Abstract
Alumina gneisses and garnet amphibolites of the Eastern part of Kitoy block of Sharyzhalgay uplift (area of the Kitoy sillinanite deposit) were studied. On the basis of petrographic studies of mineral microstructures, chemical zoning, PT-estimates and thermodynamical modelling two studies of metamorphism were found in both types of rocks. The first episode of regional metamorphism (M1) occurred at T=780–800°C and P= 8–9 kbar and was followed by decompression on the retrograde stage. The second stage (M2) occurred at low pressure P=2-4 kbar and in the wide temperature interval T=650-850°C. Two age peaks were established on the basis of U-Pb monazite and zircon dating in garnet-anthophyllite gneisses. Both of them correspond to the Neoarchean age: the age of M1 falls into the interval of ca. 2489–2496 Ma, the age of M2 – ca. 2446–2456 Ma. The high-temperature metamorphism of the Kitoy block and nearly coeval granitoid magmatism can be an evidence for the Neoarchean collision in SW Siberian craton.
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