Melting modeling of mixed peridotitic and mafic lithologies at shallow depths of the continental metasomatized lithospheric mantle: Implementation for the Early Cretaceous volcanic rocks of Eastern Mongolia

Abstract

The Eastern Mongolia volcanic area formed in the Late Mesozoic — Early Cenozoic within Central Asian Orogenic Belt. The main volcanic events of the area occurred in the Early Cretaceous when alkaline basaltic lavas erupted and formed the so-called cover volcanic complex. Geochemical and isotope features of the cover volcanic complex allowed researchers to identify the following mantle rocks as their source: metasomatized peridotites, eclogites, and pyroxenites. Thermodynamic modeling in alphaMELTS program was performed to determine whether the simultaneous melting of these rocks with subsequent processes of crystallization differentiation could lead to the formation of the studied rocks. The modeling results show that the melting of the most enriched with incompatible trace elements peridotites, eclogites, and pyroxenites cannot produce the rocks of the cover volcanic complex. At the same time, the mixing of peridotite- and eclogite- derived melts corresponds most closely to the mechanism of rock formation. However, Ti, K, P, Rb, and Sr enrichment of the studied rocks also requires participation in magma generation processes of mantle metasomatic veins enriched with rutile, apatite, phlogopite, and amphibole.