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1.
Salts produced using brines of the Mamfe Basin were analysed by XRD for their mineral composition and ICP-MS for minor element composition. Halite (NaCl) and dolomite (CaMg (CO3)2) constitute the major minerals with minor impurities from Mo and Cd in the chlorides and Sc and Cu in the carbonates. The mineral composition is evidence of dissolution of evaporites with parent brine of marine origin. Other elements analysed are suggested to be adsorbed to these salts and result from water–rock interaction. The elements partitioned based on their correlation to other elements are suggested to derive from sulphates including barite for Ba, sulphides for Pb, Zn, silicates for Zr, Mn and oxides for V, Cr. The electrical conductance of the brines is related to the salt yield by the equation; M = 9 × 10− 4E− 3.27, and it can be used to estimate salt yield throughout the year. Over 1200 tons of salt consisting dominantly of grade I halite are lost annually as brines across the basin. Purification is required for some minor elements including Ba, Pb, Hg and Cd for use as a condiment. A genetic relation between the parent brine, sulphide minerals and organic matter-rich sediments is proposed.  相似文献   

2.
Eighty-two core samples were collected from the Spring Valley #1 well which penetrates the Upper Carboniferous strata in the Late Devonian–Early Permian Maritimes Basin. The strata consist of alternating sandstones and mudstones deposited in a continental environment. The objective of this study is to characterize the relationship of sandstone porosity with depth, and to investigate the diagenetic processes related to the porosity evolution. Porosity values estimated from point counting range from 0% to 27.8%, but are mostly between 5% and 20%. Except samples that are significantly cemented by calcite, porosity values clearly decrease with depth. Two phases of calcite cement were distinguished based on Cathodoluminescence, with the early phase being largely dissolved and preserved as minor relicts in the later phase. Feldspar dissolution was extensive and contributed significantly to the development of secondary porosity. Quartz cementation was widespread and increased with depth. Fluid inclusions recorded in calcite and quartz cements indicate that interstitial fluids in the upper part of the stratigraphic column were dominated by waters with salinity lower than that of seawater, the middle part was first dominated by low-salinity waters, then invaded by brines, and the lower part was dominated by brines. Homogenization temperatures of fluid inclusions generally increase with depth and suggest a paleogeothermal gradient of 25 °C/km, which is broadly consistent with that indicated by vitrinite reflectance data. An erosion of 1.1–2.4 (mean 1.75) km of strata is inferred to have taken place above the stratigraphic column. δ18O values of calcite cements (mainly from the late phase) decrease with depth, implying increasing temperatures of formation, as also suggested by fluid-inclusion data. δ13C values of calcite cements range from −13.4‰ to −5.7‰, suggesting that organic matter was an important carbon source for calcite cements. A comparison of the porosity data with a theoretical compaction curve indicates that the upper and middle parts of the stratigraphic column show higher-than-normal porosity values, which are related to significant calcite and feldspar dissolution. Meteoric incursion and carboxylic acids generated from organic maturation were probably responsible for the abundant dissolution events.  相似文献   

3.
Inglefield Land in northwest Greenland is an ice-free 7000 km2 region underlain by the Palaeoproterozoic Inglefield mobile belt, composed of quartzo-feldspathic gneisses, meta-igneous and supracrustal rocks. These rocks are unconformably overlain by an unmetamorphosed cover of sedimentary and igneous rocks of the Mesoproterozoic Thule Basin and the Lower Palaeozoic Franklinian Basin. Mineralisation in Inglefield Land is characterised by a copper–gold metal association that can be classified in terms of the hosting rocks, namely: garnet–sillimanite paragneiss-hosted, orthogneiss-hosted and mafic–ultramafic-hosted. The paragneiss-hosted mineralisation, the topic of this paper, is essentially confined within a NE-trending structural corridor and consists of bands of sulphide±graphite-bearing, hydrothermally altered, quartzo-feldspathic gneiss, called “rust zones”. These are commonly parallel to the paragneiss main foliation, suggesting a close relationship. The rust zones have strike lengths from a few metres to more than 5 km, and widths ranging from a few centimetres to 200 m. Sulphides mainly include pyrrhotite, pyrite and chalcopyrite. The sulphides form disseminations, up to 30% by volume, but in places they form massive pods or lenses up to 20–30 m, and about 0.1–0.5 m wide. Graphite contents are up to 5 vol.%. Rust zones typically consist of a quartz–plagioclase mosaic associated with a late generation of red-brown biotite, sericite, chlorite and epidote. Mylonitic or cataclastic textures are locally recognisable. XRD analyses of graphite indicate temperatures of between 650 and 700 °C. Sulphur isotope analyses show δ34S values ranging from −6.2‰ to +9.3‰.An ore genesis model is proposed in which the Palaeoproterozoic precursor sandstone–carbonaceous shale succession is polydeformed and polymetamorphosed to granulite facies quartzo-feldspathic and pelitic gneisses, with transposition of layering to axial plane of folds, followed by ductile shearing and mylonitisation, from which future rust zones were derived. The mylonitic zones were infiltrated by fluids, whose origin can be ascribed to deep-penetrating surface waters and/or external brines. In our ore genesis model, we envisage that brines derived from the overlying Lower Palaeozoic Franklinian succession infiltrated the basement into the structural channels provided by the shear/mylonitic zones. At the regional scale, this infiltration was facilitated by a NE-trending corridor, postulated to be a deep structure.  相似文献   

