Assessment of alteration processes on circumstellar and interstellar grains in Queen Alexandra Range 97416

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10 Scopus citations

Abstract

Insight into the presolar and interstellar grain inventory of the CO3 chondrite Queen Alexandra Range (QUE) 97416 is gained through correlated secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), and synchrotron-based X-ray absorption near-edge structure spectroscopy (XANES). Only one presolar silicate grain [O17/O16=(9.96±0.75)×10-4; O18/O16=(19.49±0.96)×10-4] that may have formed in a low-mass Red Giant or Asymptotic Giant Branch star occurs in the coarse-grained matrix of QUE 97416. No other presolar grains were identified. Although presolar grains are rare in QUE 97416, numerous (898 ± 259 ppm) 15N-rich domains (δN15~+1447‰ to +3069‰) occur in the thin section. Based on TEM of an extracted section, two 15N-rich domains are amorphous, C-bearing, and texturally uniform, and they are embedded in a ferromagnesian silicate matrix with varied grain sizes. The individual 15N-rich organic regions with high δN15 (+2942 ± 107‰ and +2341 ± 140‰) exhibit diverse carbon functional groups, such as aromatic, vinyl-keto, amidyl, and carboxylic functionality, while the nitrogen XANES reveals traces of nitrile functionality. QUE 97416 appears to have escaped aqueous alteration based on the absence of hydrated minerals but is thermally altered, which could have resulted in the destruction of presolar grains. However, this process at >400°C metamorphic temperatures was inefficient in destroying the carriers of N isotope anomalies, which may indicate the resistant nature of the organic carriers and/or the limited extent of thermal metamorphism on the QUE 97416 parent body.

Original languageEnglish (US)
Pages (from-to)128-138
Number of pages11
JournalEarth and Planetary Science Letters
Volume399
DOIs
StatePublished - Aug 1 2014

Keywords

  • CO3 chondrite
  • NanoSIMS
  • Organic matter
  • QUE 97416
  • TEM
  • XANES

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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