Metasomatism driven by carbonate-rich melt: evidence from melt inclusions
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| Authors: | Xinyue Xu, Matthew Steele-Macinnis |
| Year: | 2023 |
| Journal: | AGU Fall Meeting Abstracts V41F-0158 Article Link (DOI) |
| Title: | Metasomatism driven by carbonate-rich melt: evidence from melt inclusions |
| Abstract: | Metasomatism is traditionally regarded as a primarily hydrothermal process, wherein mineral replacement reactions involve coupled dissolution and precipitation from an aqueous fluid phase. "Flame" perthite is a fairly common texture in high-grade metamorphic rocks, wherein sharp and irregular zones of albite appear to invade and replace preexisting K-feldspar. The usual interpretation is that these albite "flames" represent hydrothermal-metasomatic alkali exchange between aqueous fluid and alkali feldspar. However, here, we present a unique example of flame perthites in which the fluid medium that drove replacement of alkali feldspar and fostered growth of albite flames was in fact a carbonate-rich melt. Polymineralic, crystallized melt inclusions of are hosted only within albite flame lamellae and are absent from the surrounding K-feldspar. Petrography and Raman spectroscopy show that these inclusions are composed of calc-silicate and carbonate minerals that re-melt during laboratory heating, and thus represent aliquots of contaminated silicate-carbonate melts. Such liquids are known to have high interconnectivity, low density, and low viscosity relative to silicate melts, and as such can be capable of infiltrating and replacing alkali feldspar in a way analogous to a reactive hydrothermal fluid. |
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