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  • 1
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    Glacial isostatic adjustment in response to changing Late Holocene behaviour of ice streams on the Siple Coast, West Antarctica (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-08
    Description: The Siple Coast region of Antarctica contains a number of fast-flowing ice streams, which control the dynamics and mass balance of the region. These ice streams are known to undergo stagnation and reactivation cycles, which lead to ice thickness changes that may be sufficient to excite a viscous solid Earth response (glacial isostatic adjustment; GIA). This study aims to quantify Siple Coast ice thickness changes during the last 2000 yr in order to determine the degree to which they might contribute to GIA and associated present-day bedrock uplift rates. This is important because accurate modelling of GIA is necessary to determine the rate of present-day ice-mass change from satellite gravimetry. Recently-published reconstructions of ice-stream variability were used to create a suite of kinematic models for the stagnation-related thickening of Kamb Ice Stream since ~1850 AD, and a GIA model was used to predict present-day deformation rates in response to this thickening. A number of longer-term loading scenarios, which include the stagnation and reactivation of ice streams across the Siple Coast over the past 2000 yr, were also constructed, and used to investigate the longer term GIA signal in the region. Uplift rates for each of the ice loading histories, based on a range of earth models, were compared with regional GPS-observed uplift rates and an empirical GIA estimate. We estimate Kamb Ice Stream to have thickened by 70–130 m since stagnation ~165 years ago. Modelled present-day vertical motion in response to this load increase peaks at –17 mm yr –1 (i.e. 17 mm yr –1 subsidence) for the weakest earth models tested here. Comparison of the solid Earth response to ice load changes throughout the last glacial cycle, including ice stream stagnation and reactivation across the Siple Coast during the last 2000 yr, with an empirical GIA estimate suggests that the upper mantle viscosity of the region is greater than 1 x 10 20 Pa s. When upper mantle viscosity values of 1 x 10 20  Pa s or smaller are combined with our suite of ice-load scenarios we predict uplift rates across Siple Coast that are at least 4 mm yr –1 smaller than those predicted by the empirical GIA estimate. GPS data are unable to further constrain model parameters due to the distance of the GPS sites from the study area. Our results demonstrate that Late Holocene ice load changes related to the stagnation and reactivation of ice streams on the Siple Coast may play a dominant role in defining the present-day uplift signal. However, both the detailed Earth structure and deglacial history of the region need to be better constrained in order to reduce uncertainties associated with the GIA signal of this region.
    Keywords: Geodynamics and Tectonics
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 2
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    Vapor‐Deposited Minerals Contributed to the Martian Surface During Magmatic Degassing (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Martian magmas were likely enriched in S and Cl with respect to H2O. Exsolution of a vapor phase from these magmas and ascent of the gas bubbles through the magma plumbing system would have given rise to shallow magmas that were gas‐charged. Release and cooling of this gas from lava flows during eruption may have resulted in the addition of a significant amount of vapor‐deposited phases to the fines of the surface. Experiments were conducted to simulate degassing of gas‐charged lava flows and shallow intrusions in order to determine the nature of vapor‐deposited phases that may form through this process. The results indicate that magmatic gas may have contributed a large amount of Fe, S, and Cl to the Martian surface through the deposition of iron oxides (magnetite, maghemite, and hematite), chlorides (molysite, halite, and sylvite), sulfur, and sulfides (pyrrhotite and pyrite). Primary magmatic vapor‐deposited minerals may react during cooling to form a variety of secondary products, including iron oxychloride (FeOCl), akaganéite (Fe3+O (OH,Cl)), and jarosite (KFe3+3(OH)6(SO4)2). Vapor‐deposition does not transport significant amounts of Ca, Al, or Mg from the magma and hence, this process does not directly deposit Ca‐ or Mg‐sulfates.
