Effect of saline water bodies on the hydrogeochemical evaluation of groundwater at Kalpakkam coastal site, Tamil Nadu

Geochemical signatures of groundwater in Kalpakkam plant site were used to identify the geochemistry of the unconfined coastal aquifer. Ground water samples collected from 14 borewells around the study area were studied for four different seasons viz. Summer, South-west monsoon, North-east monsoon and Post-monsoon to identify the major geochemical processes activated in the study area. Data obtained through chemical analyses of groundwater samples were used for graphical plots and geochemical calculations. Piper, Chloro alkaline indices and Chadda’s diagram were determined for geochemical classification of the groundwaters. Identified geochemical processes were verified and quantified using hydrogeochemical aqueous speciation model, PHREEQC to find out the Saturation Indices (SI) of the possible minerals of the study area. It was observed that majority of the bore well samples were under saturated with respect to minerals such as Gypsum, Aragonite and oversaturated with respect to dolomite and calcite. Parameters such as ion exchange and reverse ion exchange, saline water incursion were observed due to the presence of saline water bodies in addition to dissolution of minerals.     

Using non-conservative tracers to characterise karstification processes in the Merinos-Colorado-Carrasco carbonate aquifer system (southern Spain)

The systematic sampling of the chemical composition of the groundwater from five karst springs (including an overflow spring) and one outflowing borehole have permitted to determine distinctive chemical changes in the waters that reflect the geochemical processes occurring in a carbonate aquifer system from southern Spain. The analysis of the dissolution parameters revealed that geochemical evolution of the karst waters basically depends on the availability of the minerals forming aquifer rocks and the residence time within the aquifers. In the three proposed scenarios in the aquifers, which include the preferential flow routines, the more important geochemical processes taking place during the groundwater flow from the recharge to the discharge zones are: CO₂ dissolution and exsolution (outgassing), calcite net dissolution, calcite and dolomite sequential dissolution, gypsum/anhydrite and halite dissolution, de-dolomitization and calcite precipitation. A detailed analysis of the hydrochemical data set, saturation indices of the minerals and partial pressure of CO₂ in the waters joined to the application of geochemical modelling methods allowed the elaboration of a hydrogeochemical model of the studied aquifers. The developed approach contributes to a better understanding of the karstification processes and the hydrogeological functioning of carbonate aquifers, the latter being a crucial aspect for the suitable management of the water resources.     

Genesis and evolution of high-pCO2 groundwaters of the Mukhen spa (Russian Far East)

We present the chemical and isotope compositions of the water and gas phases of the unique Mukhen cold high-pCO₂ spa. Estimated 5¹⁸O, 5D, and 5¹³C_tic values and data on geology and hydrogeology of the studied area indicate that the source of the groundwaters is meteoric waters, whereas carbon dioxide is of deep genesis and numerous regional faults are gas-feeding channels. Calculations of equilibrium reactions in the water-rock system show that the upper-aquifer waters (HCO₃-Ca-Mg) with low TDS are undersaturated with carbonate minerals, montmorillonites, and aluminosilicates but are oversaturated with kaolinite, whereas the lower-aquifer waters (HCO3-Na) with high TDS are oversaturated with calcite, dolomite, and clay minerals but are undersaturated with main aluminosilicates. We propose a new concept of the formation of these groundwaters, demonstrating that long interaction between rocks and groundwaters in the presence of CO₂ and considerable precipitation of secondary minerals are responsible for the high TDS of the lower-aquifer waters (up to 14 g/L) and their geochemical type (HCO₃-Na) and unusual isotope composition (5¹⁸O = -25.2%c, 5D = -69.0%c).     

