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Oxygen isotope equilibrium between muscovite and water

O'Neil, James R. and Taylor, Hugh P., Jr. (1969) Oxygen isotope equilibrium between muscovite and water. Journal of Geophysical Research, 74 (25). pp. 6012-6022. ISSN 0148-0227. doi:10.1029/JB074i025p06012.

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Oxygen isotopes have been equilibrated between muscovite and aqueous alkali chloride solution and between paragonite and alkali chloride solution in the temperature range of 400°–650°C at 1 and 1.5 kb fluid pressure. Isotopic equilibrium was inferred from the fact that compatible fractionation factors were obtained using 3 different chemical reactions to produce the mica: (1) muscovite or paragonite was prepared by reacting natural kaolinite with 2–3 molal KCl or NaCl solutions; (2) muscovite was crystallized in pure water from a gel; and (3) synthetic paragonite was reacted with 2–3 molal KCl solution, producing muscovite by an alkali ion exchange reaction. The 1 M modification of the mica was made in every experiment. In several cases the extent of oxygen exchange was traced by running companion equilibrations in solutions of unusually low O^(18)/O^(16) ratio. No isotopic fractionation was discernible between muscovite and paragonite in the temperature range studied. Per mille fractionations between muscovite and water are given by the expression 10^3 In α = 2.38(10^6T^(−2)) − 3.89. These data can be combined with the results of other laboratory equilibration studies to establish a set of calibrated oxygen isotope geothermometers. Analogous to the alkali feldspar systems previously reported, the direct relationship between cation and oxygen isotope exchange suggests that some type of solution-redeposition mechanism operated during muscovite-paragonite transformations in aqueous solutions. Also, the extensive oxygen isotope exchange (with the solution) that accompanies the formation of muscovite from kaolinite implies a breakdown of the kaolinite structure. This notion does not concur with hypotheses based on rate studies and X-ray measurements that the unaltered kaolinite structure is partially inherited by the mica.

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Additional Information:Copyright 1969 by the American Geophysical Union. (Received July 31, 1967; revised June 30, 1969.) We wish to thank Professor R. N. Clayton for his helpful criticism of the manuscript, Mr. Paul Yanagasawa for performing most of the fluorine extractions on the solid phases, Dr. John Hudson for help with the electron microscope, and Mrs. Elizabeth Bingham for emission spectrographic analyses. Financial support was provided by the National Science Foundation, grant GA-513, and by the Alfred P. Sloan Foundation. Publication authorized by the Director, U.S. Geological Survey, Publications of the Division of Geological Sciences, California Institute of Technology, Contribution No. 1479
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Caltech Division of Geological Sciences1479
Issue or Number:25
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Official Citation:O'Neil, J. R., and H. P. Taylor Jr. (1969), Oxygen isotope equilibrium between muscovite and water, J. Geophys. Res., 74(25), 6012–6022, doi:10.1029/JB074i025p06012.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51434
Deposited By: George Porter
Deposited On:07 Nov 2014 21:06
Last Modified:10 Nov 2021 19:10

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