Comparative Geochemical Characteristics and Genesis of Large Polyphase Plutons in the Cores and on the Periphery of the Mongol–Okhotsk Fold Belt Magmatic Areas of Different Ages

Abstract

The early Mesozoic Baga-Khentei pluton is a part of the Daurian–Khentei batholite that was formed under the impact of the Mongolian plume on the lower horizons of the continental crust in the collision compression zone that appeared during closing of the Mongol–Okhotsk Ocean. Mantle and crustal melt sources were involved in the formation of the batholith and its margins. The Ikh-Narotin-Khid massif tends to the boundary of the rift region on the periphery of the Late Mesozoic area. The petro-geochemical similarity of its rocks to the composition of host gneisses suggests that the latter belong to the most likely substrate in the formation of palingenic granitoids of the calc-alkaline series. The differences in the rock compositions of large plutons are shown in minor differentiation of the Baga-Khentei massif, which is likely to be determined by the anatexis conditions and the subsequent formation of melts in the collision compression setting, while the granites of the Ikh-Narotin-Khid massif were formed under extension, which favored deep differentiation of magmatic melts.