On the borders of the upper hydrogeodynamic zone in the Caspian artesian basin

This article provides the results from studying the upper part of the section of the entire Caspian artesian basin. The stratification map, the profile section and the isohyps map of the roof of the upper hydrogeodynamic zone were compiled on the basis of generalization of geological and general hydrogeological data. Systematized hydrogeological data on the depositional conditions, structural features and nature of the distribution within the upper hydrogeodynamic zone of the Caspian artesian basin, as well as the supply zones and the areas of transit and discharge of underground waters are provided. The borders of the upper hydrogeodynamic zone of the basin have been drawn as a result.     

Replenishment conditions and regimen of underground waters in Carboniferous deposits of Moscow artesian basin

There are seven principal aquifers in the Carboniferous rocks of the Moscow basin. These are replenished by 1) precipitation on the outcrops, 2) water-bearing horizons in the overlying Mesozoic and Quaternary, and 3) directly from lakes and rivers in favorable situations. Total exchange time (time for complete recharge) is estimated at 85 years, which is remarkably short for a basin of that size and capacity. Water from these aquifers has been used for almost 100 years. Cones of depression in the Upper and Middle Carboniferous are 65–90 km across, with lowering of 25–50 m of the water table; in the Lower Carboniferous, 150–180 km in diameter, with lowering up to 70 m. In areas of direct recharge from a stream the cone of depression is very small and shallow. The authors believe that because of the favorable recharge situation water yield of the basin can be greatly increased. -- E. Ingerson.     

Groundwater recharge formation in the Heihe intermountain artesian basin

The Heihe intermountain artesian basin is situated in northwestern China. The basic types of formation of groundwater recharge have been identified, viz., the percolation of river waters in the mountain regions and infiltration from irrigation canals and fields in the plain areas with a well-developed irrigation system. Such sources account for about 90% of the overall groundwater recharge.     

The geochemistry of formation waters in the molasse basin of upper Austria

The geochemistry of formation waters in the Molasse basin of Upper Austria has been investigated to ascertain the extent of meteoric water replacement of the connate interstitial fluids in these sediments. The chemistry, isotopic composition, and dissolved gas contents of the groundwaters and of oil and gas associated brines have been determined. The most superficial sediments of the basin, the Innviertel (Miocene), have been completely flushed by meteoric waters within the last 200 ka. The underlying Hall and Puchkirchen formations (Miocene/Oligocene) form gas reservoirs for biogenic methane, and the associated formation waters are chemically and isotopically modified connate brines of the original marine deposition. In the northeastern part of the basin, the connate brines of the deeper sediments (Cretaceous/Jurassic) have been partially or completely replaced by meteoric waters, whereas in the south of the basin these sediments contain high salinity fluids which are substantially of connate origin. These conclusions are supported by the stable isotope composition of the various brines. Oil-associated brines from the Eocene sediments contain large amounts of dissolved radiogenic⁴⁰Ar, which suggests that the oils have migrated from high-temperature environments. This is in contrast with the Puchkirchen, for which the observed absence of radiogenic⁴⁰Ar suggests that the biogenic methane has been formed in situ. The⁴He contents of these brines and of the Cretaceous/Jurassic groundwaters are, however, less than those in the overlying Puchkirchen formation and suggest that He has been removed from the deeper sediments as a result of flushing by meteoric water. The ratios of dissolved methane and nitrogen to argon increase with increasing ammonium content of the formation waters. All of these parameters may be used as indices for the maturation of the system. The heavy noble gases, Kr and Xe, are abnormally abundant in the dissolved gases, and this is attributed to geochemical concentration of these gases by adsorption onto shales in the sediment sequence. The overall geochemical situation confirms the existence of separate hydraulic systems with little interconnection in the several overlying geological horizons.     

