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35. Smectite Crystallite Swelling Under High Pressure of Methane

Author

Ziemianski, Paweł P., Derkowski, Arkadiusz, Szczerba, Marek, Guggenheim, Stephen, Ziemianski, Paweł P., Derkowski, Arkadiusz, Szczerba, Marek, and Guggenheim, Stephen

Abstract

Clay minerals, along with organic matter, control methane (CH4) gas adsorption properties of sediments and sedimentary rocks. These natural, high-pressure environments of sediments and sedimentary rocks are particularly important in view of hydrocarbon exploration and global warming. The present study investigates swelling of smectites in dry methane at high pressure (1–60 bar), using in situ high-pressure X-ray diffraction and Grand Canonical Ensemble Monte Carlo simulations. The results show that CH4 molecules actively expand the interlayers of divalent cation-exchanged smectites at elevated pressure (e.g., from initial 12.1 Å at 1 bar of N2 to 13.4 Å at 60 bar of dry CH4 of Mg-montmorillonite and from 11.8 Å at 1 bar of N2 to 12.1 Å at 60 bar of dry CH4 of Ca-montmorillonite). The swelling is observed when the interlayer cations are hydrated at the appropriate level of H2O content adsorbed primarily around the interlayer cations. The H2O configuration leaves CH4-accessible interlayer space outside the coordination sphere of the cations. Higher amounts of H2O in the interlayer act as a steric hindrance for CH4 and effectively decrease CH4 intercalation, whereas insufficient H2O content produces interlayer contraction preventing CH4 from entering the interlayer. The swelling was not observed in monovalent cation-exchanged smectites. Adsorption isotherms measured using overdried and fully contracted smectite allowed the determination of the interlayer adsorption component for the higher hydration state of the same sample. The swelling of smectite at an elevated pressure of CH4 is reversible and is driven by energetic factors, whereas entropy change and mechanical work are minor components of the free energy of swelling. The observed phenomenon of smectite swelling explains the occurrence of hysteresis in high-pressure CH4 adsorption isotherms and provides a previously unknown component to methane interaction with sedimentary rocks.

Published
2021
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37. A hydrothermal origin for isotopically anomalous cap dolostone cements from south China

Author

Bristow, Thomas F., Bonifacie, Magali, Derkowski, Arkadiusz, Eiler, John M., and Grotzinger, John P.

Subjects
Methane -- Environmental aspects -- Research, Dolomite -- Environmental aspects -- Research, Hydrothermal fluids -- Environmental aspects -- Research, Global warming -- Research -- Environmental aspects, Global temperature changes -- Environmental aspects -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

The release of methane into the atmosphere through destabilization of clathrates is a positive feedback mechanism capable of amplifying global warming trends that may have operated several times in the geological past (1-3). Such methane release is a hypothesized cause or amplifier for one of the most drastic global warming events in Earth history, the end of the Marinoan 'snowball Earth' ice age, ~635 Myr ago (4-7). A key piece of evidence supporting this hypothesis is the occurrence of exceptionally depleted carbon isotope signatures ([δ.sup.13][C.sub.PDB] down to -48%; ref. 8) in post-glacial cap dolostones (that is, dolostone overlying glacial deposits) from south China; these signatures have been interpreted as products of methane oxidation at the time of deposition (5,6,8). Here we show, on the basis of carbonate clumped isotope thermometry, [sup.87]Sr/[sup.86]Sr isotope ratios, trace element content and clay mineral evidence, that carbonates bearing the [sup.13]C-depleted signatures crystallized more than 1.6 Myr after deposition of the cap dolostone. Our results indicate that highly [sup.13]C-depleted carbonate cements grew from hydrothermal fluids and suggest that their carbon isotope signatures are a consequence of thermogenic methane oxidation at depth. This finding not only negates carbon isotope evidence for methane release during Marinoan deglaciation in south China, but also eliminates the only known occurrence of a Precambrian sedimentary carbonate with highly [sup.13]C-depleted signatures related to methane oxidation in a seep environment. We propose that the capacity to form highly [sup.13]C-depleted seep carbonates, through biogenic anaeorobic oxidation of methane using sulphate, was limited in the Precambrian period by low sulphate concentrations in sea water (9). As a consequence, although clathrate destabilization may or may not have had a role in the exit from the 'snowball' state, it would not have left extreme carbon isotope signals in cap dolostones., A common sedimentary motif marking the end of the severe Marinoan ice age (~635 Myr ago (10)) is observed in rocks on almost all of the present day continents. Glaciogenic [...]

