon, impacting the geological cycle. During subduction the carbonate return to the upper plate while organic carbon remains trapped to be recycled in the deep earth.
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4
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Zhang Y, Gazel E, Gaetani GA, Klein F. Serpentinite-derived slab fluids control the oxidation state of the subarc mantle. SCIENCE ADVANCES 2021; 7:eabj2515. [PMID: 34826248 PMCID: PMC8626075 DOI: 10.1126/sciadv.abj2515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 10/07/2021] [Indexed: 06/13/2023]
Abstract
Recent geochemical evidence confirms the oxidized nature of arc magmas, but the underlying processes that regulate the redox state of the subarc mantle remain yet to be determined. We established a link between deep subduction-related fluids derived from dehydration of serpentinite ± altered oceanic crust (AOC) using B isotopes and B/Nb as fluid proxies, and the oxidized nature of arc magmas as indicated by Cu enrichment during magma evolution and V/Yb. Our results suggest that arc magmas derived from source regions influenced by a greater serpentinite (±AOC) fluid component record higher oxygen fugacity. The incorporation of this component into the subarc mantle is controlled by the subduction system’s thermodynamic conditions and geometry. Our results suggest that the redox state of the subarc mantle is not homogeneous globally: Primitive arc magmas associated with flat, warm subduction are less oxidized overall than those generated in steep, cold subduction zones.
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Affiliation(s)
- Yuxiang Zhang
- Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong, China
- Laboratory for Marine Mineral Resources, Qingdao Pilot National Laboratory for Marine Science and Technology, Qingdao, Shandong, China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, Shandong, China
| | - Esteban Gazel
- Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY, USA
| | - Glenn A. Gaetani
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Frieder Klein
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
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5
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Insights on the deep carbon cycle from the electrical conductivity of carbon-bearing aqueous fluids. Sci Rep 2021; 11:3745. [PMID: 33580092 PMCID: PMC7881151 DOI: 10.1038/s41598-021-82174-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 01/15/2021] [Indexed: 01/30/2023] Open
Abstract
The dehydration and decarbonation in the subducting slab are intricately related and the knowledge of the physical properties of the resulting C-H-O fluid is crucial to interpret the petrological, geochemical, and geophysical processes associated with subduction zones. In this study, we investigate the C-H-O fluid released during the progressive devolatilization of carbonate-bearing serpentine-polymorph chrysotile, with in situ electrical conductivity measurements at high pressures and temperatures. The C-H-O fluid produced by carbonated chrysotile exhibits high electrical conductivity compared to carbon-free aqueous fluids and can be an excellent indicator of the migration of carbon in subduction zones. The crystallization of diamond and graphite indicates that the oxidized C-H-O fluids are responsible for the recycling of carbon in the wedge mantle. The carbonate and chrysotile bearing assemblages stabilize dolomite during the devolatilization process. This unique dolomite forming mechanism in chrysotile in subduction slabs may facilitate the transport of carbon into the deep mantle.
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6
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Palyanov YN, Borzdov YM, Sokol AG, Bataleva YV, Kupriyanov IN, Reutsky VN, Wiedenbeck M, Sobolev NV. Diamond formation in an electric field under deep Earth conditions. SCIENCE ADVANCES 2021; 7:7/4/eabb4644. [PMID: 33523914 PMCID: PMC7817093 DOI: 10.1126/sciadv.abb4644] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 12/01/2020] [Indexed: 06/02/2023]
Abstract
Most natural diamonds are formed in Earth's lithospheric mantle; however, the exact mechanisms behind their genesis remain debated. Given the occurrence of electrochemical processes in Earth's mantle and the high electrical conductivity of mantle melts and fluids, we have developed a model whereby localized electric fields play a central role in diamond formation. Here, we experimentally demonstrate a diamond crystallization mechanism that operates under lithospheric mantle pressure-temperature conditions (6.3 and 7.5 gigapascals; 1300° to 1600°C) through the action of an electric potential applied across carbonate or carbonate-silicate melts. In this process, the carbonate-rich melt acts as both the carbon source and the crystallization medium for diamond, which forms in assemblage with mantle minerals near the cathode. Our results clearly demonstrate that electric fields should be considered a key additional factor influencing diamond crystallization, mantle mineral-forming processes, carbon isotope fractionation, and the global carbon cycle.
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Affiliation(s)
- Yuri N Palyanov
- V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Academician Koptyug Ave., 3, Novosibirsk 630090, Russian Federation.