Model for the formation of fluorine-bearing rocks in the Carboniferous deposits of the Moscow artesian basin

The paper presents the results of the statistical and thermodynamic analysis of hydrogeochemical information on the genesis of F-bearing waters in the Carboniferous deposits of the Moscow artesian basin. The F concentration is demonstrated to increase with increasing salinity of the aqueous solution. As follows from the analysis of mineral equilibria, the saturation concentrations of the aqueous phase with respect to fluorite in association with calcite and gypsum is less than 2–3 mg of F/l. At the saturation of the aqueous phase with respect to fluorite in association with dolomite, the equilibrium concentration of F increases with increasing Mg concentration and decreasing equilibrium partial CO₂ pressure and can reach 8–10 mg of F/l. The main reason for this enrichment of the aqueous phase in F is certain features of mineral equilibria in the system of aqueous solution with Ca and Mg carbonates. An increase in the Mg²⁺ concentration in the aqueous phase decreases the Ca²⁺ concentration in the solubility equilibrium of dolomite, and this, in turn, decreases the F^? concentration in the solubility equilibrium of fluorite.     

Crystal growth and the formation of chemical zoning in garnets

A crystal growth model is developed which generalizes the Rayleigh fractionation process. The new growth model allows some insight into the interpretation of nonequilibrium behavior of minerals, primarily the chemical zoning profiles exhibited by metamorphic minerals. A nonlinear equilibrium term for exchange of constituents between a growing mineral and a reservoir is initially incorporated into the usual isothermal fractionation model. Criteria are established to decide when a simple distribution term is sufficient to describe the growth and exchange process. The model is then extended to allow for temperature changes during a cooling or heating event. Finally, an exact solution is obtained for the temperature dependent case incorporating a time dependent growth rate. The growth models are successfully used to obtain growth rates of 0.01 to 0.09 cm/million year and describe the magnesium and iron zoning profiles of garnets from Phillipston, Massachusetts. The generalized model confirms the development of zoning during the retrograde growth of garnet in the late stages of the Acadian orogeny.     

鄂尔多斯盆地西缘中新生代构造演化与铀成矿作用

受周边板块离散、汇聚的影响,中-新生代鄂尔多斯盆地及其西缘构造应力场发生了多次转变,造成不同时期盆地类型与沉积充填、构造变形特征的差异。据此,将盆地西缘中-新生代构造演化划分为7个阶段。其中,晚三叠世强烈的挤压,使盆地西侧阿拉善地块上富铀岩石剥出地表,并为盆地提供铀源;早-中侏罗世弱挤压构造背景下辫状河发育,形成了有利的含矿建造;晚侏罗世的强烈挤压,使中-下侏罗统发生构造变形并遭受地下水的渗入改造,但构造变形太强烈,影响了铀成矿的潜力;晚白垩世-渐新世早期盆地西缘整体隆升,使区内目标层长期遭受地下水渗入改造,形成了主要的铀矿化;渐新世之后,银川断陷隔断了盆地与蚀源区的联系,铀成矿作用基本停止。     

Petroleum systems and the history of their formation in the northern Caspian Sea basin

This study presents the consideration of the geological history and petroleum systems in the northern Caspian Sea basin (on the basis of basin modeling using the TemisSuite2008 software package). The key patterns of the distribution of oil and gas fields and their phase composition are described. Kulaginskii Ridge and the adjacent areas are considered. The preceding data are generalized and new data are used.     

Abnormal composition of carbon isotopes in underground alkaline waters of Kuzbass

The first data on abnormally high δ¹³С values in hydrocarbonates (НСО ₃^-) dissolved in underground waters of coal deposits of Kuzbass (up to +30.9‰) are reported. It is shown that such an unusual isotope composition of waters results from the long, strictly directed interaction in the water–rock–gas–organic material system occurring under the conditions of hindered water exchange. Extensive fractionation of C isotopes is the result of the evolution of the water–rock–gas–coal system after penetration of infiltration waters into the coal deposits and their long interaction with all these components, rather than metamorphism of organic material upon its transformation into coal. With respect to such an approach, the isotope composition of dissolved C may indicate the duration of the evolution in the water–rock–gas–organic material system.     

