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Title: Redox variations in the inner solar system with new constraints from vanadium XANES in spinels

Authors:
; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Aeronautic and Space Administration (NASA)
OSTI Identifier:
1324789
Resource Type:
Journal Article
Resource Relation:
Journal Name: American Mineralogist; Journal Volume: 101; Journal Issue: 9
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Righter, Kevin, Sutton, Steve R., Danielson, Lisa, Pando, Kellye, and Newville, Matt. Redox variations in the inner solar system with new constraints from vanadium XANES in spinels. United States: N. p., 2016. Web. doi:10.2138/am-2016-5638.
Righter, Kevin, Sutton, Steve R., Danielson, Lisa, Pando, Kellye, & Newville, Matt. Redox variations in the inner solar system with new constraints from vanadium XANES in spinels. United States. doi:10.2138/am-2016-5638.
Righter, Kevin, Sutton, Steve R., Danielson, Lisa, Pando, Kellye, and Newville, Matt. 2016. "Redox variations in the inner solar system with new constraints from vanadium XANES in spinels". United States. doi:10.2138/am-2016-5638.
@article{osti_1324789,
title = {Redox variations in the inner solar system with new constraints from vanadium XANES in spinels},
author = {Righter, Kevin and Sutton, Steve R. and Danielson, Lisa and Pando, Kellye and Newville, Matt},
abstractNote = {},
doi = {10.2138/am-2016-5638},
journal = {American Mineralogist},
number = 9,
volume = 101,
place = {United States},
year = 2016,
month = 9
}
  • The 1959 summit eruption of Kmore » $$\bar{i}$$lauea Volcano exhibited high lava fountains of gas-rich, primitive magma, containing olivine + chromian spinel in highly vesicular brown glass. Microprobe analysis of these samples shows that euhedral rims on olivine phenocrysts, in direct contact with glass, vary significantly in forsterite (Fo) content, at constant major-element melt composition, as do unzoned groundmass olivine crystals. Ferric/total iron (Fe+ 3/FeT)ratios for matrix and interstitial glasses, plus olivine-hosted glass inclusions in eight 1959 scoria samples have been determined by micro X-ray absorption near-edge structure spectroscopy (μ-XANES). These data show that much of the variation in Fo content reflects variation in oxidation state of iron in the melt, which varies with sulfur concentration in the glass and (locally) with proximity to scoria edges in contact with air. Data for 24 olivine-melt pairs in the better-equilibrated samples from later in the eruption show KD averaging 0.280 ± 0.03 for the exchange of Fe and Mg between olivine and melt, somewhat displaced from the value of 0.30 ± 0.03 given by Roeder and Emslie (1970). This may reflect the low SiO2 content of the 1959 magmas, which is lower than that in most K$$\bar{i}$$lauea tholeiites. More broadly, we show the potential of μ-XANES and electron microprobe to revisit and refine the value of KD in natural systems.« less
  • Climatically significant variation of the solar constant (the energy output of the sun) implies measurable change in the solar radius. The available data limit variations of the solar radius between 1850 and 1937 to about 0.25 arc second; modeling of the sun indicates that the solar constant did not vary by more than 0.3 percent during that time. 17 references.
  • Studies of the temporal properties of over 7000 hard X-ray solar flares as observed with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission have revealed hundreds of examples of fast spikes with durations of less than 1 s. This study quantitatively compares the spectra observed in a well-observed fast spike with the predicted spectra from a detailed, time-dependent, nonthermal beam model in order to impose new constraints on electron beam dynamics and path lengths. Assuming an instantaneous injection of electrons into the top of a coronal loop, the theoretical spectra are found to be consistent with the observedmore » spectra if the separation L, between the acceleration site and the thick target is greater than 10/sup 8/ cm. If the separation is much greater than 3 x 10/sup 9/ cm, then electrons with high pitch angles (>60/sup 0/) are either not produced or are mirrored before they reached the footpoints.« less