A model for phase equilibria in the prehnite-pumpellyite facies

✍ Scribed by William Glassley

• Publisher: Springer
• Year: 1974
• Tongue: English
• Weight: 935 KB
• Volume: 43
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00373487

✦ Synopsis

Using the method of Sehreinemakers, along with other thermodynamic considerations, a phase diagram for the system CaO--MgO--A1203--Si02--C02--tt20 was constructed. The phases prehnite, pmnI0ellyite , calcite, chlorite, dolomite, quartz, tremolite, talc, zoisite, grossularite and vapor were considered in this construction. The results indicate that prehnitepumpellyite facies mineral assemblages will only exist in equilibrium with a vapor phase in which the mole fraction of CO 2 is less than 0.2 at 1 kb, and less than 0.15 at 2 kb. Although talc could theoretically be a stable phase under these conditions, its common absence from rocks of this facies probably results from the existence of an enantiomorphic point which makes tremolite-calcite-CO 2 the stable assemblage at low XCO.~ , and the compositionally equivalent talc-calcite-CO 2 assemblage stable at moderate XCO ~.