The Lukinda dunite–troctolite–gabbro massif in the Selenga–Stanovoy superterrane on the southeastern framing of the Siberian Platform was earlier considered Precambrian. The performed 40Ar/39Ar dating of the massif plagioclase yielded an Early Permian age (285 ± 7.5 Ma). The main specific petrochemical features of the intrusion rocks during their crystallization differentiation are an increase in SiO2 and CaO contents and a decrease in FeOtot content, with TiO2 content remaining low and showing minor variations. A specific geochemical feature of the Lukinda massif ultrabasite–basites is a slight domination of LREE over HREE, with (La/Yb)N = 1.0–8.2. The depletion of the massif rocks in LILE (except for Sr and Ba), REE, and HFSE suggests that the massif formed on an active continental margin.
The performed 40Ar/39Ar geochronological studies yielded the first reliable age of trachyandesites of the Mogot volcanic field (115 ± 3 Ma), which, together with the age of trachyandesites of the Bomnak volcanic field (117 ± 1 Ma), gives grounds to recognize a new stage (117–115 Ma) of evolution of the Stanovoi volcanoplutonic belt superposed on the igneous and metamorphic complexes of the Dzhugdzhur–Stanovoi superterrane of the Central Asian Orogenic Belt and Stanovoi structural suture. The trachyandesites of the Mogot volcanic field are similar in geochemical features to adakites. Their parental melts resulted from the transformation of Precambrian continental crust under postcollisional extension after the formation of the Mongolo–Okhotsk orogen or under sliding along the boundary between the North Asian craton and the Amurian microcontinent.
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