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Journal articleSephton MA, James RH, Fehr MA, et al., 2013,
Lithium isotopes as indicators of meteorite parent body alteration, Meteoritics & Planetary Science, Vol: 48, Pages: 872-878, ISSN: 1086-9379
Hydrothermal processing on planetesimals in the early solar system produced new mineral phases, including those generated by the transformation of anhydrous silicates into their hydrated counterparts. Carbonaceous chondrites represent tangible remnants of such alteration products. Lithium isotopes are known to be responsive to aqueous alteration, yet previously recognized variability within whole rock samples from the same meteorite appears to complicate the use of these isotopes as indicators of processing by water. We demonstrate a new way to use lithium isotopes that reflects aqueous alteration in carbonaceous chondrites. Temperature appears to exert a control on the production of acetic acid-soluble phases, such as carbonates and poorly crystalline Fe-oxyhydroxides. Temperature and degree of water-rock interaction determines the amount of lithium isotope fractionation expressed as the difference between whole rock and acetic acid-leachable fractions. Using these features, the type 1 chondrite Orgueil (d7Li(whole rock) = 4.3&; D7Li(acetic-whole) = 1.2&) can be distinguished from the type 2 chondrites Murchison (d7Li(whole rock) = 3.8; D7Li(acetic whole) = 8.8&) and carbonate-poor Tagish Lake (d7Li(whole rock) = 4.3; D7Li(acetic-whole) = 9.4&). This initial study suggests that lithium isotopes have the potential to reveal the role of liquid water in the early solar system.
Journal articleMatthewman R, Martins Z, Sephton MA, 2013,
Type IV kerogens as analogues for organic macromolecular materials in aqueously altered carbonaceous chondrites, Astrobiology, Vol: 13, Pages: 324-333, ISSN: 1531-1074
Conference paperMontgomery W, Sephton MA, Court RW, et al., 2013,
Quantitative Laboratory Assessment Of Aquathermolysis Chemistry During Steam-assisted Recovery Of Heavy Oils And Bitumen, With A Focus On Sulfur, SPE Heavy Oil Conference, Publisher: Society of Petroleum Engineers
The production of gaseous sulfur-containing species during the steam-assisted recovery of heavy oil and bitumen presents problems owing to their toxicity, corrosion properties and odor. In order to quantitatively study aquathermolysis sulfur chemistry during the thermal (steam-assisted) recovery of heavy oils we have subjected a well-characterized and sulfur-rich bitumen core sample to 150 - 325°C and 70 - 1740 psia (0.48 - 12 MPa) conditions in the continued presence of liquid water for 24 hours. The reaction products include gases, oil flotate, oil sinkate, water-soluble products, and water- insoluble residues. All have been studied with a variety of analytical techniques, including FTIR spectroscopy, chromatographic fractionation (SARA analysis), GC-FPD and GC-MS. Moreover, these techniques have been extended to analysis of the asphaltene fractions. Results suggest that some in-situ upgrading of the oil occurs under these conditions; additionally, gaseous hydrogen sulfide is released at temperatures at and above 250 °C. Variations in the relative abundances of solubility classes and chemical fractions imply that the source of sulfur is via the thermal degradation of resins and/or asphaltenes. The experimental methods, results and quantification approach discussed herein will be useful to support the development of models for engineering design of facilities for the steam-assisted recovery of heavy oils and bitumen.
Journal articleSephton MA, Sims MR, Court RW, et al., 2013,
Searching for biomolecules on Mars: Considerations for Operation of a Life Marker Chip instrument, Planetary and Space Science, Vol: 86, Pages: 66-74, ISSN: 0032-0633
The search for life on Mars requires instruments that detect organic matter and discriminate between potential sources. One such instrument is the Life Marker Chip that recognizes small molecules which are characteristic of particular organic provenances. The use of an antibody-based detection system requires the delivery of small organic compounds in a suitable solvent. Dedicated extraction protocols have been developed partly through the use of a Life Marker Chip breadboard system. Techniques which provide the strong diagnostic potential of the Life Marker Chip necessitate specific extraction protocols and appropriate sample types. Clay mineral-rich rocks are attractive targets owing to their i) association with liquid water, ii) propensity for organic matter and clay mineral co-deposition following transport from a wide hinterland, and iii) relatively large surface area and therefore potential for trapping/adsorption of organic materials. The most appropriate target organic compounds are the hydrocarbon-dominated lipids that can be highly diagnostic and have relatively high preservation potentials. The sample sites on Mars and sample preparation steps that are needed for successful detection require careful consideration. In this paper we explore the scientific results that may be obtained through the operation of a Life Marker Chip instrument on Mars.
