Early Precambrian Granitoid Magmatism of the Kitoy Block and Stages of Collisional Events in the Southwestern Siberian Craton

Abstract

Abstract —The paper presents the zircon U–Pb age and geochemical and isotopic characteristics of granitoids from the Kitoy block (Sharyzhalgai uplift, southwestern Siberian craton). The studied granitoids compose vein bodies of different scales. According to structural relations of rocks and their zircon U–Pb ages, early Precambrian granite formation proceeded in three stages: at ~2.99, 2.54, and 1.88 Ga. The Neoarchean and Paleoproterozoic granites contain inherited zircons of ~3.00–2.97 Ga, which are close in age to magmatic zircons from the Mesoarchean granite-gneiss. The Kitoy granitoids of different ages share similar enrichment in SiO2, K2O, and incompatible trace elements. In terms of trace-element composition and crystallization temperatures, the Mesoarchean granite-gneisses are similar to the A-type granite, while the Neoarchean and Paleoproterozoic granitoids are close to the I-type one. Inherited ~3.00–2.97 Ga zircons and the narrow range of model Nd ages (TNd(DM) = 3.3–3.0 Ga) indicate that Neoarchean and Paleoproterozoic granitoids formed through recycling of the Mesoarchean crust. The Neoarchean (~2.54 Ga) and Paleoproterozoic (~1.88 Ga) stages of granite emplacement in the northwest of the Kitoy block correlate with formation of granitoids and high-temperature metamorphism in the Irkut block and the border zone between two blocks. Coeval granite formation and metamorphism at ~2.54 Ga are strong evidence that the amalgamation of the Kitoy and Irkut blocks resulted from collisional orogeny in the terminal Neoarchean.