The Stability of Sodalite in a Synthetic Syenite plus Aqueous Chloride Fluid System |
| |
| Authors: | WELLMAN THOMAS ROBERT |
| |
| Institution: | Department of Geology and Geophysics, Yale University, New Haven, Connecticut, 06520 |
| |
| Abstract: | Natural feldspathoidal syenites may be approximated by assemblagescontaining some or all of the phases sodalite, nepheline, oneor two alkali feldspars, and aqueous chloride fluid in the systemNaAISi3O8-KAISi3O8-NaAISiO4-KAISiO4-NaCI-KCI-H2O. The stabilityof sodalite in these assemblages was studied in the range 500–700°C and 600–2000 bars fluid pressure. Sodalite appears to be a stable phase on the vapor-saturatedliquidus in this system over a wide range of pressure. At or near the vapor-saturated liquidus minimum in this system,three distinct types of sodalite-bearing syenite can crystallize.Nepheline-sodalite-one alkali feldspar rocks, nepheline-sodalite-twoalkali feldspars rocks and sodalite-analcime-bearing rocks crystallizebelow 1600 bars, between 1600 and 2750 bars and above 2750 barsfluid pressure, respectively. The effects of closed-system cooling on the assemblage sodalite-nepheline-twoalkali feldspars-aqueous fluid are different and distinguishablefrom the effects of metasomatism. Closed-system cooling resultsin replacement of K-feldspar by albite, feldspathoids remainingnearly unchanged, while metasomatism generally results in sismultaneousenrichment or impoverishment in sodalite plus K-feldspar. |
| |
| Keywords: | |
| 本文献已被 Oxford 等数据库收录！ |
|