    Print ISSN: 2169-9097
    Electronic ISSN: 2169-9100
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    The origin and implications of clay minerals from Yellowknife Bay, Gale crater, Mars (2015)
    Mineralogical Society of America
    Details
    Publication Date: 2015-04-02
    Description: The Mars Science Laboratory (MSL) rover Curiosity has documented a section of fluvio-lacustrine strata at Yellowknife Bay (YKB), an embayment on the floor of Gale crater, approximately 500 m east of the Bradbury landing site. X-ray diffraction (XRD) data and evolved gas analysis (EGA) data from the CheMin and SAM instruments show that two powdered mudstone samples (named John Klein and Cumberland) drilled from the Sheepbed member of this succession contain up to ~20 wt% clay minerals. A trioctahedral smectite, likely a ferrian saponite, is the only clay mineral phase detected in these samples. Smectites of the two samples exhibit different 001 spacing under the low partial pressures of H 2 O inside the CheMin instrument (relative humidity 〈1%). Smectite interlayers in John Klein collapsed sometime between clay mineral formation and the time of analysis to a basal spacing of 10 Å, but largely remain open in the Cumberland sample with a basal spacing of ~13.2 Å. Partial intercalation of Cumberland smectites by metal-hydroxyl groups, a common process in certain pedogenic and lacustrine settings on Earth, is our favored explanation for these differences. The relatively low abundances of olivine and enriched levels of magnetite in the Sheepbed mudstone, when compared with regional basalt compositions derived from orbital data, suggest that clay minerals formed with magnetite in situ via aqueous alteration of olivine. Mass-balance calculations are permissive of such a reaction. Moreover, the Sheepbed mudstone mineral assemblage is consistent with minimal inputs of detrital clay minerals from the crater walls and rim. Early diagenetic fabrics suggest clay mineral formation prior to lithification. Thermodynamic modeling indicates that the production of authigenic magnetite and saponite at surficial temperatures requires a moderate supply of oxidants, allowing circum-neutral pH. The kinetics of olivine alteration suggest the presence of fluids for thousands to hundreds of thousands of years. Mineralogical evidence of the persistence of benign aqueous conditions at YKB for extended periods indicates a potentially habitable environment where life could establish itself. Mediated oxidation of Fe 2+ in olivine to Fe 3+ in magnetite, and perhaps in smectites provided a potential energy source for organisms.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 4
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    Mid-infrared emission spectroscopy and visible/near-infrared reflectance spectroscopy of Fe-sulfate minerals (2014)
    Mineralogical Society of America
    Details
    Publication Date: 2014-12-24
    Description: Sulfate minerals are important indicators for aqueous geochemical environments. The geology and mineralogy of Mars have been studied through the use of various remote-sensing techniques, including thermal (mid-infrared) emission and visible/near-infrared reflectance spectroscopies. Spectral analyses of spacecraft data (from orbital and landed missions) using these techniques have indicated the presence of sulfate minerals on Mars, including Fe-rich sulfates on the iron-rich planet. Each individual Fe-sulfate mineral can be used to constrain bulk chemistry and lends more information about the specific formational environment [e.g., Fe 2+ sulfates are typically more water soluble than Fe 3+ sulfates and their presence would imply a water-limited (and lower Eh) environment; Fe 3+ sulfates form over a range of hydration levels and indicate further oxidation (biological or abiological) and increased acidification]. To enable better interpretation of past and future terrestrial or planetary data sets, with respect to the Fe-sulfates, we present a comprehensive collection of mid-infrared thermal emission (2000 to 220 cm –1 ; 5–45 μm) and visible/near-infrared (0.35–5 μm) spectra of 21 different ferrous- and ferric-iron sulfate minerals. Mid-infrared vibrational modes (for SO 4 , OH, H 2 O) are assigned to each thermal emissivity spectrum, and the electronic excitation and transfer bands and vibrational OH, H 2 O, and SO 4 overtone and combination bands are assigned to the visible/near-infrared reflectance spectra. Presentation and characterization of these Fe-sulfate thermal emission and visible/near-infrared reflectance spectra will enable the specific chemical environments to be determined when individual Fe-sulfate minerals are identified.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 5