高压-超高压变质岩石中石榴石的环带和成因

在俯冲带变质过程中,石榴石是高压-超高压变质榴辉岩和片麻岩的常见变质矿物。由于石榴石具有难熔和流体中的低溶解能力的特点,通常可以很好地保存下来,并且能够保留复杂的化学成分环带,以及不同类型的矿物或流体包裹体,为解释石榴石寄主岩石经历的变质演化历史提供了重要信息。石榴子石的主微量元素成分受控于很多因素,如全岩成分、变质的温压条件、控制石榴子石形成的相关变质反应、与石榴子石共生的矿物种类和成分等。因此,在利用石榴石探讨超高压变质的演化历史时,对石榴石进行系统的主要元素、微量元素、氧同位素以及矿物包裹体分析,以及相互间的成因关系。同时,对石榴石中的锆石或独居石包裹体并进行原位U-Pb定年和微量元素分析,可以为变质石榴石的形成时代提供直接的时间制约。深入研究超高压变质岩中石榴石的生长阶段,不仅可以为含石榴石寄主岩石的变质过程提供岩石学和地球化学证据,而且对于理解石榴石的形成机制、生长规律及其变质化学动力学过程具有重要的科学意义。     

Specific features of the formation of elementary sedimentary rhythms of rock salt in facies zones of the Permian halogenic basin of the Caspian region

Based on the composition of brine inclusions in halite, the formation conditions of elementary sedimentation rhythms of rock salt were determined in facies zones of the Permian halogenic basin of the Caspian region. The distribution of structural types of halite was analyzed and the rate of brine condensation was estimated by calculating the K⁺ concentration coefficients during the precipitation of 1 m rock salt (K₁ g/l/m) and one elementary rhythm (K₂ g/l/rhythm). It was established that the rock salt of the Karpensk and Lugovsk rhythmic beds (hereafter, rhythmites) at the base and middle part of the halogenic sequence of the Baskunchak structure precipitated in a relatively deep-water lithofacies zone at a constant influx of NaCl-saturated brine and its slow condensation. This is reflected in insignificant variations of the thickness of elementary rhythms. In troughs at the northwestern framing of the depression, rocks salts of the Privolzhsk and partially, Lugovsk rhythmites were precipitated without the condensation of brine owing to the partial dissolution of halite in the coastal zones of the basin. The anomalously thick elementary rhythms (up to 30–40 cm) were composed of coarse-crystalline and water-transparent feather halite deposited at the bottom. A rapid condensation of brine was also noted during the precipitation of rock salt underlying the K-Mg saliferous rocks in the troughs. In this area, the brine experienced density stratification, with the influx of both condensed brine from the central part of the basin and less dense brine from the inlet.     

Model for Sr accumulation in the Carboniferous deposits of the Moscow artesian basin

Statistical and thermodynamic analysis of hydrogeochemical information on Sr accumulation in the waters of Carboniferous deposits in the Moscow artesian basin indicates that Sr concentration increases mostly with increasing salinity of the aqueous solution and its Mg and sulfate contents. The highest Sr concentrations are 8–10 mg/l, and Sr accumulation in groundwaters is constrained by the precipitation of strontiantie in the system aqueous solution + dolomite + calcite + strontianite. An increase in Sr concentrations in the Carboniferous waters is symbate with the accumulation of F, and the accumulation of Sr (as well as F) is largely controlled by two factors: a change in the hydrogeochemical type of the groundwaters toward its transition and an overprinted process of the slowing of water filtration from the recharge area of the aquifers (where the Carboniferous deposits are exposed at the surface) down the dips of the water-hosting strata.     

The isotopic and chemical composition of CO2-rich thermal waters in the Mont-Dore region (Massif-Central,France)

Chemical and isotope compositions of fluid samples, collected between 1974 and 1986 from 52 springs or shallow boreholes located in the Mont-Dore region (Massif Central, France), were examined. Some springs and wells were sampled several times during this period. The fluids emerge from Quaternary volcanic rocks or Paleozoic granite at temperatures between 4 and 62°C, and the origin of the H₂O is meteoric. The waters can be classified into three groups: bicarbonate fluids, mixed bicarbonate-chloride fluids (with a mineralization up to 8 g/l), and acid-sulfate fluids. Only two fluids contain sufficient Cl⁻ to be considered as ‘mature’ waters. Previous work has demonstrated that they all contain partly mantle-derived CO₂ gas, and that the CO₂-rich gas phase and bicarbonate-chloride waters are separated at substantial depth.Mineralized fluids circulate at depth and undergo several processes, such as cooling or dilution with recent freshwater, during their ascent to the surface. Therefore, the CO₂-rich gas phase can be partly dissolved in the freshwater, or in deep fluids after their dilution. This process leads to the dissolution of surrounding rocks; such dissolution is discussed on the basis of major-element concentrations (Na, K, Ca, Mg), as well as the Sr 87/86 isotope ratio. Dissolution of S-bearing minerals has also been demonstrated. The presence of the CO₂-rich gas phase also leads to isotope exchange between CO₂ and H₂O. Some mineralized fluids are less affected by these processes than others, in which case they display the chemical and isotopic characteristics of the original deep fluids.It was shown that the applicability of geothermometer calculations for these waters is hampered by several processes that modify the chemical composition. However, some geothermometers can be used for estimating the temperature of the deep fluids using the chemical composition of the less modified fluids. They indicate that fluids emerging from volcanic rocks in the Dordogne valley reach temperatures of around 100–130°C at depth, while the temperature of the fluid that issues from the granite at Saint-Nectaire is 160–175°C at depth.     

