Paleoproterozoic Shoshonite Mafic Associations of the Irkut Block (Sharyzhalgai Uplift, Southwest Siberian Craton): U–Pb Age and Conditions of Zircon Crystallization

Abstract —The paper presents data on the composition and age of mafic rocks shoshonitic series in Irkut block Sharyzhalgai uplift (southwest Siberian ?raton). According to U–Pb dating magmatic zircon, formation monzodiorites Poludennyi massif gabbro-dolerites endo- exocontact zones Toisuk pluton occurred at 1.87 1.86–1.85 Ga, respectively. The intrusion magmas their underplating into basement crust under postcollisional extension resulted near-coeval granitoid magmatism between 1.84 Ga. Paleoproterozoic associations belong are characterized by enrichment incompatible elements, including Zr, low negative ?Nd(T) values. These geochemical isotopic characteristics point derivation magma from a long-lived enriched-mantle source, such as subcontinental lithospheric mantle. crystallization zircon last portions evolved melt is evidenced zirconium saturation temperatures (710–965 °C) U Th with increasing Th/U, reflecting growth concentrations highly elements residual melt.