Structural-crystallochemical features of minerals of the glauconite-illite series with high Mg contents from Upper Proterozoic deposits of Eastern and Northern Siberia

At the current level of research, a generalization of previously studied and new lithological-mineralogical and structural-crystal-chemical characteristics of globular phyllosilicates (GPS) of the glauconite-illite series with a high Mg content from Upper Proterozoic sections of Eastern and Northern Siberia (Uchur-May region, Anabar uplift) has been carried out. The classification of glauconite-illite minerals was carried out in accordance with the recommendations of the International Nomenclature Committees for mica and clay minerals, as well as on the basis of literature and our own data. The degree of aluminum content of minerals (КAl = VIAl / [VIFe3+ + VIAl]) of the glauconite-illite series varies from 0.40 to 0.85, the content of Mg and K cations varies from 0.51 to 0.75 and from 0.63 to 0.80 f.u. (formula units), respectively. Using X-ray modeling method of diffraction patterns of oriented and non-oriented preparations of Upper Proterozoic GPS, the following were determined: the content of swelling layers (4–10%), their types (mica, smectite, chlorite), the nature of the alternation (short-range order factor R = 0), unit cell parameters csinβ, ccosß/a, average value of parameter b (9.018–9.074 Å). The conditions of glauconite formation in the Upper Proterozoic basins are considered, their influence on the structural and crystal-chemical features of magnesian hydrocarbons is discussed.