FINDING OF LATE PROTEROZOIC ONGONITE DIKES ON THE UKRAINIAN SHIELD

Abstract

The structures, the geologic positions, the petrography, and the compositions and the geochemical specializations of the ongonite, granite-porphyry, quartz-porphyry, and altered granite dikes of the Yekaterinovskiy pluton suggest that they are genetically related. Geologic observations in the field and the data given also suggest the occurrence of the following several phases of emplacement of these subvolcanic silicic rocks in the Malo-Yanisol' dike belt: the granite porphyry, the quartz porphyry, the granite, and the ongonite. Evidently, these rocks were emplaced approximately simultaneously, from intermediate magma chambers, although the Rb/Sr ratios that we obtained for the ongonite, granite porphyry and granite of the Malo-Yanisol' dike belt indicate a crustal source of the magmatic melts.