Abstract
For the reaction: 1 diopside+3 dolomite ⇌2 forsterite+4 calcite+2 CO2 (14) the following P total−T-brackets have been determined experimentally in the presence of a gasphase consisting of 90 mole%CO2 and 10 mole%H2O∶1 kb, 544°±20° C; 3kb, 638°±15° C; 5kb, 708°±10° C; 10kb, 861°±10° C. The determination was carried out with well defined synthetic minerals in the starting mixture.
The MgCO3-contents of the magnesian calcites formed by the reaction in equilibrium with dolomite agree very well with the calcite-dolomite miscibility gap, which can be recalculated from the activities and the activity coefficients of MgCO3 as given by Gordon and Greenwood (1970).
The equilibrium constant K 14b was calculated with respect to the reference pressure P 0=1 bar using the experimentally determined \(P_{total} TX_{CO_2 }\) brackets, the activities of MgCO3 and CaCO3 (Gordon and Greenwood 1970; Skippen 1974) and the fugacities of CO2 Holloway (1977) considering the correction of Flowers (1979).
Results are plotted as function of the absolute reciprocal temperature in Fig. 1. For the temperature range of 530° to 750° C the following linear expression can be given for the natural logarithm of K14b:
where P is the total pressure in bars and T the temperature in degrees Kelvin. Combining Equation (g) with the activities of MgCO3 and CaCO3 gives the equilibrium fugacity\(f_{CO_2 }\):
Equation (i) and the fugacities of CO2 permit to calculate the equilibrium data in terms of \(P_{CO_2 }\) and T (see Fig. 3) or P total, T and \(X_{CO_2 }\) (see Fig. 5).
Combining the \(P_{total} TX_{CO_2 }\) equilibrium data of the above reaction with those of the previously investigated reaction (Metz 1976): 1 tremolite+11 dolomite ⇌8 forsterite+13 calcite+9 CO2+1 H2O yields the stability conditions of the four-mineral assemblage: diopside+calcian dolomite+forsterite +magnesian calcite and the stability conditions of the five-mineral assemblage: tremolite+calcian dolomite+forsterite +magnesian calcite+diopside both shown in Fig. 6. Since these assemblages are by no means rare in metamorphic siliceous dolomites (Trommsdorff 1972; Suzuki 1977; Puhan 1979) the data of Fig. 6 can be used to determine the pressure of metamorphism and to estimate the composition of the CO2-H2O fluid provided the temperature of the metamorphic event was determined using the calcite-dolomite geothermometer.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Anderson, G.M.: Some thermodynamics of dehydration equilibria. Am. J. Sci. 269, 392–401 (1970)
Boyd, F.R., England, J.L.: Apparatus for phase equilibrium measurements at pressures up to 50 kilobars and temperatures up to 1750° C. J. Geophys. Res. 65, 741–748 (1960)
Eggler, D.H., Kushiro, I., Holloway, J.R.: Stability of carbonate minerals in a hydrous mantle. Annual Report of the Director, Geophysical Laboratory, 1975–76, 631–636 (1975–1976)
Flowers, G.C.: Correction of Holloway's (1977) adaptation of the modified Redlich-Kwong equation of state for calculation of the fugacities of molecular species in supercritical fluids of geologic interest. Contrib. Mineral. Petrol. 69, 315–318 (1979)
Goldsmith, J.R., Graf, D.L.: Relations between lattice constants and composition of the Ca-Mg carbonates. Am. Mineral. 43, 84–101 (1958)
Goldsmith, J.R., Graf, D.L., Heard, H.C.: Lattice constants of the calcium-magnesium carbonates. Am. Mineral. 46, 453–457 (1961)
Goldsmith, J.R., Heard, H.C.: Subsolidus phase relations in the system CaCO3-MgCO3. J. Geol. 69, 45–74 (1961)
Goldsmith, J.R., Newton, R.C. (1969): P−T−X relations in the system CaCO3-MgCO3 at high temperatures and pressures. Am. J. Sci. 267-A (Schairer vol.), 160–190 (1969)
