What is a rhyodacite in geology ?
Rhyodacite : definition
A rhyodacite is a volcanic rock intermediate between rhyolite and dacite that occurs in the same deposits as the latter, particularly along active continental margins and in island arcs.
Rhyodacite is mineralogically distinguished from rhyolite by a greater rarity of orthoclase in favor of sodium plagioclase (oligoclase and andesine), and usually a relative abundance of biotite, quartz being present in notable but lesser amounts than in rhyolite. Rhyodacite is the microlitic equivalent of granodiorites and quartz monzonites.
Rhyodacite is mineralogically distinguished from rhyolite by a greater rarity of orthoclase in favor of sodium plagioclase (oligoclase and andesine), and usually a relative abundance of biotite, quartz being present in notable but lesser amounts than in rhyolite. Rhyodacite is the microlitic equivalent of granodiorites and quartz monzonites.
