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dacite A light-coloured, fine-grained igneous rock containing 63–70 wt.% SiO2, as well as plagioclase feldspar, alkali feldspar, quartz, biotite, and hornblende as essential minerals, and sphene, apatite, and magnetite as accessory minerals. Plagioclase feldspar dominates over alkali feldspar in a 2:1 ratio. Dacites are the volcanic equivalents of granodiorites and are found as members of the calc-alkaline series, typically developed as eruptive products on the continental side of oceanic-continental plate subduction zones. They are often surprisingly coarse-grained for lavas.

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