Geochemical features of pyrite pseudomorphs according to plant residues from the Upper Jurassic deposits of the Middle Volga river area (Russian Federation)

Abstract

The study of the mineralogy and geochemistry of biomorphic ore formations has great importance for studying the processes of transformation of plant tissues during the formation of the sedimentary rocks, including ore mineralization. Forms of biogenic mineralization in sedimentary rocks are represented by various processes. The pyritization of organic residues is one of the most common forms. The purpose of this work was to conduct a detailed mineralogical and geochemical study of biomorphic ore formations collected from Mesozoic (Upper Jurassic) deposits of the right bank of the Volga river. The initial conditions for the fossilization of the objects of study were the same. Therefore, the structural and morphological features of the pyrite aggregate developing on them can be caused not only by geochemical conditions but also by the structure of the residues themselves. Samples were examined by optical microscopy, X-ray phase analysis, gamma-ray spectrometric analysis, X-ray computed tomography and X-ray fluorescence analysis. As a result of research, the stages of mineralization of wood were established, which reflect the features of sedimentation.