Differentiated volcanic association of the Minusa Trough: Mechanisms of formation and sources of melts, as exemplified by Batenevo Rise

Abstract

The paper addresses the formation of the Early-Middle Devonian volcanic sequences of the Byskar Group of the Batenevo Rise in the Minusa Trough. The volcanic association is represented by the rocks of a wide compositional range from basalt to rhyolite. It is established that the compositional variations are driven by fractionation only within basalt-trachyandesite-trachyte series (47.7–64.5 wt % SiO2). Rocks with SiO2 = 65–74 wt % correspond to mixing products between trachytic differentiates and anatectic crustal melt of rhyolitic composition (∼77 wt % SiO2). It is shown that the compositionally differentiated volcanic series of the Minusa Trough and, presumably, Altai-Sayan rift system, are not analogues of the differentiated magmatic series of continental margin. They were generated by mantle melting, which is typical of within-plate magmatism. The plume impact on the lithosphere resulted in the formation of intracrustal chambers of basite magmas, which caused the anatexis of host crust and subsequent interaction of anatectic felsic magmas with derivatives of basite melts.