Model of the formation of monzogabbrodiorite-syenite-granitoid intrusions by the example of the Akzhailau massif (East Kazakhstan)

Abstract

This paper presents a model of the formation of a multiphase granitoid Akzhailau massif, formed within a Caledonian block of the Earth’s crust in Hercynian time. This work is based on the results of studies of petrogenic and rare elements composition, geochronological, mineralogical and isotope-geochemical studies. Three stages of the formation of the Akzhailau massif are distinguished, which differ significantly from the previously accepted ideas about the multicomplexity and polychronicity of this intrusive: 1) the formation of moderate alkaline A2-type leuсogranites (308–301 Ma); 2) intrusion of monzodiorites into the base of leucogranites (~295 Ma) increasing of partial melting degree of substrates with the formation of syenites and moderate alkaline granites of I-type (294–292 Ma); 3) the intrusion of dikes and small bodies of alkaline ferroekermanite A1-type leucogranites in the west and north of massif (~289 Ma). The Akzhailau massif was formed in the interval of about 15 million years in the middle-upper crust during the interaction of subalkaline basitic magmas of plume nature with metamorphosed crustal substrates of the orogenic structure.