scholarly journals Deep hydrocarbon cycle

LITOSFERA ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 289-305
Author(s):  
V. G. Kutcherov ◽  
K. S. Ivanov ◽  
A. Yu. Serovaiskii
Keyword(s):  
High Pressure ◽  
Iron Carbide ◽  
Hydroxyl Group ◽  
Ultramafic Rocks ◽  
The Urals ◽  
Saturated Hydrocarbons ◽  
Iron Carbides ◽  
Hydrocarbon Fluid ◽  
Thermobaric Conditions ◽  
Iron Bearing

Research subject. Experimental modelling of the transformation of complex hydrocarbon systems under extreme thermobaric conditions was carried out. The results obtained were compared with geological observations in the Urals, Kamchatka and other regions.Material and methods. The materials for the research were a model hydrocarbon system similar in composition to natural gas condensate and a system consisting of a mixture of saturated hydrocarbons and various iron-containing minerals enriched in 57Fe. Two types of high-pressure equipment were used: a diamond anvils cell and a Toroid-type high-pressure chamber. The experiments were carried out at pressures up to 8.8 GPa in the temperature range 593–1600 K.Results. According to the obtained results, hydrocarbon systems submerged in a subduction slab can maintain their stability down to a depth of 50 km. Upon further immersion, during contact of the hydrocarbon fluid with the surrounding iron-bearing minerals, iron hydrides and carbides are formed. When iron carbides react with water under the thermobaric conditions of the asthenosphere, a water-hydrocarbon fluid is formed. Geological observations, such as methane finds in olivines from ultramafic rocks unaffected by serpentinization, the presence of polycyclic aromatic and heavy saturated hydrocarbons in ophiolite allochthons and ultramafic rocks squeezed out from the paleo-subduction zone of the Urals, are in good agreement with the experimental data.Conclusion. The obtained experimental results and presented geological observations made it possible to propose a concept of deep hydrocarbon cycle. Upon the contact of hydrocarbon systems immersed in a subduction slab with iron-bearing minerals, iron hydrides and carbides are formed. Iron carbides carried in the asthenosphere by convective flows can react with hydrogen contained in the hydroxyl group of some minerals or with water present in the asthenosphere and form a water-hydrocarbon fluid. The mantle fluid can migrate along deep faults into the Earth’s crust and form multilayer oil and gas deposits in rocks of any lithological composition, genesis and age. In addition to iron carbide coming from the subduction slab, the asthenosphere contains other carbon donors. These donors can serve as a source of deep hydrocarbons, also participating in the deep hydrocarbon cycle, being an additional recharge of the total upward flow of a water-hydrocarbon fluid. The described deep hydrocarbon cycle appears to be part of a more general deep carbon cycle.

scholarly journals Formation of iron hydride and iron carbide from hydrocarbon systems at ultra high thermobaric conditions

2019 ◽  
Vol 64 (9) ◽  
pp. 995-1002
Author(s):  
A. Yu. Serovaiskii ◽  
A. Yu. Kolesnikov ◽  
V. G. Kutcherov
Keyword(s):  
Upper Mantle ◽  
Laser Heating ◽  
Chemical Interaction ◽  
Iron Carbide ◽  
Iron Carbides ◽  
The Earth ◽  
Iron Hydride ◽  
Thermobaric Conditions ◽  
Diamond Anvils ◽  
Iron Bearing

The chemical interaction of hydrocarbon systems and iron-bearing minerals was investigated under extreme thermobaric conditions, corresponding to the Earth upper mantle. As a result of the reaction, the formation of iron carbide and iron hydride was detected. The experiments were carried out in diamond anvils cells with laser heating. Natural petroleum from the Korchaginskoe deposit and a synthetic mixture of paraffin hydrocarbons were used as hydrocarbon systems, and pyroxene-like glass and ferropericlase (57Fe enriched) as iron bearing minerals. The experiments were carried out in the pressure range of 26–95 kbar and temperature range of 1000–1500°C (±100°C). As a result of the experiments, the formation of iron hydride was detected at pressure of 26–69 kbar (corresponds to a depth of 100–200 km), and a mixture of iron carbide and iron hydride at pressure of 75–95 kbar (corresponds to a depth of 210–290 km). The formation of hydrides and iron carbides as a results of the interaction of hydrocarbon systems with iron-bearing minerals may indicate the possible existence of these compounds in the upper mantle.

scholarly journals The Role of Iron Carbide in the Abyssal Formation of Hydrocarbons in the Upper Mantle

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 163
Author(s):  
Aleksandr Serovaiskii ◽  
Vladimir Kutcherov
Keyword(s):  
Upper Mantle ◽  
Iron Carbide ◽  
Hydrocarbon Mixture ◽  
Abiogenic Synthesis ◽  
Hydrocarbon Fluid ◽  
High Pressure High Temperature ◽  
Wide Range ◽  
Thermobaric Conditions ◽  
Volume Unit