- Novosibirsk State University, Pirogova str., 2, Novosibirsk 630090, Russian Federation
| | - Yuri M Borzdov
- V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Academician Koptyug Ave., 3, Novosibirsk 630090, Russian Federation
| | - Alexander G Sokol
- V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Academician Koptyug Ave., 3, Novosibirsk 630090, Russian Federation
| | - Yuliya V Bataleva
- V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Academician Koptyug Ave., 3, Novosibirsk 630090, Russian Federation
| | - Igor N Kupriyanov
- V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Academician Koptyug Ave., 3, Novosibirsk 630090, Russian Federation
| | - Vadim N Reutsky
- V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Academician Koptyug Ave., 3, Novosibirsk 630090, Russian Federation
| | | | - Nikolay V Sobolev
- V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Academician Koptyug Ave., 3, Novosibirsk 630090, Russian Federation
- Novosibirsk State University, Pirogova str., 2, Novosibirsk 630090, Russian Federation
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7
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Subduction hides high-pressure sources of energy that may feed the deep subsurface biosphere. Nat Commun 2020; 11:3880. [PMID: 32759942 PMCID: PMC7406650 DOI: 10.1038/s41467-020-17342-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 06/25/2020] [Indexed: 11/10/2022] Open
Abstract
Geological sources of H2 and abiotic CH4 have had a critical role in the evolution of our planet and the development of life and sustainability of the deep subsurface biosphere. Yet the origins of these sources are largely unconstrained. Hydration of mantle rocks, or serpentinization, is widely recognized to produce H2 and favour the abiotic genesis of CH4 in shallow settings. However, deeper sources of H2 and abiotic CH4 are missing from current models, which mainly invoke more oxidized fluids at convergent margins. Here we combine data from exhumed subduction zone high-pressure rocks and thermodynamic modelling to show that deep serpentinization (40–80 km) generates significant amounts of H2 and abiotic CH4, as well as H2S and NH3. Our results suggest that subduction, worldwide, hosts large sources of deep H2 and abiotic CH4, potentially providing energy to the overlying subsurface biosphere in the forearc regions of convergent margins. Geological sources of H2 and abiotic CH4 have had a critical role in the evolution of life and sustainability of the deep subsurface biosphere, yet the origins of these sources remain largely unconstrained. Here the authors show that deep serpentinization (40–80 km) during subduction generates significant amounts of H2 and abiotic CH4, potentially providing energy to the overlying subsurface biosphere.
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8
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Piccoli F, Hermann J, Pettke T, Connolly JAD, Kempf ED, Vieira Duarte JF. Subducting serpentinites release reduced, not oxidized, aqueous fluids. Sci Rep 2019; 9:19573. [PMID: 31862932 PMCID: PMC6925189 DOI: 10.1038/s41598-019-55944-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 12/05/2019] [Indexed: 11/09/2022] Open
Abstract
The observation that primitive arc magmas are more oxidized than mid-ocean-ridge basalts has led to the paradigm that slab-derived fluids carry SO2 and CO2 that metasomatize and oxidize the sub-arc mantle wedge. We combine petrography and thermodynamic modelling to quantify the oxygen fugacity (fO2) and speciation of the fluids generated by serpentinite dehydration during subduction. Silicate-magnetite assemblages maintain fO2 conditions similar to the quartz-fayalite-magnetite (QFM) buffer at fore-arc conditions. Sulphides are stable under such conditions and aqueous fluids contain minor S. At sub-arc depth, dehydration occurs under more reducing conditions producing aqueous fluids carrying H2S. This finding brings into question current models in which serpentinite-derived fluids are the cause of oxidized arc magmatism and has major implications for the global volatile cycle, as well as for redox processes controlling subduction zone geodynamics.
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Affiliation(s)
- F Piccoli
- University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland.
| | - J Hermann
- University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland
| | - T Pettke
- University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland
| | - J A D Connolly
- Department of Earth Science, Swiss Federal Institute of Technology, Zurich, Switzerland
| | - E D Kempf
- University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland
| | - J F Vieira Duarte
- University of Bern, Institute of Geological Sciences, Balzerstrasse 1+3, 3012, Bern, Switzerland
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9
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Molybdenum systematics of subducted crust record reactive fluid flow from underlying slab serpentine dehydration. Nat Commun 2019; 10:4773. [PMID: 31636258 PMCID: PMC6803652 DOI: 10.1038/s41467-019-12696-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 09/19/2019] [Indexed: 11/13/2022] Open
Abstract
Fluids liberated from subducting slabs are critical in global geochemical cycles. We investigate the behaviour of Mo during slab dehydration using two suites of exhumed fragments of subducted, oceanic lithosphere. Our samples display a positive correlation of δ98/95MoNIST 3134 with Mo/Ce, from compositions close to typical mantle (−0.2‰ and 0.03, respectively) to very low values of both δ98/95MoNIST 3134 (−1‰) and Mo/Ce (0.002). Together with new, experimental data, we show that molybdenum isotopic fractionation is driven by preference of heavier Mo isotopes for a fluid phase over rutile, the dominant mineral host of Mo in eclogites. Moreover, the strongly perturbed δ98/95MoNIST 3134 and Mo/Ce of our samples requires that they experienced a large flux of oxidised fluid. This is consistent with channelised, reactive fluid flow through the subducted crust, following dehydration of the underlying, serpentinised slab mantle. The high δ98/95MoNIST 3134 of some arc lavas is the complement to this process. Fluid liberation and migration from subducted oceanic slabs play a critical role in arc magmatism but the volume and origin of the released fluids is unclear and difficult to trace. Here, the authors use Molybdenum isotope ratios to tackle these problems.