Hydrogeochemical factors effecting the scaling problem in Balçova geothermal field,İzmir, Turkey

Reservoir fluid compositions have been assessed from analytical data on water samples collected from thermal and cold waters in Balçova geothermal field. The results of mineral equilibrium modelling indicate that the waters, with some exceptions, are systematically supersaturated with respect to calcite, aragonite, dolomite, chalcedony and quartz, but undersaturated with respect to amorphous silica, celestite, anhydrite and gypsum and undersaturated or supersaturated with respect to barite, low-albite, K-feldspar, gibbsite and Fe(OH)₃(a). Calculation of mineral saturation states and geochemical analyses of scale and field observations show that carbonate minerals (calcite, aragonite and dolomite) are most likely to be precipitated as a scale type. Besides carbonates, scale formation risk of amorphous silica, Fe(OH)₃(a), anhydrite, barite and celestite minerals should be taken into account in some wells and surface equipment. Most of the waters, with some exceptions, have carbonate scaling risk at all temperatures, whereas the other scaling risks only exist over a limited temperature range. While silica, Fe(OH)₃(a) and barite show a scaling tendency at low temperatures, anhydrite and celestite scaling occurs at higher temperatures.     

Isotope–geochemical characterization and geothermometrical modeling of Uttarakhand geothermal field,India

Uttarakhand geothermal area, located in the central belt of the Himalayan geothermal province, is one of the important high temperature geothermal fields in India. In this study, the chemical characteristics of the thermal waters are investigated to identify the main geochemical processes affecting the composition of thermal waters during its ascent toward the surface as well as to determine the subsurface temperature of the feeding reservoir. The thermal waters are mainly Ca–Mg–HCO₃ type with moderate silica and TDS concentrations. Mineral saturation states calculated from PHREEQC geochemical code indicate that thermal waters are supersaturated with respect to calcite, dolomite, aragonite, chalcedony, quartz (SI > 0), and undersaturated with respect to gypsum, anhydrite, and amorphous silica (SI < 0). XRD study of the spring deposit samples fairly corroborates the predicted mineral saturation state of the thermal waters. Stable isotopes (δ¹⁸O, δ²H) data confirm the meteoric origin of the thermal waters with no oxygen-18 shift. The mixing phenomenon between thermal water with shallow ground water is substantiated using tritium (³H) and chemical data. The extent of dilution is quantified using tritium content of thermal springs and non-thermal waters. Classical geothermometers, mixing model, and multicomponent fluid geothermometry modeling (GeoT) have been applied to estimate the subsurface reservoir temperature. Among different classical geothermometers, only quartz geothermometer provide somewhat reliable estimation (96–140 °C) of the reservoir temperature. GeoT modeling results suggest that thermal waters have attained simultaneous equilibrium with respect to minerals like calcite, quartz, chalcedony, brucite, tridymite, cristobalite, talc, at the temperature 130 ± 5 °C which is in good agreement with the result obtained from the mixing model.     

Groundwater Chemistry of the Mornag Aquifer System in NE Tunisia

The present paper investigates hydrochemical processes and water quality in the Mornag aquifer in NE Tunisia. Groundwater samples were collected during a field campaign, and were analysed for major and trace elements. The collected waters have a chemical facies rich in Ca²⁺, Na⁺ and Cl^-. Piper diagram shows a progressive increase in chloride ions along with increasing salinity. Saturation indexes calculated by using PHREEQC (USGS) show that the Mornag waters are slightly saturated with respect to carbonates (calcite and dolomite), while undersaturated with respect to gypsum, halite and other evaporitic minerals. The current composition of waters takes place via dissolution of halite and Ca-sulfates, where the increase in calcium is partially balanced by possible calcite precipitation. The relevant recorded pollutant is nitrate, which was likely dispersed from agricultural soils, while heavy metals were generally far below values of pollution thresholds, indicating no influence by mining activity.     

