Isotopic composition (H, O, Cl, Sr) of ground brines of the Siberian Platform

Abstract

New data on the geochemistry and isotopic composition of chloride brines of the Siberian Platform are presented. The distribution of stable isotopes (2H, 18O, and 37Cl) in brines of the Tunguska, Angara-Lena, western part of the Yakutian and Olenek artesian basins and 87Sr/86Sr in brines of the western part of the Olenek artesian basin was studied in the context of the problem of genesis of highly mineralized groundwaters. Results of the study and comparative analysis of the geochemical and isotopic peculiarities of the Siberian Platform brines conform to the theory of brine formation through the interaction of connate waters with enclosing rocks.

Seasonal variability of element fluxes in two Central Siberian rivers draining high latitude permafrost dominated areas

“…In the region, continuous permafrost thickness varies between 200 and 400 m. In the central part of the plateau the tholeiitic flood basalts are 1500-2000 m and in the southern part 200-300 m thick. These basalts are characterized by very homogeneous mineralogical and chemical compositions (Sharma et al, 1992) and overlie Cambrian sedimentary series mainly composed of terrigenous deposits, limestones and evaporitic salts (Petrychenko et al, 2005;Alexeev et al, 2007;Shouakar-Stash et al, 2007). These sedimentary series host highly concentrated brines of various genesis, with notably brines originating from the leaching of evaporite beds (mostly sodic brines present in the Nizhnyaya Tunguska watershed) and brines stemming from buried bittern that evolved by reacting with enclosing rocks (mostly calcic brines present in the Kochechum watershed) (Alexeev et al, 2007 and references therein).…”

“…Temporal evolution of the soluble flux composition in Kochechumo river waters in a mixing diagram using Na-normalized mass ratios. Comparison with Kulingdakan stream waters, Kulingdakan soil solutions and Siberian brines (brines values from Alexeev et al, 2007). changes in the source of the dissolved load carried by these rivers or in the nature of water-rock interactions controlling Kochechum and Nizhnyaya Tunguska dissolved fluxes during flood periods. For example, for Kochechum river waters, variation trends defined by the data points in the concentration ternary diagram (Fig.…”

“…9. Mixing diagram presenting the evolution of Sr isotopic compositions for Kochechumo river waters (brines values from Shvartsev, 2000;Alexeev et al, 2007).…”

“…Indeed, Nizhnyaya Tunguska river flows from the South where discontinuous permafrost can extend downwards for only 10 m ( Fig. 1; Alexeev et al, 2007). Much shallower permafrost within Nizhnyaya Tunguska watershed could consequently constitute a less important barrier between surficial (suprapermafrost) and deep (subpermafrost) underground waters and hence induce less contrasted variations between winter and summer waters in Nizhnyaya Tunguska river.…”

The "exceptionally fresh" Udachanaya-east kimberlite: evidence for brine and evaporite contamination

“…Nowhere in the world kimberlites erupt through thick sediments that contain that much deeply buried highly mineralized groundwater (>0.2-0.4 g/cm3). These ancient parental brines buried together with syngenetic sediments (Alekseev et al, 2007) in deep strata. Terrigeneous carbonate and halmeic country rocks of Mid-Paleozoic kimberlites of the southernmost kimberlite field (Mir, International'naya) rocks are saturated with groundwaters of the Yakutian artesian basin that vary in composition from ultrafresh to Na and Ca brines.…”