Hydrogeochemical genesis of groundwaters with abnormal fluoride concentrations from Zhongxiang City,Hubei Province,central China

The groundwaters from Zhongxiang City, Hubei Province of central China, have high fluoride concentration up to 3.67 mg/L, and cases of dental fluorosis have been found in this region. To delineate the nature and extent of high fluoride groundwaters and to assess the major geochemical factors controlling the fluoride enrichment in groundwater, 14 groundwater samples and 5 Quaternary sediment samples were collected and their chemistry were determined in this study. Some water samples from fissured hard rock aquifers and Quaternary aquifers have high fluoride concentrations, whereas all karst water samples contain fluoride less than 1.5 mg/L due to their high Ca/Na ratios. For the high fluoride groundwaters in the fissured hard rocks, high HCO₃ ⁻ concentration and alkaline condition favor dissolution of fluorite and anion exchange between OH⁻ in groundwater and exchangeable F⁻ in some fluoride-bearing minerals. For fluoride enrichment in groundwaters of Quaternary aquifers, high contents of fluoride in the aquifer sediments and evapotranspiration are important controls.     

Hydrogeochemical evolution of groundwaters with excess fluoride concentrations from Dashtestan, South of Iran

Hydrogeochemical investigations were carried out in the Dashtestan, the eastern part of Borazjan, with a focus on fluoride content. The study area is underlain by a complex geology that is dominated by three lithological units, namely marl, alluvial sediments, and carbonate rocks. To assess the major geochemical factors controlling the fluoride enrichment in water, 37 groundwater and 12 surface water samples were collected from the three lithological units. Fluoride concentrations ranged up to 3?mg/L, and average concentrations varied from 1.12 (in carbonate aquifers) to 1.73 (in alluvial aquifers) to 1.82?mg/L (in marl aquifers). To study the influence of rocks and soils on groundwater quality, an additional 41 soil and rock samples were also taken and analyzed for fluoride. The order of average fluoride content in both rocks and soils is: marl?>?alluvial sediments?>?limestone, which confirms that marl is a likely source of fluoride.     

Chemical analysis of drinking water from some communities in the Brong Ahafo region

This study consisted of the determination of the trace metals and some physiochemical properties in drinking water samples from the Brong Ahafo region of the Republic of Ghana, where drinking water samples are not treated before it is consumed. The purpose was to ascertain the quality of water from these sources. Samples were taken from fifteen sampling points and analyzed for the following parameters Fe, Cu, Mn, Zn, Al, NO₃ ^?, NO₂ ^?, SO₄ ², PO₄ ^2?, and F^? using the procedure outline in the palintest photometer method. The data showed the variation of the investigated parameters in samples as follows: pH 5.57-7.54, conductivity (EC) 35-1216 us/cm, turbidity 3.25-72.50 NTU,PO₄ ^2?1 0.32-9.30 mg/L,F 0.32-1.05 mg/L,NO₃ ^? 0.09-0.99 mg/L,NO₂ ^? 0.006-0.114 mg/L, SO₄ ^2? 3.33-8.02 mg/L, Cu 1.19-2.75 mg/L Fe 0.05-0.85mg/L, Zn 0.04-0.15 mg/L, Mn 0.003-0.011 mg/L and Al 0.05-0.15 mg/L. The concentrations of most of the investigated parameters in the drinking water samples from Brong Ahafo region were within the permissible limits of the World Health Organization drinking water quality guidelines. There were no correlations between metal concentrations in the drinking water samples.     

