恢复蚀变火山岩原岩的重要性,随着火山岩与成矿作用的关系越来越密切而变得愈来愈重要了。火山喷出岩的生成条件较特殊,其结构往往细小而复杂。既有斑状结构,也有隐晶质结构,有时为玻璃质结构。成分也比较复杂。有成分较稳定的结晶矿物,也有成分不定的火山玻璃。由于析出的晶体迅速冷却,来不及与岩浆反应,还可出现一些反常现象。如斜长石斑 The importance of restoring original rocks of altered volcanics has become increasingly important as volcanic rocks have become more closely related to metallogenesis. Volcanic eruption rock formation conditions are more special, the structure is often small and complex. Both spot-like structure, but also cryptocrystalline structure, sometimes vitreous structure. Composition is also more complicated. A more stable composition of crystalline minerals, there are indefinite composition of volcanic glass. Due to the rapid cooling of the precipitated crystals, no time to react with the magma, but also some abnormal phenomena. Such as plagioclase plaque