Publications
283 results found
Lewis JMT, Najorka J, Watson JS, et al., 2018, The search for Hesperian organic matter on Mars: Pyrolysis studies of sediments rich in sulfur and iron, Astrobiology, Vol: 18, Pages: 454-464, ISSN: 1531-1074
Jarosite on Mars is of significant geological and astrobiological interest as it forms in acidic aqueous conditions that are potentially habitable for acidophilic organisms. Jarosite can provide environmental context and may host organic matter. The most common analytical technique used to search for organic molecules on the surface of Mars is pyrolysis. However, thermal decomposition of jarosite produces oxygen, which degrades organic signals. At pH values greater than 3 and high water to rock ratios jarosite has a close association with goethite. Hematite can form by dehydration of goethite or directly from jarosite under certain aqueous conditions. Goethite and hematite are significantly more amenable for pyrolysis experiments searching for organic matter than jarosite. Analysis of the mineralogy and organic chemistry of samples from a natural acidic stream revealed a diverse response for organic compounds during pyrolysis of goethite-rich layers but a poor response for jarosite-rich or mixed jarosite-goethite units. Goethite units that are associated with jarosite but do not contain jarosite themselves should be targeted for organic detection pyrolysis experiments on Mars. These findings are extremely timely as future exploration targets for Mars Science Laboratory include Hematite Ridge, which may have formed from goethite precursors.
Schulze-Makuch D, Wagner D, Kounaves SP, et al., 2018, Transitory microbial habitat in the hyperarid Atacama Desert, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 115, Pages: 2670-2675, ISSN: 0027-8424
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- Citations: 113
Montgomery W, Sephton MA, Watson JS, et al., 2018, The role of minerals in hydrogen sulfide generation during steam-assisted recovery of heavy oil, Energy and Fuels, Vol: 32, Pages: 4651-4654, ISSN: 0887-0624
Heavy oil is recovered from reservoirs using steam-assisted technology, which can lead to H2S generation if the oil is relatively sulfur-rich. We have used laboratory aquathermolysis to simulate the steam-assisted gravity drainage process and have compared free heavy oil to that contained within the mineral matrix. The presence of a mineral matrix was found to affect the amount of H2S produced and the chemical properties of the oil generated. Our findings show that H2S production is initiated by the presence of naturally occurring minerals at specific temperatures and pressures and production techniques that avoid these conditions will minimize H2S production.
Sephton MA, 2018, Selecting Mars Samples to Return to Earth, Astronomy and Geophysics, ISSN: 1366-8781
When the search for life on Mars turns to returning samples to Earth for analysis, the choice of what to bring is complex. Mark A Sephton considers how to select the most valuable samples to bring back to Earth from Mars.
Mohialdeen IMJ, Mustafa KA, Salih DA, et al., 2018, Biomarker analysis of the upper Jurassic Naokelekan and Barsarin Formations in the Miran Well-2, Miran oil field, Kurdistan region, Iraq, Arabian Journal of Geosciences, Vol: 11, Pages: 51-51, ISSN: 1866-7538
The Miran oilfield is one of the new oil fields in Kurdistan region, northern Iraq, located in the Sulaimani Governorate. TwelveCuttings samples from the Upper Jurassic Naokelekan and Barsarin formations in well Miran-2 were selected for detailed organicgeochemical investigations. All the samples were subjected to bitumen extraction in order to study any biomarkers present usinggas chromatography-mass spectrometry. The dominance of low-molecular-weight n-alkanes and other calculated parameters indicate a marine source for the organic matter derived from planktonic algal and bacterial precursors deposited under anoxic conditions. The isoprenoids/n-alkanes ratios indicate type II and mixed II/III kerogen for both formations. The type II/III kerogen is characteristic of transitional environment under anoxic to dysoxic conditions as also indicated by the homohopane index for studied samples. More argillaceous carbonate rocks were deposited when reducing conditions were prevalent. Medium to high gammacerane index values in the rock extracts probably indicate a stratified water column during deposition of both formations.The studied samples from both formations have entered peak oil window maturity as reflected from the biomarker ratios fromboth aliphatic and aromatic fractions of the extracts.
