Geochemistry and Petrogenesis of Late Mesozoic Volcanites of the Torey and Kharanor Depressions (Eastern Transbaikalia)
Geological structure of the Late Jurassic - Early Cretaceous volcanic rocks of the Kharanor and Torey rift depressions of Eastern Transbaikalia are considered. Rock classification and features of differentiation of their melts on the basis of chemical data are shown. We concluded the main petrogenetic process in the formation of volcanic depressions is fractional crystallization. As part of the Onon terrane of the Agin megazone, the Kharanor and Torey rift basins are distinguished, in which late Jurassic-early Cretaceous volcanic rocks are localized. The lower and upper volcanic layers are devided in the Kharanor depression. Their rocks are similar in many petrochemical characteristics and different in TiO2 content and geochemical features. The upper volcanic layer is correlated with the Torey depression volcanic rocks. Our studies of the petrochemical and geochemical characteristics of the rocks have shown that the lower volcanic suits of the Kharanor depression classified as the shoshonite-latite series and the process of fractional crystallization is main petrogenetic process in their genesis. These volcanites are correlated with the middle-late Jurassic shoshonite-latite volcanites of the lower Kailas suit of the Alexandrovo-Zavodskaya depression. The Torey depression volcanic rocks of the and the upper layer of Haranor depression related to trachybasaltic series and have similar geochemical characteristics the volcanic rocks of the upper part Kailas suite Aleksandrovo-Zavodskoy depression, but having low concentration of the some large ion lithophile elements (Th and U). Assimilation-fractional crystallization processes are recognized in genesis trachibasalt volcanic rock series of the Kharanor and Torey depressions by this study. Similar petro-geochemical characteristics Kharanor and Torey volcanic rocks and the late Mesozoic volcanic rocks of the Alexandrovo-Zavodskaya depression of the reflects a single large-scale process of intraplate post-accretion magmatism in Eastern Transbaikalia.