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    The petrochemistry of Jake_M: a martian mugearite (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-09-28
    Description: "Jake_M," the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the Curiosity rover, differs substantially in chemical composition from other known martian igneous rocks: It is alkaline (〉15% normative nepheline) and relatively fractionated. Jake_M is compositionally similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. By analogy with these comparable terrestrial rocks, Jake_M could have been produced by extensive fractional crystallization of a primary alkaline or transitional magma at elevated pressure, with or without elevated water contents. The discovery of Jake_M suggests that alkaline magmas may be more abundant on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for example, phonolites and trachytes).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stolper, E M -- Baker, M B -- Newcombe, M E -- Schmidt, M E -- Treiman, A H -- Cousin, A -- Dyar, M D -- Fisk, M R -- Gellert, R -- King, P L -- Leshin, L -- Maurice, S -- McLennan, S M -- Minitti, M E -- Perrett, G -- Rowland, S -- Sautter, V -- Wiens, R C -- MSL Science Team -- New York, N.Y. -- Science. 2013 Sep 27;341(6153):1239463. doi: 10.1126/science.1239463.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Caltech, Pasadena, CA 91125, USA. ems@gps.caltech.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24072927" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale crater, Mars (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-12-11
    Description: Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine-rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of Mars.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McLennan, S M -- Anderson, R B -- Bell, J F 3rd -- Bridges, J C -- Calef, F 3rd -- Campbell, J L -- Clark, B C -- Clegg, S -- Conrad, P -- Cousin, A -- Des Marais, D J -- Dromart, G -- Dyar, M D -- Edgar, L A -- Ehlmann, B L -- Fabre, C -- Forni, O -- Gasnault, O -- Gellert, R -- Gordon, S -- Grant, J A -- Grotzinger, J P -- Gupta, S -- Herkenhoff, K E -- Hurowitz, J A -- King, P L -- Le Mouelic, S -- Leshin, L A -- Leveille, R -- Lewis, K W -- Mangold, N -- Maurice, S -- Ming, D W -- Morris, R V -- Nachon, M -- Newsom, H E -- Ollila, A M -- Perrett, G M -- Rice, M S -- Schmidt, M E -- Schwenzer, S P -- Stack, K -- Stolper, E M -- Sumner, D Y -- Treiman, A H -- VanBommel, S -- Vaniman, D T -- Vasavada, A -- Wiens, R C -- Yingst, R A -- MSL Science Team -- New York, N.Y. -- Science. 2014 Jan 24;343(6169):1244734. doi: 10.1126/science.1244734. Epub 2013 Dec 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geosciences, State University of New York, Stony Brook, NY 11794, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24324274" target="_blank"〉PubMed〈/a〉
    Keywords: Bays ; Calcium Sulfate/analysis/chemistry ; Chlorine/analysis/chemistry ; *Exobiology ; Extraterrestrial Environment/*chemistry ; Ferrosoferric Oxide/analysis/chemistry ; Geologic Sediments/*chemistry ; Halogens/analysis/chemistry ; Hydrogen-Ion Concentration ; Iron/analysis/chemistry ; Magnesium/analysis/chemistry ; *Mars ; Silicates/analysis/chemistry ; Water/chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Characteristics of pebble and cobble-sized clasts along the Curiosity rover traverse from Bradbury Landing to Rocknest (2013)
    Wiley
    Details
    Publication Date: 2013-10-19
    Description: [1]  We have assessed the characteristics of clasts along Curiosity's traverse to shed light on the processes important in the genesis, modification and transportation of surface materials. Pebble- to cobble-sized clasts at Bradbury Landing, and subsequently along Curiosity's traverse to Yellowknife Bay, reflect a mixing of two endmember transport mechanisms. The general clast population likely represents material deposited via impact processes, including meteorite fragments, ejecta from distant craters, and impactites consisting of shocked and shock melted materials from within Gale Crater, which resulted predominantly in larger, angular clasts. A subset of rounded pebble-sized clasts has likely been modified by intermittent alluvial or fluvial processes. The morphology of this rounded clast population indicates that water was a more important transporting agent here than at other Mars sites that have been studied in situ. Finally, we identified populations of basalt clasts and porphyritic clasts of undetermined composition by their morphologic and textural characteristics; basalts are confirmed by geochemical data provided by ChemCam.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Electronic Resource
    Electronic Resource
