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  • Book chapter
    Morgan J, Rebolledo-Vieyra M, 2013,

    Geophysical studies of impact craters

    , Impact Cratering, Editors: Osinski, Pierazzo, Publisher: Wiley-Blackwell, Pages: 211-222, ISBN: 9781405198295
  • Book chapter
    Kenkmann T, Collins GS, Wuennemann K, 2013,

    The modification stage of crater formation

    , Impact Cratering: Processes and Products, Editors: Osinski, Pierazzo, Publisher: Wiley-Blackwell, ISBN: 9781405198295
  • Book chapter
    Collins GS, Wuennemann K, Artemieva N, Pierazzo Eet al., 2013,

    Numerical modelling of impact processes

    , Impact Cratering: Processes and Products, Editors: Osinski, Pierazzo, Publisher: Wiley-Blackwell, ISBN: 9781405198295
  • Journal article
    Goldberg T, Gordon G, Izon G, Archer C, Pearce CR, McManus J, Anbar AD, Rehkaemper Met al., 2013,

    Resolution of inter-laboratory discrepancies in Mo isotope data: an intercalibration

    , JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY, Vol: 28, Pages: 724-735, ISSN: 0267-9477
  • Journal article
    Lambelet M, Rehkaemper M, de Flierdt TV, Xue Z, Kreissig K, Coles B, Porcelli D, Andersson Pet al., 2013,

    Isotopic analysis of Cd in the mixing zone of Siberian rivers with the Arctic Ocean-New constraints on marine Cd cycling and the isotope composition of riverine Cd

    , EARTH AND PLANETARY SCIENCE LETTERS, Vol: 361, Pages: 64-73, ISSN: 0012-821X
  • Journal article
    Theis KJ, Schoenbaechler M, Benedix GK, Rehkaemper M, Andreasen R, Davies Cet al., 2013,

    Palladium-silver chronology of IAB iron meteorites

    , EARTH AND PLANETARY SCIENCE LETTERS, Vol: 361, Pages: 402-411, ISSN: 0012-821X
  • Journal article
    Muxworthy AR, Evans ME, 2013,

    Micromagnetics and magnetomineralogy of ultrafine magnetite inclusions in the Modipe Gabbro

    , Geochemistry Geophysics Geosystems, ISSN: 1525-2027
  • Conference paper
    Shah J, Ashley J, Muxworthy AR, Matzka J, Leonhardt R, Leitner Met al., 2013,

    Palaeomagnetic investigation of the South Atlantic geomagnetic anomaly using Quaternary Tristan da Cunha lavas

    , Magnetic Interactions
  • Conference paper
    Hodgson E, Biggin AJ, Hill M, Muxworthy ARet al., 2013,

    Understanding non-ideal behaviour in interacting single domain and multi-domain magnetite using synthetic magnetite samples (poster)

    , Magnetic Interactions
  • Conference paper
    Lappe S-CLL, Feinberg J, Muxworthy AR, Harrison Ret al., 2013,

    Comparison and calibration of non-heating palaeointensity methods: a case study using dusty olivine

    , Magnetic Interactions
  • Conference paper
    Muxworthy AR, Evans ME, Scourfield S, King JGet al., 2013,

    Revisiting the the Modipe Gabbro: new palaeointensity data

    , Magnetic Interactions
  • Conference paper
    Abubakar R, Muxworthy AR, Sephton MA, Fraser Aet al., 2013,

    Experimental investigation of magnetic mineral formation in hydrocarbon environments (poster)

    , Magnetic Interactions
  • Journal article
    Elbeshausen D, Wünnemann K, Collins GS, 2013,

    The transition from circular to elliptical impact craters

    , Journal of Geophysical Research: Planets, Vol: 118, Pages: 2295–2309-2295–2309, ISSN: 2169-9100

    Elliptical impact craters are rare among the generally symmetric shape of impact structures on planetary surfaces. Nevertheless, a better understanding of the formation of these craters may significantly contribute to our overall understanding of hypervelocity impact cratering. The existence of elliptical craters raises a number of questions: Why do some impacts result in a circular crater whereas others form elliptical shapes? What conditions promote the formation of elliptical craters? How does the formation of elliptical craters differ from those of circular craters? Is the formation process comparable to those of elliptical craters formed at subsonic speeds? How does crater formation work at the transition from circular to elliptical craters? By conducting more than 800 three-dimensional (3-D) hydrocode simulations, we have investigated these questions in a quantitative manner. We show that the threshold angle for elliptical crater generation depends on cratering efficiency. We have analyzed and quantified the influence of projectile size and material strength (cohesion and coefficient of internal friction) independently from each other. We show that elliptical craters are formed by shock-induced excavation, the same process that forms circular craters and reveal that the transition from circular to elliptical craters is characterized by the dominance of two processes: A directed and momentum-controlled energy transfer in the beginning and a subsequent symmetric, nearly instantaneous energy release.

