Age and tectonic setting of charnockites of the Tatarnik Complex (Northwestern part of the Baikal region)

Abstract

Charnockite intrusions of the Tatarnik Complex located in the Davan shear zone are the youngest man� ifestations of granitoid magmatism in the northwest� ern part of the Baikal region [1]. The shear zone has a submeridional zone of dislocations separating the Chuya salient composed of Early Precambrian high� grade metamorphic rocks and granitoids and the North Baikal volcano–plutonic belt comprised of Early Proterozoic (1.88–1.85 Ga) volanogenic–sedi� mentary rocks of the Akitkan Group and granitoids of the Irel Complex. Earlier Paleoproterozoic metamor� phic rocks of the Sarma Group are located to the south of this belt. It is necessary to mention that the latest events of Early Proterozoic magmatism within the considered region, such as volcanic rocks of the North Baikal belt, granitoids of the Chuya–Kodar, Kodar, Sayan, and Tarak Complexes, as well as rapakivi of the Primorsk and charnockite of the Shumikhin Com� plexes, are related to the formation of the postcolli� sional Southern Siberian magmatic belt (1.88– 1.84 Ga) extending for a distance of >2500 km along the southwestern boundary of the Siberian Platform from the Yenisei Ridge to the Aldan Shield [2]. Charnockite of the Tatarnik Complex usually forms relatively small intrusive bodies located in the Davan zone and cuts blastomilonites of this zone, as well as rocks of the Sarma and Akitkan Groups (Fig. 1). As a rule, they have a massive texture. Only sometimes is trachytic texture observed in endocontact zones. The chemical composition of charnockite relates to quartz