Wolf S, Elsaesser A, Quinn R, et al., 2018, OreoCube (Organics exposure in orbit): In-situ UV-Vis spectroscopy of organic compounds on the International Space Station, ISSN: 0074-1795
OREOcube is a next-generation exposure platform with in-situ spectroscopic instrumentation, to be placed on the exterior of the International Space Station (ISS). OREOcube is part of a new European space exposure facility, which is currently under development by the European Space Agency. The anticipated launch is scheduled for 2020. The scientific focus of OREOcube is to study the carbon chemistry of astrobiologically interesting compounds directly in space. This avoids the limitations and technical challenges of laboratory simulation experiments on the ground. Via in-situ UV-Vis spectroscopy, photochemical changes of organic/inorganic dual-layer thin films will be monitored for a duration of up to 18 months. Afterwards, samples will return to Earth for further in-depth chemical analysis. With each specific experiment on the OREOcube platform, we aim to understand the photostability of potential biomarkers and the formation of decomposition products. Furthermore, we will investigate the role minerals and inorganic surfaces play in these photochemical decomposition processes. Currently, pre-flight experiments are being performed in order to select and test flight candidates. As a subset, we will show ground-simulation results of organic molecules belonging to the class of porphyrins, quinones and amino acids, important molecules found in terrestrial organisms. Thin films of organic molecules will be in contact with iron oxide and mineral surfaces during irradiation, simulating a Mars-soil environment. The organic/inorganic composite films will be hermetically sealed within a so-called sample cell, which can be filled with gas mixtures at various pressures simulating Martian atmospheric conditions. Upon irradiation in the laboratory with simulated solar light, photochemical changes of the organics will be monitored and analysed via UV-Vis spectroscopy. By measuring in-situ the changes in the UV-Vis spectra of samples as a function of time, OREOcube will provide data
Davey R, Smalley C, Sephton M, 2018, A new approach to predict shale gas decline trends in unconventional reservoirs using molecular weight fractionation
Various aspects of the exploitation of shale reservoirs, whether for hydrocarbon extraction or carbon storage, depend strongly on understanding how the gas is situated at a pore scale within the shale: for example in (isolated) macro-micropores, adsorbed onto the surfaces of pores or absorbed into the matrix of solid shale components. We are testing the hypothesis that gas compositional fractionation during depressurization can be used as a marker for gas stored in these different sites within the shale. This identifies how gas is stored within shales, total gas initially in place (GIP) and location on the estimated ultimate recovery curve (EUR). We created a purpose built sample cell coupled with a GC-FID in order to isolate individual shale constituents and measure molecular weight fractionation between shale gas components from 100% total GIIP to gas depleted. Effects of shale mineralogy on molecular weight fractionation were explored using samples representing key shale constituents as well as “real” shale samples.
Davey R, Smalley C, Sephton M, 2018, A new approach to predict shale gas decline trends in unconventional reservoirs using molecular weight fractionation
© 2018 Society of Petroleum Engineers. All rights reserved. Various aspects of the exploitation of shale reservoirs, whether for hydrocarbon extraction or carbon storage, depend strongly on understanding how the gas is situated at a pore scale within the shale: for example in (isolated) macro-micropores, adsorbed onto the surfaces of pores or absorbed into the matrix of solid shale components. We are testing the hypothesis that gas compositional fractionation during depressurization can be used as a marker for gas stored in these different sites within the shale. This identifies how gas is stored within shales, total gas initially in place (GIP) and location on the estimated ultimate recovery curve (EUR). We created a purpose built sample cell coupled with a GC-FID in order to isolate individual shale constituents and measure molecular weight fractionation between shale gas components from 100% total GIIP to gas depleted. Effects of shale mineralogy on molecular weight fractionation were explored using samples representing key shale constituents as well as “real” shale samples.
