Zircons and the Problem of Precambrian in the Main Granite Belt of the Urals: Evidence from the Kozhubaevo Metamorphic Complex

摘要

Metamorphic rocks of the Kozhubaevo Complex (KC) surround the Dzhabyk-Karagai granite massif in the north and northwest (Fig. 1). Together with granites, the metamorphic rocks belong to the Ural-Tobol'sk anticlinorium of the East Uralian Anticlinorium. The issue of the KC age is a characteristic problem of all similar gneissic complexes in the Urals, since geological data suggest both Paleozoic and Precambrian ages for the gneisses, while geochronological data are limited by only a few K-Ar datings within 250-350 Ma. According to, regional metamor-phism of the KC gneisses corresponds to the amphibo-lite facies. Repeated events of granitization and migma-tization, block movements, and cataclasis produced numerous small bodies of granites, pegmatites, and quartz veins.