Rare earth elements in ultramafic and mafic rocks and their minerals. Minor and accessory minerals / Редкоземельные элементы в ультраосновных и основных породах и их минералах. Главные и акцессорные минералы

Garnets occur in more than 30 natural mineral parageneses forming the rocks of magmatic, metamorphoric and metasomatic origin, which suggests their crystallization in a wide range of physicochemical parameters. By the ratio of main components (Ca, Mg, Al, Fe, Cr, Mn), garnets are divided into two major groups: almandine (pyrope, almandine, and spessartite) and andradite (grossular, andradite, and uvarovite). Pyropes are contained mainly in high-temperature peridotites and eclogites from deep xenoliths carried by kimberlite and alkaline-basaltic melts. In high-temperature and mesobaric metamorphic complexes (eclogites, granulites, gneisses, and schist), as well as in metasomatic rocks (skarns) garnets are represented by the varieties of almandine-grossular-pyrope series. When systematizing garnets by chemical compositions and parageneses in which they occur, normally different binary diagrams are used, including the diagrams in CaO–Cr2O3 coordinates [Sobolev, 1964; Sobolev et al., 1973]. <...>