Royle SH, Montgomery W, Kounaves SP, et al., 2017, Effect of hydration state of Martian perchlorate salts on their decomposition temperatures during thermal extraction, Journal of Geophysical Research: Planets, Vol: 122, Pages: 2793-2802, ISSN: 2169-9097
Three Mars missions have analyzed the composition of surface samples using thermal extraction techniques. The temperatures of decomposition have been used as diagnostic information for the materials present. One compound of great current interest is perchlorate, a relatively recently discovered component of Mars' surface geochemistry that leads to deleterious effects on organic matter during thermal extraction. Knowledge of the thermal decomposition behavior of perchlorate salts is essential for mineral identification and possible avoidance of confounding interactions with organic matter. We have performed a series of experiments which reveal that the hydration state of magnesium perchlorate has a significant effect on decomposition temperature, with differing temperature releases of oxygen corresponding to different perchlorate hydration states (peak of O2 release shifts from 500 to 600°C as the proportion of the tetrahydrate form in the sample increases). Changes in crystallinity/crystal size may also have a secondary effect on the temperature of decomposition, and although these surface effects appear to be minor for our samples further investigation may be warranted. A less than full appreciation of the hydration state of perchlorate salts during thermal extraction analyses could lead to misidentification of the number and the nature of perchlorate phases present.
Abrams MA, Gong C, Garnier C, et al., 2017, A new thermal extraction protocol to evaluate liquid rich unconventional oil in place and in-situ fluid chemistry, Marine and Petroleum Geology, Vol: 88, Pages: 659-675, ISSN: 0264-8172
Potiszil C, Montgomery W, Sephton MA, 2017, The Effects of Pressure on Model Compounds of Meteorite Organic Matter, ACS Earth and Space Chemistry, Vol: 1, Pages: 475-482, ISSN: 2472-3452
Extraterrestrial organic matter has been widely studied; however, its response to pressure has not. Primitive organic matter bearing meteorites, such as CI and CM carbonaceous chondrites, have experienced variable pressures, up to 10 GPa. To appreciate the effects of these pressures on the organic content of these bodies, the model compounds isophthalic acid, vanillin and vanillic acid were subjected to pressures of up to 11.5 GPa and subsequently decompressed. High resolution synchrotron source Fourier Transform Infrared (FTIR) was used to determine the effects of different benzene substituents at high pressure on both the vibrational assignments of the benzene core of the molecules and the ability of the aromatic compounds to form intermolecular hydrogen bonds. The presence of additional peaks at high pressure was found to coincide with molecules that contain carboxyl groups, these features are interpreted as C-H---O intermolecular hydrogen bonds. The formation of these hydrogen bonds has implications for the origination of macromolecular organic matter (MOM), owing to the importance of such attractive forces during episodes of cross linking, such as esterification. Pressure-induced hydrogen bond formation is a process by which aromatic MOM precursors could have cross linked to generate the organic polymers found within extraterrestrial bodies today.
Sephton MA, 2017, Thermal extraction for organic-matter containing materials to answer questions both on Earth and in Space, First Break, Vol: 35, Pages: 113-117, ISSN: 1365-2397
The role of heat in the generation of petroleum has led to the study of organic matter-containing rocks by laboratory heating techniques. In particular, heat is used for the thermal extraction of organic matter in preparation for characterization by a range of detectors. Recently, thermal extraction has been used to answer certain planetary science questions such as the history of habitability for planets in the solar system and the search for evidence of life outside the Earth. The development of new thermal extraction protocols for challenging planetary science objectives provide methods that are readily translatable back to petroleum activities and include new shale screening and assessment techniques.
Zafar R, Watson JS, Weiss DJ, et al., 2017, Organic compound-mineral interactions: Using flash pyrolysis to monitor the adsorption of fatty acids on calcite, JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS, Vol: 123, Pages: 184-193, ISSN: 0165-2370
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- Citations: 4
Jardine JE, Fraser WT, Lomax BH, et al., 2016, Pollen and spores as biological recorders of past ultraviolet irradiance, Scientific Reports, Vol: 6, ISSN: 2045-2322
Solar ultraviolet (UV) irradiance is a key driver of climatic and biotic change. Ultraviolet irradiance modulates stratospheric warming and ozone production, and influences the biosphere from ecosystem-level processes through to the largest scale patterns of diversification and extinction. Yet our understanding of ultraviolet irradiance is limited because no method has been validated to reconstruct its flux over timescales relevant to climatic or biotic processes. Here, we show that a recently developed proxy for ultraviolet irradiance based on spore and pollen chemistry can be used over long (105 years) timescales. Firstly we demonstrate that spatial variations in spore and pollen chemistry correlate with known latitudinal solar irradiance gradients. Using this relationship we provide a reconstruction of past changes in solar irradiance based on the pollen record from Lake Bosumtwi in Ghana. As anticipated, variations in the chemistry of grass pollen from the Lake Bosumtwi record show a link to multiple orbital precessional cycles (19-21 thousand years). By providing a unique, local proxy for broad spectrum solar irradiance, the chemical analysis of spores and pollen offers unprecedented opportunities to decouple solar variability, climate and vegetation change through geologic time and a new proxy with which to probe the Earth system.
