Sources of the Melts of Quaternary Hauyne Alkaline Basaltoids in the Lesser Caucasus. Communication 2. The Nature of the Enriched Lithospheric Source

Abstract

Geochemical and isotopic–geochemical (Sr‒Nd‒Pb) data on the Quaternary intraplate hauyne basanites and ordanshites in the Lesser Caucasus provide an insight into the most probable nature (characteristics of the composition and the depth of occurrence) of the EM II-type enriched mantle source, from which, and from the CAUCASUS OIB-type plume–asthenospheric source, the parental melts of the rocks were derived. The source of the type is demonstrated to have been modified by a subduction-related component. Data are presented on the probable timing and mechanisms of contamination of the magma-generation regions with slab material. Our data suggest that the residue in the mantle source contained garnet, amphibole, and rutile. Results obtained in the course of this study led us to conclude that the source enriched in incompatible elements was most probably subduction-modified (in the course of Mesozoic and, perhaps, also Paleogene subduction events) subcontinental lithospheric mantle of the EM II type, which likely corresponded to rutile-bearing amphibole–garnet peridotite.