Published
2011
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40. Thermal Analysis and Thermal Reactions of Smectites: a Review of Methodology, Mechanisms, and Kinetics

Author

Derkowski, Arkadiusz and Kuligiewicz, Artur

Abstract

Smectites are a group of minerals traditionally analyzed by thermal methods due to their exceptionally large adsorbed-water contents and the presence of OH groups, which makes them unique among all common soil- and rock-forming minerals. The dehydration reaction of smectite is a low-temperature endothermic effect that ends typically below 200°C. Although the removal of bulk interlayer water requires activation energy (Ea) of just above 30 kJ/mol, the removal of the last few H2O molecules attached strongly to interlayer cations requires Ea> 100 kJ/mol. Dehydroxylation is the loss of structural OH groups that proceeds as evolution of H2O molecules out of the smectite structure and occurs in the 300–900°C range. In trioctahedral species, dehydroxylation is combined with recrystallization and proceeds usually at > 700°C. In dioctahedral species, the temperature of dehydroxylation is controlled by the type of octahedral vacancy, having trans-vacantand cis-vacantdistinguished by the boundary at ~ 600°C, and by the octahedral cation–OH bond strength, following the order Mg > Al > Fe. The Eaof dehydroxylation correlates linearly with the temperature of maximum dehydroxylation; from > 170 kJ/mol for Cs+-exchanged beidellite and nontronite, through ~ 300 kJ/mol in Mg-rich montmorillonite, to > 500 kJ/mol in trioctahedral saponite. Dehydration and dehydroxylation of smectites can be accompanied by a number of other phenomena, such as dehydrogenation or defluorination. At high temperatures, smectite amorphization and recrystallization occurs. Unless amorphized and/or recrystallized, smectites can undergo rehydration and rehydroxylation, which are opposite reactions to dehydration and dehydroxylation, respectively. This review discusses the details of the above-mentioned thermal reactions of smectites, focusing on thermogravimetric methods, evolved gas analysis, and structural alterations. Factors affecting the accuracy and precision of thermal analysis of smectite are discussed along with examples of best laboratory practices. The paper also provides the most recent description and critical evaluation of smectite reaction kinetics.

Published
2023
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50. Paleomagnetic, tectonic and geochronological constraints for Permian–Triassic oroclinal bending of the Mongolian collage.

Author

Schulmann, Karel, Edel, Jean Bernard, Lexa, Ondrej, Xiao, Wenjiao, Třebínová, D, Spikings, Richard, Schaltegger, Urs, Derkowski, Arkadiusz, and Szczerba, Marek

Subjects
COLLAGE, SUTURE zones (Structural geology), SHEAR zones, OROGENIC belts
Abstract

Since a small part of the B components is syn-folding, the remagnetization is associated with the late Triassic-Jurassic shortening [[2]] while post-tectonic C and D components were acquired after the late Jurassic tightening. All these data can be interpreted as a result of: (i) Permian exhumation of HP mélange along the Solonker suture associated with the pure shear 270-260 Ma shortening of the MAW and TAZ units (Fig. The SP 40 sp Ar/ SP 39 sp Ar and K-Ar data show three peaks at ~270-260, 250-230 and 220-160 Ma [[9], [11]] that are all related to: (i) mid-Permian shortening and pegmatite dyke intrusion and (ii) Triassic sinistral shearing associated with the shortening and anticlockwise rotation of pure shear dominated "S"-shaped lithons (Fig. [Extracted from the article]

Published
2023
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