In situ 60Fe-60Ni systematics of chondrules from unequilibrated ordinary chondrites

Myriam Telus, Gary R. Huss, Kazuhide Nagashima, Ryan C. Ogliore, Shogo Tachibana

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25 Scopus citations

Abstract

The initial 60Fe/56Fe of chondrules from unequilibrated ordinary chondrites (UOCs) can potentially constrain the stellar source of short-lived radionuclides and develop the 60Fe-60Ni (t1/2 = 2.6 Ma) system for early solar system chronology. However, progress with the 60Fe-60Ni system has been hindered by discrepancies between initial ratios inferred from bulk and in situ Fe-Ni analyses. Telus et al. (2016) show that discrepancies between these different techniques stem from late-stage open-system Fe-Ni mobilization. Here, we report in situ analyses of the Fe-Ni isotopic composition of ferromagnesian silicates in chondrules from UOCs using the ion microprobe. Of the 24 chondrules analyzed for this study, a few chondrules have resolved excesses in 60Ni of up to 70‰; however, the correlations with Fe/Ni are weak. Although complications from Fe-Ni redistribution make it difficult to interpret the data, we show that the initial 60Fe/56Fe for UOC chondrules is between 5 × 10−8 and 3.0 × 10−7. This is consistent with a late supernova source for 60Fe, but self-enrichment of the molecular cloud is another possible mechanism for incorporating 60Fe in the solar system. Discrepancies between bulk and in situ analyses remain, but likely stem from late-stage open-system Fe-Ni mobilization.

Original languageEnglish
Pages (from-to)342-357
Number of pages16
JournalGeochimica et Cosmochimica Acta
Volume221
DOIs
StatePublished - Jan 15 2018

Keywords

  • Fe
  • Chondrules
  • Ion microprobe
  • Ordinary chondrites
  • Radionuclides

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