The Cambrian–Ordovician diorite–granodiorite–granite association of the Mamyn Terrane (Central Asian Fold Belt): U–Pb geochronological and geochemical data

Abstract

New results of U–Pb geochronological and geochemical studies of rocks that form two structurally different massifs in the Mamyn Terrane are presented here. It has been found that the age of amphibole–biotite granites in the Kosmataya Massif, Oktyabrskii Complex is 488 ± 5 Ma. The same age has been defined for gneissose diorite 488 ± 8 and granodiorite 488 ± 5 Ma of the Ust–Inkan Massif. The results indicate that all the studied rocks have an identical Late Cambrian–Early Ordovician age of about 488 Ma. Considering that they were formed within a single tectonic structure (Mamyn Terrane), spatially close to each other and have similar geochemical characteristics, they may be considered as a single diorite–granodiorite–granite association. The results obtained indicate that a stage of intensive felsic magmatism occurred in the Mamyn Terrane in the eastern part of the Central Asian Fold Belt. This stage of magmatic activity is also clearly expressed in other continental massifs in the eastern part of this belt, which may indicate their common geodynamic history.