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 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.

Formation of Iron Hydride and Iron Carbide from Hydrocarbon Systems at Ultra-High Thermobaric Conditions

2019 ◽  
Vol 57 (9) ◽  
pp. 1008-1014 ◽  
Author(s):  
A. Yu. Serovaiskii ◽  
A. Yu. Kolesnikov ◽  
V. G. Kutcherov
Keyword(s):  
Iron Carbide ◽  
Iron Hydride ◽  
Thermobaric Conditions

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.

THE CRUST AND UPPER MANTLE STRUCTURES IN CENTRAL ANATOLIA, TURKEY, CONSTRAINED BY GRAVITY AND SEISMIC DATA

2020 ◽  
Author(s):  
Yagmur Yilmaz ◽  
◽  
Alain Plattner ◽  
Rezene Mahatsente ◽  
Ibrahim Çemen ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Seismic Data ◽  
Central Anatolia ◽  
Crust And Upper Mantle
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