Age, main geochemical characteristics, and sources of late Cenozoic volcanic rocks in the Udurchukan volcanic area (Amur Region)

Abstract

This paper presents new mineralogical, petrographic, geochemical, and isotope–geochronological data on the Cenozoic basaltic trachyandesites from the Udurchukan volcanic area (Amur region), which occupies the watersheds of the Uril, Mutnaya, and Khingan rivers. Based on the available geochrolonological data and new K–Ar dating, the basaltic trachyandesites are middle Miocene in age (18.9–17.1 Ma). Petrogeochemically, they are divided into two groups. These groups differ in the contents of MgO, TiO₂, P₂O₅, as well as Sr, Ba, Nb, Ta, and LREE, which is presumably related to the different degrees of metasomatic reworking of the mantle sources and their melting. In terms of the trace-element distribution and ratios, the basaltic trachyandesites from the Udurchukan area are close to the within-plate rocks and were contributed by enriched lithospheric mantle previously subjected to fluid metasomatism.