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Geochemical and Sm–Nd isotope–geochemical studies of synnyrite and syenite from the Synnyr massif and high-K syenite from the Tas massif of the Late Paleozoic (eastern Siberia) corresponding to one of the largest provinces of high-K and ultrapotassic magmatism worldwide are performed. It is shown that their formation was controlled by transformation of the Precambrian continental crust of the Siberian Craton and Central Asian Mobile Belt under the influence of the Siberian mantle plume.

This work presents the results of U–Pb isotope dating of zircons from granodiorites and plagiogranites of the Tallainskii gabbro–granodiorite–plagiogranite complex of the Karalon–Mamakan zone of the Baikal–Muya belt, ascribed to the Tallainskii pluton. The age datings obtained for granodiorite of the Eleninskii massif (605 ± 6 Ma) and plagiogranite of the Ust-Berezovo massif (609 ± 6 Ma) are in close agreement within the limits of error. Taking into account previously published data, the emplacement of the Tallainskii complex occurred within the age interval of 615–603 Ma in connection with postcollision extension. The “island arc” geochemical characteristics of granodiorites and plagiogranites can be explained by magmatic differentiation and (or) participation in the formation of a melt source enriched in the suprasubduction component involved in petrogenesis during the preceding Neoproterozoic period.

The Kichera zone of the Baikal–Muya Belt consists of alternating tectonic plates with rocks of different metamorphic facies. Garnet–cordierite–sillimanite gneiss from the tectonic fragment in granite–gneiss of the Baikal massif with an age of 755 ± 15 Ma from the Goremyka plate and two-pyroxene schist of the granulite complex with an age of 617 ± 5 Ma from the Boguchan plate were studied. Thermobarometric studies of these key metamorphic rocks were carried out using the avPT (THERMOCALC) and TWEEQU (TWQ 2.01) methods. The P–T parameters estimated for the cordierite⎯sillimanite gneiss of the Goremyka plate correspond to the boundary between the amphibolite and granulite facies. Granulites of the Boguchan plate belong to the HT–LP type. Exhumation of metamorphic rocks could be caused by extension upon the evolution of the Late Baikal rifting.

It was established that amphibolites of the Kichera zone of the Baikal-Muya belt (BMB) belong, at least, to two age groups: (I) Early Neoproterozoic large metamafic xenoliths entrapped by granitic rocks of 750 Ma and (II) Late Neoproterozoic (650-620 Ma) amphibolites, which compose individual tectonic sheets and lenses. The rocks of these groups are distinct in chemical composition: the low-Ti amphibolites of the first group with increased Al 2 O 3 contents are similar to modern IABs, whereas the highly-Ti amphibolites of the second group correspond to MORBs and OIBs. The geochemical data showed that the igneous protoliths of amphibolites of the Kichera zone were formed during different stages of the BMB evolution distinct in geodynamic settings.