Jarosite, argon diffusion, and dating aqueous mineralization on Earth and Mars

Joseph Kula, Suzanne L. Baldwin

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Jarosite 40Ar/39Ar ages can be used to date surface processes such as weathering and environmental transitions (i.e. aridification) on Earth and Mars. To better interpret jarosite ages from a thermochronological perspective, the diffusion kinetics of argon in jarosite were determined. Incremental fractional loss measurements indicate an activation energy (E) of 37.8±1.5kcal/mol and a log Do/a2 of 5.68±0.63s-1 corresponding to a closure temperature of 143±28°C, assuming a cooling rate 100°C/Ma. Downward extrapolation of these parameters to Martian surface temperatures (≤22°C) predicts <1% fractional loss of Ar over 4.0Ga. Forward modeling of 40Ar/39Ar age spectra using the least retentive E, Do/a2 pairs predict that if held at 22°C or less for 4.0Ga, supergene jarosite would preserve original growth ages manifest as plateau ages consisting of >95% of the gas release. Because of its susceptibility to mineralogical breakdown, 40Ar/39Ar ages on preserved Martian jarosite will reflect the time since water was present at a location that has since undergone aridification and remained hydrologically inactive and thermally quiescent.

Original languageEnglish (US)
Pages (from-to)314-318
Number of pages5
JournalEarth and Planetary Science Letters
Volume310
Issue number3-4
DOIs
StatePublished - Oct 15 2011

Keywords

  • Argon diffusion
  • Dating aqueous environments
  • Jarosite
  • Mars
  • Thermochronology

ASJC Scopus subject areas

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

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