Rock composition and origin of the Duwi Formation calcareous rocks, Upper Egypt

Upper Cretaceous phosphorite beds of the Duwi Formation, Upper Egypt, are intercalated with limestone, sandy limestone, marl, calcareous shales, and calcareous sandstone. Calcareous intercalations were subjected to field and detailed petrographic, mineralogical and geochemical investigations in order to constrain their rock composition and origin. Mineralogically, dolomite, calcite, quartz, francolite and feldspars are the non-clay minerals. Smectite, kaolinite and illite represent the clay minerals. Major and trace elements can be classified as the detrital and carbonate fractions based on their sources. The detrital fraction includes the elements that are derived from detrital sources, mainly clay minerals and quartz, such as Si, Al, Fe, Ti, K, Ba, V, Ni, Co, Cr, Zn, Cu, Zr, and Mo. The carbonate fraction includes the elements that are derived from carbonates, maily calcite and dolomite, such as Ca, Mg and Sr. Dolomite occurs as being dense, uniform, mosaic, very fine-to-fine, non-ferroan, and non-stoichiometrical, suggesting its early diagenetic formation in a near-shore oxidizing shallow marine environment. The close association and positive correlation between dolomite and smectite indicates the role of clay minerals in the formation of dolomite as a source of Mg^2＋ -rich solutions. Calcareous rocks were deposited in marine, oxidizing and weakly alkaline conditions, marking a semi-arid climatic period. The calcareous/argillaceous alternations are due to oscillations in clay/carbonate ratio.     

Model of the Lomonosov diamond deposit as a water–rock system: Migration Species,Groundwater Saturation with Rock-Forming and Ore Minerals,and Ecological Assessment of Water Quality

Thermodynamic numerical simulations were carried out to determine the principal simple and complex migration species of Ca, Mg, Na, K, Al, B, Mn, Mo, Sr, and U with Cl^–, OH^–, SO₄^?2, HCO₃^?, and CO₃^2? in waters at the Lomonosov diamond deposit and to estimate the saturation indexes with respect to kaolinite, Na- and Mg-montmorillonite, Mg- and Na-saponite, muscovite and paragonite, biotite, phlogopite, chromite, pyrite, plagioclase (anorthite, labradorite, and andesine), olivine (forsterite and fayalite), diopside, pyrope, gypsum, anhydrite, barite, magnesite, calcite, dolomite, talc, chrysotile, chlorite, goethite, quartz, microcline, and albite. The waters are proved not to be saturated with respect to the primary (hydrothermal) minerals. The saturation of certain water samples with uranophane suggests that this mineral is of secondary genesis. The ascent of highly mineralized deep waters shall result in the dissolution of minerals whose concentrations are near the saturation ones. To maintain the ecological standards of the discharged waters, they should be diluted and/or purified by adsorbing dissolved U on a reducing reactive barrier.     

Geochemistry of thermal springs,Alhama de Granada (southern Spain)

The waters of the thermal springs at Alhama de Granada vary in temperature between 27 and 45°C. Temporal changes in the composition of the principal spring (Baños Viejos) indicate that a small degree of mixing may occur between deep thermal waters and shallow groundwater. Slight compositional variations also occur between the various thermal springs in the study area. These spatial variations are due to the different local hydrodynamic conditions in the springs. Towards the north in less hydraulically transmissive rocks, cooling of the rising water is more noticeable, as are ion exchange and processes of SO₄ reduction. The chemical composition of the water is related to the dissolution of evaporites (SO₄ and Cl salts), carbonates and silicates, and to the possible existence of sources of S within the rock. Estimates of the mean residence times have been obtained based on ¹⁴C_DIC and T. The state of thermodynamic equilibrium at the spring discharge was calculated using the SOLMINEQ.88 program. The results indicate that all the samples are supersaturated with respect to quartz, chalcedony, cristobalite, calcite, aragonite and dolomite, and undersaturated with respect to gypsum, anhydrite and halite. The use of different geothermometers and modelling of saturation indices for quartz, albite and anhydrite indicate temperatures of about 110°C.     

