plagioclaseamphibole

Plagioclaseamphibole is a term used in petrology to describe rocks that contain both plagioclase feldspar and amphibole minerals. This combination is common in a variety of igneous and metamorphic rock types. In igneous rocks, plagioclaseamphibole assemblages are typically found in intermediate to mafic compositions, such as andesites, diorites, and basalts, where plagioclase feldspar is a dominant mineral and amphibole (often hornblende) is a significant mafic component. The presence and relative abundance of these two mineral groups provide clues about the cooling history and magma source of the rock.

In metamorphic settings, plagioclaseamphibole rocks can form from the metamorphism of various protoliths, including basaltic lavas, gabbros, and even some sedimentary rocks under appropriate pressure and temperature conditions. Examples include amphibolites, where amphibole is the dominant mineral and plagioclase is present in varying amounts. The specific type of plagioclase (e.g., albite, andesine, labradorite) and amphibole (e.g., hornblende, actinolite) can indicate the metamorphic grade. The coexistence of plagioclase and amphibole in these rocks reflects the equilibrium mineral assemblage stable under specific metamorphic conditions. Understanding these mineral associations is crucial for interpreting the geological history and conditions of rock formation.