Hydrogen isotopes in Mariana arc melt inclusions: Implications for subduction dehydration and the deep-Earth water cycle

Shaw, A. M.; Hauri, E. H.; Fischer, Tobias P.; Hilton, David R.; Kelley, K. A.

doi:10.1016/j.epsl.2008.08.015

Cited by 173 publications

(161 citation statements)

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“…The black line is the Petrolog3 fractionation model, using a starting composition equal to Agri04-05 and fractionating olivine, clinopyroxene, and plagioclase at 1 kbar, using mineral melt models of Roeder and Emslie (1970) and Danyushevsky (2001), treating Fe 2+ /Fe 3+ as a closed system (Danyushevsky & Plechov, 2011). Shaw et al (2008), respectively. Black circles are whole rock data for lavas collected at Pagan volcano, compiled using GeoROC (Electronic appendix J).…”

Section: Sensitivity Test Of Primary Melt Model Resultsmentioning

confidence: 99%

“…Mineral melt models of Roeder and Emslie (1970), Danyushevsky (2001), and Ariskin and Barmina (1999) were used, treating Fe 2+ /Fe 3+ as a closed system (Danyushevsky & Plechov, 2011 Kelley et al (2010) and Shaw et al (2008), respectively. The white circles are whole rock data for tephras collected at Alamagan volcano (Plank, unpublished data).…”

Section: Sensitivity Test Of Primary Melt Model Resultsmentioning

confidence: 99%

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Variations in Fe3+/∑Fe of Mariana Arc Basalts and Mantle Wedge fO2

Brounce

Kelley

Cottrell

2014

Journal of Petrology

221

145

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When collecting Fe-µ-XANES spectra on olivine-hosted melt inclusions, it is important to avoid hitting the olivine crystal with the beam during analysis. Olivine contains several weight percent of Fe 2+ and even a very small amount of olivine interference will "contaminate" the pre-edge structure of Fe-µ-XANES spectra collected for melt inclusions and bias the result towards more reduced values. The region of XANES spectra at higher energies than the Fe-Kα absorption edge contains information related to Fe-coordination and can be used to distinguish glass structure (random and on average, uncoordinated) from olivine signal (strong coordination, Fig. A1). All melt inclusion and seafloor glass spectra were visually inspected and compared to spectra taken on San Carlos olivine and standard glasses from Cottrell et al. (2009) in order to screen for crystal contamination. Any spectra demonstrating signs of spectral features similar to those observed in San Carlos olivine were not considered in this study and additional spectra were collected to accommodate for this elimination. Model liquid lines of descentTo constrain the effects of fractional crystallization on magmatic Fe 3+ /∑Fe ratios, model liquid lines of descent that match the observed major element variations were generated using PetroLog3 (Danyushevsky & Plechov, 2011). The mineral-melt models that most closely replicate the natural data were chosen for each location, resulting in some variation in the models used from volcano to volcano. Individual model parameters

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Section: Sensitivity Test Of Primary Melt Model Resultsmentioning

confidence: 99%

Section: Sensitivity Test Of Primary Melt Model Resultsmentioning

confidence: 99%

Variations in Fe3+/∑Fe of Mariana Arc Basalts and Mantle Wedge fO2

Brounce

Kelley

Cottrell

2014

Journal of Petrology

221

145

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“…In contrast, waters degassed from silicic arc magmas (subduction-related volcanic vapors, SRVV) may have much higher δD H2O (-10 to -30‰) and δ 18 O H2O (+6 to +10‰) values (Giggenbach, 1992;Hedenquist and Lowenstern, 1994). Degassing-related fractionation and slab-derived seawater inputs can both increase the δD H2O value of magmatic waters at convergent margins Giggenbach, 1992;Taylor, 1997;Pineau et al, 1998;Shaw et al, 2008). While it is impossible to accurately constrain the isotopic composition of magmatic water added, the array of A crude estimate of the minimum quantity of magmatic H 2 O added to circulating fluids can be constrained by simple hydrogen isotope mass balance.…”

Section: Isotopic Evidence For Magmatic H 2 Omentioning

confidence: 99%

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Reeves¹

2010

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This thesis presents the results of four discrete investigations into processes governing the organic and inorganic chemical composition of seafloor hydrothermal fluids in a variety of geologic settings. Though Chapters 2 through 5 of this thesis are disparate in focus, each represents a novel investigation aimed at furthering our understanding of subsurface geochemical processes affecting hydrothermal fluid compositions. Chapters 2 and 3 concern the abiotic (nonbiological) formation of organic compounds in high temperature vent fluids, a process which has direct implications for the emergence of life in early Earth settings and sustainment of present day microbial populations in hydrothermal environments. Chapter 2 represents an experimental investigation of methane (CH 4 ) formation under hydrothermal conditions. The overall reduction of carbon dioxide (CO 2 ) to CH 4 , previously assumed to be kinetically inhibited in the absence of mineral catalysts, is shown to proceed on timescales pertinent to crustal residence times of hydrothermal fluids. In Chapter 3, the abundance of methanethiol (CH 3 SH), considered to be a crucial precursor for the emergence of primitive chemoautotrophic life, is characterized in vent fluids from ultramafic-, basalt-and sediment-hosted hydrothermal systems. Previous assumptions that CH 3 SH forms by reduction of CO 2 are not supported by the observed distribution in natural systems. Chapter 4 investigates factors regulating the hydrogen isotope composition of hydrocarbons under hydrothermal conditions. Isotopic exchange between low molecular weight n-alkanes and water is shown to be facilitated by metastable equilibrium reactions between alkanes and their corresponding alkenes, which are feasible in natural systems. In Chapter 5, the controls on vent fluid composition in a backarc hydrothermal system are investigated. A comprehensive survey of the inorganic geochemistry of fluids from sites of hydrothermal activity in the eastern Manus Basin indicates that fluids there are influenced by input of acidic magmatic solutions at depth, and subsequently modified by variable extents of seawater entrainment and mixing-related secondary acidity production. CHAPTER 1 IntroductionSeafloor hydrothermal systems associated with the generation of oceanic crust represent a dramatic expression of heat and mass transfer from the interior of the Earth. In addition to profound effects on ocean chemistry, convective circulation of seawater through volcanically active oceanic crust leads to the formation of metal sulfide deposits. In addition, seafloor hot springs are often invoked as ideal settings from which early microbial life could have emerged.Since the initial discovery of low temperature venting at the Galápagos Spreading Center in 1977 (CORLISS et al., 1979), our understanding of the composition and diversity of hydrothermal solutions has expanded greatly. During convection through oceanic crust of basaltic composition, O 2 -replete seawater reacts with crustal rock, typically producin...

