Types and Average Composition of Miarolitic Pegmatites From the Malkhan Ridge

Three types of pegmatities (K-feldspar, two-feldspar, and oligoclase) were revealed from the ratio of rock-forming feldspars. On the basis of structural-textural features, internal structure, and gem productivity, each of them can be subdivided into the following subtypes: nonproductive (no gem), poorly productive (noncommercial occurrences) and highly productive (deposits themselves). In all pegmatites, average compositions of 34 elements have been determined. Various groups of elements were shown to be dependent on the type (Ca), subtype (Si, Al, F, Li, Ta, Nb, Bi, Be, Sn), or type and subtype (K, Na, Mn, Rb, Cs, Ba, Sr) of pegmatites. Average contents of Mg, Fe, Ti, B, P, CO2, Cl, Zr, Hf, Pb, Zn, Co, Sc, Cu, Mo, and Th were shown to be independent of type or subtype of pegmatites. In general, the average composition of miarolitic pegmatites is the most close to the pegmatite composition of rare-metal-muscovite formation.