  • Book chapter
    Jones AP, Genge MJ, Carmody L, 2013,

    Carbonate Melts and Carbonatites

    , Carbon in the Earth, Publisher: Mineralogical Society of America, Pages: 289-322
  • Journal article
    Sephton MA, Hazen RM, 2013,

    On the origins of deep hydrocarbons

    , Reviews in Mineralogy & Geochemistry, Vol: 75, Pages: 449-465, ISSN: 1529-6466

    Deep deposits of hydrocarbons, including varied reservoirs of petroleum and natural gas,represent the most economically important component of the deep carbon cycle. Yet despitetheir intensive study and exploitation for more than a century, details of the origins of somedeep hydrocarbons remain a matter of vocal debate in some scientific circles. This long andcontinuing history of controversy may surprise some readers, for the biogenic origins of “fossilfuels”—a principle buttressed by a vast primary scientific literature and established as textbookorthodoxy in North America and many other parts of the world—might appear to be settled fact.Nevertheless, conventional wisdom continues to be challenged by some scientists.The principal objectives of this chapter are: (1) to review the overwhelming evidence for thebiogenic origins of most known deep hydrocarbon reservoirs; (2) to present equally persuasiveexperimental, theoretical, and field evidence that components of some deep hydrocarbondeposits appear to have an abiotic origin; and (3) to suggest future studies that might help toachieve a more nuanced resolution of this sometimes polarized topic.

  • Journal article
    Jacobs CT, Collins GS, Piggott MD, Kramer SC, Wilson CRGet al., 2013,

    Multiphase flow modelling of volcanic ash particle settling in water using adaptive unstructured meshes

    , Geophysical Journal International, Vol: 192, Pages: 647-665

    Small-scale experiments of volcanic ash particle settling in water have demonstrated that ash particles can either settle slowly and individually, or rapidly and collectively as a gravitationally unstable ash-laden plume. This has important implications for the emplacement of tephra deposits on the seabed. Numerical modelling has the potential to extend the results of laboratory experiments to larger scales and explore the conditions under which plumes may form and persist, but many existing models are computationally restricted by the fixed mesh approaches that they employ. In contrast, this paper presents a new multiphase flow model that uses an adaptive unstructured mesh approach. As a simulation progresses, the mesh is optimized to focus numerical resolution in areas important to the dynamics and decrease it where it is not needed, thereby potentially reducing computational requirements. Model verification is performed using the method of manufactured solutions, which shows the correct solution convergence rates. Model validation and application considers 2-D simulations of plume formation in a water tank which replicate published laboratory experiments. The numerically predicted settling velocities for both individual particles and plumes, as well as instability behaviour, agree well with experimental data and observations. Plume settling is clearly hindered by the presence of a salinity gradient, and its influence must therefore be taken into account when considering particles in bodies of saline water. Furthermore, individual particles settle in the laminar flow regime while plume settling is shown (by plume Reynolds numbers greater than unity) to be in the turbulent flow regime, which has a significant impact on entrainment and settling rates. Mesh adaptivity maintains solution accuracy while providing a substantial reduction in computational requirements when compared to the same simulation performed using a fixed mesh, highlighting the benefits of an adapt

  • Journal article
    Sephton MA, Court RW, Lewis JM, Wright MC, Gordon PRet al., 2013,

    Selecting samples for Mars sample return: Triage by pyrolysis-FTIR

    , Planetary and Space Science, Vol: 78, Pages: 45-51, ISSN: 0032-0633

    A future Mars Sample Return mission will deliver samples of the red planet to Earth laboratories for detailed analysis. A successful mission will require selection of the best samples that can be used to address the highest priority science objectives including assessment of past habitability and evidence of life. Pyrolysis is a commonly used method for extracting organic information from rocks but is most often coupled with complex analytical steps such as gas chromatography and mass spectrometry. Pyrolysis-Fourier transform infrared spectroscopy is a less resource demanding method that still allows sample characterization. Here we demonstrate how pyrolysis-Fourier transform infrared spectroscopy could be used to triage samples destined to return to Earth, thereby maximising the scientific return from future sample return missions.

  • Journal article
    Sephton MA, 2013,

    Pyrolysis, spectroscopy and extraterrestrial organic matter

    , SpectroscopyEurope, Vol: 25, Pages: 6-11, ISSN: 0966-0941
  • Journal article
    Sephton MA, James RH, Fehr MA, Bland PA, Gounelle Met 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 article
    Matthewman 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

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