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10
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Eickenbusch P, Takai K, Sissman O, Suzuki S, Menzies C, Sakai S, Sansjofre P, Tasumi E, Bernasconi SM, Glombitza C, Jørgensen BB, Morono Y, Lever MA. Origin of Short-Chain Organic Acids in Serpentinite Mud Volcanoes of the Mariana Convergent Margin. Front Microbiol 2019; 10:1729. [PMID: 31404165 PMCID: PMC6677109 DOI: 10.3389/fmicb.2019.01729] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 07/12/2019] [Indexed: 11/17/2022] Open
Abstract
Serpentinitic systems are potential habitats for microbial life due to frequently high concentrations of microbial energy substrates, such as hydrogen (H2), methane (CH4), and short-chain organic acids (SCOAs). Yet, many serpentinitic systems are also physiologically challenging environments due to highly alkaline conditions (pH > 10) and elevated temperatures (>80°C). To elucidate the possibility of microbial life in deep serpentinitic crustal environments, International Ocean Discovery Program (IODP) Expedition 366 drilled into the Yinazao, Fantangisña, and Asùt Tesoru serpentinite mud volcanoes on the Mariana Forearc. These mud volcanoes differ in temperature (80, 150, 250°C, respectively) of the underlying subducting slab, and in the porewater pH (11.0, 11.2, 12.5, respectively) of the serpentinite mud. Increases in formate and acetate concentrations across the three mud volcanoes, which are positively correlated with temperature in the subducting slab and coincide with strong increases in H2 concentrations, indicate a serpentinization-related origin. Thermodynamic calculations suggest that formate is produced by equilibrium reactions with dissolved inorganic carbon (DIC) + H2, and that equilibration continues during fluid ascent at temperatures below 80°C. By contrast, the mechanism(s) of acetate production are not clear. Besides formate, acetate, and H2 data, we present concentrations of other SCOAs, methane, carbon monoxide, and sulfate, δ13C-data on bulk carbon pools, and microbial cell counts. Even though calculations indicate a wide range of microbial catabolic reactions to be thermodynamically favorable, concentration profiles of potential energy substrates, and very low cell numbers suggest that microbial life is scarce or absent. We discuss the potential roles of temperature, pH, pressure, and dispersal in limiting the occurrence of microbial life in deep serpentinitic environments.
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Affiliation(s)
- Philip Eickenbusch
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Zurich, Switzerland
| | - Ken Takai
- SUGAR Program, Institute for Extra-Cutting-Edge Science and Technology Avant-Garde Research (X-star), Japan Agency for Marine-Earth Science Technology, Yokosuka, Japan
| | | | - Shino Suzuki
- Geomicrobiology Research Group, Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan
| | - Catriona Menzies
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, United Kingdom.,Department of Geology and Petroleum Geology, University of Aberdeen, Aberdeen, United Kingdom
| | - Sanae Sakai
- SUGAR Program, Institute for Extra-Cutting-Edge Science and Technology Avant-Garde Research (X-star), Japan Agency for Marine-Earth Science Technology, Yokosuka, Japan
| | - Pierre Sansjofre
- Laboratoire Géosciences Océan UMR 6538, Université de Bretagne Occidentale, Brest, France
| | - Eiji Tasumi
- SUGAR Program, Institute for Extra-Cutting-Edge Science and Technology Avant-Garde Research (X-star), Japan Agency for Marine-Earth Science Technology, Yokosuka, Japan
| | | | - Clemens Glombitza
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Zurich, Switzerland.,NASA Ames Research Center, Moffett Field, CA, United States
| | - Bo Barker Jørgensen
- Department of Bioscience, Center for Geomicrobiology, Aarhus University, Aarhus, Denmark
| | - Yuki Morono
- Geomicrobiology Research Group, Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Kochi, Japan
| | - Mark Alexander Lever
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Zurich, Switzerland
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11
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Beaudry P, Longpré MA, Economos R, Wing BA, Bui TH, Stix J. Degassing-induced fractionation of multiple sulphur isotopes unveils post-Archaean recycled oceanic crust signal in hotspot lava. Nat Commun 2018; 9:5093. [PMID: 30504764 PMCID: PMC6269480 DOI: 10.1038/s41467-018-07527-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 10/28/2018] [Indexed: 11/09/2022] Open
Abstract