Matthewman R, Crawford IA, Jones AP, et al., 2016, Organic matter responses to radiation under lunar conditions, Astrobiology, Vol: 16, Pages: 900-912, ISSN: 1557-8070
Large bodies, such as the Moon, which have remained relatively unaltered for long periods of time have the potential to preserve a record of organic chemical processes from early in the history of the solar system. A record of volatiles and impactors may be preserved in buried lunar regolith layers that have been capped by protective lava flows. Of particular interest is the possible preservation of prebiotic organic materials delivered by ejected fragments of other bodies, including those originating from the surface of the early Earth. Lava flow layers would shield the underlying regolith and any carbon-bearing materials within them from most of the effects of space weathering, but the encapsulated organic materials would still be subject to irradiation before they were buried by regolith formation and capped with lava. We have performed a study to simulate the effects of solar radiation on a variety of organic materials mixed with lunar and meteorite analogue substrates. A fluence of ~3 x 1013 protons cm-2 at 4-13 MeV, intended to be representative of solar energetic particles, has little detectable effect on low molecular weight (≤C30) hydrocarbon structures that can be used to indicate biological activity (biomarkers) or the high molecular weight hydrocarbon polymer poly(styrene-co-divinylbenzene), and has little apparent effect on a selection of amino acids (≤C9). Inevitably, more lengthy durations of exposure to solar energetic particles may have more deleterious effects and rapid burial and encapsulation will always be more favourable to organic preservation. Our data indicate that biomarker compounds that may be used to infer biological activity on their parent planet can be relatively resistant to the effects of radiation, and may have a high preservation potential in paleoregolith layers on the Moon.
Gordon PR, Sephton MA, 2016, Organic matter detection on Mars by pyrolysis-FTIR: an analysis of sensitivity and mineral matrix effects, Astrobiology, Vol: 16, Pages: 831-845, ISSN: 1557-8070
Pyrolysis-FTIR is a potentially attractive triage instrument that considers both the past habitability of the sample depositional environment and the presence of organic matter which may reflect actual habitation. An important consideration for triage protocols is the sensitivity of the instrumental method. Experimental data indicate pyrolysis-FTIR sensitivities for organic matter at the tens of parts per million level. The mineral matrix in which the organic matter is hosted also has an influence on organic detection and here to provide an insight to matrix effects we simply mix well characterised organic matter with dry minerals prior to analysis. During pyrolysis-FTIR, serpentinites that may be encountered in the Phyllosian Era lead to no negative effects on organic matter detection, sulfates that may be recovered from the Theiikian Era can lead to the combustion of organic matter, and palagonites that may represent samples from the Siderikian Era can lead to the chlorination of organic matter. Any negative consequences brought about by mineral effects can be mitigated by the correct choice of thermal extraction temperature. Our results offer an improved understanding of how pyrolysis-FTIR can perform during sample triage on Mars.
Montgomery WB, Watson JS, Potiszil C, et al., 2016, Sporopollenin, a natural copolymer, is robust under high hydrostatic pressure, Macromolecular Chemistry and Physics, Vol: 217, Pages: 2494-2500, ISSN: 1521-3935
Lycopodium sporopollenin, a natural copolymer, shows exceptional stability underhigh hydrostatic pressures (10 GPa) as determined by in situ high pressuresynchrotron source FTIR spectroscopy. This stability is evaluated in terms of thecomponent compounds of the sporopollenin: p-coumaric acid, phloretic acid, ferulicacid, and palmitic and sebacic acids, which represent the additional n-acid and ndiacidcomponents. This high stability is attributed to interactions between thesecomponents, rather than the exceptional stability of any one molecular component.We propose a biomimetic solution for the creation of polymer materials that canwithstand high pressures for a multitude of uses in aeronautics, vascular autografts,ballistics and light-weight protective materials.
