Classification of Granitic Pegmatites and Pegmatite-Bearing Granitic Systems

The paper discusses the concepts of pegmatitic rocks, pegmatite and pegmatoid bodies, and classification of granitic pegmatites and their relationships with various types of granite. Six types of pegmatitebearing granitic systems (PGS) are proposed: (I–PGS) granitic series with normal alkalinity in the form of central-type plutons with crystal-bearing chamber pegmatites; rare-metal Li–F granite and related pegmatoids, which are hosted in sequences of virtually unmetamorphosed rocks and formed at low pressure with no evidence of high alkalinity of granites (e.g., Zhanchivlan, Zuun-Bayan, and Gorikho in Mongolia; Adun- Chelon and Sokhondo-Ugdyri in the Transbaikal region); (II–PGS) granitic series with elevated alkalinity in the form of central-type plutons with crystal-bearing chamber pegmatites occasionally with indications of Y–REE mineralization; rare-metal, including REE, alkali granites and related pegmatoids hosted in almost unmetamorphosed sequences, where they formed under low pressure (e.g., Aqzhailau, Zerenda, Bayan-Aul, and Kent in Kazakhstan; Korosten in Ukraine; Pikes Peak and Mount Princeton in the United States; Ulkan and Ingur in Russia; Strange Lake in Canada; and Khalzaan-Buregte and Khan-Bogdo in Mongolia); (III–PGS) granitic series with lower alkalinity expressed in fields of dikes, layers, and stocks with rare-metal-bearing pegmatites; rare-metal albite and spodumene–albite granites, related pegmatoids, and complex raremetal pegmatites hosted in sequences of rocks metamorphosed under greenschist and amphibolite facies conditions, which correspond to pegmatite formation under medium pressure (e.g., Koktogai in China; Bernick Lake in Canada; Bikita in Zimbabwe; Karibib in Namibia; and Vishnyakovsky in Russia); (IV–PGS) granite series with elevated alkalinity represented by dike fields, layers, stocks with rare-metal, including REE pegmatites, which form under medium pressure in host rocks metamorphosed under epidote-amphibolite facies conditions (e.g., the Ilmeny Mountains in the Urals; the Western Keivy on the Kola Peninsula; and Sludyanka- 2 and Abchad in the Olkhon region); (V–PGS) low-alkaline granitic series expressed in fields of dikes, layers, stocks of mica-bearing and muscovite–rare-metal pegmatites formed under high pressure in zones of the kyanite–sillimanite-type amphibolite-facies metamorphism (e.g., in northern Karelia, Eastern Siberia, etc.); (VI–PGS) synorogenic granites and migmatites of potassium series with elevated alkalinity are expressed as dike fields, layers, stocks with high-pressure ceramic and uranium–REE pegmatites hosted in rock sequences metamorphosed under amphibolite- and granulite-facies conditions (e.g., northern Ladoga region, Bug River Basin, etc.).