Comparative Analysis of the Chemical Composition of Rock-Forming and Accessory Minerals of Granite and Psephites from Dinosaur Layers of the Ukureyskaya Formation of the Kulinda Locality in Eastern Transbaikalia (Russia)

The relevance of the study lies in determining the sources of clastic material of gruss and sandstones that make up a significant part of the sediments of the Middle Jurassic Ukurey Formation, which contains the remains of the most ancient feathered dinosaur, Kulindadromeus zabaikalicus. These deposits are a part of the section composed of interlayered gruss, sandstones, siltstones, tuff siltstones and chlidolites. They are represented by a fragment of a downed block of the Ukurey Formation preserved from erosion among granites, the tectonic contact with which is in close proximity to the dinosaur layers. The purpose of the study is to determine the source of clastic material from the woodlands. The object of study is the sediments of the Ukurey formation and granites in the Kulinda tract. The subject of the study is the mineral composition of the clastic fraction of these rocks. The objectives are presented by the study of the composition of rock-forming and accessory minerals of granites and gruss deposits of the Ukurey Formation in the Kulinda tract. The method and methodology consist of sampling, comparative study of the mineral and chemical composition of rocks, diagnostics and study of the chemical composition of minerals using electron microscopy and ICP MS. The results of the study are based on a comparative analysis of the chemical and mineral composition of granites and gruss, during which their proximity is determined. Quartz and feldspar of granites and gruss deposits are characterized by similar composition; the average values of the formula coefficients for quartz of granites and gruss deposits are almost identical. Most quartz individuals are characterized by stoichiometric composition, due to the compensation of the Si deficiency by the inclusion of isomorphic Al and, less commonly, Ti and trivalent Fe. For K-Na feldspar, an excess of the sum of cations and a deficiency of Si are typical. Associations of accessory minerals of gruss and granites (zircon, rutile, apatite, magnetite) and their chemical compositions are similar. Zircons are characterized by an excess of Zr with a deficiency of Si, admixtures of Fe and V in rutile, and a deficiency of Ca and P in apatite. The data obtained prove that the gruss deposits are a redeposited product of granite weathering.