O. V. Chudaev

RARE EARTH ELEMENT CONTENTS OF HIGH pCO2 GROUNDWATERS OF PRIMORYE, RUSSIA: MINERAL STABILITY AND COMPLEXATION CONTROLS

The rare earth element (REE) geochemistry of cold, high pCO2 groundwaters was studied in springs and boreholes in the Primorye region of the Russian Far East. The gas phase in these waters is dominated by mantle-derived CO2 (up to 2.6 atm.), being introduced to shallow groundwaters along major fault systems. The aggressive nature of these moderately acidic groundwaters has led to unusual trace element characteristics with high concentrations of relatively immobile elements such as Al, Be, heavy REEs and Zr. They are also marked by extremely high concentrations of Fe and Mn, up to 80 mg 1−1 and 4 mg 1−1, respectively. The REE patterns generally show enrichment in the middle to heavy REEs and low concentrations of the light REEs (La-Nd). Most groundwaters show relatively flat shale-normalised middle to heavy REE profiles, with the exception of Eu, which may form positive or negative anomalies depending on local mineralogy. A characteristic of many of the groundwaters is the presence of positive Sm-Eu anomalies. A range of potential ligands is present in the groundwaters and model calculations show that the dominant species are Ln3+, carbonate complexes (i.e., predominantly LnCO3 +), and LnF2+. Concentrations of Cl− and SO4 2− are very low in most waters and nitrate and phosphate are below detection limit. The role of organic completing is not known due to lack of data, but such complexes may be important since limited TOC data show that organic contents may be high. The middle to heavy REE enrichment found in the groundwaters is consistent with dissolution of Fe-Mn oxyhydroxides and release of adsorbed REE. Positive Eu anomalies in some groundwaters correlate with high Ca and Sr, pointing to control by plagioclase dissolution. High Y/Ho ratios and positive Y spikes on REY plots in high-F− waters suggest an important control by F− completing, which is confirmed by speciation calculations. Extreme enrichments in the heavy REEs are found in two groups of mineral waters with Yb/La ratios up to 9.8. The extreme enrichments in heavy/light REEs present in these areas are too high to be simply controlled by speciation fractionation and it is suggested that a weathering phase with heavy REE enrichment is responsible. The source is suggested to be zircon, which typically displays such heavy REE enrichments. Although zircon is generally stable during low-temperature weathering, it is know to break down in acidic carbonated solutions. This is supported by high Zr concentrations (as well as high U, Be) in these groundwaters and a correlation between Zr and heavy REE enrichment.

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 Thermal Waters of Continental Margin of Far East of Russia

O 分别地。REE 模式反映高 pH，从水岩石相互作用的 resultfing 和氧化条件。用 Na-K 和石英地温计的深含水土层温度的计算分别地显示出 116.8-131.1 ° C 和 82.2-125.8 °C。深差错的存在两个与反常热坡度(∼45-50 K/km ) 定义 Sikhote-Alin 的热水的唯一的 geochemical 形状，区域，在没有现在的暴烈的活动被登记的地方。

REE fractionation in the rivers of eastern and southern Sikhote Alin with natural and anthropogenic anomalies

The behavior of REE in the rivers of eastern and southern Sikhote Alin (Primorye) is discussed. The high-resolution ICP-MS (HR-ICP-MS) technique is used for determining the REE concentrations and degree of REE fractionation in the background unpolluted rivers and in the Rudnaya River, affected by mining industry waste products. In addition, water streams from tailing storages (Dal’negorsk) and from the rivers of Vladivostok are subjected to study. It is shown that the studied rivers differ from each other in the studied parameters and in migration forms. These differences are explained by the different degrees of chemical denudation of rocks in their drainage areas by and anthropogenic impacts on the surface water streams.

Geochemical features of major and rare-earth element behavior in the Paratunka and Bol’shebannyi hydrothermal systems of Kamchatka

This paper presents original data on the content and distribution of major and rare-earth elements in the modern hydrothermal systems of the Paratunka and Bol’shebannyi thermal water deposits. In spite of the similar geochemical type of the waters, the individual sites of the hydrothermal systems differ in the major component composition, which is caused by the time of water–rock interaction, temperature control, and the possible influence of seawater intrusions. The REE concentrations in the studied thermal waters are extremely low (a few tenths of ppb). A distinctive feature of these thermal waters is the presence of a positive Eu anomaly. The possible reasons for its appearance are discussed. Calculation of REE speciation shows that the main parameters controlling the formation of the REE complexes in the Paratunka and Bol’shebannyi hydrothermal systems are their individual chemical properties, as well as pH, Eh, and temperature of the aqueous solution.