Mantle source regions feeding hotspot volcanoes likely contain recycled subducted material. Anomalous sulphur (S) isotope signatures in hotspot lavas have tied ancient surface S to this deep geological cycle, but their potential modification by shallow magmatic processes has generally been overlooked. Here we present S isotope measurements in magmatic sulphides, silicate melt inclusions and matrix glasses from the recent eruption of a hotspot volcano at El Hierro, Canary Islands, which show that degassing induces strongly negative δ34S fractionation in both silicate and sulphide melts. Our results reflect the complex interplay among redox conditions, S speciation and degassing. The isotopic fractionation is mass dependent (Δ33S = 0‰), thus lacking evidence for the recycled Archaean crust signal recently identified at other hotspot volcanoes. However, the source has an enriched signature (δ34S ~ + 3‰), which supports the presence of younger 34S-rich recycled oceanic material in the Canary Island mantle plume. Mantle-sourced magmas erupted at hotspot volcanoes can provide clues to the sulphur cycle over geological timescales. In this work, sulphur isotopes were analysed in crystal-hosted inclusions entrapped at depth, and reveal the presence of post-Archaean recycled material in the Canary Island mantle.
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Affiliation(s)
- Patrick Beaudry
- School of Earth and Environmental Sciences, Queens College, City University of New York, Queens, NY, 11367, USA. .,Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
| | - Marc-Antoine Longpré
- School of Earth and Environmental Sciences, Queens College, City University of New York, Queens, NY, 11367, USA.,Earth and Environmental Sciences, The Graduate Center, City University of New York, New York, NY, 10016, USA
| | - Rita Economos
- Department of Earth Sciences, Southern Methodist University, Dallas, TX, 75275, USA
| | - Boswell A Wing
- Department of Earth and Planetary Sciences, McGill University, Montréal, QC, H3A 0E8, Canada.,Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, 80309, USA
| | - Thi Hao Bui
- Department of Earth and Planetary Sciences, McGill University, Montréal, QC, H3A 0E8, Canada
| | - John Stix
- Department of Earth and Planetary Sciences, McGill University, Montréal, QC, H3A 0E8, Canada
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12
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Rielli A, Tomkins AG, Nebel O, Brugger J, Etschmann B, Paterson D. Garnet peridotites reveal spatial and temporal changes in the oxidation potential of subduction. Sci Rep 2018; 8:16411. [PMID: 30401916 PMCID: PMC6219559 DOI: 10.1038/s41598-018-34669-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 10/17/2018] [Indexed: 11/09/2022] Open
Abstract
Changes in the oxygen fugacity (fO2) of the Earth's mantle have been proposed to control the spatial and temporal distribution of arc-related ore deposits, and possibly reflect the evolution of the atmosphere over billions of years. Thermodynamic calculations and natural evidence indicate that fluids released from subducting slabs can oxidise the mantle, but whether their oxidation potential varied in space and time remains controversial. Here, we use garnet peridotites from western Norway to show that there is a linear decrease in maximum fO2 with increasing depth in the mantle wedge. We ascribe this relation to changes in the speciation of sulfur released in slab fluids, with sulfate, controlling maximum oxidation, preferentially released at shallow depths. Even though the amount of sulfate in the Precambrian oceans, and thus in subducted lithologies, is thought to have been dramatically lower than during the Phanerozoic, garnet peridotites metasomatised during these two periods have a comparable fO2 range. This opens to the possibility that an oxidised mantle with fO2 similar to modern-day values has existed since the Proterozoic and possibly earlier. Consequently, early magmas derived from partial melting of metasomatised mantle may have had suitable fO2 to generate porphyry Cu-Au and iron-oxide Cu-Au deposits.
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Affiliation(s)
- Andrea Rielli
- Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126, Pisa, Italy.
| | - Andrew G Tomkins
- School of Earth, Atmosphere and the Environment, Monash University, Melbourne, Victoria, 3800, Australia
| | - Oliver Nebel
- School of Earth, Atmosphere and the Environment, Monash University, Melbourne, Victoria, 3800, Australia
| | - Joël Brugger
- School of Earth, Atmosphere and the Environment, Monash University, Melbourne, Victoria, 3800, Australia
| | - Barbara Etschmann
- School of Earth, Atmosphere and the Environment, Monash University, Melbourne, Victoria, 3800, Australia
| | - David Paterson
- Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria, 3168, Australia
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