Quantitative evolved gas analysis: Winchcombe in comparison with other CM2 meteorites |
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| Authors: | A В Verchovsky F A J Abernethy M Anand S J Barber R Findlay I A Franchi R C Greenwood M M Grady |
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| Institution: | School of Physical Sciences, The Open University, Milton Keynes, UK |
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| Abstract: | Two bulk Winchcombe along with six other CM2 meteorite samples were subjected to quantitative evolved gas analysis. The observed release patterns for almost all volatile species demonstrate close similarity for all the samples and especially between those for Winchcombe. This can be considered as a fingerprint for this petrological type of meteorites. We identified several gases including H2, H2O, O2, CO, CO2, and SO2 released in different temperature ranges. The sources and mechanisms of their release were also established. Some of the gases, H2, CO, and CO2, are released as a result of oxidation of macromolecular organic material from oxygen derived from oxygen-bearing minerals (a part of CO2 is also released as a result of decomposition of carbonates). The others, O2 and H2O, are associated with the phase transformation/decomposition of phyllosilicates and (oxy)hydrates, while a high-temperature release of SO2 is associated mostly with the decomposition of sulfides and in few cases also with sulfates. A low-temperature release of SO2 is due to evaporation and oxidation of elemental sulfur from the meteoritic matrix and organic material. The total concentrations of H (mostly represented by H2O), C, and S, calculated according to calibration of the quadrupole mass spectrometer with reference gases and decomposition of solid samples (CaSO4·2H2O and NaHCO3) are in reasonable agreement with those determined by independent methods. Variations in the ratio of the carbon amounts released as CO2 and CO ( /CCO) between the samples could be an indicator of their terrestrial weathering. |
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