Hulko V. Geochronology and nature of charnockitoids of the Upper Pobuzhja

The purpose of this work is to determine the time of formation and the source of the parent magmas of Pobuzhja charnockitoids using the methods of isotopic geochemistry. In the work, on the basis of geological material selected from the quarries of Verkhniy Pobuzhie, the following research methods were used: isotopic - Sm-Nd, U-Pb, Rb-Sr and Lu-Hf, the ICP-MS method using the ELEMENT-2 analyzer and mineralogical studies of zircons. Analytical studies were carried out in the laboratories of the M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the National Academy of Sciences of Ukraine and in the John de Laeter center of Curtin University, Perth, Australia. The study of isotopic systems of U-Pb, Lu-Hf, Sm-Nd in individual grains by the methods of local isotopic analysis allows to obtain objective information both about the age of zircons and about the geochemical features of the protolith of these rocks. The study of zircons from "crust" enderbites (sample 110/79) and "juvenile" (samples 117/79 and 127/79) was carried out in the John de Laeter center of Curtin University, Perth, Australia. The isotopic composition of hafnium was determined separately using a Nu Plasma II multi-collector device. At the same time, the ablation craters were located near the uranium-lead dating craters. Charnoenderbit 110/79 (Sabariv), had a very complex geological history. The age of individual grains varies in the range from 1800 to 3400 million years. In contrast, enderbit 117/79 is represented by a cluster of points around the value of 2080 Ma on the concordia, which is almost identical to the previous data of 2096 Ma.