Vol 59, No 4 (2017)

The paper discusses questions related to the generation of increasing crustal horizontal compressive stresses compared to the idea of the standard gravitational state at the elastic stage or even from the prevalence of horizontal compression over vertical stress equal to the lithostatic pressure. We consider a variant of superfluous horizontal compression related to internal lithospheric processes occurrin in the crust of orogens, shields, and plates. The vertical ascending movements caused by these motions at the sole of the crust or the lithosphere pertain to these and the concomitant exogenic processes giving rise to denudation and, in particular, to erosion of the surfaces of forming rises. The residual stresses of the gravitational stressed state at the upper crust of the Kola Peninsula have been estimated for the first time. These calculations are based on the volume of sediments that have been deposited in Arctic seas beginning from the Mesozoic. The data speak to the possible level of residual horizontal compressive stresses up to 90 MPa in near-surface crustal units. This estimate is consistent with the results of in situ measurements that have been carried out at the Mining Institute of the Kola Science Center, Russian Academy of Sciences (RAS), for over 40 years. It is possible to forecast the horizontal stress gradient based on depth using our concept on the genesis of horizontal overpressure, and this forecasting is important for studying the formation of endogenic deposits.

The Plavica Au–Ag–Cu deposit is related to the large Neogene volcanic center, which complicates the paleocaldera in the central Kratovo–Zletovo ore district of eastern Macedonia. Based on the geology, ore mineralogy, wall-rock alteration, and fluid inclusions, the Plavica deposit has been referred to the epithermal high-sulfidation type. The general 3D model of orebody at this deposit is based on its general geological structure and complex distribution of metal contents. The framework of the 3D model, which has been constructed in the ArcGIS System, comprises 195 exploration boreholes 47295.8 m in total length. The 3D model allows to a better understanding of distribution of mineralization and supplements the geological data on the deposit.

The paper discusses the mineralogy and geochemistry of altered rocks associated with calcite and dolomite–ankerite carbonatites of the Onguren dyke–vein complex in the Western Transbaikal Region. The alteration processes in the Early Proterozoic metamorphic complex and synmetamorphic granite hosting carbonatite are areal microclinization and riebeckitization; carbonates, phlogopite, apatite, and aegirine occur in the near-contact zones of the dolomite–ankerite carbonatite veins; and silicification is displayed within separated zones adjacent to the veins. In aluminosilicate rocks, microclinization was accompanied by an increasing content of K, Fe³⁺, Ti, Nb (up to 460 ppm), Th, Cu, and REE; Na, Ti, Fe³⁺, Mg, Nb (up to 1500 ppm), Zr (up to 2800 ppm), Ta, Th, Hf, and REE accumulated in the inner zone of the riebeckitization column. High contents of Ln_Ce (up to 11200 ppm), U (23 ppm), Sr (up to 7000 ppm), Li (up to 400 ppm), Zn (up to 600 ppm), and Th (up to 700 ppm) are typical of apatite–phlogopite–riebeckite altered rock; silicified rock contains up to (ppm): 2000 Th, 20 U, 13000 Ln_Ce, and 5000 Ва. Ilmenite and later rutile are the major Nb carriers in alkali altered rocks. These minerals contain up to 2 and 7 wt % Nb₂O₅, respectively. In addition, ferrocolumbite and aeschynite-(Ce) occur in microcline and riebeckite altered rocks. Fluorapatite containing up to 2.7 wt % (Ln_Ce)₂O₃, monazite-(Ce), cerite-(Ce), ferriallanite-(Ce), and aeschynite-(Ce) are the REE carriers in riebeckite altered rock. Bastnäsite-(Ce), rhabdophane-group minerals, and xenotime-(Y) are typical of silicified rock. Thorite, monazite-(Ce), and rhabdophane-group minerals are the Th carriers.