peridotiiteissä

Peridotite is a dense, coarse-grained ultramafic igneous rock. It is composed primarily of the mineral olivine, with lesser amounts of pyroxenes. Other accessory minerals such as spinel, garnet, and amphibole may also be present depending on the specific conditions of its formation and subsequent geological history. The name "peridotite" itself is derived from "peridot," another name for olivine, highlighting the mineral's dominant role.

Peridotites are the principal component of the Earth's upper mantle. While they are rarely found at the surface in large quantities, they can be brought up through tectonic processes such as continental rifting or the uplift of ancient mantle sections. They are also common in xenoliths, which are fragments of the mantle carried to the surface by volcanic eruptions. The composition and texture of peridotites provide crucial insights into the physical and chemical conditions deep within the Earth.

The density of peridotite plays a significant role in plate tectonics. Oceanic crust, which is denser than continental crust, is made of basalt, and when it subducts back into the mantle, it is essentially sinking into a peridotitic mantle. The melting of peridotite under reduced pressure can lead to the formation of basaltic magma, which erupts to form new oceanic crust. Understanding peridotite is therefore fundamental to comprehending mantle dynamics and the large-scale processes that shape our planet.