The impact of dolomite and plagioclase weathering on the chemistry of shallow groundwaters circulating in a granodiorite-dominated catchment of the Sila Massif (Calabria,Southern Italy)

This work is aimed at investigating the weathering processes of the granodiorites cropping out in a small catchment of the Sila Massif. The mineral constituents in this granodiorite are plagioclase, often zoned with a Ca-rich core and a Na-rich rim, quartz, chlorite, K-feldspar, white mica and epidote. During this study, dolomite was discovered in local stream sediments, as separate monomineralic grains, probably resulting from erosion of veins cutting the crystalline rocks. Prevailing dissolution of foreign dolomite and a Ca-rich plagioclase is suggested by the Ca–Mg–HCO₃ chemical composition of local groundwaters and stream waters, which is rather unexpected for waters interacting with granitoid rocks. These qualitative observations are quantitatively confirmed by reaction path modelling of the weathering processes occurring in the study area, which was carried out using the EQ3/6 software package, version 8.0, and the Double Solid Reactant Method. Indeed, it was possible to ascertain that the release of both major dissolved constituents and several trace elements (Ba, Co, Cr, Fe, Mn, Ni, Pb, Sr, V and Zn), from rocks to waters, is chiefly controlled by the dissolution of foreign dolomite and the Ca-rich core of zoned plagioclases.     

黄骅坳陷三马地区中-深部储层成岩作用及主控因素分析

黄骅坳陷三马地区储集岩样品的显微特征及成岩矿物的组合关系分析结果表明，三马地区下第三系中深层储层主要处于晚成岩A期，成岩现象包括石英、长石的次生加大、碳酸盐矿物胶结作用、矿物交代作用、溶解作用和粘土矿物转化作用等。其中石英次生加大于2700m左右开始出现，随埋深增大，石英增生加强；长石次生加大现象不十分普遍；碳酸盐胶结作用包括早期自生泥晶方解石胶结作用、连晶方解石和晚期白云石(或铁方解石)的胶结作用。在扫描电镜下可见到方解石与含铁方解石集合体充填在粒间孔隙中或与石英、钠长石及粘土矿物共生，白云岩多呈菱形粒状分布于粒间；常见的交代现象主要有方解石交代长石、石英及粘土矿物，粘土矿物交代长石、石英等；溶解作用主要有长石的溶解、碳酸盐颗粒的溶解和方解石胶结物的溶解等，粘土矿物的转化主要为蒙脱石、高岭石向伊利石(或绿泥石)转化。还讨论了储层岩相、岩性特征、孔隙水中有机酸含量、早期方解石的充填、烃类早期注入等因素对储层成岩演化的控制作用。     

Meteoric water-basalt interactions. II: A field study in N.E. Iceland

The compositions of rain, snow, melt, spring and geothermal waters from the rift zone of N.E. Iceland can be explained by seaspray addition, chemical fractionation at the seawater-air interface, burning of fossil fuel, farming activities, purification by partial melting of snow and ice, dissolution of basalts and buffering by alteration minerals. The dissolution of the rocks appears to be incongruent. During solute acquisition, spring compositions move through the stability fields of kaolinite and smectite to the laumontite and illite fields. All but four of the springs are undersaturated with respect to calcite. Silica concentrations are compatible with the solubility of basaltic glass. The reactions reflected in the spring waters appear to have taken place sealed off from atmospheric CO₂ after initial saturation.The geothermal waters which are recharged by the spring waters are depleted in Mg and Ca but enriched in carbon and sulfur with respect to dissolution of primary rocks. Expressions are derived relating dissolution rates of rocks, age of groundwaters, physical properties of groundwaters and mass transfer. The characteristic rock particle radii in the cold water aquifers range from 0.2 to 2 cm and the characteristic crack openings are of the order 0.04 to 0.4 cm. Using laboratory studies on the Icelandic lavas as a guide, the residence times of the cold waters in the aquifers can be estimated at 60 days to 4 years. The average active surface area of the aquifers enclosing 1000 g of spring water is of the order of 0.6 to 6 m² and these 1000 g of water have reacted with 0.1 to 1 g of basaltic rocks. The same mass of thermal water has interacted with 100 to 300 g of unaltered rocks.     