4.
The Albanian fold-and-thrust belt and the Peri-Adriatic Depression are well documented by means of seismic reflection profiles, GPS reference points, potential data, wells and outcrops. The continuous Oligocene to Plio-Quaternary sedimentary records help to constrain both the burial history of Mesozoic carbonate reservoirs, the timing of their deformation, and the coupled fluid flow and diagenetic scenarios.Since the mid-90s, the Albanian foothills were used as a natural laboratory to develop a new integrated methodology and work flow for the study of sub-thrust reservoir evolution, and to validate on real case studies the use of basin modelling tools as well as the application of new analytical methods for the study petroleum systems in tectonically complex areas.The integration of the interactions between petrographic and microtectonic studies, kinematic, thermal and fluid flow basin modelling, is described in detail. The fracturing of the reservoir intervals has a pre-folding origin in the Albanides and relates to the regional flexuring in the foreland. The first recorded cement has a meteoric origin, implying downward migration and the development of an earlier forebulge in the Ionian Basin. This fluid, which precipitates at a maximum depth of 1.5 km, is highly enriched in strontium, attesting for important fluid–rock interaction with the Triassic evaporites, located in diapirs. From this stage, the horizontal tectonic compression increases and the majority of the fluid migrated under high pressure, characterised by brecciated and crack-seal vein. The tectonic burial increased due to the overthrusting, that is pointed out by the increase of the precipitation temperature of the cements. Afterwards, up- or downward migration of SO42−, Ba2+ and Mg2+-rich fluids, which migrated probably along the décollement level, allows a precipitation in thermal disequilibrium. This period corresponds to the onset of the thrusting in the Ionian Zone. The last stage characterised the uplift of the Berati belt, developing a selective karstification due likely to the circulation of meteoric fluid.The main results of the fluid flow modelling show that the Upper Cretaceous–Paleocene carbonate reservoirs in the Ionian zone have been charged from the Tortonian onward, and that meteoric fluid migration should have intensely biodegraded the hydrocarbon in place. Concerning the migration paths, it has been demonstrated that the thrusts act principally as flow barriers in Albania, mainly due the occurrence of evaporites (non-permeable), except in the foreland, where they do not occur.  相似文献   

5.
Analysis of hydraulic heads and chemical compositions of Devonian formation waters in the west central part of the Alberta Basin, Canada, characterizes the origin of formation waters and migration of brines. The Devonian succession in the study area lies 2000–5000 m below the ground surface, and has an approximate total thickness of 1000 m and an average slope of 15 m/km. Four Devonian aquifers are present in the study area, which form two aquifer systems [i.e., a Middle–Upper Devonian aquifer system (MUDAS) consisting of the Elk Point and Woodbend–Beaverhill Lake aquifers, and an Upper Devonian aquifer system (UDAS) consisting of the Winterburn and Wabamun aquifers]. The Ireton is an effective aquitard between these two systems in the eastern parts of the study area. The entire Devonian succession is confined below by efficient aquitards of the underlying Cambrian shales and/or the Precambrian basement, and above by overlying Carboniferous shales of the Exshaw and Lower Banff Formations.The formation water chemistry shows that the Devonian succession contains two distinct brine types: a ‘heavy brine,’ located updip, defined approximately by TDS >200 g/l, and a ‘light brine’ with TDS <200 g/l. Hydraulic head distributions suggest that, presently, the ‘light brine’ attempts to flow updip, thereby pushing the ‘heavy brine’ ahead. The interface between the two brines is lobate and forms large-scale tongues that are due to channeled flow along high-permeability pathways. Geological and hydrogeochemical data suggest that the following processes determined the present composition of the ‘light’ and ‘heavy’ brines: original seawater, evaporation beyond gypsum but below halite saturation, dolomitization, clay dehydration, gypsum dewatering, thermochemical sulfate reduction (TSR), and halite dissolution. The influx of meteoric (from the south) and metamorphic (from the west) waters can be recognized only in the ‘light brine.’ Albitization can be unequivocally identified only in the ‘heavy brine.’ The ‘heavy brine’ may be residual Middle Devonian evaporitic brine from the Williston Basin or the Elk Point Basin, or it may have originated from partial dissolution of thick, laterally extensive Middle Devonian evaporite deposits to the east of the study area. The ‘light brine’ most probably originated from dilution of ‘heavy brine’ in post-Laramide times.  相似文献   

