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U-Pb (LA-ICPMS) geochronological studies established the minimum age of detrital zircons from metasedimentary rocks of the Uril Formation of the Amur Group of ∼240 Ma, which approximately corresponds to the lower age boundary of formation of their protoliths. The upper boundary of accumulation of sedimentary rocks of this formation is governed by the age of superimposed structural-metamorphic transformations (220-210 Ma). It follows that the age of protoliths of metasedimentary rocks of the Uril Formation is Triassic in contrast to the previously suggested Early Precambrian age. At the same time, previous estimations of the Nd model age of metasedimentary rocks of the Tulovchikha Formation of the Amur Group and intruding gabbroic rocks are 1.7 and 0.5 Ga, respectively. In other words, the age of this formation is 1.7-0.5 Ga. All of this indicates a combination of sedimentary and volcanic rocks of different ages in the section of the Amur Group. Judging from the Lu-Hf isotopic-geochemical studies of zircons, the major sources of protoliths for metasedimentary rocks of the Uril Formation are Neoproterozoic igneous rocks and also Early and Late Paleozoic and Early Mesozoic igneous rocks, the formation of which was related to the reworking of the Neo- and Mesoproterozoic continental crust. [ABSTRACT FROM AUTHOR]

The article presents information on a study which determines the age of the protolith for metamorphic rocks of the Gonzha Group. It provides information on Gonzha Group which unites metamorphic rocks of the tectonic block located in the north-eastern part of the Argun terrane in the Central Asian fold belt. It reveals that uranium-lead (U-Pb) geochronological and Lutetium-Hafnium (Lu-Hf) isotopic-geochemical investigations of detrital zircons from metasedimentary rocks of the Gonzha Group were performed in the study. A graph with concordia for zircons from meta-sedimentary rocks of the Gonzha Group is presented. A geological map is also presented.