REE geochemistry in groundwater of the Sikhote Alin fold region (Russian Far East)

Analysis of the distribution and fractionation of rare earth elements in the groundwater of the Sikhote Alin fold region reveals that their concentrations, geochemistry, and fractionation ability vary in different groundwater types depending on many factors, including the pH–Eh parameters and mineralization of the solutions and the composition of the host rocks. The results of monitoring of changes in the REE concentrations in the groundwater of the region over ten years provides the opportunity to establish the range of their variations. Inorganic forms of REE migration are rated for all geochemical types of water in the meteoric–surface–ground water system.     

Geochemistry of carbonated mineral waters from the Fadeevskoe deposit of the Primorye region

The geochemical study of bed rocks, underground and surface waters, and associated gases in the Fadeevskoe deposit of carbonated waters (Sikhote Alin, Primorye region) revealed that the chemical composition of these waters is formed in the zone of active water exchange in the limited area of the discharge zone, where hydro carbonate calcic waters with mineralization of up to 1 g/1 are formed in largely potassic-sodic rocks. Calculations of the saturation indices show that the mineral waters are characterized by the early stage of Ca saturation, being undersaturated with carbonates and aluminosilicates. The main factors that influence the water mineralization are the excess carbon dioxide in water and the circulation time. The oxygen and carbon isotope ratios indicate the atmospheric genesis of the aqueous component (δ²H = —117; δ¹⁸O = —15.4%o) and the carbon isotope content in the CO₂ implies the mantle nature of the carbon dioxide (δ¹³C = -9.9%o).     

Nature of the scattered seismic response from zones of random clusters of cavities and fractures in a massive rock

The scattering of elastic energy by random clusters of fractures and/or cavities in a massive rock is studied. The interpretation of the scattered seismic response reveals crucial information about the clusters of inhomogeneities (fractures/cavities), which may correspond to reservoirs. The study is based on a new two‐dimensional numerical‐modelling method that relaxes the constraints on the location and orientation of the inhomogeneities, accounts for inhomogeneities that have almost no volume but a finite surface area (fractures) and improves the accuracy of the calculation when the size of the inhomogeneities is comparable to the mesh size. It is shown that the nature of the seismic response of zones of diffuse fracturing and/or cavities is associated with the non‐uniformity of micro‐inhomogeneities in such zones; accumulations of these micro‐inhomogeneities are known as clusters. The relationship between the non‐uniformity of micro‐inhomogeneities and the strength of the seismic response has been established and measured. Considerable differences in the structure of the seismic response of zones of diffuse fracturing and diffuse cavities have been identified. Converted PS‐waves dominate in the scattered wavefield associated with fractures. This is explained, as the modelling results show, by a greater transparency of fluid‐filled fractures, which reduces the reflected energy of compressional waves. The wavefield associated with cavities is characterized by the predominance (in terms of strength) of compressional PP‐waves. The strength of converted PS‐waves in the scattered wavefields for both media is approximately the same. On the whole, according to the results of the modelling, the energy of the scattered response of fractured reservoirs is considerably less (about two times) than that of cavernous reservoirs.     

Genesis of the mineral groundwaters of the Razdol’nenskii occurrence in Primorye

Original isotopic and chemical data are reported on the groundwater and gases from the unique occurrence of mineral water in the coastal zone of southern Primorye. Results of the δ¹⁸O and δ²H analysis of the underground and surface water of the area integrated with their δ¹³C composition made it possible to solve the problem of the genesis and evolution of groundwater and gases in the coastal part of the Sea of Japan. It was established that meteoric waters penetrate into the Mesozoic terrigenous rocks and changed their chemical composition under the influence of transformation of organic matter from the host rocks. CO₂ released owing to reactions provides multiple enrichment of the water in HCO₃ and stimulates Na influx via dissolution of aluminosilicates.     

Geochemistry of the mineral waters and gases of the Mukhen deposit,Far East

This work reports new hydrochemical data on the two types of cold high p CO₂ groundwaters from the Mukhen deposit (Khabarovsk district). The first type is classed with HCO₃-Ca-Mg waters with a relatively low TDS (up to 1.7 g/l) and high concentrations of Fe²⁺, Mn²⁺, Ba²⁺, and SiO₂. The second type is of HCO₃-Na composition with high TDS (up to 14 g/l) and elevated Li⁺, B, Sr²⁺, Br^?, and I^?. New oxygen (δ¹⁸O) and hydrogen (δD) isotopic data on the waters and carbon (δ¹³C) isotopic data on the gas phase, together with a detailed geological and hydrogeological analysis of the study area, allowed us to decipher the origin of both the mineral waters. Based on the tritium content (³H) in the ground and surface waters of the area, the duration of the mineral water circulation was estimated. It was established that the both types of groundwaters were formed during interaction of meteoric water with bedrock under active influence of CO₂, however HCO₃-Na groundwaters have longer residence time than HCO₃-Ca-Mg groundwaters.