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Granite porphyry describes a granite rock texture with large crystals (phenocrysts) embedded in a finer but coarse-grained groundmass.
Very large Potassium Feldspar Phenocrysts in a phaneritic (coarse-grained) groundmass. Tectonic Environment. Convergent Boundary – Intruded into batholiths above Andean-type Subduction Zone. Type. Igneous Rock. Texture. Porphyritic. Origin. Intrusive/Plutonic.
Porphyry (/ ˈ p ɔːr f ə r i / POR-fə-ree) is any of various granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate-rich, generally aphanitic matrix or groundmass.
Some igneous rocks have a mix of coarse-grained minerals surrounded by a matrix of fine-grained material in a texture called porphyritic. The large crystals are called phenocrysts and the fine-grained matrix is called the groundmass or matrix .
Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts.
Porphyritic granite contains a set of crystals that are distinctly larger than the rest of the crystals in the granite. The large crystals are referred to as phenocrysts and the rest of the smaller crystals are referred as the groundmass.
Porphyritic texture describes an igneous rock texture with large crystals embedded in a finer-grained matrix. It can occur in virtually all igneous rocks, i.e., intrusive and extrusive.
Porphyry (pronounced as POR-fə-ree) describes any intrusive or extrusive igneous texture rock with large-grained crystals embedded in a finer-grain matrix. The finer-grained groundmass or matrix can be aphanitic or phaneritic. However, the larger crystals must be easily noticed and distinguishable.
Porphyritic granites, on the other hand, are characterized by megacrystals that are several centimeters long and are set in a matrix which actually consist of medium- to coarse-grained crystals (1-5 mm or more) but that are significantly smaller than the phenocrysts.
Granites are coarsely crystalline igneous rocks, having a phaneritic texture. Porphyritic granites have a mix of large & small crystals, but all crystals are still fairly decent-sized. Large crystals in a porphyritic rock are called phenocrysts. The smaller crystals make up the groundmass.