LATE PERMIAN GRANITOIDS OF THE GAMOV BATHOLITH (SOUTHWESTERN PRIMORYE): GEOCHEMICAL FEATURES AND PETROGENESIS

The present study examines petrogeochemical characteristics of the late Permian granitoids in the Gamov batholith. The petrological and geochemical data indicate the presence of two groups of granitoids: S- and I-type granitoids. The rocks are predominantly magnesian, calcareous and calc-alkaline, moderately and highly aluminous. They display higher concentrations of Rb, Ba, Th, U, K, Pb and LREE and lower concentrations of Nb, Sr, P, and Ti. The distribution of rare earth elements is moderately fractionated. The topology of the distribution spectrum of rare elements is similar for all types of rocks, differing only in the size of anomalies of individual elements. An evaluation of the PT parameters of crystallization of the main phase – biotite-amphibole granites and granodiorites – showed that they formed at a temperature of 666–818 °C and a pressure of 2.1–2.8 kbar. The Nd isotopic composition of granites indicates the involvement of crustal and mantle material in magma formation, the contribution of the latter reaching 50 %. The emplacement of the Gamov batholith is associated with the closure of the Solonker Paleo-Asian Ocean in the Late Permian.