It may form from the partial melting of oceanic crust in subduction zones, though it is more commonly a product of fractional crystallization caused by hydration in the Wadati- Benioff Zone or assimilation of continental crust by basaltic melts.
Though its dark biotite and hornblende phenocrysts give it a porphyritic appearance, this rock is never (*) volcanic. It may form from the partial melting of oceanic crust in subduction zones, though it is more commonly a product of fractional crystallization caused by hydration in the Wadati- Benioff Zone or assimilation of continental crust by basaltic melts. This phanerite may form stocks around granitic plutons, and it typically has gradational contacts with gabbro, leading to its erroneous classification as black granite.  Composed of 90% intermediate plagioclase, FTP, name this plutonic equivalent of andesite.
Though its dark biotite and hornblende phenocrysts give it a porphyritic appearance, this rock is never (*) volcanic.
diorite (accept ”andesite” or ”andesite porphyry” before (*)).