Gordon, T.M., Greenwood, H.J.: The reaction: dolomite+quartz +water⇌talc+calcite+carbon dioxide. Am. J. Sci. 268, 225- 242 (1970)
Graf, D.L., Goldsmith, J.R.: The solid solubility of MgCO3 in CaCO3: A revision. Geochim. Cosmochim. Acta 13, 218–219 (1958)
Harker, A., Tuttle, O.F.: Studies in the system CaO-MgO-CO2. Pt. 2. Limits of solid solution along the binary join CaCO3-MgCO3. Am. J. Sci. 253, 274–282 (1955)
Holloway, J.R.: Fugacity and activity of molecular species in supercritical fluids. In: Thermodynamics in Geology (D.G. Fraser, ed.). Dordrecht-Holland/Boston-USA: D. Reidel Publ. Co. 1977
Metz, P.: Experimentelle Bildung von Forsterit und Calcit aus Tremolit and Dolomit. Geochim. Cosmochim. Acta 31, 1517–1532 (1967)
Metz, P.: Experimentelle Untersuchung der Metamorphose von kieselig dolomitischen Sedimenten. Habilitationsschrift, Universität Göttingen 1970
Metz, P.: Experimental investigation of the metamorphism of siliceous dolomites. III. Equilibrium data for the reaction: 1 tremolite+11 dolomite⇌8 forsterite+13 calcite +9CO2 +1 H2O. Contrib. Mineral. Petrol. 58, 137–148 (1976)
Metz, P., Puhan, D.: Experimentelle Untersuchung der Metamorphose von kieselig dolomitischen Sedimenten I. Die Gleichgewichtsdaten der Reaktion: 3 Dolomit+4 Quarz+1 H2O⇌1 Talk+3 Calcit+3 CO2 für die Gesamtgasdrucke von 1000, 3000 und 5000 Bar. Contrib. Mineral. Petrol. 26. 302–314 (1970)
Metz, P., Puhan, D.: Korrektur zur Arbeit Experimentelle Untersuchung der Metamorphose von kieselig dolomitischen Sedimenten I. Contrib. Mineral. Petrol. 31, 169–170 (1971)
Metz, P., Trommsdorff, V.: On phase equilibria in metamorphosed siliceous dolomites. Contrib. Mineral. Petrol. 18, 305–309 (1968)
Puhan, D.: Petrologische und geothermometrische Untersuchungen an Silikat-führenden Dolomit-Calcit Marmoren zur Ermittlung der Metamorphosebedingungen im zentralen Damara-Orogen (Südwest-Afrika). Habilitationsschrift, Universität Göttingen 1979
Robie, R.A., Hemingway, B.S., Fisher, J.R.: Thermodynamic properties of minerals and related substances at 298,15 K and 1 Bar (105 Pascals) pressure and at higher temperatures. Geol. Surv. Bull. 1492 (1978)
Ryzhenko, B.K., Malinin, S.P.: The fugacity rule for the systems CO2-H2O, CO2-CH4, CO2-N2, CO2-H2. Geochem. Int. 8, 562–574 (1971)
Skippen, G.B.: An experimental study of the metamorphism of siliceous carbonates. Ph. D. dissert., John Hopkins Univ., Baltimore 1967
Skippen, G.B.: Experimental data for reactions in siliceous marbles. J. Geol. 79, 457–481 (1971)
Skippen, G.B.: An experimental model for low pressure metamorphism of siliceous dolomitic marble. Am. J. Sci. 274, 487–509 (1974)
Slaughter, J., Kerrick, D.M., Wall, V.J.: Experimental and thermodynamic study of equilibria in the system CaO-MgO-SiO2-H2O-CO2. Am. J. Sci. 275, 143–162 (1975)
Suzuki, K.: Local equilibrium during the contact metamorphism of siliceous dolomites in Kasugamura, Gifu-ken, Japan. Contrib. Mineral. Petrol. 61, 79–89 (1977)
Trommsdorff, V.: Change in T−X during metamorphism of siliceous dolomitic rocks of the Central Alps. Schweiz. Mineral. Petrogr. Mitt. 52, 1–4 (1972)
Usdowski, H.-E.: Die Genese von Dolomit in Sedimenten. Berlin-Heidelberg-New York: Springer 1967
Author information
Authors and Affiliations
Additional information
Simplified equation neglecting solid solution between calcite and dolomite (see pp. 153); numbers of reactions after Metz and Trommsdorff (1968)
Rights and permissions
About this article
Cite this article
Käse, H.R., Metz, P. Experimental investigation of the metamorphism of siliceous dolomites. Contr. Mineral. and Petrol. 73, 151–159 (1980). https://doi.org/10.1007/BF00371390
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00371390