6.
One of the most important processes leading to the deterioration of groundwater in Israel is the migration of brines penetrating into fresh groundwater bodies. Such manifestations occur at an ever increasing frequency and in unexpected locations. The hydrochemistry of these processes reveals the possibility of involvement of several types of brines. The distribution and the hydrostratigraphic sequence of the brines is correlated with the evolution of paleoenvironments during the geological history of the region. Several major phases of brine and evaporite formation are discerned: The earliest phase occurred in the Paleozoic–Early Mesozoic (Yam Suf–Ramon–Lower Arad Groups) during which brines were generated by dissolution of evaporites. The second major phase in the evolution of brines occurred during the Mio-Pliocene. In the western areas of the country, the brines were generated mainly by the post-Messinian ingression of seawater which dissolved evaporites and reacted with the invaded rock sequence. In the Rift and in adjoining areas, the dominant brine was the final product of the evaporation of an inland marine lagoon (the Sdom Sea) which penetrated into an environment prevalently built of previously formed rocks and, particularly of clastic beds filling at that time, the nascent rift. From this evaporating lagoon precipitated evaporates, the dissolution of which produced brines. A further step in the hydrochemical evolution in the Rift was the creation of the Lisan Lake, which became progressively saline, probably as the result of dissolution and flushing of salts derived from the previous hypersaline Sdom Sea. The contemporary phase in the Rift is characterized by an ongoing process of flushing-out of residual brines and dissolution of evaporites by currently recharged fresh water. Throughout the geological history of the area, four major periods of flushing stand out. These occurred between the Triassic and the Jurassic, at the end of the Jurassic, as the result of the Oligocene uplift and as part of the Messinian event. As the result of these processes, the rock-sequences were flushed off previously formed brines and evaporites and were “made ready” for following generations of liquids.  相似文献   

7.
古近纪时期,华南江汉盆地的潜江凹陷和江陵凹陷发育盐湖,沉积了巨厚的蒸发岩,并形成和储藏了富锂、钾、铷、铯、溴、碘等元素的卤水资源,这些元素含量达到工业品位或综合利用品位;富锂卤水属于深层地下卤水型锂矿资源,镁锂比值低,是非常优质的锂资源。本文总结了江汉盆地大地构造特征、火成岩及古气候背景,论述了古盐湖沉积岩相特征、富锂卤水水化学、分布及储层特征、卤水中锂的来源与富集机理、卤水型锂矿成矿模式以及富锂卤水勘查与开采技术进展,提出了卤水开发利用中存在的问题和解决途径。江汉盆地富锂卤水成因包括:古盐湖锂可能主要来自高温水岩反应产生的富锂热液流体的补给;在干旱的气候下,古湖水不断蒸发浓缩,导致卤水中锂浓缩富集;在盐湖演化末期,逐渐埋藏的盐类晶间富锂卤水被转移至裂隙、砂岩及玄武岩储层中储集;在较高的地热背景值下,埋藏卤水与储层岩石可能发生水岩反应,进一步促进了卤水中锂的富集。江汉盆地深层卤水初步勘查显示,氯化锂资源量已达到大型工业规模,展示了巨大的资源潜力。此外,卤水锂开采技术已基本形成,建议进一步加强富锂卤水的绿色开发技术研究,制定相关勘查开发规范。  相似文献   