Permeability generation and resetting of tracers during metamorphic fluid flow: implications for advection-dispersion models

Advection-dispersion fluid flow models implicitly assume that the infiltrating fluid flows through an already fluid-saturated medium. However, whether rocks contain a fluid depends on their reaction history, and whether any initial fluid escapes. The behaviour of different rocks may be illustrated using hypothetical marble compositions. Marbles with diverse chemistries (e.g. calcite + dolomite + quartz) are relatively reactive, and will generally produce a fluid during heating. By contrast, marbles with more restricted chemistries (e.g. calcite + quartz or calcite-only) may not. If the rock is not fluid bearing when fluid infiltration commences, mineralogical reactions may produce a reaction-enhanced permeability in calcite + dolomite + quartz or calcite + quartz, but not in calcite-only marbles. The permeability production controls the pattern of mineralogical, isotopic, and geochemical resetting during fluid flow. Tracers retarded behind the mineralogical fronts will probably be reset as predicted by the advection-dispersion models; however, tracers that are expected to be reset ahead of the mineralogical fronts cannot progress beyond the permeability generating reaction. In the case of very unreactive lithologies (e.g. pure calcite marbles, cherts, and quartzites), the first reaction to affect the rocks may be a metasomatic one ahead of which there is little pervasive resetting of any tracer. Centimetre-scale layering may lead to the formation of self-perpetuating fluid channels in rocks that are not fluid saturated due to the juxtaposition of reactants. Such layered rocks may show patterns of mineralogical resetting that are not predicted by advection-dispersion models. Patterns of mineralogical and isotopic resetting in marbles from a number of terrains, for example: Chillagoe, Marulan South, Reynolds Range (Australia); Adirondack Mountains, Old Woman Mountains, Notch Peak (USA); and Stephen Cross Quarry (Canada) vary as predicted by these models. Received: 3 February 1997 / Accepted: 26 June 1997     

X射线粉晶衍射仪在大理岩鉴定与分类中的应用

大理岩主要有方解石大理岩、白云石大理岩和菱镁矿大理岩三种。以往大理岩是依据偏光显微镜下观察岩石结构构造及矿物成分进行分类定名,由于方解石、白云石、菱镁矿都属于三方晶系,具有闪突起、高级白干涉色、一轴晶负光性和菱形解理等相同晶体光学特征,偏光显微镜下区分十分困难。为了准确鉴定大理岩中碳酸盐矿物种类及其相对含量,本文利用岩石薄片偏光显微镜和X射线粉晶衍射技术对32件大理岩岩石样品进行分析测试。岩石薄片鉴定结果表明:大理岩造岩矿物主要有方解石、白云石、菱镁矿、石英、斜长石、白云母、黑云母、绿泥石、黏土和金属矿物。根据岩石结构构造及矿物组分特征,可把32件大理岩样品划分为方解石大理岩、长英质方解石大理岩、石英绿泥白云石大理岩、白云石大理岩、云英质白云石大理岩和菱镁矿大理岩等15个类型。X射线粉晶衍射分析表明:大理岩造岩矿物主要有方解石、白云石、菱镁矿、石英、斜长石、钾长石、云母、绿泥石、滑石和蒙脱石。综合分析认为:岩石薄片偏光显微镜鉴定技术很难区分方解石、白云石和菱镁矿等碳酸盐矿物,以及细小的石英、钾长石和斜长石、滑石和白云母等鳞片状硅酸盐矿物;X射线粉晶衍射分析技术不仅能准确检测出大理岩中方解石、白云石和菱镁矿等碳酸盐矿物种类及相对含量(方解石、白云石和菱镁矿的X射线衍射主峰有明显差异,d值分别为0.303 nm、0.288 nm和0.274 nm),而且能够有效鉴别岩石中粉砂级斜长石、钾长石与石英(三种矿物的X射线衍射主峰d值分别为0.319 nm、0.324 nm、0.334 nm);且能区分蒙脱石、绿泥石、云母和滑石等层状硅酸盐矿物(四种硅酸盐矿物的X射线衍射主峰d值分别为1.400 nm、0.705 nm、0.989 nm、0.938 nm)。综合岩石薄片偏光显微镜鉴定和X射线粉晶衍射分析结果,最终确定32件大理岩样品划分为22个岩石类型。研究认为:仅根据岩石薄片偏光显微镜鉴定或X射线粉晶衍射技术其中一种方法不能准确鉴定大理岩岩石,应将大理岩岩石野外观察、岩石薄片鉴定和X射线粉晶衍射技术结合起来,才能准确确定大理岩岩石类型。     

