The age and geochemistry of volcanic rocks on the eastern flank of the Umlekan–Ogodzha volcanoplutonic belt (Amur region)

40Ar/39Ar dating yielded the reliable ages of andesite from the Unerikan complex (102.1 ± 1.4 Ma) and basaltic andesite from the Burunda complex (107.3 ± 2.4 Ma). The established age of volcanism is close to one of the stages of formation of the Khingan–Okhotsk volcanoplutonic belt. The petrography and geochemistry of basic, normal-basic, and normal rocks point to their dual character: They combine features specific for tholeiitic and calc-alkalic rocks. Most likely, these rocks formed in the setting of transform continental margin.