    Core level photoelectron microscopy with synchrotron radiation (invited) : INTERNATIONAL CONFERENCE ON SYNCHROTRON RADIATION INSTRUMENTATION (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 1686-1689 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The capabilities of a direct imaging photoelectron microscope (MicroESCA from Surface Science Instruments) have been demonstrated in a set of experiments carried out at the Stanford Synchrotron Radiation Laboratory (SSRL) using a torroidal grating monochromator in the photon energy range 20–170 eV. Photoelectrons from a 300×300 μm2 sample area are projected in the diverging magnetic field of a superconducting solenoid and an image reflecting the variation in photoelectron yield is recorded digitally with a resistive anode imaging detector. Lateral resolution is better than 5 μm. A retarding field analyzer located in front of the imaging detector acts as a high-pass filter and allows us to obtain a series of spectrally resolved images which can be processed to give a spot XPS analysis of areas as small as 5×5 μm2. Images from a sample of patterned aluminum on silicon are presented to demonstrate the potential of the instrument.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141066
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  • 9
    Electronic Resource
    Electronic Resource
    An optical cell for photographic studies of gas evolution during molten salt electrolysis (1972)
    Springer
    Journal of applied electrochemistry 2 (1972), S. 23-29 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The simple optical cell described is useful for providing supplementary information on the evolution of gases during the electrolysis of fused salts or other electrolytes. Its use with PbS-PbCl2 and PbS-PbCl2-NaCl melts demonstrated that, for anodic sulphur gas production, residual gas evolution occurs, indicating the formation of a chemisorbed species as a reaction intermediate. Dissolution of the sulphur in the melt also takes place; its rate increases with increase in temperature and sulphide concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00615188
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  • 10
    Electronic Resource
    Electronic Resource
    FTIR micro-reflectance measurements of the CO3 2– ion content in basanite and leucitite glasses (1996)
    Springer
    Contributions to mineralogy and petrology 125 (1996), S. 311-318 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Infrared spectroscopy provides a reliable method for rapid, non-destructive quantitative analysis of volatile species in silicate glasses, with applications to geochemistry and volcanology. The technique has been extensively calibrated for transmission measurements, in which the species concentration present is correlated with the height or area of characteristic absorption peaks, for doubly polished samples of known thickness. There are several drawbacks associated with this method, including the need for double polishing of parallel faces on thin samples, the errors associated with sample thickness measurement, and total absorption of the IR beam intensity for samples with high volatile content. We have tested an alternative method for quantitative IR determination of volatile concentrations in silicate glasses, based on analysis of the IR reflectivity signal. The reflectivity method requires preparation of a single polished glass surface, and no thickness measurement of the sample is necessary. The technique is applied easily as a microbeam technique using apertures as small as a few μm in diameter. The method should be particularly useful for volatile analysis of glass inclusions in phenocrystals, or standard samples in thin section. We have developed the methodology for the technique using a series of basanite and leucitite glasses with high carbonate contents (〉1 wt% CO2), which could not be easily analyzed via IR transmission. We have used SIMS to standardize the technique. Two features observed in the reflectance spectra near 1400 cm–1 and 1500 cm–1 are due to resonance of the infrared beam with the asymmetric stretching vibrations of carbonate groups. The contribution of these species to the total reflectivity is directly correlated with the carbon abundance in the samples. This forms the basis for an empirical quantitative analysis. The optical constants, including the IR absorption coefficients associated with the CO3 2– stretching vibrations, have been extracted by Kramers-Kronig analysis of the reflectivity data. The molar extinction coefficients are 1119 ± 138 L mol–1 cm–1 and 1198 ± 145 L mol–1 cm–1 for the 1400 and 1500 cm–1 bands, respectively, in excellent agreement with results of previous transmission studies, after orientation effects are taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050224
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