The Posol'nensk and Nizhnekansk massifs include two rock associations. The first association (diorites-tonalites-granodiorites-low-alkali granites) contains both amphibole (25-30% in diorites to <1% in granodiorites) and biotite (1-8%). The second association (syenites-subalakline granites-subalkaline leucogranites) is barren of amphibole and dominated by rocks with low biotite content (approximately 1%). The granitoids considered in this paper compositionally correspond to the calc-alkaline (granite I) and alkaline-calcareous (granite A ) intrusive series. The performed studies yielded U-Pb geochronological data for granodiorite of the Nizhnekansk Massif and subalkaline granite of the Posolnensk Massif (Sample)