Chemical and stable isotope composition of the high grade metamorphic rocks from the Arendal area,Southern Norway

A group of high grade metamorphic rocks from the Arendal area in Southern Norway has been analyzed for bulk geochemistry, and carbon and sulfur isotopic composition. A good correspondence between the composition of the Arendal rocks and common unmetamorphosed sedimentary and magmatic rocks suggests that except for some volatile compounds no mass transport took place during metamorphism. The high grade mafic rocks interlayered with the metasediments originate from basaltic tuffs and/or intrusives.Carbon occurs as graphite and also in small amounts in a still unidentified form. The carbon of the silicic metasedimentary rocks is isotopically light with an average ¹³C of –20.2, but significantly heavier than carbonaceous matter from unmetamorphosed Precambrian sediments. This is probably due to thermal pyrolysis of the original sedimentary organic matter and to the escape of a gas phase enriched in light carbon by reactions with the graphitic substance during metamorphism.Both the metasediments and the high grade mafic rocks have relatively high sulfur contents. The mean ³⁴S values are 3.3 and 1.8, respectively. This can be explained by isotopically heavy sulfur in the original sediment. Some migration of sulfur probably has occurred from the metasediments into the metamafic rocks.No influence of the hypersthene isograd on the chemical and stable isotope composition could be detected.     

Classification of mineral water types and comparison with drinking water standards

In a study of 291 mineral waters from 41 different countries, 9–20% exceeded the Dutch drinking water standards for chloride, calcium, magnesium, potassium, sodium, sulphate, and fluorine. The mineral water quality cannot be qualified as bad because the standards for these compounds (with the exception of fluorine) are not based on health issues, but matters regarding undesirable taste and possible adverse effects on the water supply system. For the mineral water data set, the amount of dissolved compounds, hardness, and chloride content appear to be the most distinctive criteria. A mineral water type classification based on these criteria will offer consumers a tool for assessing mineral water on the basis of the chemical composition data on the bottle label. In terms of the criteria mentioned, average Dutch tap water strongly resembles the Belgian and Dutch mineral waters. This similarity does not extend to the price, since Dutch tap water is about 500 times cheaper.     

Chemical weathering of the Indo-Gangetic alluvium with special reference to release of fluoride in the groundwater,Unnao district,Uttar Pradesh

In the central part of Indo-Gangetic alluvium in the Unnao district, Uttar Pradesh there are many pockets where groundwater shows high fluoride content. Drinking of fluorinated ground water has effected a large population and in many villages more than 80% of the population is suffering from fluorosis. The source of this fluoride appears to be the alluvial sediments deposited in the geological past as no hard rock terrain is present in the nearby areas. The area is dominantly made up of mud with pockets of sand. The sand fraction is made up of quartz, plagioclase, microcline, muscovite and biotite along with some accessory minerals like garnet, epidote, chlorite, tourmaline, hornblende, kyanite and a few opaque minerals. Moreover, the fluoride content in the groundwater varies both spatially and with depth indicating a sporadic occurrence. The surface water is devoid of high content of fluoride but is reported in hand pumps and in the dug wells. This paper deals with the geochemical study of the sediments up to a depth of 45m as most of the hand pumps are up to this depth to understand the source of fluoride. ¹⁴C dates of calcretes have suggested that the 45 m thick succession must have been formed in about 45000 years.     

Evaluation of bank filtration as a pretreatment method for the provision of hygienically safe drinking water in Norway: results from monitoring at two full-scale sites

Two case studies were carried out in central Norway in order to assess the performance of bank filtration systems in cold-climate fluvial aquifers relying on recharge from humic-rich surface waters with moderate microbial contamination. Three municipal wells and two surface-water sources at operative bank filtration systems were monitored for naturally occurring bacteriophages, fecal indicators, natural organic matter (NOM) and physico-chemical water quality parameters during a 4-month period. Aquifer passage effectively reduced the microorganism and NOM concentrations at both study sites. Bacteriophages were detected in 13 of 16 (81%) surface-water samples and in 4 of 24 (17%) well-water samples, and underwent 3 ± 0.3 log₁₀ reduction after 50–80-m filtration and 20–30 days of subsurface passage. NOM reductions (color: 74–97%; dissolved organic carbon: 54–80%; very hydrophobic acids: 70%) were similar to those achieved by conventional water-treatment processes and no further treatment was needed. Both groundwater dilution and sediment filtration contributed to the hygienic water quality improvements, but sediment filtration appeared to be the most important process with regard to microbial and NOM reductions. A strengths-weaknesses-opportunities-threats analysis showed that bank filtration technology has a high potential as a pretreatment method for the provision of hygienically safe drinking water in Norway.     

