Iron carbide as a source of carbon for graphite and diamond formation under lithospheric mantle P-T parameters

Bataleva, Yuliya V.; Palyanov, Yuri N.; Borzdov, Yuri M.; Bayukov, O. A.; Zdrokov, E. V.

doi:10.1016/j.lithos.2017.06.010

Cited by 18 publications

(7 citation statements)

References 51 publications

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“…The run products obtained with the Fe 3 C and MgCO 3 proportion used in the study were free from graphite/diamond, possibly, because all excess carbon was reduced at buffered f H 2 . The formation of graphite and diamond by Fe 3 C oxidation and by Fe 3 C reactions with carbonate was reproduced in previous experiments [50,61,62]. Excess carbon required for HC formation and Fe 3 C-to-Fe 7 C 3 conversion appeared in reaction 7 on account of Fe 3 C oxidation and CO 2 reduction by hydrogen.…”

Section: Formation Of Hydrocarbons In the Presence Of A Metal Phasesupporting

confidence: 68%

Formation of Hydrocarbons in the Presence of Native Iron under Upper Mantle Conditions: Experimental Constraints

et al. 2020

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The formation of hydrocarbons (HCs) upon interaction of metal and metal–carbon phases (solid Fe, Fe3C, Fe7C3, Ni, and liquid Fe–Ni alloys) with or without additional sources of carbon (graphite, diamond, carbonate, and H2O–CO2 fluids) was investigated in quenching experiments at 6.3 GPa and 1000–1400 °C, wherein hydrogen fugacity (fH2) was controlled by the Fe–FeO + H2O or Mo–MoO2 + H2O equilibria. The aim of the study was to investigate abiotic generation of hydrocarbons and to characterize the diversity of HC species that form in the presence of Fe/Ni metal phases at P–T–fH2 conditions typical of the upper mantle. The carbon donors were not fully depleted at experimental conditions. The ratio of H2 ingress and consumption rates depended on hydrogen permeability of the capsule material: runs with low-permeable Au capsules and/or high hydrogenation rates (H2O–CO2 fluid) yielded fluids equilibrated with the final assemblage of solid phases at fH2sample ≤ fH2buffer. The synthesized quenched fluids contained diverse HC species, predominantly light alkanes. The relative percentages of light alkane species were greater in higher temperature runs. At 1200 °C, light alkanes (C1 ≈ C2 > C3 > C4) formed either by direct hydrogenation of Fe3C or Fe7C3, or by hydrogenation of graphite/diamond in the presence of Fe3C, Fe7C3, and a liquid Fe–Ni alloy. The CH4/C2H6 ratio in the fluids decreased from 5 to 0.5 with decreasing iron activity and the C fraction increased in the series: Fe–Fe3C → Fe3C–Fe7C3 → Fe7C3–graphite → graphite. Fe3C–magnesite and Fe3C–H2O–CO2 systems at 1200 °C yielded magnesiowüstite and wüstite, respectively, and both produced C-enriched carbide Fe7C3 and mainly light alkanes (C1 ≈ C2 > C3 > C4). Thus, reactions of metal phases that simulate the composition of native iron with various carbon donors (graphite, diamond, carbonate, or H2O–CO2 fluid) at the upper mantle P–T conditions and enhanced fH2 can provide abiotic generation of complex hydrocarbon systems that predominantly contain light alkanes. The conditions favorable for HC formation exist in mantle zones, where slab-derived H2O-, CO2- and carbonate-bearing fluids interact with metal-saturated mantle.

