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

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16 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

Bibliographical note

Funding Information:
This research was initiated while one of the authors (S.-T. Kim) was visiting the stable isotope laboratory of the Center for Mineral Resources Research (CMR) at Korea University. The authors acknowledge CMR for providing access to its stable isotope laboratory facilities. This research was funded by a grant from the Environmental Geosphere Research Laboratory (EGRL) of Korea University to S.-T. Yun and a NSERC Discovery grant to A.M. The authors would like to thank Lora Wingate and C.-S. Kim for their assistance in the laboratory. Finally, the authors wish to acknowledge Drs. Gilg, Romanek, Chacko and one anonymous reviewer for their constructive comments/recommendations on the original version of this manuscript.

Copyright:
Copyright 2011 Elsevier B.V., All rights reserved.

ASJC Scopus subject areas

  • Geochemistry and Petrology

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