A Younger Dryas Ash Bed in western Norway,and its possible correlations with tephra in cores from the Norwegian Sea and the North Atlantic

A bed of volcanic ash up to 23 cm thick is found in lacustrine and marine sediments in western Norway. It is formally mamed the Vedde Ash Bed, and its age is approximately 10,600 yr B.P., i.e., mid-Younger Dryas. The bed consits of pure glass having a bimodal basaltic and rhyolitic somposition. The geochemistry of the glass shards suggests an Icelandic source. By means of stratigraphic position and geochemistry, the ash is correlated with ash zones found in cores from the continental shelf, the Norwegian Sea, and the North Atlatic.     

Chemical composition and stable carbon isotopic ratios of crude oils from Southern Germany

Thirty crude oils were sampled in the South German Molasse Basin. The crude oils were chemically separated into five component groups and their stable carbon isotopic ratios were determined by mass spectrometry. A distinct differentiation of four regionally connected groups can be inferred from the results of the δ¹³C values and chemical analyses. This grouping is in accordance with the present geologic information on the origin of crude oils in the Molasse Basin.The chemistry of crude oils seems to have been influenced by secondary processes in the eastern part of the Molasse Basin.     

Geochemical assessment of groundwater contamination with special emphasizes on fluoride,a case study from Midyan Basin,northwestern Saudi Arabia

Water samples for chemical analyses were collected in January 2012. A total of 72 samples of groundwater were collected from 72 boreholes in the Midyan Basin, northwestern Saudi Arabia. Samples were collected in polyethylene bottles and preserved and the used analytical techniques were in accordance with the standard methods from American public health association. Geochemical analyses of the groundwater samples from Midyan Basin reveal the concentration of fluoride (F) between 0.98 and 2.1 mg/l. Other parameters, e.g, pH, EC, TDS, HCO₃, SO₄, NO₃, Cl, K, Na, Mg, and Ca have been found in a variable proportion. Among them, the concentration of EC, HCO₃, K, Na and Mg is higher than the permissible limits. According to thermodynamical considerations, most of the analysed samples are graded under-saturated with respect to calcite and fluoride, while saturation has been observed in some samples. The under-saturation could probably be attributed to low concentration of calcite and fluoride in the studied wells. Fluoride concentration shows weak positive correlation with EC, TDS, Na, Cl, and SO₄. Factors controlling the concentration of fluoride (F) in the studied samples are the area climate, water chemistry and the presence of accessory minerals in the rocks through which groundwater is circulating, besides the anthropogenic activities in the area.     

Chemical composition of nyerereite and gregoryite from natrocarbonatites of Oldoinyo Lengai volcano,Tanzania

Alkali carbonates nyerereite, ideally Na₂Ca(CO₃)₂ and gregoryite, ideally Na₂CO₃, are the major minerals in natrocarbonatite lavas from Oldoinyo Lengai volcano, northern Tanzania. They occur as pheno- and microphenocrysts in groundmass consisting of fluorite and sylvite; nyerereite typically forms prismatic crystals and gregoryite occurs as round, oval crystals. Both minerals are characterized by relatively high contents of various minor elements. Raman spectroscopy data indicate the presence of sulfur and phosphorous as (SO₄)²⁻ and (PO₄)³⁻ groups. Microprobe analyses show variable composition of both nyerereite and gregoryite. Nyerereite contains 6.1–8.7 wt % K₂O, with subordinate amounts of SrO (1.7–3.3 wt %), BaO (0.3–1.6 wt %), SO₃ (0.8–1.5 wt %), P₂O₅ (0.2–0.8 wt %) and Cl (0.1–0.35 wt %). Gregoryite contains 5.0–11.9 wt % CaO, 3.4–5.8 wt % SO₃, 1.3–4.6 wt % P₂O₅, 0.6–1.0 wt % SrO, 0.1–0.6 wt % BaO and 0.3–0.7 wt % Cl. The content of F is below detection limits in nyerereite and gregoryite. Laser ablation ICP-MS analyses show that REE, Mn, Mg, Rb and Li are typical trace elements in these minerals. Nyerereite is enriched in REE (up to 1080 ppm) and Rb (up to 140 ppm), while gregoryite contains more Mg (up to 367 ppm) and Li (up to 241 ppm) as compared with nyerereite.     

