Rhyodacite
Appearance
This article needs additional citations for verification. (September 2013) |
Rhyodacite is an extrusive volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of granodiorite. Phenocrysts of sodium-rich plagioclase, sanidine, quartz, and biotite or hornblende are typically set in an aphanitic to glassy light to intermediate-colored matrix.
Rhyodacite is a high silica rock containing 20% to 60% quartz with the remaining constituents being mostly feldspar. The feldspar is a mix of alkaline feldspar and plagioclase, with plagioclase forming 35% to 65% of the mix.[1]
Rhyodacite often exists as explosive pyroclastic volcanic deposits.
References
Wikimedia Commons has media related to Rhyodacite.
- ^ "Geologic units containing rhyodacite". usgs.gov.