Fe-Mn crusts from underwater rises of the Kashevarov Trough (Sea of Okhotsk)

Dredging on nonvolcanic underwater rises in the Kashevarov Trough area (Sea of Okhotsk) carried out during Cruise 178 of R/V “Sonne” yielded sedimentary (conglomerates), metamorphic (biotite hornfels, tectonic breccia with inclusions of biotite hornfels), and igneous (granodiorite) rocks as well as Fe-Mn crusts up to 15 cm thick. The study of the structural-textural properties and the thorough analysis of the mineral and chemical compositions of these crusts, including the REE and Y distribution, show that the ore sediments are hydrogenic in nature.

Geochemistry of the thermal waters of Sikhote Alin

This paper reports new geochemical data on the low temperature nitric thermal waters of Sikhote Alin. The studied alkaline waters belong to the HCO3-Na type with significant trace element variations. The waters demonstrate an increase in temperature and TDS from the south northward of Sikhote Alin. The oxygen and hydrogen isotopic data suggest their infiltration origin. The chemical composition of these waters was formed by water-rock interaction.

Behavior of rare earth elements during mixing of different types of water (Kunashir, the Kurile Islands)

The fractionation of rare earth elements (REE) was evaluated under the conditions of natural acidic water mixing with fresh and sea waters using the example of unique objects on Kunashir Island (the Kislaya and Lesnaya rivers). It was shown that the concentrations and fractionation of REE in the water types considered are diverse and controlled by a number of factors. The concentrations of dissolved REE normalized to the North American Shale Composite show an increase from the light to the heavy REE, which reflects both the character of the REE input with the thermal waters and the more active sorption of the light REE and their preferential removal to suspended solids. This is supported by the similar REE patterns in the suspended matter of the Kislaya River. The mixing of the waters of the Kislaya and Lesnaya rivers, which are assigned to different chemical types, is accompanied by active REE coprecipitation with Fe, Al, and Mn oxides and the more extensive removal of the light REE compared with the heavy REE. During acidic water mixing with seawater, more than 80% of the REE were precipitated at a salinity of 8‰.

Chemical and isotopic (18O/16O and D/1H) composition of groundwaters of central and southern Primorye

Groundwaters of Primorye, including its coastal areas, were studied during the past ten years. The macro-and microelement composition of more than 130 samples showed that shallow groundwaters of southern Primorye with pH ranging between 5.4 and 8.4 contain oxygen (up to 10 mg/l) and typically have a mixed ionic composition. The microelement variations reflect both the natural features of the host rocks and possible anthropogenic pollution in the most populated areas. No seawater intrusions were recognized in the study areas, which is confirmed by the chemical composition of the waters, the oxygen and hydrogen isotopic composition of the groundwaters, the atmospheric precipitation, and the coastal seawaters of Primorye. In spite of the variations of individual components, the quality of the groundwaters used for potable purposes is rather satisfactory as compared to the Russian and the World Health Organization standards. At the same time, taking into account the increase of various microelements and biogenic components in the waters, the monitoring and control of the water composition is strongly recommended to preserve their potable quality.

REY geochemistry in groundwater from Paratunka geothermal area (Kamchatka peninsula, Far East of Russia)

New data on geochemistry of the Paratunka deposit of mineral waters—Russian biggest geothermal system is presented in this paper. Studied waters are thermal (Tu2009=u200945–80xa0°C), alkaline (phu2009=u20097.9–8.7), belong to Ca–Na Cl–SO4 type with reducing environment (Ehu2009=u2009−u2009150 to −u2009180xa0mV) leading to Ce- (+u20090.31) and Eu- (+u20090.8) anomalies. Evolution of chemical type of thermal water from Na–SO4 to Ca–Cl is discussed from the point of water–rock interaction and marine water intrusion as well. REY concentrations are extremely low due to alkaline pH (∑REYu2009=u200925–165xa0ppt). First reliable data on REY concentration in alkaline thermal water, surrounding river water and suspended matter of these waters gave an opportunity to discuss cerium, europium and yttrium anomalies in terms of sorption/desorption processes and pH/Eh dependencies, confirmed by thermodynamic calculations of the REE migration forms.