Chemical composition and palaeobotanical origin of Miocene resins from Kerala-Konkan Coast,western India

The terpenoid composition of resins from the Miocene lignite horizons from the Kerala-Konkan Coast, western India was analyzed by Curie-point pyrolysis-gas chromatography-mass spectrometry (Cupy-GC-MS). The major pyrolysates were cadalene-based bicyclic sesquiterpenoids including some C₃₀-C₃₁ bicadinenes and bicadinanes typical of dammar resin from angiosperm plants of Dipterocarpaceae family. These plants are typically supported by tropical climates which the western Indian region was known to have experienced during early Tertiary period. The present study suggests that these palaeoclimatic conditions persisted until at least the Miocene epoch. These sesquiterpenoids which are commonly detected in many SE Asian crude oils may be utilised as useful biomarkers for petroleum exploration in the western Indian region.     

Chemical composition and species attribution of tourmalines from a rare-metal pegmatite vein with scapolite, Sangilen Upland, Tuva

A detailed study of the chemical composition and substitutions in calcium tourmalines from a scapolite-bearing rare-metal pegmatite vein from the Sol’bel’der River basin has shown that their species attribution is determined by occupancy of octahedral site Y. The composition of the yellow tourmaline most abundant in the central part of the pegmatite bodyis rather constant and characterized by the ideal formula Ca(Mg₂Li)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃F. Variations in the chemical composition of zonal tourmaline crystals from the contact part of the pegmatite are controlled by abrupt change in the chemical medium during their formation. The yellow cores of these crystals are close in composition to tourmaline from the central part of the pegmatite vein. The Mg content abruptly decreases toward the crystal margin: Mg²⁺ → Fe²⁺, 2Mg²⁺ → Li⁺ + Al³⁺, and Mg²⁺ + OH → Al³⁺ + O²⁻. The composition of dark green marginal zones in tourmaline is characterized by the ideal formula Ca(Al_1.5Li_1.5)Al₆(Si₆O₁₈)(BO₃)₃ (OH₂O)(F). The results indicate specific formation conditions of pegmatite. The crystallochemical formulas of the studied tourmalines allow us to regard them as new mineral species in the tourmaline group.     

Chemical and isotopic (<Superscript>18</Superscript>O/<Superscript>16</Superscript>O and D/<Superscript>1</Superscript>H) 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.     

Composition of groundwaters associated with porphyry-Cu deposits, Atacama Desert, Chile: Elemental and isotopic constraints on water sources and water-rock reactions

Groundwaters were collected around the Spence porphyry copper deposit, Atacama Desert, northern Chile, to study water-porphyry copper ore bodies interaction and test hypotheses regarding transport of metals through thick overburden leading to the formation of soil geochemical anomalies. The deposit contains 400 Mt of 1% Cu and is completely buried by piedmont gravels of Miocene age. Groundwaters were recovered from the eastern up hydraulic gradient (upflow) margin of the Spence deposit, from within the deposit, and for two kilometers down flow from the deposit. Water table depths decrease from 90 m at the upflow margin to 30 m 1.5 km down flow. Groundwaters at the Spence deposit are compositionally variable with those upflow of the deposit characterized by relatively low salinities (900-7000 mg/L) and Na⁺-SO₄²⁻-type compositions. These waters have compositions and stable isotope values similar to regional groundwaters recovered elsewhere in the Atacama Desert of Northern Chile. In contrast, groundwaters recovered within and down flow of the deposit range in salinity from 10,000 to 55,000 mg/L (one groundwater at 145,000 mg/L) and are dominantly Na⁺-Cl⁻-type waters. Dissolved sulfate values are, however, elevated compared to upflow waters, and δ³⁴S_CDT decreases into the deposit (from >4‰ to 2‰), consistent with increasing influence of sulfur derived from oxidation of sulfide minerals within the deposit. The increase in salinity and conservative tracers (Cl⁻, Br⁻, Li⁺, and Na⁺) and the relationship between oxygen and hydrogen isotopes suggests that in addition to water-rock reactions within the deposit, most of the compositional variation can be explained by groundwater mixing (with perhaps a minor role for evaporation). A groundwater-mixing scenario implies a deeper, more saline groundwater source mixing with the less saline regional groundwater-flow system. Flow of deeper, more saline groundwater along pre-existing structures has important implications for geochemical exploration and metal-transport models.     

