Mineral assemblages of titanium-zirconium sands at the Central deposit,the east European platform

The study of mineral assemblages at the Central deposit allowed us to substantially refine the evolutionary model of the deposit and reveal the two main factors that control the variability of its mineralic space: (1) heterogeneity of the ore layer, consisting of a sublittoral bottom placer (the lower part) and a subaerial dune complex partly reworked in the course of a new transgression (the upper part), and (2) postore epigenetic alteration of the ore constituent of sands, which affected the quality of ore concentrates. The results obtained will be used in geological and technological mapping and development of the production program.     

Discharge of Salt Groundwater in the Estuary of the Razdol’naya River (Amur Bay) in February 2020

Water Resources - In February 2020, geochemical tracers along with hydrochemical and hydrological characteristics were used to reveal a discharge site of salt groundwaters in the head of the...     

Freshwater Sources in the Bays of Yuzhnyi Island of the Novaya Zemlya Archipelago According to Isotopic (δD, δ18O) Data

Doklady Earth Sciences - An isotope–geochemical study was performed on the waters of Abrosimov and Stepovoi bays along the southeastern coasts of the Novaya Zemlya Archipelago. The waters...     

The Oxygen Isotope Composition of Late Pleistocene and Holocene Ice Wedges of Kotelny Island

The aim of the work was to perform paleotemperature reconstructions for the Late Pleistocene and Holocene of Kotelny Island according to oxygen isotope analysis of syngenetic ice wedges. Variations of δ¹⁸O in the Late Pleistocene ice wedges formed on Kotelny Island are significant, exceeding 8‰ (from –30‰ to –22.9‰), while they are insignificant at –1.5‰ (from –23.1‰ to –21.6‰) for those in the Holocene. Reconstructions showed that the mean January temperature in the Late Pleistocene changed over 8 to 13°C. The mean annual temperature of frozen soils was about –19 or –20°C in the Late Pleistocene, and about –13 to –15°C in the Holocene, while the current temperature is about –14°C.

     

Oxygen isotope composition of water and snow-ice cover of isolated lakes at various stages of separation from the White Sea

This study aimed to analyze the oxygen isotope composition of water, ice, and snow in water bodies isolated from the White Sea and to identify the structural peculiarities of these pools during the winter period. The studies were performed during early spring in Kandalaksha Bay of the White Sea, in Velikaya Salma Strait and in Rugoserskaya Inlet. The studied water bodies differ in their degree of isolation from the sea. In particular, Ermolinskaya Inlet has normal water exchange with the sea; the Lake on Zelenyi Cape represents the first stage of isolation; i. e., it has permanent water exchange with the sea by the tide. Kislo-Sladkoe Lake receives sea water from time to time. Trekhtsvetnoe Lake is totally isolated from the sea and is a typical meromictic lake. Finally, Nizhnee Ershovskoe Lake exhibits some features of a saline water body. The oxygen isotope profile of the water column in Trekhtsvetnoe Lake allows defining three layers; this lake may be called typically meromictic. The oxygen isotope profile of the water column in Kislo-Sladkoe Lake is even from the surface to the bottom. The variability of δ¹⁸O is minor in Lake on Zelenyi Cape. A surface layer (0–1 m) exists in Nizhnee Ershovskoe Lake, and the oxygen isotope variability is well pronounced. Deeper, where the freshwater dominates, the values of ?18Îvary insignificantly disregarding the water depth and temperature. This fresh water lake is not affected by the seawater and is not stratified according to the isotope profile. It is found that applying the values of ?18Î and profiles of temperature and salinity may appear as an effective method in defining the water sources feeding the water bodies isolated from the sea environment.     

Variations of Stable Oxygen and Hydrogen Isotopes in the Ice Core of the Pingo (Southern Part of Gydan Peninsula)

Doklady Earth Sciences - The vertical isotopic profile of the ice core of a Messoyakha-1 bulgunniakh (pingo)—was obtained. The pingo is situated at 68°30′32″ N,...     

Oxygen isotope and deuterium indication of the origin and <Superscript>14</Superscript>C age of the massive ice,Bovanenkovo, Central Yamal peninsula

The conditions and forming time of massive ice were specified (Bovanenkovo gas condensate field, Central Yamal). Here, massive ice lies as stratums, laccoliths, stocks, and lenses. Three thousand boreholes 10–100 m in depth were analyzed. In 260 of them massive ice was broached. The ice foot is situated from 1 to 57 m deep. The maximal thickness of ice broached with boreholes came to 28.5 m; on average, it was about 8 m. The extension of massive ice is sometimes more than 2000 m, and its area is quite often more than 10 km². According to the radiocarbon method, loams of the third terrace, containing and overlapping ice deposits, were formed from 25 000 to 20 000 years ago or somewhat later. These strongly peat loams containing massive ice formed either in shallow sea conditions or during periodical draining conditions of beaches or low laida, where organic matter appeared due to erosion and deposition and accumulated during draining and overgrowing of drains. In more inclement conditions than at present, loam deposits were frozen immediately, forming massive ice, which occupied the barely water-saturated layers. The oxygen isotope composition (δ18O) of massive ice samples varied from −12.49‰ (here and further, relative to SMOW) to −22.95‰. The deuterium concentration (δD) varied from −91.7 to −177.1‰. Deuterium kurtosis (d _exc) varied from 3.4 to 10.6‰. In one seam outcrop, the content of stable isotopes varied significantly. Here, at a depth of 0.2–0.8 m, the δ¹⁸O content varied by more than 10‰ (from −12.49 to −22.75), and the δD content, from −91.7 to −171.9‰. Such variations testify about ice extraction upon freezing of water-saturated grounds in a closed system. According to palynological analysis of ice stratums, numerous remains of unicellular green algae and diatoms were revealed. It is possible that this is evidence of the existence of a fresh well, which was a source of water, feeding the layer. Most probably these were near-bottom silt waters of a large lake or desalted bay, which were frozen syngenetically. This accentuates the new type of massive ice, syncriogenic segregative ice, which probably formed 25 000–20 000 yr BP.     

Variations of δ<Superscript>18</Superscript>O in Rivers of Crimea in Winter

The results of studies of variations of δ¹⁸O values in river water in Crimea Peninsula in January–February 2015–2017 are given. The variation range of δ¹⁸О in river water over the three years of studies never exceeded 3‰. A tendency toward an increase in δ¹⁸О in the water of the Salgir, Kacha, Al’ma, Bel’bek, Biyuk-Karasu from their sources to mouths was identified and explained by a decrease in evaporation in the mouth areas of the rivers relative to their sources and upper reaches, and the inflow of isotopically light precipitation (rain and snow) into the rivers in their upper reaches. The values of δ¹⁸О in waters of the rivers with regulated stream were found to increase under the effect of the Simferopol Reservoir on the Salgir River and the Izobil’nenskoe Reservoir on the Ulu-Zen’ River. The values of δ¹⁸О in the upper reaches of the large rivers of Kacha and Bel’bek (the northwestern slope of the Crimean Mountains) vary from ?8.7 to ?9.7‰, except for the rivers of Al’ma (?7.7‰) and Kokozka (?10.2‰) because of the different shares of groundwater in the recharge of these rivers.     

Water Dynamics and Structure in the Estuary of the Partizanskaya River (Nakhodka Bay,Sea of Japan)

Water Resources - Field studies of the seasonal and daily dynamics of the mixing zone were carried out in the microtidal estuary of the Partizanskaya River. The position of the mixing zone was...