Montgomery WB, Bromiley GB, Sephton MA, 2016, The nature of organic records in impact excavated rocks on Mars, Scientific Reports, Vol: 6, ISSN: 2045-2322
Impact ejected rocks are targets for life detection missions to Mars. TheMartian subsurface is more favourable to organic preservation than thesurface owing to an attenuation of radiation and physical separation fromoxidising materials with increasing depth. Impact events bring materials tothe surface where they may be accessed without complicated drillingprocedures. On Earth, different assemblages of organic matter types arederived from varying depositional environments. Here we assess whetherthese different types of organic materials can survive impact eventswithout corruption. We subjected four terrestrial organic matter types toelevated pressures and temperatures in piston-cylinder experimentsfollowed by chemical characterisation using whole-rock pyrolysis-gaschromatography-mass spectrometry. Our data reveal that long chainhydrocarbon-dominated organic matter (types I and II; mainly microbial oralgal) are unresistant to pressure whereas aromatic hydrocarbondominatedorganic matter types (types III and IV; mainly land plant,metamorphosed or degraded, displaying some superficial chemicalsimilarities to abiotic meteoritic organic matter) are relatively resistant.This suggests that the impact excavated record of potential biology onMars will be unavoidably biased, with microbial organic matterunderrepresented while metamorphosed, degraded or abiotic meteoriticorganic matter types will be selectively preserved.
Montgomery W, Sephton MA, 2016, Pressure effects in polycyclic aromatic nitrogenated heterocycles (PANHs): Diagnostic qualities and cosmobarometry potential, The Astrophysical Journal, Vol: 819, ISSN: 0004-637X
The influence of polycyclic aromatic nitrogen heterocycles (PANHs), which have been suggested as contributors to the interstellar IR emission bands, on interstellar emission features is difficult to constrain because their infrared characteristics are strongly similar to those for polycyclic aromatic hydrocarbons (PAHs). One possible solution is to seek a means of visualising the presence of PANHs that provides information which is distinct from that for PAHs. Although PANHs and PAHs have similar infrared characteristics in many settings, this relationship may not be universally maintained. We have used in-situ high pressure synchrotron-source Fourier transform infrared (FTIR) spectroscopy to determine that the responses of two representative molecules, acridine and anthracene, differ at high pressures (> ca. 1 GPa). Because there are a number of high pressure environments that can be remotely observed by infrared spectroscopy they represent a potential to glimpse the distribution of PANHs across the Cosmos.
Najorka J, Lewis JMT, Spratt J, et al., 2016, Single-crystal X-ray diffraction study of synthetic sodium-hydronium jarosite, Physics and Chemistry of Minerals, Vol: 43, Pages: 377-386, ISSN: 1432-2021
Na–H3O jarosite was synthesized hydrothermally at 413 K for 8 days and investigated using single-crystal X-ray diffraction (XRD) and electron microprobe analysis (EMPA). The chemical composition of the studied crystal is [Na0.57(3) (H3O)0.36 (H2O)0.07]A Fe2.93(3) (SO4)2 (OH)5.70 (H2O)0.30, and Fe deficiency was confirmed by both EMPA and XRD analysis. The single-crystal XRD data were collected at 298 and 102 K, and crystal structures were refined in space group R3¯¯¯mR3¯m . The room-temperature data match structural trends of the jarosite group, which vary linearly with the c axis. The low-temperature structure at 102 K shows an anisotropic decrease in the unit cell parameters, with c and a decreasing by 0.45 and 0.03 %, respectively. Structural changes are mainly confined to the A site environment. Only minor changes occur in FeO6 and SO4 polyhedra. The structure responds upon cooling by increasing bond length distortion and by decreasing quadratic elongation of the large AO12 polyhedra. The structural parameters at low temperature follow very similar patterns to structural changes that correspond to compositional variation in the jarosite group, which is characterised by the flexibility of AO12 polyhedra and rigidity of Fe(OH)4O2–SO4 layers. The most flexible areas in the jarosite structure are localized at AO12 edges that are not shared with neighbouring FeO6 octahedra. Importantly, for the application of XRD in planetary settings, the temperature-related changes in jarosite can mimic compositional change.