U/Pb zircon ages of basement gneisses and discordant felsic dykes from Vestranden,westernmost Baltic Shield and central Norwegian Caledonides

Four new U/Pb-zircon ages are reported from northern Vestranden, the northernmost part of the Western Gneiss Region of Norway, Scandinavian Caledonides. The age of a basement tonalite (1819±6 Ma), together with earlier datings on granites, indicates that the dominantly granitoid basement in Vestranden began to form more than 1800 Ma years ago. The minimum age of a subsequent Precambrian migmatization event is given by a U/Pb age of 1630±80 Ma found a granite dyke which cuts migmatitic veining in the basement gneisses. While age and lithology suggest general similarity and thereby favour a correlation between the basement granites of the northern part of Vestranden and Svecofennian granites farther to the east, no detailed chronological information is at present available that support such a correlation.No Sveconorwegian-Grenvillian ages have previously been reported from northern Vestranden. Also in the presently studied cases events between c. 1630 Ma and 430 Ma ago did not affect the U-Pb isotope system of zircons. About 430 Ma ago, substantial parts of Vestranden experienced Caledonian high-grade metamorphism and partial anatectic melting. Migmatite neosomes in northern Vestranden, yielded an U/Pb zircon age of 434±22 Ma. Relatively high temperatures persisted throughout much of the Silurian and probably into the Devonian. Large amounts of pegmatite intruded at the end of this period. One of these dykes yielded an U/Pb-zircon age of 404±2 Ma.

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Zusammenfassung Vier neue U-Pb-Zirkonalter liegen aus dem nördlichen Vestranden-Bereich des westnorwegischen Gneissgebiets vor. Das Alter einer Tonalitintrusion (1819±6 Ma) bestätigt zusammen mit anderen Altersbestimmungen, daß das präkambrische Fundament der zentralskandinavischen Kaledoniden sich im Vestrandengebiet bereits vor mehr als 1800 Ma zu bilden begann. Das Minimalalter einer darauf folgenden präkambrischen Migmatisierung wird durch ein 1630±20 Ma Alter durchsetzender Granitgänge begrenzt. Zwar deuten die bisher vorliegenden Ergebnisse eine Gleichaltrigkeit der Granitgesteine im nördlichen Vestranden und den Svekofenniden weiter östlich an, ermöglichen aber derzeit noch keine präzise Korrelation des geologischen Geschehens.Sveconorwegische (Grenville) Isotopenalter sind bisher nicht aus dem nördlichen Vestranden bekannt. Auch die neuen Daten weisen keine Störung der U-Pb-Isotopensysteme zwischen etwa 1630 und 430 Ma auf.Beträchtliche Teile des Vestrandenbereiches wurden vor ca. 430 Ma einer kaledonischen, höhergradigen Metamorphose und anatektischer Aufschmelzung unterworfen. Die Neosome eines Migmatites ergaben ein Alter von 434±22 Ma, was erneut die Existenz zweier verschiedener Migmatisierungsetappen im Präkambrium bzw. in Silur bestätigt. Höhere Temperaturen bestanden danach bis in das Devon. Größere Pegmatitmengen wurden am Ende dieser Zeitspanne gebildet. Einer dieser Pegmatitkörper ergab ein U-Pb-Zirkonalter von 404±2 Ma.