Hydrogeochemical modeling of the water seepages through Tannur Dam,southern Jordan

This paper reveals the geochemical processes of dissolution, precipitation and cation exchange that took place during water–rock interaction between water seepages through the Tannur Dam. The Schoeller diagram indicates that there are three major water types originating during water–rock interaction. The first water type is characterized by low salinity that ranges from 1,300 to 2,800 µs/cm, which represents the reservoir water and the water in the right side of the central gallery. The second water type is in the left side of the central gallery, which exhibits medium salinity that reaches about 4,400 µs/cm. The third water type is characterized by very high salinity that reaches a value of around 8,500 µs/cm and represents the water in the right existing adit. The increase of salinity can be explained due to the dissolution of carbonate and sulfate minerals that form the matrix of the foundation and the abutment rocks, and the dissolution of the grout curtain, which is composed of cement and bentonite. Hydrogeochemical modeling, using a computer code PHREEQC, was used to obtain the saturation indices of specific mineral phases, which might be related to interaction with water seepages, and to identify the chemical species of the dissolved ions. The thermodynamic calculations indicate that most of the water samples were undersaturated with respect to gypsum, anhydrite and halite, and were saturated and/or supersaturated with respect to calcite and dolomite. Ca(HCO₃)₂ is the primary water type, as a result of dissolution of carbonate minerals such as calcite and dolomite prevailing at the dam site. However, cation-exchange processes are responsible for the formation of the Na₂SO₄ water type from the CaSO₄ type that formed due to the dissolution of gypsum.     

River water quality in weathered limestone: A case study in upper Mahanadi basin, India

Stromatolitic limestone and calcareous shale belonging to Chattisgarh Supergroup of Proterozoic age dominate the upper part of the Mahanadi river basin. X-ray diffractogram (XRD) of limestone rocks show presence of a significant amount of calcite, dolomite and ankerite. Shales of various colours contain calcite and dolomite. It is observed that congruent dissolution of carbonate minerals in the Charmuria pure limestone has given rise to a typical karst topography. On the other hand, limestones are also seen to support red and black soil profiles. This indicates that the limestone bedrock undergoes a parallel incongruent weathering, which leaves a residue of decomposed rock. The XRD analyses reveal that the limestone soils thus formed contain an assemblage of quartz, clays and Fe-oxides. It is likely that the silicate component trapped during deposition of the stromatolitic limestone weathers incongruently resulting in diverse soil profiles. Carbonate and silicate mineral weathering schemes have been worked out to explain the soil formation, fixation of Al in clay minerals, and Fe in goethite. The water quality parameters such as Ca, Mg and HCO₃ in the river water suggest under saturation with respect to calcite and dolomite. The mineral stability diagrams indicate that kaolinite and Ca-smectite are stable in the river water environment, hence they occur in suspended sediments and soils. The dominant influence of carbonate weathering on the water quality is observed even in the downstream part of the river outside the limestone terrain.     