Journal articleMontgomery W, Court RW, Rees AC, et al., 2013,
High temperature reactions of water with heavy oil and bitumen: insights into aquathermolysis chemistry during steam-assisted recovery, Fuel, Vol: 113, Pages: 426-426, ISSN: 0016-2361
To better understand the hot water-mediated organic transformation process (aquathermolysis) that occurs during the steam-assisted recovery of heavy oils and bitumen we have performed a series of experiments that subject a heavy oil to progressively higher temperatures and pressures in the presence of liquid water. As temperature and pressure increases, from ambient conditions to 300 °C and 1250 psig (8.6 MPa), a floating oil (flotate) is generated and is composed of mostly aliphatic hydrocarbons that appear to be generated at the expense of polars and asphaltenes. Analyses of hopane maturity parameters for the flotate indicate lower temperatures than the starting material suggesting the liberation of hopanes and, therefore, other hydrocarbons, from asphaltenes. Infrared spectra confirm changes in overall organic constitution as the relative abundance of hydrocarbons to oxygen-containing functional groups increases in the flotate. At the highest temperatures and pressures (325 °C, 1750 psig (13.8 MPa)) the flotate is at a maximum relative amount, the untransformed heavy oil is at a minimum and significant amounts of methane are generated indicating the onset of cracking. Steam-assisted recovery of heavy oil, therefore, leads to changes in the chemical constitution of a number of chemical fractions generating a lighter oil and gases that must be taken into account when planning field operations for production.
Journal articlePotter RWK, Kring DA, Collins GS, et al., 2013,
Numerical modeling of the formation and structure of the Orientale impact basin, Journal of Geophysical Research: Planets, Pages: n/a-n/a, ISSN: 2169-9100
Journal articlePotter RWK, Collins GS, 2013,
Numerical modeling of asteroid survivability and possible scenarios for the Morokweng crater-forming impact, Meteoritics & Planetary Science, Vol: 48, Pages: 744-757, ISSN: 1945-5100
ReportMustard JF, Adler M, Allwood A, et al., 2013,
Report of the Mars 2020 Science Definition Team, Report of the Mars 2020 Science Definition Team, Publisher: Mars Exploration Analysis Group (MEPAG)
Journal articleWainipee W, Cuadros J, Sephton MA, et al., 2013,
The effects of oil on As(V) adsorption on illite, kaolinite, montmorillonite and chlorite, Geochimica et Cosmochimica Acta, Vol: 121, Pages: 487-502, ISSN: 0016-7037
The effect of oil on As(V) adsorption on clay minerals has been investigated using batch experiments at low and high pH, NaCl concentration and oil contents. Four clay minerals were chosen because of their abundance in sediments and their different crystal chemistry: illite, kaolinite, montmorillonite, and chlorite. The values for pH were 4 and 8 and salt concentrations were 0.001 and 0.7 M NaCl to appreciate the effects of changing salinity, e.g from fresh water to seawater conditions. For the coating experiments, a well-characterised oil was used to survey the main effects of complex organic mixtures on adsorption and oil to clay mineral (w/w) ratios were 0.0325 and 0.3250. As(V) adsorption increased with increasing NaCl concentration, suggesting that the mechanisms of As(V) adsorption are related to the formation of inner-sphere complexes in which Na+ ions act as bridges between the clay surface and the As(V) anions. Cation bridging is also indicated by zeta potential measurements which show that higher NaCl concentrations along with the presence of As(V) can cause the clay particles and adsorbed ions to have a more negative overall charge. Adsorption is lower at higher pH due to the reduced number of positively charged sites on the edge of clay mineral layers. Oil coating reduces As(V) adsorption by decreasing the available surface area of clay minerals, except in the case of oil-coated montmorillonite, where surface area following dispersion in water is increased. The main variables controlling As(V) adsorption are surface area and surface charge density, as confirmed by a simplified quantitative model. These findings advance our ability to predict the effects of complex pollution events in various freshwater and marine settings.
