One of the remarkable features of the geology of the Chiatura manganese deposit is the presence of different facies of ore-bearing sediments. Of particular interest is the change in these facies in the vertical section of the manganese ore strata, which was well traced both from outcrops and from numerous drill holes. Analysis of the geological structure of the formation of ore-bearing sediments and host rocks led to the conclusion that the vertical change of facies depended on the orogenic movements that took place at the time of formation of the manganese ore strata. A very interesting fact was that within the area of the Chiatura deposit, which occupies an area of about 100 square meters. km, the amplitude of these movements in different parts of it was apparently unequal, which affected the mineralogical composition and structure of various facies. The proposed work contains a brief summary of the main provisions relating mainly to this phenomenon, almost unknown in the literature, among sedimentary ore deposits. There is reason to assume that changes in the composition of facies in the vertical section in the Oligocene deposits of the Chiatura region were caused by orogenic movements, which were the last echoes of the pre-Oligocene orogenic phase.
In this article, the author makes an attempt to present in general his views, on the one hand, on the methodology for studying chromium deposits in the most general form, and on the other, on the geological nature of these deposits. The author himself has been involved in the study of predominantly Ural platinum-bearing chromium iron ores. For identification purposes, non-platinum-bearing chromites were also studied at the same time.The latter were studied in more detail in Transcaucasia (in the area of Lake Gokcha), as well as in the North Caucasus (in the area of the Bolshaya Laba River). We can outline the following genetic types of chrome spinels formations: 1) chrome spinels formed in an earlier magmatic period; 2) accumulations of chromespiedids formed in a later igneous period, when the main mass of the host rocks was almost formed; 3) chrome spinels formed by hydrothermal processes, mainly during serpentinization of rocks. Leningrad, Fedorov Institute of Crystallography, Mineralogy, Petrography and the Study of Ore Deposits.
