What term describes the coarse-grained intrusive equivalent of andesite?

The correct term that describes the coarse-grained intrusive equivalent of andesite is diorite. Andesite itself is an intermediate volcanic rock primarily composed of plagioclase feldspar, with smaller amounts of hornblende, biotite, and other minerals. When this volcanic rock crystallizes slowly beneath the Earth’s surface, it forms diorite, which has a similar mineral composition but is coarse-grained due to the slower cooling process that allows larger crystal growth.

Diorite typically exhibits a characteristic speckled appearance due to its mineral composition, which includes dark-colored amphibole or biotite alongside lighter plagioclase feldspar. This relationship between the fine-grained (volcanic) and coarse-grained (intrusive) varieties of rock is crucial in understanding igneous petrology and the processes that shape the Earth's crust.

The other options represent different types of igneous rocks: granite is a coarse-grained equivalent of rhyolite, gabbro is the equivalent of basalt, and peridotite is primarily composed of ultramafic minerals. Hence, diorite is the direct intrusive counterpart to andesite, making it the correct choice in this context.