Ortoamfiboliittien

Ortoamfiboliitti is a metamorphic rock that originates from igneous precursors. The term "orto" indicates this igneous origin, distinguishing it from paraamphibolite, which forms from sedimentary rocks. Ortoamfiboliitti is characterized by the abundance of amphibole minerals, most commonly hornblende, and plagioclase feldspar. Other common minerals may include quartz, garnet, and biotite, depending on the specific composition of the original igneous rock and the conditions of metamorphism.

The formation of ortoamfiboliitti typically occurs under medium to high-grade metamorphic conditions, involving elevated temperatures and pressures. These conditions cause the minerals in the original igneous rock, such as basalt or gabbro, to recrystallize and transform into amphibole and plagioclase. The texture of ortoamfiboliitti is often granoblastic or nematoblastic, reflecting the interlocking nature of the recrystallized mineral grains. The rock can range in color from dark green to black, due to the presence of amphiboles. Geologically, ortoamfiboliitti is found in areas that have undergone significant tectonic activity and mountain-building processes. Its presence can provide valuable insights into the geological history and metamorphic evolution of a region.