Paraamphibolites

Paraamphibolites are metamorphic rocks that are characterized by the presence of hornblende and plagioclase feldspar, but crucially, they contain scapolite in addition to these main minerals. This distinguishes them from amphibolites, which lack scapolite. The formation of paraamphibolites typically occurs under conditions of high temperature and moderate to high pressure, often associated with contact metamorphism or regional metamorphism in carbonate-rich environments. The scapolite in paraamphibolites is thought to form from the metasomatism of plagioclase feldspar by chlorine- or sulfate-bearing fluids. These rocks can also contain other minerals such as garnet, diopside, epidote, and quartz, depending on the original composition of the protolith and the specific metamorphic conditions. Paraamphibolites are commonly found in metamorphic terrains where saline or evaporitic sedimentary rocks have been subjected to metamorphism. Their geological occurrence provides clues about the fluid composition and metamorphic history of a region, particularly highlighting the involvement of chlorine or sulfate-rich fluids during their formation. The texture of paraamphibolites can vary from fine-grained to coarse-grained, with the characteristic minerals often exhibiting a granoblastic or nematoblastic texture.