granophyric

Granophyric is a texture term used in igneous petrology to describe a mosaic-like intergrowth of quartz and alkali feldspar in a rock. In hand specimen and thin section, the quartz and alkali feldspar form tightly interwoven crystals with curved or irregular boundaries, producing a distinctive granophyric fabric. The texture is most often observed in granitic to granophyric rocks and is commonly described in granophyres and some rhyolites.

Microscopically, granophyric rocks show a fine to medium intergrowth of quartz with alkali feldspar (typically microcline or orthoclase). Plagioclase is usually scarce or absent. The intergrowths can appear blocky or bladed, but the key feature is the close, interlocking relationship between quartz and feldspar crystals. The texture helps differentiate granophyric rocks from graphic textures, in which quartz and feldspar intergrowths are arranged in a more regular, letter-like pattern.

Formation and interpretation: granophyric textures are interpreted as forming during late-stage crystallization of silica-saturated felsic magmas, where quartz and alkali feldspar crystallize in close succession from a cooling, viscous melt. The resulting mosaic reflects crystallization conditions that favor simultaneous growth of the two minerals, often in intrusive or cupola settings within larger granitic bodies.

Occurrence: granophyric textures are reported in granitoid plutons, granophyres, and related rocks worldwide. Their presence provides petrologists with clues about the crystallization history and cooling regime of silicic magmas.