Basic formation mechanisms of Lake Doroninskoye soda water,East Siberia,Russia

The primary scientific goal of studying salt lakes is to better understand the formation of small continental-type hydrogeochemical systems. Many scientists have attributed the metamorphism of the chemical composition of salt lakes to the evaporative concentration of water. However, the formation of soda water is inconsistent with this hypothesis. Thus, analyzing intrabasinal biochemical processes and water—rocks interactions during the evaporative concentration of water allows us to understand the major mechanisms of the formation and evolution of water compositions. Therefore, the aim of this paper is to identify the key processes involved in the formation of the chemical composition of the water in Lake Doroninskoye. An analysis of the distribution of major components shows that Na⁺, HCO₃ ^?, CO₃ ^2?, and Cl^? are dominant in this water. High concentrations of these elements are the result of evaporative water concentration. Calcium, magnesium, and potassium are not accumulated because the water is saturated in minerals containing these elements. The main barrier to the growth of the sulfate content of water is sulfate reduction. This process also contributes to the additional reproduction of carbon dioxide, which reacts with the products of the hydrolysis of aluminosilicates OH^? to form HCO₃ ^? and CO₃ ^2?, thus further contributing to the natural processes of soda formation.     

Argo floats revealing bimodality of large-scale mid-depth circulation in the North Atlantic

Analysis of Argo float trajectories at 1 000 m and temperature at 950 m in the North Atlantic between November 2003 and January 2005 demonstrates the existence of two different circulation modes with fast transition between them. Each mode has a pair of cyclonic - anticyclonic gyres. The difference is the location of the cyclonic gyre. The cyclonic gyre stretches from southeast to northwest in the first mode and from the southwest to the northeast in the second mode. The observed modes strongly affect the heat and salt transport in the North Atlantic. In particular, the second mode slows down the westward transport of the warm and saline water from the Mediterranean Sea.     

Parameterization of iron and manganese cycling in the Black Sea suboxic and anoxic environment

New and published data on the distribution and speciation of manganese and iron in seawater are analyzed to identify and parameterize major biogeochemical processes of their cycling within the suboxic (15.6σ_t16.2) and anoxic layers (σ_t16.2) of the Black Sea. A steady-state transport-reaction model is applied to reveal layering and parameterize kinetics of redox and dissolution/precipitation processes. Previously published data on speciation of these elements in seawater are used to specify the nature of the transformations. Two particulate species of iron (Fe(III) hydroxide and Fe(II) sulfide) are necessary to adequately parameterize the vertical profile of suspended iron, while three particulate species (hydrous Mn(IV) oxide, Mn(II) sulfide, and Mn(II) carbonate) are necessary to describe the profile of suspended manganese. In addition to such processes as mixing and advection, precipitation, sinking, and dissolution of manganese carbonate are found to be essential in maintaining the observed vertical distribution of dissolved Mn(II). These results are used to interpret the observed difference in the form of vertical distribution for dissolved Mn(II) and Fe(II). Redox transformations of iron and manganese are coupled via oxidation of dissolved iron by sinking suspended manganese at σ_t16.2±0.2 kg m⁻³. The particulate manganese, necessary for this reaction, is supplied through oxidation of dissolved Mn(II). The best agreement with observations is achieved when nitrate, rather than oxygen, is set to oxidize dissolved Mn(II) in the lower part of the suboxic layer (15.90σ_t16.2). The results support the idea that, after sulfides of these metals are formed, they sink with particulate organic matter. The sinking rates of the particles and specific rates of individual redox and dissolved-particulate transformations have been estimated by fitting the vertical profile of the net rate.     

Environmental evolution of the southern Chukchi Sea in the Holocene

The molluscan shells from three drill and two piston cores obtained in the southern Russian sector of the Chukchi Sea are dated by the AMS ¹⁴C measurement method back to 0.8–3.5 and 9.2–10.5 ka. The period of 9–10 ka was marked by increased sedimentation rates related to the transgression onset. The fossils in the lower Holocene section exhibit the successive upward replacement of brackish-water organisms by their marine counterparts. After the opening of the Bering Strait in the middle Holocene, the sedimentation was under influence of the increased bioproductivity of the waters. The climatic optimum in the Chukotka region corresponds to the early Holocene, while the late Holocene was characterized by the wider development of the ice cover on the shelf.     