Gordon PR, Sephton MA, 2016, Rapid habitability assessment of Mars samples by pyrolysis-FTIR, Planetary and Space Science, Vol: 121, Pages: 60-75, ISSN: 1873-5088
Pyrolysis Fourier transform infrared spectroscopy (pyrolysis FTIR) is a potential sample selection method for Mars Sample Return missions. FTIR spectroscopy can be performed on solid and liquid samples but also on gases following preliminary thermal extraction, pyrolysis or gasification steps. The detection of hydrocarbon and non-hydrocarbon gases can reveal information on sample mineralogy and past habitability of the environment in which the sample was created. The absorption of IR radiation at specific wavenumbers by organic functional groups can indicate the presence and type of any organic matter present. Here we assess the utility of pyrolysis-FTIR to release water, carbon dioxide, sulphur dioxide and organic matter from Mars relevant materials to enable a rapid habitability assessment of target rocks for sample return. For our assessment a range of minerals were analysed by attenuated total reflectance FTIR. Subsequently, the mineral samples were subjected to single step pyrolysis and multi step pyrolysis and the products characterised by gas phase FTIR.Data from both single step and multi step pyrolysis-FTIR provide the ability to identify minerals that reflect habitable environments through their water and carbon dioxide responses. Multi step pyrolysis-FTIR can be used to gain more detailed information on the sources of the liberated water and carbon dioxide owing to the characteristic decomposition temperatures of different mineral phases. Habitation can be suggested when pyrolysis-FTIR indicates the presence of organic matter within the sample. Pyrolysis-FTIR, therefore, represents an effective method to assess whether Mars Sample Return target rocks represent habitable conditions and potential records of habitation and can play an important role in sample triage operations.
Abubakar R, Muxworthy AR, Sephton M, et al., 2016, Mapping Petroleum Migration Pathways in Wessex Basin Using Magnetics and Seismic Mapping (poster), Magnetic Interactions 2016
Walter N, Rettberg P, Fellous JL, et al., 2016, Considering planetary protection of outer space bodies - The European PPOSS project, ISSN: 0074-1795
The PPOSS (Planetary Protection of Outer Solar System bodies) project, coordinated by the European Science Foundation is supported by the European Commission Horizon 2020 programme. This project kicked-off in January 2016 and will last for three years. The PPOSS project intends to consider how planetary protection policy has been developed and is being implemented, it will look at case studies, lessons learnt and good practices in order to produce a Planetary Protection handbook that will be widely disseminated. The project will also look forward and address the complex issues of organic and biological contamination of outer solar system bodies, in particular small bodies and moons of gas giant planets. PPOSS will identify knowledge gaps, propose scientific goals and suggest activities to overcome the main hurdles to reach these goals. Besides scientific issues, PPOSS will consider the European engineering landscape and the capacity of the European industry to meet the challenges raised by planetary protection of outer solar system bodies, an engineering roadmap will result from this effort. As a one of the main outcomes, the PPOSS project will eventually review the international planetary protection regulation structure, process and categorization related to outer solar system bodies, it will suggest policy improvements to COSPAR Panel on Planetary Protection. PPOSS is implemented by a consortium of seven European and international organisations (European Science Foundation, DLR, COSPAR, Eurospace, INAF, Space Technology Ireland, Imperial College) as well as by international partners, including the Chinese Academy of Sciences and China Academy of Space Technology. The project intends to broaden its international footprint and allow a dedicated forum to address the scientific, technical and policy challenges raised by planetary protection of outer solar system bodies.