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Section: Formation Of Hydrocarbons In the Presence Of A Metal Phasesupporting

confidence: 68%

Formation of Hydrocarbons in the Presence of Native Iron under Upper Mantle Conditions: Experimental Constraints

et al. 2020

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“…The procedure for the ampoule assembly, in which starting reagents are finely crushed (grain sizẽ 20 µm) and homogenized, was used. The reaction charges were placed in graphite capsules (diameter of 5 mm, height of 2 mm), which are suitable for HPHT-experiments in sulfur-and iron-bearing systems [27][28][29]. These graphite capsules provide carbon-saturated conditions, which initiate the decomposition of sulfate ("desulfation") and S-rich fluid generation.…”

Section: Methodsmentioning

confidence: 99%

Sulfide Formation as a Result of Sulfate Subduction into Silicate Mantle (Experimental Modeling under High P,T-Parameters)

2018

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Ca,Mg-sulfates are subduction-related sources of oxidized S-rich fluid under lithospheric mantle P,T-parameters. Experimental study, aimed at the modeling of scenarios of S-rich fluid generation as a result of desulfation and subsequent sulfide formation, was performed using a multi-anvil high-pressure apparatus. Experiments were carried out in the Fe,Ni-olivine–anhydrite–C and Fe,Ni-olivine–Mg-sulfate–C systems (P = 6.3 GPa, T of 1050 and 1450 °C, t = 23–60 h). At 1050 °C, the interaction in the olivine–anhydrite–C system leads to the formation of olivine + diopside + pyrrhotite assemblage and at 1450 °C leads to the generation of immiscible silicate-oxide and sulfide melts. Desulfation of this system results in the formation of S-rich reduced fluid via the reaction olivine + anhydrite + C → diopside + S0 + CO2. This fluid is found to be a medium for the recrystallization of olivine, extraction of Fe and Ni, and subsequent crystallization of Fe,Ni-sulfides (i.e., olivine sulfidation). At 1450 °C in the Ca-free system, the generation of carbonate-silicate and Fe,Ni-sulfide melts occurs. Formation of the carbonate component of the melt occurs via the reaction Mg-sulfate + C → magnesite + S0. It is experimentally shown that the olivine-sulfate interaction can result in mantle sulfide formation and generation of potential mantle metasomatic agents—S- and CO2-dominated fluids, silicate-oxide melt, or carbonate-silicate melt.

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“…In subducting slabs, carbon is usually considered to be in the form of organic carbon in sediments [1], carbonates [2,3], and pure crystalline graphite [3]. Known carbon species in the Earth's interior are CO 2 and CH 4 fluid or gas [4,5], diamond [1,6], carbonates [2,3], carbides [7], and carbonated silicate melts [4]. Petroleum as a carbon-containing substance within subducting slabs has not been strongly considered.…”

Section: Introductionmentioning

confidence: 99%

Fate of Hydrocarbons in Iron-Bearing Mineral Environments during Subduction

et al. 2019

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Subducted sediments play a key role in the evolution of the continental crust and upper mantle. As part of the deep carbon cycle, hydrocarbons are accumulated in sediments of subduction zones and could eventually be transported with the slab below the crust, thus affecting processes in the deep Earth’s interior. However, the behavior of hydrocarbons during subduction is poorly understood. We experimentally investigated the chemical interaction of model hydrocarbon mixtures or natural oil with ferrous iron-bearing silicates and oxides (representing possible rock-forming materials) at pressure-temperature conditions of the Earth’s lower crust and upper mantle (up to 2000(±100) K and 10(±0.2) GPa), and characterized the run products using Raman and Mössbauer spectroscopies and X-ray diffraction. Our results demonstrate that complex hydrocarbons are stable on their own at thermobaric conditions corresponding to depths exceeding 50 km. We also found that chemical reactions between hydrocarbons and ferrous iron-bearing rocks during slab subduction lead to the formation of iron hydride and iron carbide. Iron hydride with relatively low melting temperature may form a liquid with negative buoyancy that could transport reduced iron and hydrogen to greater depths.

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Iron carbide as a source of carbon for graphite and diamond formation under lithospheric mantle P-T parameters

Cited by 18 publications

References 51 publications

Formation of Hydrocarbons in the Presence of Native Iron under Upper Mantle Conditions: Experimental Constraints

Formation of Hydrocarbons in the Presence of Native Iron under Upper Mantle Conditions: Experimental Constraints

Sulfide Formation as a Result of Sulfate Subduction into Silicate Mantle (Experimental Modeling under High P,T-Parameters)

Fate of Hydrocarbons in Iron-Bearing Mineral Environments during Subduction

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