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Résumé Cette note fait état de 4 nouvelles déterminations d'âge (méthode U/Pb sur zircon) dans le Vestranden septentrional, qui forme la partie nord de la région gneissique occidentale de la Norvège (Calédonides). L'âge d'une tonalite (1819±6 Ma), joint à des datations antérieures effectuées sur des granites, indique que la formation du socle granitoîde dans le Vestranden a commencé il y a plus de 1800 Ma. L'âge maximal d'une migmatitisation précambrienne ultérieure est donné par la mesure de 1630±80 Ma effectuée sur un dyke de granite qui recoupe le rubanement migmatitique. L'âge et la lithologie indiquent une similitude d'ensemble et, partant, suggèrent une corrélation entre les granites du nord du Vestranden et ceux des Svécofennides situés plus à l'est; toutefois, on ne dispose aujourd'hui d'aucune donnée chronologique à l'appui d'une telle corrélation.Jusqu'à présent, aucun âge svéconorvégien-grenvillien n'a été enregisré dans le Vestranden septentrional. De même, dans les cas étudiés ici, aucun événement n'a affecté le système isotopique U-Pb entre 1630 et 430 Ma. A environ 430 Ma, des parties importantes du Vestranden ont enregistré un métamorphisme calédonien de degré élevé et une fusion anatectique partielle. Les néosomes d'une migmatite ont fourni un âge U/Pb sur zircon de 434±22 Ma. Des températures relativement élevées se sont maintenues pendant la plus grande partie du Silurien et jusqu'au cours du Dévonien. De grandes quantités de pegmatite ont été intrudées à la fin de cette période; un de ces dykes a donné un âge U/Pb sur zircon de 404±2 Ma.

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- - . 1819±6 . , , - 1800 . . , , 1630±80 . , . , .- - 1630-430 . . . 434=22 . . , , , ; , , -, 404=2 . .

     

赣中盛源盆地及邻区橄榄玄粗岩系列火山岩中黑云母化学成分特征

本文利用电子探针技术对赣中盛源盆地及邻区橄榄玄粗岩系列火山岩中黑云母的类型、化学成分及结晶时的温度和氧逸度条件等进行了研究.黑云母为镁质黑云母;结晶时温度的大致范围为1 060°C~1 100°C,氧逸度大致范围为10-7bar~10-9 bar.本文研究表明,黑云母的化学成分研究是揭示岩石成因类型的一种有效途径,可为研究岩体成因类型以及成岩时的物理化学条件提供依据,并对成岩具有重要的指示意义.     

西天山智博铁矿床黄铁矿成分特征及硫同位素研究

智博大型磁铁矿床位于新疆西天山阿吾拉勒铁铜成矿带东段,主要矿石矿物为磁铁矿,主要共生金属矿物为黄铁矿。文章通过对黄铁矿进行矿物成因研究来推测矿床成因及特征。本次研究选择2个成矿期的矿石及围岩中的黄铁矿进行电子探针及硫同位素研究。电子探针数据显示岩浆期黄铁矿w(Co)平均为4703×10~(-6),大于热液期w(Co)(735.71×10~(-6)),Co/Ni比值(平均18.53)也大于热液期黄铁矿Co/Ni比值(平均0.96);S/Se比值多数集中于1000～8000之间。部分Co/Ni、Se/Te、S/Se比值落入热液成因范围内,暗示了热液流体参与成矿的可能性。而Co-Co/Ni图解显示岩浆期矿石和热液期矿石具有一定的继承性。黄铁矿中δ~(34)S值介于-1.2‰和0.3‰之间,表明硫主要来源于幔源硫。智博铁矿床矿石主要为岩浆成因,但岩浆期后热液及其他热液流体也参与了晚阶段的成矿作用。     

青海沱沱河地区赛多浦岗日二长花岗岩中黑云母化学成分特征及地质意义

电子探针分析结果表明,沱沱河地区赛多浦岗日二长花岗岩中黑云母具有富MgO、SiO_2、(Na_2O+K_2O),相对贫Al_2O_3、FeO~t的特征;镁质率(M=0.60~0.65)高,∑Al值(1.30~1.39)偏低,中等Fe/(Mg+Fe)(0.42~0.44)比值,为镁质黑云母;估算其结晶温度为580℃~645℃,且岩浆体系具有较高的氧逸度。黑云母的成分特征显示其寄主岩体为造山背景下形成的钙碱性花岗岩,其源区具有壳-幔混源的特征。