Hydrogeochemical exploration for uranium ore deposits: Use of the computer model wateqfc

Groundwaters in contact with hidden ore deposits may acquire chemical compositions that offer a guide for exploration, if the chemistry of the waters can be properly interpreted. Hydrogeochemical computer models allow significant progress to be made in the interpretation of the chemistry of all types of natural waters. The computer program, WATEQFC, an expansion and restructuring of WATEQF, is directed toward geochemical exploration for uranium and base metals. The expanded program can now solve the simultaneous equilibria involved in the aqueous geochemistry of 47 chemical elements, represented by approximately 540 minerals and solid compounds and 650 aqueous species.Calibration of the model with groundwaters from known deposits of uranium ore suggests that hidden ore bodies may be revealed by the state of saturation of the waters with respect to a suite of potential ore and gangue minerals. The saturation index (SI) is a reliable predictor of the presence of uranium ore from known deposits in Texas, Wyoming, and Czechoslovakia. The use of groundwater for regional reconnaissance strongly suggests that uranium mineralization is present in the subsurface near Colorado City, Colorado, whereas a similar modeling of groundwaters from a large area of Triassic sandstones in England virtually eliminates that area from consideration as a host for hidden uranium ore.     

Mineral equilibria and geothermometry of the Dalaman–Köyceğiz thermal springs,southern Turkey

The Dalaman and Köyceğiz thermal springs are from karstic limestones belonging to Upper Cretaceous to Burdigalian Beydağları autochthon and Carboniferous to Lutetian Lycian nappes. They have measured temperatures of 24– 41 °C, specific electrical conductivities of 14,310–45,600 μS/cm, and are dominated by Na (1550–8500 mg/kg) and Cl (2725–15,320 mg/kg). The heat source of the geothermal systems of the area is tectonic related and the occurrence of the thermal springs is related to the young normal faults. Meteoric waters and seawaters recharge the reservoir rocks, are heated at depth with increasing geothermal gradient, and move up to the surface through the fractures and faults by convection trend and emerge as thermal springs. While thermal waters move up to the surface, they mix with different proportions of seawater and cold fresh waters. The seawater contribution to the thermal waters varies from 24% to 78%. Lake waters in the area are connected with thermal waters. Consequently, their chemical composition is influenced by the chemistry of thermal waters. Chemical equilibrium modelling based on measured outlet temperatures and measured pH shows that all the waters are oversaturated with respect to quartz and K-mica and undersaturated with respect to Al(OH)₃, anorthite, gypsum, siderite and SiO₂(a). Albite, alunite, aragonite, Ca-montmorillonite, calcite, chalcedony, chlorite, dolomite, Fe(OH)₃(a), fluorite, gypsum, illite, K-feldspar, kaolinite and sepiolite minerals are mostly oversaturated or undersaturated. Mineral saturation studies of the thermal springs indicate that dolomite, chalcedony and quartz are most likely to cause scaling at outlet conditions. Assessments from various chemical geothermometers, and Na–K–Mg ternary and mineral equilibrium diagrams suggest that the reservoir temperature is around 65–90 °C. The temperatures obtained from quartz, quartz-steam loss, Mg/Li geothermometers and mineral equilibrium diagrams give the most reasonable results.     

X射线粉晶衍射仪在山东蒙阴金伯利岩蚀变矿物鉴定中的应用

山东蒙阴金伯利岩组成矿物以蚀变矿物为主,X射线粉晶衍射仪鉴定结果显示无矿金伯利岩矿物组分为方解石、白云石、石英、钙锆钛矿,标志性矿物为白云石和钙锆钛矿;贫矿金伯利岩矿物组分为蛇纹石、方解石、钙铝榴石、磁铁矿和金云母,标志性矿物为钙铝榴石;富矿金伯利岩矿物组分为蛇纹石、方解石、绿泥石、磷灰石、磁铁矿和金云母,标志性矿物为绿泥石和磷灰石。采用X射线粉晶衍射仪鉴定金伯利岩蚀变矿物组合,寻找蚀变矿物组分变化与金伯利岩含矿性的关系,利用标志性的蚀变矿物判断金伯利岩无矿、贫矿还是富矿,是非常有意义的。     

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.