Which igneous rock type is primarily composed of olivine and pyroxene and forms the upper mantle?

Peridotite is the igneous rock type primarily composed of olivine and pyroxene, and it is found in the upper mantle of the Earth. This rock is significant because it represents the primary composition of the Earth's mantle and plays a crucial role in understanding the geology beneath the Earth's crust. The high content of olivine gives peridotite its characteristic green color and indicates a high degree of magmatic differentiation typical of the mantle composition. The presence of pyroxene complements olivine, contributing to the overall mineralogy of this rock.

In contrast, gabbro is a coarse-grained igneous rock that primarily contains plagioclase feldspar along with pyroxene and other minerals, making it more associated with oceanic crust rather than the upper mantle. Andesite is a volcanic rock generally formed from the subduction of plates and is characterized by a composition that includes plagioclase and amphibole, along with other minerals, which are not representative of the upper mantle materials. Diorite also contains plagioclase as a dominant mineral but is a result of crystallization in the Earth's crust, thus it does not form in the upper mantle like peridotite does.

Understanding the composition and formation of per