珠江三角洲含N亚硝胺地下水与地区性癌症

肆虐我国南方局部区数百年以鼻咽癌和肝癌为主的恶性肿瘤病,为典型的地区性癌症。本文以珠江三角洲为例,应用流行病学与生态地球化学相结合的调查方法,检出了病区环境水和饮水中存在致癌物质N亚硝胺,研究了癌病区生态系统由地质构造背景、气候、水文和生态条件制约,自然形成水体N亚硝胺的机理。实验改进、优化了环境饮水微量亚硝胺测定方法,新建立的固相萃取气相色谱串联质谱(GC/El-MS/MS)测定纳克级N亚硝胺方法一次可测9种N亚硝胺化合物,检出限达到0.34~2.19 ng/L。在珠江三角洲癌病区环境饮水中首次发现9种亚硝胺化合物,含量为307~0.34 ng/L,总检出率为40%。四会等较低工业污染区古井水、手压井水和自来水的亚硝胺有相近似的含量统计特点:亚硝基二甲胺和亚硝基二正丁胺的均值和峰值为不高的超标值,均值分别为21.77和15.54 ng/L。这批水样大多采自0~20 m深度井水,属本区代表性特殊地质构造和气候生态环境中形成的地下水,也是研究区生产和生活开发最多的水源层;所含超标亚硝胺可能是本区数百年高发癌症的主因。近年工业发展带来的亚硝胺污染源的叠加,增高了该区环境饮水亚硝胺超标率及癌症发病率。文中分析了珠江三角洲土壤和地下水富氮营养化现象和区域氮的来源。     

Contamination of deep formation waters by drilling fluids: correction of the chemical and isotopic composition and evaluation of errors

Contamination of deep formation waters by drilling fluids is a problem that concerns most types of drilling operations (petroleum wells, geothermal boreholes) and is crucial in the course of feasibility and safety studies of potential radioactive-waste repositories. Residual contamination of formation-water samples has an important impact on the accuracy of the characterisation of the natural hydrogeochemical background of the study sites. Based on a literature review and on experience acquired on the sites of the French Agency for Nuclear Waste Disposal (ANDRA), this article proposes a general method for the correction of residual contamination, including estimates of the associated errors. The quantification of the contamination is based on tracing techniques and on a geochemical survey during the pumping test preceding sampling. The correction and estimation of errors require repeated measurements of the tracer(s) and the chemical and isotopic species during pumping. The method is applied to a pumping test in a research well in deep granite of the Vienne district (France) where multi-tracing of drilling fluids has been used.     

Isotopic composition of formation waters from deep drillings in southern Israel

Formation water samples from deep drillings in southern Israel fall into three regional groups, each of which shows distinct chemical and isotopic characteristics. Waters from the Mediterranean coastal plain appear to be of marine lagoonal origin; some of these brines are associated with occurrences of oil. In the mountain region the top part of the sedimentary sequence has been flushed by fresher waters, apparently during Pleistocene time. In Jurassic and deeper-lying formations one encounters concentrated brines of seawater origin, with low Na/Ca ratios, which have undergone a process of ultrafiltration. In the Rift Valley proper, magnesium-rich brines have invaded the deeper formations, and are evidently of continental lake origin.The absence of oil occurrences in association with the CaCl₂ brines of the inland locations is interpreted as being due mainly to loss of oil as a result of the tectonic events associated with the formation of the Jordan Rift Valley.