Journal articleHoward KT, Bailey MJ, Berhanu D, et al., 2013,
Biomass preservation in impact melt ejecta, Nature Geoscience
Meteorites can have played a role in the delivery of life to Earth only if organic compounds are able to survive the high pressures and temperatures of an impact event. Although experimental impact studies have reported the survival of organics there are uncertainties in scaling experimental conditions to those of a meteorite impact on Earth and organic matter has not been found in highly shocked impact materials in a natural setting. Impact glass linked to the 1.2-km-diameter Darwin crater in western Tasmania is strewn over an area exceeding 400 km2 and is thought to have been ejected by a meteorite impact about 800 kyr ago into terrain consisting of rainforest and swamp. Here we use pyrolysis–gas chromatography–mass spectrometry to show that biomarkers representative of plant species in the local ecosystem—including cellulose, lignin, aliphatic biopolymer and protein remnants—survived the Darwin impact. We find that inside the impact glass the organic components are trapped in porous carbon spheres.We propose that the organic material was captured within impact melt and preserved when the melt quenched to glass, preventing organic decomposition since the impact. We suggest that organic material can survive capture and transport in products of extreme impact processing, at least for a Darwin-sized impact event.
Conference paperDodd S, Muxworthy AR, Mac Niocaill C, 2013,
Taking the pulse of the Parana-Etendeká large igneous province (poster), IAGA
Journal articlePotter RWK, Kring DA, Collins GS, 2013,
Quantifying the attenuation of structural uplift beneath large lunar craters, Geophysical Research Letters, Vol: 40, Pages: 5615–5620-5615–5620, ISSN: 1944-8007
Terrestrial crater observations and laboratory experiments demonstrate that target material beneath complex impact craters is uplifted relative to its preimpact position. Current estimates suggest maximum uplift is one tenth of the final crater diameter for terrestrial complex craters and one tenth to one fifth for lunar central peak craters. These latter values are derived from an analytical model constrained by observations from small craters and may not be applicable to larger complex craters and basins. Here, using numerical modeling, we produce a set of relatively simple analytical equations that estimate the maximum amount of structural uplift and quantify the attenuation of uplift with depth beneath large lunar craters.
Journal articleLarner F, Dogra Y, Dybowska A, et al., 2012,
Tracing Bioavailability of ZnO Nanoparticles Using Stable Isotope Labeling, ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 46, Pages: 12137-12145, ISSN: 0013-936X
- Author Web Link
- Citations: 59
Book chapterElmore RD, Muxworthy AR, Aldana MM, 2012,
Remagnetization and chemical alteration of sedimentary rocks, Remagnetization and Chemical Alteration of Sedimentary Rocks, Editors: Elmore, Muxworthy, Aldana, Mena, London, Publisher: Geological Society
Journal articleChang L, Roberts AP, Williams W, et al., 2012,
Giant magnetofossils and hyperthermal events, Earth and Planetary Science Letters, Vol: 351-352, Pages: 258-269
Journal articlePotter RWK, Kring DA, Collins GS, et al., 2012,
Estimating transient crater size using the crustal annular bulge: Insights from numerical modeling of lunar basin-scale impacts, GEOPHYSICAL RESEARCH LETTERS, Vol: 39, ISSN: 0094-8276
- Author Web Link
- Open Access Link
- Citations: 38
Journal articleBoyle EA, John S, Abouchami W, et al., 2012,
GEOTRACES IC1 (BATS) contamination-prone trace element isotopes Cd, Fe, Pb, Zn, Cu, and Mo intercalibration, LIMNOLOGY AND OCEANOGRAPHY-METHODS, Vol: 10, Pages: 653-665, ISSN: 1541-5856
- Author Web Link
- Citations: 85
Conference paperAlmeida TP, Muxworthy AR, Williams W, et al., 2012,
Dynamic exsolution of titanomagnetites and their associated magnetic response examined by complementary environmental TEM and off-axis electron holography, European Microscopy Congress
Conference paperGenge MJ, 2012,
THE ATMOSPHERIC ENTRY AND ABUNDANCE OF BASALTIC MICROMETEORITES, 75th Annual Meeting of the Meteoritical-Society, Publisher: WILEY, Pages: A145-A145, ISSN: 1086-9379
Conference paperGiscard MD, Hammond SJ, Bland PA, et al., 2012,
TRACE ELEMENT COMPOSITION OF METAL AND SULPHIDES IN IRON METEORITES DETERMINED USING ICP-MS, 75th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A149-A149, ISSN: 1086-9379
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