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“…Oxygen and hydrogen isotope compositions of oceanic sedimentary rocks provide a commonly used proxy record, but interpretations remain inconclusive (1)(2)(3)(4). Average δ 18 O values of Archaean marine sediments (cherts and carbonates) are tens of per mil lower than present-day values, and systematically increase over geologic time (2,3). This trend has been attributed either to lower δ 18 O SEA WATER in the Archaean (1,3), or to ocean temperatures up to approximately 70°C (5-8).…”

mentioning

confidence: 98%

“…Serpentine-group minerals are hydrous magnesian silicates commonly formed by hydrothermal infiltration of seawater into ultramafic oceanic crust, hydration of the mantle wedge by slabderived fluids, or fluid-rock interaction in continentally emplaced ultramafic lithologies (16)(17)(18). Serpentinized oceanic peridotites are dominantly composed of low-temperature (<300°C) polymorphs lizardite and chrysotile, and to a lesser extent antigorite, which forms at temperatures >250°C (17).…”

Section: Serpentine Isotope Geochemistrymentioning

confidence: 99%

Isotope composition and volume of Earth’s early oceans

Pope

Bird

Rosing

2012

Proc. Natl. Acad. Sci. U.S.A.

130

145

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Oxygen and hydrogen isotope compositions of Earth's seawater are controlled by volatile fluxes among mantle, lithospheric (oceanic and continental crust), and atmospheric reservoirs. Throughout geologic time the oxygen mass budget was likely conserved within these Earth system reservoirs, but hydrogen's was not, as it can escape to space. Isotopic properties of serpentine from the approximately 3.8 Ga Isua Supracrustal Belt in West Greenland are used to characterize hydrogen and oxygen isotope compositions of ancient seawater. Archaean oceans were depleted in deuterium [expressed as δD relative to Vienna standard mean ocean water (VSMOW)] by at most 25 AE 5‰, but oxygen isotope ratios were comparable to modern oceans. Mass balance of the global hydrogen budget constrains the contribution of continental growth and planetary hydrogen loss to the secular evolution of hydrogen isotope ratios in Earth's oceans. Our calculations predict that the oceans of early Earth were up to 26% more voluminous, and atmospheric CH 4 and CO 2 concentrations determined from limits on hydrogen escape to space are consistent with clement conditions on Archaean Earth. Both interpretations have been questioned based on the susceptibility of chemical sediments to diagenetic alteration over geologic time (2, 4), and for the latter, a lack of geologic evidence for the extreme greenhouse gas concentrations required to sustain such high temperatures under a less luminous young Sun (9).Minerals formed by metasomatic reactions between seawater and oceanic lithosphere provide an alternative proxy for early ocean chemistry (10-14). Here we report hydrogen and oxygen isotope compositions of 114 silicate mineral separates from the ca. 3.8 Ga Isua Supracrustal Belt (ISB) of West Greenland, including metamorphosed basalts, gabbros, and ultramafic rocks that represent fragments of Eoarchaean oceanic crust (see Fig. S1, Table S2). Minerals formed during heterogeneous late-stage CO 2 -or meteoric-dominated metamorphic overprinting are distinguished by characteristic trends in their coupled δD and δ 18 O values (Fig. S2). In contrast, serpentine minerals formed by reaction of seawater with ultramafic rocks (peridotites) preserved in a low-strain enclave of the ISB (15) define a different isotopic trend. Here we use these serpentines to constrain D∕H and 18 O∕ 16 O ratios of the Eoarchaean ocean. Serpentine Isotope GeochemistrySerpentine-group minerals are hydrous magnesian silicates commonly formed by hydrothermal infiltration of seawater into ultramafic oceanic crust, hydration of the mantle wedge by slabderived fluids, or fluid-rock interaction in continentally emplaced ultramafic lithologies (16)(17)(18). Serpentinized oceanic peridotites are dominantly composed of low-temperature (<300°C) polymorphs lizardite and chrysotile, and to a lesser extent antigorite, which forms at temperatures >250°C (17). In modern oceanic serpentinites, antigorites have δD between −46 and −30‰ (Figs. 1 and 2A, filled squares), values that indicate equilibrium with modern-...

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Hydrogen isotopes in Mariana arc melt inclusions: Implications for subduction dehydration and the deep-Earth water cycle

Cited by 173 publications

References 46 publications

Variations in Fe3+/∑Fe of Mariana Arc Basalts and Mantle Wedge fO2

Variations in Fe3+/∑Fe of Mariana Arc Basalts and Mantle Wedge fO2

Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems

Isotope composition and volume of Earth’s early oceans

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