Possible geochemical conditions of local reducing environments in the Earth’s crust and upper mantle

Yaroshevskii, A. A.

doi:10.1134/s0016702906030086

Cited by 5 publications

(1 citation statement)

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“…In addition, experimental results (Yaroshevskii, 2006;Seyfried et al, 2007;McCollom and Bach, 2009) on fluctuations of redox conditions during serpentinization demonstrated that chemical and mineralogical changes in the root zone (or reactor zone) of a serpentinite-hosted hydrothermal system, are induced by fH 2 , rather than by the progressive increase in seawater penetration. The amount of dissolved H 2 in hydrothermal fluids, which decreases in a stepwise pattern with reaction progress, is strictly dependent on the oxidation state of iron, which controls the H 2 /H 2 O ratio (Yaroshevskii, 2006;McCollom and Bach, 2009), following reaction 9:…”

Section: Physicochemical Conditions In Serpentinitehosted Hydrothermamentioning

confidence: 99%

Can nanodiamonds grow in serpentinite-hosted hydrothermal systems? A theoretical modelling study

Manuella¹

2013

Mineral. mag.

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Nanodiamonds can be synthesized hydrothermally in the laboratory by using a C-O-H fluid in the graphite stability field, in which the graphite/nanodiamond transition depends on the crystal size as a function of temperature. In nature, the hydrothermal circulation of seawater in serpentinites plays an important role in the carbon speciation in the oceanic crust and exposed mantle, in which hydrocarbons (mainly CH4) of abiogenic origin (via Fischer-Tropsch-type reaction) and occasionally graphite particles are detected. Can nanodiamonds nucleate and grow in serpentinite-hosted hydrothermal systems? To answer this question, a theoretical modelling study which compares the physico-chemical conditions in hydrothermal synthesis with those observed in modern and fossil serpentinite-hosted hydrothermal systems is proposed. Nanodiamonds are predicted to precipitate from a C-O-H fluid, consisting of CH4-CO2-H2O at 350 – 400°C andP<0.2 GPa near the FMQ buffer (Fayalite-Magnetite-Quartz), which are conditions compatible with those existing in serpentinite-hosted hydrothermal systems. In these environments, carbon-supersaturated fluids can be derived from water consumption (serpentine formation) under low water/rock ratios, which may promote the growth of nanodiamonds. This theoretical approach sheds light on the intriguing problem of carbon speciation in abyssal-type hydrothermal systems, suggesting that serpentinites may host nanodiamond deposits, even though none have been found yet.

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Section: Physicochemical Conditions In Serpentinitehosted Hydrothermamentioning

confidence: 99%

Can nanodiamonds grow in serpentinite-hosted hydrothermal systems? A theoretical modelling study

Manuella¹

2013

Mineral. mag.

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Advancing the mechanistic understanding of corrosion in supercritical CO2 with H2O and O2 impurities

Zeng

2023

Corrosion Science

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P–T–X parameters of metamorphogene and hydrothermal fluids, isotopy and age of the Bogunai gold deposit, southern Yenisei Ridge (Russia)

Ryabukha

Гибшер

Томиленко

et al. 2015

Russian Geology and Geophysics

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Fluid inclusions in quartz, sulfides from quartz veins, and quartz, garnet, plagioclase, and orthoclase from granulites of the Bogunai gold deposit located in the granulites of the Angara–Kan block of the Yenisei Ridge were studied by thermobarometry, gas chromatography, chromato-mass-spectrometry, Raman spectroscopy, and mass spectrometry with inductively coupled plasma. The formation temperatures (850–950 °C) and pressures (8.5–9.0 kbar) of minerals of the granulite metamorphic facies are much higher than the crystallization temperatures (220–420 °C) and pressures (0.1–1.6 kbar) of gold–quartz veins of the Bogunai deposit. These veins formed with the participation of H2O–CO2–hydrocarbon fluids with a salt (predominantly MgCl2) concentration of 2–19 wt.% NaCl equiv. The gas phase of fluid inclusions from quartz, pyrite, chalcopyrite, galena, and sphalerite contains not only H2O, CO2, CH4, and N2 but also the first found compounds of sulfur (CS2, O2S, COS, C2H6S2) and nitrogen (C3H7N, C3H7NO, C4H8N2O) and numerous hydrocarbons of different classes (paraffins, arenes, naphthenes, alcohols, aldehydes, ketones, carbonic acids, and furans). The age of the Krasnoyarsk mineralized zone, one of the sites of the Bogunai deposit, is 466 ± 3.2–461.6 ± 3.1 Ma, which is almost 1400 Ma younger than the age of granulite metamorphism and 255 Ma younger than the age of diaphthoresis but is close to the age of the Lower Kan granitoid pluton (455.7 ± 3.4 Ma). The sulfur isotope ratios (δ34S) of sulfides (pyrite, chalcopyrite, sphalerite, and galena) are close to the mantle values, 0.8 to 3.5%c, and are in the range of the granitoid values, which indicates the crustal source of the fluid sulfur. Gold of the Bogunai deposit accumulated with the participation of H2O–CO2–hydrocarbon fluids generated both in deep-fault zones and in granitoid intrusions.

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Possible geochemical conditions of local reducing environments in the Earth’s crust and upper mantle

Cited by 5 publications

References 1 publication

Can nanodiamonds grow in serpentinite-hosted hydrothermal systems? A theoretical modelling study

Can nanodiamonds grow in serpentinite-hosted hydrothermal systems? A theoretical modelling study

Advancing the mechanistic understanding of corrosion in supercritical CO2 with H2O and O2 impurities

P–T–X parameters of metamorphogene and hydrothermal fluids, isotopy and age of the Bogunai gold deposit, southern Yenisei Ridge (Russia)

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