Amfibolittisiksi

Amfibolittisiksi is a term used in geology to describe rocks that have undergone amphibolite facies metamorphism. This type of metamorphism occurs at moderate to high temperatures and pressures, typically between 500 to 700 degrees Celsius and 3 to 7 kilobars. The key characteristic of amphibolite facies is the stable coexistence of amphibole minerals, such as hornblende, with plagioclase feldspar.

Rocks metamorphosed under amphibolite facies conditions can originate from various protoliths, including igneous rocks like basalts and gabbros, as well as sedimentary rocks such as shales and sandstones. The mineral assemblages found in amphibolite facies rocks provide valuable clues about the temperature and pressure conditions under which they formed, allowing geologists to reconstruct the geological history of an area. Common minerals found in amphibolites include garnet, epidote, and biotite, in addition to amphibole and plagioclase.

The appearance of amphibolite facies rocks can vary significantly depending on their original composition. They are often characterized by a banded or foliated texture due to the alignment of platy minerals like biotite and amphibole. However, some amphibolites can be massive and granular. The study of amphibolite facies rocks is crucial for understanding mountain-building processes, the evolution of continental crust, and the thermal regimes within the Earth's crust and upper mantle.