流纹英安岩是一种组成上介于英安岩和流纹岩之间的喷出性火山岩。与之对应的侵入岩是花岗闪长岩。流纹英安岩常见的组成矿物为隐晶质到玻璃质的富钠斜长石、透长石、石英、黑云母或角闪石。流纹英安岩是一种富硅的岩石，常存在于普林尼式喷发火山碎屑沉积中。

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. Rhyodacite often exists as explosive pyroclastic volcanic deposits.