Abubakar R, Muxworthy AR, Sephton MA, et al., 2015, Formation of magnetic minerals at hydrocarbon-generation conditions, Marine and Petroleum Geology, Vol: 68, Pages: 509-519, ISSN: 0264-8172
Watson JS, Sephton MA, 2015, Heat, clay and aromatic units: a mechanism for making macromolecules in the early solar system, Astrobiology, Vol: 15, Pages: 787-792, ISSN: 1557-8070
The major organic component in carbonaceous chondrites is ahighly aromatic macromolecular material. Aromatic organic matter andphyllosilicates are co-located in these meteorites and it is possible that thephysical association represents a synthetic chemical relationship. To explore thepotential reactions that could take place to produce the aromatic macromolecularmaterial we heated various simple aromatic units in the presence ofmontmorillonite with different exchanged cations. The majority of cationexchanged montmorillonites tested, sodium-, aluminium-, iron-, nickel- andcobalt-rich montmorillonites, do not produce polymerisation products. By contrastFe3+ cation exchanged montmorillonite readily facilitates addition reactionsbetween aromatic hydrocarbons. A feasible mechanism for the process isoxidative coupling which involves a corresponding reduction of the Fe3+ cation to its Fe2+ counterpart. A similar reduction process for the other metal cations does not take place highlighting the importance of iron. This simple process is a feasible mechanism for the addition to the aromatic macromolecules such as thosefound in carbonaceous chondrites. The search for a relationship between Fe3+-richphyllosilicates and aromatic organic structures (particularly dimers, trimers and more polymerised forms) in carbonaceous chondrites would represent an effective test for constraining the role of clay catalysis in the early solar system.
Mustafa KA, Sephton MA, Watson JS, et al., 2015, Organic geochemical characteristics of black shales across the Ordovician-Silurian boundary in the Holy Cross Mountains, Central Poland, Marine and Petroleum Geology, Vol: 66, Pages: 1042-1055, ISSN: 1873-4073
Black shales in the Holy Cross Mountains area of Poland provide a record of environmental change across the Ordovician-Silurian boundary. The changing depositional conditions have generated a variation in organic matter contents above and below the boundary. Investigating the organic constitution of these black shales has the potential to reveal how their organic matter contents were generated and how suitable these rocks and their lateral equivalents may be for exploitation as shale gas reservoirs. One outcrop at the Holy Cross Mountains with a continuous section across the Ordovician-Silurian boundary occurs near the village of Bardo Stawy in the Kielce region, and contains sandy-silty mudstones, as well as grey and black shales. Organic geochemical analyses of samples at Bardo Stawy reveals low Total Organic Carbon (TOC) contents for Ordovician samples and higher TOC values for Silurian samples. Organic biomarkers indicate that the Ordovician rocks were deposited in a shallow-marine shelf setting, while the Silurian rocks were deposited in a deeper marine environment. The progressive increase in TOC from the uppermost Ordovician to the lowermost Silurian rocks reflects increasingly oxygen-poor depositional conditions during the post-glacial transgression. Following the deposition and preservation of organic matter in the Ordovician and Silurian rocks, these rocks were buried and subjected to thermal maturation. Rock Eval and biomarker thermal maturity parameters all indicate that the organic matter is mature and lies within the oil window. The Ordovician and Silurian shales have direct relevance to recent attempts to discover and exploit shale gas reservoirs in Poland. Our data and interpretations suggest that the relatively low TOC values (<2%) and low maturities for gas generation render these rocks unsuitable for commercial shale gas production. The progressive improvement in conditions for preserving organic matter across the Ordovician-Silurian boundary d
Wright MC, Court RW, Kafantaris F-CA, et al., 2015, A new rapid method for shale oil and shale gas assessment, Fuel, Vol: 153, Pages: 231-239, ISSN: 0016-2361
Sephton MA, Carter JN, 2015, The chances of detecting life on Mars, PLANETARY AND SPACE SCIENCE, Vol: 112, Pages: 15-22, ISSN: 0032-0633
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- Citations: 11
Luong D, Sephton MA, Watson JS, 2015, Subcritical water extraction of organic matter from sedimentary rocks, ANALYTICA CHIMICA ACTA, Vol: 879, Pages: 48-57, ISSN: 0003-2670
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Matthewman R, Court RW, Crawford IA, et al., 2015, The Moon as a Recorder of Organic Evolution in the Early Solar System: A Lunar Regolith Analog Study, Astrobiology, Vol: 15, Pages: 154-168, ISSN: 1531-1074
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