The existence of iron carbide in the upper mantle allows an assumption to be made about its possible involvement in the abyssal abiogenic synthesis of hydrocarbons as a carbon donor. Interacting with hydrogen donors of the mantle, iron carbide can form hydrocarbon fluid. In order to investigate the role of iron carbide in the abiogenic synthesis of hydrocarbons, the chemical reaction between cementite Fe3C and water was modeled under thermobaric conditions, corresponding to the upper mantle. A series of experiments were conducted using a high-pressure high-temperature Toroid-type large reactive volume unit with further analysis by means of gas chromatography. The results demonstrated the formation of hydrocarbon fluid in a wide range of thermobaric conditions (873–1223 K, 2.5–6.0 GPa) corresponding to the upper mantle. A strong correlation between the composition of the fluid and the pT conditions of the synthesis was illustrated in the investigation. The higher temperature of the synthesis resulted in the formation of a “poor” hydrocarbon mixture, primarily comprising methane, while a higher pressure yielded the opposite effect, converting iron carbide into a complex hydrocarbon system, containing normal and iso-alkanes up to C7 and benzene. This correlation explains the diversity of hydrocarbon systems produced experimentally, thus expanding the thermobaric range of the possible existence of complex hydrocarbon systems in the upper mantle. The results support the suggestion that the carbide—water reaction can be a source of both the carbon and hydrogen required for the abyssal abiogenic synthesis of hydrocarbons.

scholarly journals Fate of Hydrocarbons in Iron-Bearing Mineral Environments during Subduction

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 651
Author(s):  
Aleksandr Serovaiskii ◽  
Elena Mukhina ◽  
Leonid Dubrovinsky ◽  
Aleksey Chernoutsan ◽  
Daniil Kudryavtsev ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Ferrous Iron ◽  
Subduction Zones ◽  
Chemical Interaction ◽  
Iron Carbide ◽  
Crust And Upper Mantle ◽  
Iron Hydride ◽  
Thermobaric Conditions ◽  
Natural Oil ◽  
Iron Bearing

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.

scholarly journals Influence of Phase Composition and Pretreatment on the Conversion of Iron Oxides into Iron Carbides in Syngas Atmospheres

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 773
Author(s):  
Aleks Arinchtein ◽  
Meng-Yang Ye ◽  
Michael Geske ◽  
Marvin Frisch ◽  
Ralph Kraehnert
Keyword(s):  
Phase Composition ◽  
Iron Oxide ◽  
Self Assembly ◽  
Iron Carbide ◽  
Active Phase ◽  
Physicochemical Analysis ◽  
Carbide Formation ◽  
Iron Carbides ◽  
Carbide Phases ◽  
Higher Hydrocarbons

CO2 Fischer–Tropsch synthesis (CO2–FTS) is a promising technology enabling conversion of CO2 into valuable chemical feedstocks via hydrogenation. Iron–based CO2–FTS catalysts are known for their high activities and selectivities towards the formation of higher hydrocarbons. Importantly, iron carbides are the presumed active phase strongly associated with the formation of higher hydrocarbons. Yet, many factors such as reaction temperature, atmosphere, and pressure can lead to complex transformations between different oxide and/or carbide phases, which, in turn, alter selectivity. Thus, understanding the mechanism and kinetics of carbide formation remains challenging. We propose model–type iron oxide films of controlled nanostructure and phase composition as model materials to study carbide formation in syngas atmospheres. In the present work, different iron oxide precursor films with controlled phase composition (hematite, ferrihydrite, maghemite, maghemite/magnetite) and ordered mesoporosity are synthesized using the evaporation–induced self–assembly (EISA) approach. The model materials are then exposed to a controlled atmosphere of CO/H2 at 300 °C. Physicochemical analysis of the treated materials indicates that all oxides convert into carbides with a core–shell structure. The structure appears to consist of crystalline carbide cores surrounded by a partially oxidized carbide shell of low crystallinity. Larger crystallites in the original iron oxide result in larger carbide cores. The presented simple route for the synthesis and analysis of soft–templated iron carbide films will enable the elucidation of the dynamics of the oxide to carbide transformation in future work.

scholarly journals Exsolution Lamellae in Orthopyroxene of Lherzolite from the Pauza Ultramafic Rocks, Ne Iraq: Evidence of Deep Mantle Signature in the Zagros Suture Zone

2013 ◽  
Vol 2 (9) ◽  
pp. 102-115
Author(s):  
Yousif Osman Mohammad ◽  
Nabaz Rashid Hama Aziz
Keyword(s):  
High Pressure ◽  
Upper Cretaceous ◽  
Suture Zone ◽  
Ultramafic Rocks ◽  
Chromian Spinel ◽  
Spinel Peridotite ◽  
Incongruent Melting ◽  
Fine Grained ◽  
Ultra High Pressure ◽  
Deep Mantle

