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ON CRITERIA FOR DIFFERENTIATION OF THE LOWER-PALEOZOIC GABBRO-MONZODIORITE FORMATION OF THE KUZNETSK ALATAU IN THE KOGTAKH AND KASHPAR INTRUSIVE COMPLEXES OF THE KUZNETSK ALATAU

A. D. Kotelnikov, N. A. Makarenko

Tomsk National Research State University, Tomsk, Russia

New data on magmatic formations of the gabbro-monzodiorite formation of the eastern slope of the Kuznetsk Alatau have been obtained. It is established that two different age groups of rocks of a similar petrographic appearance were previously included. They were certified in the literature as a single Kogtakh gabbro-monzodiorite-syenite intrusive complex, whose monzodiorites in the petrotype massif, according to the author’s uranium-lead dating, are 500.8 ± 4.6 million years old. Other U-Pb dates have been established for gabbroids (487.4±3.8 Ma) and quartz monzodiorites (483.1±4.8 Ma) for the Kashpar massif, which, taking into account the isotope age of the related syenitoids, makes it possible to single out a new (for the region) younger (472–487 Ma) Late Cambrian – Early Ordovician Kashpar gabbro-diorite-quartzmonzodiorite-syenite intrusion complex preceding the formation of Tigertysh granitoids. Argumented geological-petrographic, mineralogical and petrochemical distinctive features of superficially similar formations of the Kashpar and Kogtakh complexes are presented. It is shown that by the distribution of rare elements, the rocks of the complexes show intermediate characteristics between OIB-type intraplate and IAB-type marginal continental basalts, but therewith have a number of geochemical differences.

Keywords: Kuznetsk Alatau, Kashpar and Kogtakh complexes, petrotypical massifs, distinctive features of complexes, uranium-lead dating, multielement spectra, geodynamic environment.

DOI 10.20403/2078-0575-2018-2-49-60