Petrology of Microcline-Albite Granites of the Kester Deposit

Abstract

Petrography, mineralogy and chemistry of rare-metal microcline-albite granites of the Kester har- polith, intruding granites of the Arga-Ynnakh massif of the Adychan anticlinorium of the Verkhoyansk continental margin are described in the article. It shows that, particularity of their composition is not comparable to the particularity of host granites and cannot be due to metasomatic change of the lat- ter. They are characterized by magmatic structures, mica lithium composition, rich accessory frac- tions, containing cassiterite, spodumene, lithium phosphates, columbite-tantalite etc., and represent derivatives of fluid-saturated magmatic melt. They are very different from host graniroids by high con- tents of rare metals and evolution on high phosphorous trend. Rb-Sr isotopic analysis indicates a crust nature of protolith. At the same time, the presence of magnesian pyroxene, high chromic magnetite, zircons of “D” and “E” morphotypes in rocks suggests that, crust magma forming substrate contains horizons of basic rocks, and that fluids related to high alkali basic melts supply the zone of magma generation.