The Pauza ultramafic body is part of Upper Cretaceous Ophiolitic massifs of the Zagros Suture Zone, NE Iraq. The present study reveals evidence of Ultra-high pressure (UHP), and deep mantle signature of these peridotites in the Zagros Suture Zone throughout the observation of backscattered images and micro analyses which have been performed on orthopyroxen crystals in lherzolite of Pauza ultramafic rocks.Theorthopyroxen shows abundant exsolution lamellae of coarse unevenly distributed clinopyroxene coupled with the submicron uniformly distributed needles of Cr-spinel. The observed clusters of Opx–Cpx–Spl represent the decompression products of pyrope-rich garnet produced as a result of the transition from ultra-high pressure garnet peridotite to low-pressure spinel peridotite (LP). Neoblastic olivine (Fo92 – 93) with abundant multi-form Cr- spinel inclusions occurs as a fine-grained aggregate around orthopyroxene, whereas coarse olivine (Fo90-91) free from chromian-spinel is found in matrix. The similarity of the Cr-spinel lamellae orientations in both olivine and orthopyroxene, moreover, the enrichments of both Cr and Fe3+ in the Cr-spinel inclusions in neoblastic olivine relative to Cr-spinel lamellae in orthopyroxene, suggest that spinel inclusions in olivine have been derived from former Cr-spinel lamellae in orthopyroxene. Neoblastic olivine is formed by reaction of silica-poor ascending melt and orthopyroxene. It is inferred that the olivines with multi-form spinel inclusions has been formed by incongruent melting of pre-existing spinel lamellae-rich orthopyroxene.

scholarly journals Phase Stability and Vibrational Properties of Iron-Bearing Carbonates at High Pressure

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1142
Author(s):  
Chaoshuai Zhao ◽  
Liangxu Xu ◽  
Weibin Gui ◽  
Jin Liu
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Spin Transition ◽  
Laser Raman ◽  
Electronic Spin ◽  
Pressure Medium ◽  
Raman Modes ◽  
Sample Chamber ◽  
The Stability ◽  
Iron Bearing

The spin transition of iron can greatly affect the stability and various physical properties of iron-bearing carbonates at high pressure. Here, we reported laser Raman measurements on iron-bearing dolomite and siderite at high pressure and room temperature. Raman modes of siderite FeCO3 were investigated up to 75 GPa in the helium (He) pressure medium and up to 82 GPa in the NaCl pressure medium, respectively. We found that the electronic spin-paring transition of iron in siderite occurred sharply at 42–44 GPa, consistent with that in the neon (Ne) pressure medium in our previous study. This indicated that the improved hydrostaticity from Ne to He had minimal effects on the spin transition pressure. Remarkably, the spin crossover of siderite was broadened to 38–48 GPa in the NaCl pressure medium, due to the large deviatoric stress in the sample chamber. In addition, Raman modes of iron-bearing dolomite Ca1.02Mg0.76Fe0.20Mn0.02(CO3)2 were explored up to 58 GPa by using argon as a pressure medium. The sample underwent phase transitions from dolomite-Ⅰ to -Ⅰb phase at ~8 GPa, and then to -Ⅱ at ~15 and -Ⅲb phase at 36 GPa, while no spin transition was observed in iron-bearing dolomite up to 58 GPa. The incorporation of FeCO3 by 20 mol% appeared to marginally decrease the onset pressures of the three phase transitions aforementioned for pure dolomite. At 55–58 GPa, the ν1 mode shifted to a lower frequency at ~1186 cm−1, which was likely associated with the 3 + 1 coordination in dolomite-Ⅲb. These results shed new insights into the nature of iron-bearing carbonates at high pressure.

scholarly journals XRD and EBSD Measurements of Directional Solidification Fe-C Eutectic Alloy

2016 ◽  
Vol 16 (4) ◽  
pp. 169-174 ◽  
Author(s):  
M. Trepczyńska-Łent
Keyword(s):  
Directional Solidification ◽  
Electron Backscatter Diffraction ◽  
Iron Carbide ◽  
Longitudinal Section ◽  
Optical Microscope ◽  
Hexagonal Structure ◽  
Crystallographic Analysis ◽  
X Ray Diffraction ◽  
Iron Carbides ◽  
X Ray

Abstract In a vacuum Bridgman-type furnace, under an argon atmosphere, directionally solidified sample of Fe - C alloy was produced. The pulling rate was v = 83 μm/s (300 mm/h) and constant temperature gradient G = 33,5 K/mm. The microstructure of the sample was examined on the longitudinal section using an Optical Microscope and Scanning Electron Microscope. The X-ray diffraction and electron backscatter diffraction technique (EBSD) have been used for the crystallographic analysis of carbide particles in carbide eutectic. The X-ray diffraction was made parallel and perpendicular to the axis of the goniometer. The EBSD shows the existence of iron carbide Fe3C with orthorhombic and hexagonal structure. Rapid solidification may cause a deformation of the lattice plane which is indicated by different values of the lattice parameters. Such deformation could also be the result of directional solidification. Not all of the peaks in X–ray diffractograms were identified. They may come from other iron carbides. These unrecognized peaks may also be a result of the residual impurity of alloy.

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