Mesoarchean Silicic Volcanics in the Kursk Block of the Voronezh Crystalline Massif: Composition, Age, and Correlations with the Ukrainian Shield

摘要

Metarhyiolites are found along with metapelites and metabasites in sedimentary-volcanic sections of Archean greenstone belts of the Kursk block of the Eastern Sarmatia. The age of igneous protoliths of metarhyolites is about 3.12 Ga. A positive value of epsilon Nd(3122) = +0.9 for metarhyolite and a model age of TNd(DM) = 3.30 Ga, as well as the age of the inherited zircon grain (3250 Ma), testify to the contribution of a more ancient crustal component in the formation of rhyolite magmas. In terms of the geochemical characteristics, metarhyolites are quite similar to tonalites and trondhjemites of the TTG association of about 3 Ga in age within the framework greenstone belts of the Kursk block. These data confirm the hypothesis of the common geological history of the eastern part of the Ukrainian Shield and the Kursk block during the Mesoarchean.