TYPOMORPHISM OF PLAGIOCLASES OF THE MEDVEDEVSKY AND TAYOZHNY MASSIFS OF THE EVOTINSKY ORE FIELD (ALDAN SHIELD, SOUTH YAKUTIA)

The paper presents the results of studies of the chemical composition of plagioclases from Mesozoic igneous rocks of the Medvedev and Taiga massifs. Which are represented by two generations, the early - porphyry individuals, the late - microcrystals of the groundmass. Plagioclases in the magmatic formations of the Medvedevsky massif from early to late phases of intrusion change from albite to andesine with an increase in crystallization temperature and an increase in reducing conditions in the final stages. In plagioclases of the Taiga massif, a reverse variability of chemical composition (a decrease in An) is observed with a similar drop in the crystallization temperature and log fO2 (to oxidative ones) values as the massif evolves.