Lower Eocene glauconite deposits of the south west of the Volga monocline and the potential for their use (Volgograd region)

Abstract

Introduction: As a result of geological exploration, a new core material was obtained from the sedimentary cover of the south-western part of the Volga monocline. The top of the Lower Eocene deposits is characterized by a horizon with a significant amount of glauconite. An extended band of glauconite distribution in the Paleogene deposits of the Voronezh anteclise and the Volga monocline, together with information about its intrastructural and crystal-chemical features, expands knowledge about the geological history of the considered region. Methodology: The core material was studied in detail in the intervals of development of sandy-aleuritic deposits with glauconite. Petrographic and granulometric analyses, optical microscopy, X-ray analysis and scanning electron microscopy with local geochemical microanalysis were performed. Results and discussion: Glauconite is represented by globules and angular grains, often with syneresis cracks. Mineral inclusions could be visualized in the form of xenoliths, and also as nuclei of development of glauconite along them as pseudomorphs on electron microscopic images. According to X-ray analysis of incomplete monofractions of the mineral, in addition to the main hydromicaceous reflections, traces of kaolinite and smectite could be detected. Conclusions: The considered mineral tends to form shallow marine facies and has a clearly authigenic genesis, the formation of which occurred in unique local conditions. The characteristic features of this horizon according to geophysical logging data allow using the obtained results in further exploration work. The increased content of glauconite in Ypresian loose deposits and their sustained thickness allow to recommend them a chlorine-free potassium fertilizer, which can be used as valuable mineral raw material.