We propose a detailed lithostratigraphic description of the key section of the Kunda Regional Stage (Middle Ordovician) on the Volkhov River. The section is subdivided into 35 beds, grouped into 8 members; the lowerest Khamontovo Member belongs to the Volkhov Formation, the overlying Yakhnovo, Syas, Zvanka, Izvoz, Ilinskoye, Chernavino and Simankovo Members form the Obukhovo Formation. The lower and upper “Oolite Beds” are considered only as informal subdivisions. The lithological markers (bed boundaries, discontinuity surfaces, etc.) are compared with trilobite zones and serve for a detailed correlation of Kunda deposits along the Ingermanland Klint (more than 200 km).

   The analysis and assessment of hydrogeological and engineering-geological factors during underground mining and the predictive assessment of the engineering-geological situation in natural conditions are considered. Deposits are distinguished into three categories: weakly, moderately, and highly stable. Based on hydrogeological features, seven groundwater horizons were identified in the area. The mineralization of aquifers, chemical composition, permeability coefficient, actual and expected water inflow of underground mine workings are given.

   The evidence obtained for hot heterogeneous accretion of the Earth indicates the formation of the lithosphere of ancient platforms, kimberlites, and diamonds as a result of the fractionation of a layered global magma ocean, which arose due to the massive impact heat release during accretion. This explains the confinement of diamond-bearing kimberlites only to ancient platforms. The worldwide distribution of the magma ocean determined the presence of kimberlites on all ancient platforms. Their bottom residual magmatic origin is the reason for the small volume of kimberlite bodies and their relatively late formation. Diamonds crystallized as a result of the accumulation of carbon in residual melts. Extremely low viscosity of the bottom peridotite layer of the magma ocean determined the low rate of carbon diffusion in them and the formation of early octahedral diamonds through layer-by-layer tangential growth. The accumulation of multivalent elements in residual melts during fractionation led to an increase in the viscosity of the melts by thousands of times and to the formation of
diamond rhombic dodecahedrons and cubes as a result of radial growth. A decrease in the rate of carbon diffusion with an increase in the viscosity of the melts caused a reduction in the area of the formed layers on diamonds and the appearance of their rounded crystals. A slow decrease in temperature in the early magma ocean led to the long-term crystallization of giant diamonds and their predominantly octahedral cut.

   The article presents the results of mineralogical, petrographic, and geochemical studies of hydrothermally altered and metamorphic formations of the Olympiada deposit. It shows that the combination of beresitization halos, which control the distribution of stratiform gold-sulphide mineralization in space, with multiplicative positive geochemical anomalies
of Au-As-Te-Sb-Hg composition close to them in morphology, can be used as hydrothermal alteration and geochemical criteria for predicting gold-sulphide mineralization in the Olympiada ore field. We discuss geological and genetic model of the Olympiada deposit formation, give recommendations on the use of this technique for predictive and prospecting purposes.

   The article discusses new data obtained during the mineralogical, petrographic, petrogeochemical, and isotope geochronological study of igneous rocks of the Jerooy ore field, located in the western part of the Northern Tien Shan. The large Jerooy gold deposit of the gold-quartz type is confined to the diorites of the Jerooy complex. The results of geochronological studies (U-Pb SIMS study of accessory zircons) revealed the age of magmatic crystallization of the Jerooy complex diorites, which host gold mineralization, in the range of 462–469 Ma, and the more ancient Precambrian granites of the Tabalyk complex, in the range of 1160–1161 Ma. The petrochemical and geochemical characteristics of intrusive rocks participating in the geological structure of the Jerooy ore field are given. A model for the formation of the Jerooy deposit is proposed and its geodynamic position is determined.

   The article shows the transformations of the Meso-Cenozoic rifts of the Alpine-Himalayan mobile belt and the region of its junction with the Pacific belt with the Holocene orogenic tectonics and erosion. Rift structures are presented as indicators of the Holocene activation, as part of the Holocene orogenic structure of these belts. During the Holocene activation, they were divided into separate blocks, upthrown, eroded, and significantly reduced their outlines. In the rifts of the deep part of the continent, oxidation zones with hydrogenous uranium mineralization developed in them were transformed. These rifts developed in the Pliocene-Pleistocene under arid climate conditions. Their grey-coloured sedimentary section was exposed to oxidative epigenesis and ore genesis. In the relict structures of the Mongolian Gobi rifts, the mineralization of the surface oxidation zone was brought to the surface by the Holocene erosion. Rifts of Eastern Asia developed under conditions of a stable humid climate, unfavourable for the development of oxidative ore genesis. They were exposed for oxidation only in the Holocene. The erosion of their sediments developed so actively that it often outstripped the development of oxidation.

   Petrophysical, geochemical, and mineralogical studies of the rocks from the Litsevsky and Priozerny uranium ore sites in the Litsevsky ore district of the Kola region were carried out. The results showed that the density and elastic anisotropy of rocks reflect the intensity of mineralization. High density (3.39 g/cm³) with low values of elastic anisotropy (2.3 %) were noted in rock samples with uranium and sulphide mineralization. Electron microscopy of uranium and thorium phases in the rocks of the Litsevsky ore sites confirmed two stages in the formation of uranium mineralization, separated by the stage of sulphides (pyrite and chalcopyrite) formation. The data obtained can be used in assessing the potential ore content of areas with the manifestation of multi-stage hydrothermal alterations.