Abstract
Published phase diagrams for the siliceous carbonate system CaO−MgO−SiO2−CO2−H2O are contradictory because of different estimates of the relative stability of magnesite. Experimental data on magnesite are too ambiguous to determine the validity of these estimates. Therefore, field evidence is used to select the correct phase diagram topology for siliceous carbonate and carbonate ultramafic rocks at pressures of about 2–5 kbar. The primary selection criterion is provided by the existence of the stable assemblage talc+dolomite+forsterite+tremolite+antigorite, which occurs in the Bergell contact aureole and Swiss Central Alps. Field evidence also is used to argue that the reaction magnesite+quartz=enstatite must occur at lower temperature than the reaction dolomite+quartz=diopside. T-X CO 2 and P CO 2-T phase diagrams consistent with these observations are calculated from experimental and thermo-dynamic data. For antigorite ophicarbonate rocks, remarkable agreement is obtained between the spatial distribution of low variance mineral assemblages and the calculated diagrams.
Similar content being viewed by others
References
Berman RG (1988) Internally consistent thermodynamic data for minerals in the system Na2O−K2O−CaO−MgO−FeO−Fe2O3−SiO2−TiO2−H2O−CO2 J Petrol 29:445–552
Bucher-Nurminen K (1988) Metamorphism of ultramafic rocks in the central Scandinavian Caledomides. Nor Geol Unders Spec Publ 31:86–95
Carmichael DM (1978) Metamorphic bathozones and bathograds: a measure of the depth of post-metamorphic uplift and erosion on the regional scale. Am J Sci 278:769–797
Chernosky JV, Berman RG, Bryndzia LT (1988) Stability, phase relations and thermodynamic properties of chlorite and serpentine group minerals. Rev Mineral 19:295–346
Chernosky JV, Berman RG (1989) Experimental reversal of the equilibrium: clinochlore+2 magnesite=3 forsterite+spinel+2 CO2+4 H2O and revised thermodynamic properties for magnesite. Am J Sci 289:249–266
Connolly JAD (1989) Calculation of multivariable phase diagrams: a computer strategy based on generalized thermodynamics. Am J Sci (in review)
Connolly JAD, Kerrick DM (1987) An algorithm and computer program for calculating computer phase diagrams. CALPHAD 11:1–55
Connolly JAD, Trommsdorff V, Philipp R (1989) A revised Gibbs free energy for Magnesite. Am J Sci (in review)
Cornelius HP (1925) Über einige Gestiene der, Fedozserie aus dem Disgraziagebiet (Rhaetische Alpen). N Jahrb Mineral Beil Bd LII Abt A:1–50
Evans BW, Guggenheim S (1988) Talc, pyrophyllite and related minerals. Rev Mineral 19:225–294
Evans BW, Trommsdorff V (1974) Stability of enstatite+talc and CO2-metasomatism of metaperidotite, Val d'Efra, Lepontine Alps Am J Sci 274:274–296
Evans BW, Trommsdorff V (1983) Flourine hydroxyl titanian clinohumite in alpine recrystalized peridotite: compositional controls and petrologic significance. Am J Sci 283-A:355–369
Evans BW, Johnnes W, Oterdoom H, Trommsdorff V (1976) Stability of chrysotile and antigorite in the serpentine multisystem. Schweiz Mineral Petrogr Mitt 56:79–93
Goldsmith JR, Heard HC (1961) Subsolidus phase relations in the system CaCO3−MgCO3. J Geol 69:45–74
Harker RI, Tuttle OF (1955) Studies in the system CaO−MgO−CO2, Part I: The thermal dissociation of calcite, dolomite and magnesite. Am J Sci 253:209–224
Helgeson HC, Delany JM, Nesbitt HW, Bird DK (1978) Summary and critique of the thermodynamic properties of rock-forming minerals. Am J Sci 278-A:1–229
Hemingway BS, Robie RA, Fisher JR, Wilson JH (1977) The heat capacities of Gibbsite, Al(OH)3, between 13 and 480 K and Magnesite, MgCO3, between 13 and 380 K and their standard entropies at 298.15 K and the heat capacities of Calorimetry Conference Benzoic Acid between 12 and 316 K. US Geol J Res 5:797–806
Holloway JR (1977) Fugacity and activity of molecular species in supercritical fluids. In: D Fraser (ed) Thermodynamics in geology. Reidel, Boston, pp 161–181
Johannes W, Metz P (1968) Experimentelle Bestimmung von Gleichgewichtsbeziehungen im System MgO−CO2−H2O. N Jb Mineral Monatsh 112:15–26
Kerrick DM, Jacobs GK (1981) A modified Redlich-Kwong equation for H2O, CO2 mixtures at elevated pressures and temperatures. Am J Sci 281:735–767
Ohnmacht W (1974) Petrogenesis of carbonate orthopyroxenites (sagvandites) and related rocks from Troms, Northern Norway. J Petrol 15:303–323
Peretti A (1988) Occurrence and stabilities of opaque minerals in the Malenco serpentinite (Sondrio, Northern Italy). Ph D Thesis ETH Zurich No 8740
Pfeifer HR (1979) Fluid-Gesteins-Interaktion in metamorphen Ultramafititen der Zentralalpen. Ph D Thesis ETH Zurich No 6379
Philipp R (1988) Phasenbeziehungen in System MgO−H2O−CO2−NaCl. Ph D Thesis ETH Zurich No 8641
Philipp R, Girsperger S (1989) Experimental determination of phase transitions in the system MgO−H2O−CO2 using a pressure-analysis method. Contrib Mineral Petrol (in review)
Schramke JA, Kerrick DM, Blencoe JG (1982) The experimental determination of the brucite=periclase+water equilibrium with a new volumetric technique. Am Mineral 67:269–276
Schreyer W, Ohnmacht W, Mannchen J (1972) Carbonate orthopyroxenites (sagvandites from Troms, Northern Norway). Lithos 5:345–364
Skippen GB (1971) Experimental data for reactions in siliceous marbles. J Geol 79:457–481
Skippen GB (1974) An experimental model for low pressure metamorphism of siliceous dolomitic marble. Am J Sci 274:487–509
Skippen GB, Hutcheon I (1974) The experimental calibration of continuous reactions in siliceous carbonate rocks. Can Mineral 12:327–333
Skippen GB, Trommsdorff V (1986) The influence of NaCl and KCl on phase relations in metamorhosed carbonate rocks. Am J Sci 286:81–104
Trommsdorff V, Evans BW (1974) Alpine metamorphism of peridotitic rocks. Schweiz Mineral Petrogr Mitt 56:79–93
Trommsdorff V, Evans BW (1972) Progressive metamorphism of antigorite schist in the Bergell tonalite aureole. Am J Sci 272:423–437
Trommsdorff V, Evans BW (1977a) Antigorite-Ophicarbonates: Contact metamorphism in Valmalenco, Italy Contrib Mineral Petrol 62:301–312
Trommsdorff V, Evans BW (1977b) Antigorite-Ophicarbonates: PHase relations in a portion of the system CaO−MgO−SiO2−H2O−CO2. Contrib Mineral Petrol 60:39–56
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Trommsdorff, V., Connolly, J.A.D. Constraints on phase diagram topology for the system CaO−MgO−SiO2−CO2−H2O. Contr. Mineral. and Petrol. 104, 1–7 (1990). https://doi.org/10.1007/BF00310641
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00310641