Knowra Dacite Dacite Dacite is a silica-rich volcanic rock with a fine-grained groundmass, typically containing plagioclase feldspar and quartz or other minerals. Its composition lies between andesite and rhyolite.
Igneous rock : Rock formed when molten magma or lava cools and solidifies. Dacite is an igneous rock produced when magma reaches or approaches the surface.
Fractional crystallization : The process in which crystals separate from cooling magma, changing the composition of the remaining melt. Removing early-forming minerals can enrich residual magma in silica toward dacitic composition.
Andesite : An intermediate-composition volcanic rock commonly composed of plagioclase with amphibole, pyroxene, or other minerals. Andesite generally has less silica than dacite and helps define its lower-composition boundary.
Dacite dome : A steep-sided volcanic mound built from viscous dacitic lava that accumulates near a vent. Dacitic lava can pile up rather than flow far, forming domes.
Volcanic rock : Igneous rock formed when lava or volcanic fragments cool at or near Earth’s surface. Dacite’s fine-grained texture commonly forms as lava cools rapidly at the surface.
Partial melting : The melting of only part of a rock, producing magma with a composition different from its source. Partial melting of crustal or mantle-derived rocks can generate dacitic magma.
Rhyolite : A silica-rich volcanic rock, commonly containing quartz and alkali feldspar. Rhyolite is generally more silica-rich than dacite and marks the higher-composition comparison.
Dacitic lava flow : A surface flow of lava with dacitic composition, often thick and slow-moving. Its behavior reflects dacite’s high viscosity compared with more fluid basaltic lava.
Silica : A chemical compound, silicon dioxide, found in minerals such as quartz. Dacite’s relatively high silica content helps distinguish it from less silicic volcanic rocks.
Magma mixing : The blending of magmas with different compositions, temperatures, or crystal contents. Mixing can produce dacitic melts and crystals recording more than one magma condition.
Show all 22