Experimental studies of oxygen isotope fractionation between rhodochrosite (MnCO3) and water at low temperatures

Sang Tae Kim, Jung Ok Kang, Seong Taek Yun, James R. O'Neil, Alfonso Mucci

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Rhodochrosite crystals were precipitated from Na-Mn-Cl-HCO3 parent solutions following passive, forced and combined passive-to-forced CO2 degassing methods. Forced and combined passive-to-forced CO2 degassing produced rhodochrosite crystals with a small non-equilibrium oxygen isotope effect whereas passive CO2 degassing protocols yielded rhodochrosite in apparent isotopic equilibrium with water. On the basis of the apparent equilibrium isotopic data, a new temperature-dependent relation is proposed for the oxygen isotope fractionation between rhodochrosite and water between 10 and 40 °C: 1000 ln αrhodochrosite s(-) water = 17.84 ± 0.18 (103 / T) - 30.24 ± 0.62 or 1000 ln αrhodochrosite s(-) water = 2.65 ± 0.03 (106 / T2) - 0.26 ± 0.35 where αrhodochrosite-water is the fractionation factor between rhodochrosite and water, and T is in kelvins. Over the temperature range investigated, rhodochrosite concentrates 18O relative to both calcite and aragonite, a result that is consistent with the relative ionic radii of Ca2+ and Mn2+ and recent theoretical calculations.

Original languageEnglish
Pages (from-to)4400-4408
Number of pages9
JournalGeochimica et Cosmochimica Acta
Volume73
Issue number15
DOIs
Publication statusPublished - 2009 Aug 1

    Fingerprint

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this