Hydrogeology of the vicinity of Homestake mine, South Dakota, USA

The former Homestake mine in South Dakota (USA) cuts fractured metamorphic rock over a region several km² in plan, and plunges to the SE to a depth of 2.4 km. Numerical simulations of the development and dewatering of the mine workings are based on idealizing the mine-workings system as two overlapping continua, one representing the open drifts and the other representing the host rock with hydrologic properties that vary with effective stress. Equating macroscopic hydrologic properties with characteristics of deformable fractures allows the number of parameters to be reduced, and it provides a physically based justification for changes in properties with depth. The simulations explain important observations, including the co-existence of shallow and deep flow systems, the total dewatering flow rate, the spatial distribution of in-flow, and the magnitude of porosity in the mine workings. The analysis indicates that a deep flow system induced by ~125 years of mining is contained within a surface-truncated ellipsoid roughly 8 km by 4 km in plan view and 5.5 km deep with its long-axis aligned to the strike of the workings. Groundwater flow into the southern side of the workings is characterized by short travel times from the ground surface, whereas flow into the northern side and at depth consists of old water removed from storage.     

Uranium Concentration in Altered Brown Coals Located under Burnt Rocks from the Kansk-Achinsk Basin, West Siberia

West Siberian brown coals from the Kansk-Achinsk basin and their combustion products are generally characterized by a low uranium content. In some places where brown coal has been altered (losing density, becoming cracked or friable), the uranium content has increased by concentrations ranging from 1001000 μg g⁻¹. At these locations distinct signs of underground fires are visible. The uranium distribution patterns suggest that the burnt organic matter was a source of uranium and altered varieties of coal serve as a geochemical barrier to uranium transport.     

峨眉火成岩省内带岩浆硫化物含矿岩体橄榄石的成因意义

岩浆镍-铜-铂族元素(PGE)硫化物矿床是峨眉火成岩省地幔柱活动形成的两个重要的成矿系列之一[1～3].目前已发现的与峨眉火成岩省相关的40余个镍-铜-铂族元素硫化物矿床(或矿点)中,多数分布在内带[3,4].它们可分为:1)富Ni、Cu而贫PGE的Ni-Cu型(如力马河和清水河);2)富Ni,Cu且PGE中等的Ni-Cu-PGE型(如清矿山和黄草坪);3)贫Ni、Cu富PGE的PGE型(如金宝山和杨合武).     

Isotopic composition of noble gases in geothermal fluids of the Krušné Hory Mts., Czechoslovakia,and the nature of the local geothermal anomaly

The contents and isotopic composition of all noble gases in the fluids from two localities (Karlovy Vary and Franti?kovy Lázně) in Western Czechoslovakia are given. The data show: (1) atmospheric Ne, Ar, Kr and Xe, which indicates meteoric recharge; (2) excess He, attributed to radiogenic contributions; (3) a small excess of Ne, but the data shed no light on its origin. Even though there is no evidence of any juvenile component in these mineral waters, part of the dissolved He is believed to be of deep (mantle) origin.Correlation between the ratio ${}^3\text{He}{}^4$He and heat flow has been reported in the literature: our data enabled a direct test of this relationship and proved its fairly good validity. The combined interpretation of the heat flow and isotopic composition shows that the local heat flow anomaly in the Kru?né Hory graben is of deep origin and was produced by the mass outflow which occurred during the Alpine activation of the Bohemian Massif.     

Hydrogeochemical anomalies of fluorine in Transbaikalia, Russia

本文通过对在外贝加尔大骨节病区水文地球化学研究结果表明,该地区天然水呈现出高浓度的磷(高达3.5 me/L),同时,锰、硅、铅等元素也呈现出高浓度的地球化学特征.分析水文地球化学数据,认为大骨节病可能与生物地球化学性质的多种因素有关系.进一步研究大骨节病的成因机制需要新的可靠的环境地球化学数据.