8.
In the Meskala-Kourimat area, the Bouabout Syncline aquifer system, intersected by the Igrounzar Wadi, feeds most of the karstic sources of the region. This aquifer is contained within Cenomanian and Turonian limestones and dolomitic limestones. The base of the system corresponds to the lower Cenomanian grey clays, and the top to the Senonian white marls. Hydrodynamic studies of various springs shows that each water source is different from the other, indicating a heterogeneous underground reservoir belonging to a complex karst system. The springs waters show a large chemical variability in space and time. These waters are a mixture of chloride, sulphate, Na and Mg. High Mg contents of some springs result from dissolution of evaporite, confirmed by low Ca/Mg ratios. The total dissolved solids (TDS) in spring water increases from upstream to downstream, probably as a response to residency time, but also due to interaction with Cenomanian evaporites. However, the springs are good for drinking water, as well as for irrigation. The monthly survey of selected springs indicated a large chemical variability but with little or no correlation between discharge and TDS.Stable isotope data (18O) suggests that the altitude of the recharge area, for this aquifer system, is 1200 m. The 18O gradient versus altitude, established on springs whose recharge areas are well known is, −0.25% versus SMOW/100 m. When compared with the ‘Meteoric Water Line’ established on worldwide spring water whose recharge areas are well known, the Essaouira Basin shows rain recharge without any significant evaporation.  相似文献   

9.
Saline alkaline lakes that precipitate sodium carbonate evaporites are most common in volcanic terrains in semi‐arid environments. Processes that lead to trona precipitation are poorly understood compared to those in sulphate‐dominated and chloride‐dominated lake brines. Nasikie Engida (Little Magadi) in the southern Kenya Rift shows the initial stages of soda evaporite formation. This small shallow (<2 m deep; 7 km long) lake is recharged by alkaline hot springs and seasonal runoff but unlike neighbouring Lake Magadi is perennial. This study aims to understand modern sedimentary and geochemical processes in Nasikie Engida and to assess the importance of geothermal fluids in evaporite formation. Perennial hot‐spring inflow waters along the northern shoreline evaporate and become saturated with respect to nahcolite and trona, which precipitate in the southern part of the lake, up to 6 km from the hot springs. Nahcolite (NaHCO3) forms bladed crystals that nucleate on the lake floor. Trona (Na2CO3·NaHCO3·2H2O) precipitates from more concentrated brines as rafts and as bottom‐nucleated shrubs of acicular crystals that coalesce laterally to form bedded trona. Many processes modify the fluid composition as it evolves. Silica is removed as gels and by early diagenetic reactions and diatoms. Sulphate is depleted by bacterial reduction. Potassium and chloride, of moderate concentration, remain conservative in the brine. Clastic sedimentation is relatively minor because of the predominant hydrothermal inflow. Nahcolite precipitates when and where pCO2 is high, notably near sublacustrine spring discharge. Results from Nasikie Engida show that hot spring discharge has maintained the lake for at least 2 kyr, and that the evaporite formation is strongly influenced by local discharge of carbon dioxide. Brine evolution and evaporite deposition at Nasikie Engida help to explain conditions under which ancient sodium carbonate evaporites formed, including those in other East African rift basins, the Eocene Green River Formation (western USA), and elsewhere.  相似文献   

10.
塔里木盆地西南部和北部盐泉水化学特征及找钾指标探讨   总被引：6，自引：0，他引：6  
对塔里木盆地西南部及北部盐泉水化学特征、成因进行了研究, 同时对研究区水化学离子比值作了探讨并提出相应的找钾指标体系。野外采样分析和收集文献资料共获得192件盐泉水样数据。塔里木盆地西南部(莎车盆地)水化学类型主要为硫酸盐型(硫酸镁亚型和硫酸钠亚型), 少数为氯化物型, 而北部(库车盆地)氯化物型占主导, 其次是硫酸盐型。盐泉水演化过程较复杂, 包含了深部物源补给、盐岩溶滤、地表水的混合以及强烈蒸发作用的影响。从水化学特征系数(离子比值)看, 研究区钾氯系数、镁氯系数、钠氯系数, 结合硼氯系数, 较适合作为找钾指标; 盐泉水贫溴的特点导致大部分数据点溴氯系数极低、钾溴系数又极高, 建议不作为最主要的水化学找钾指标。利用SPSS软件对盐泉水各化学组分、矿化度和离子比值的环境背景值作了统计计算。水化学特征系数背景值和异常值指标体系的确定为今后在开展水化学方法找钾和预测成钾靶区提供了有利的数据支持和依据。  相似文献   

11.
Major element chemistry, rare-earth element distribution, and H and O isotopes are conjointly used to study the sources of salinisation and interaquifer flow of saline groundwater in the North East German Basin. Chemical analyses from hydrocarbon exploration campaigns showed evidence of the existence of two different groups of brines: halite and halite Ca–Cl brines. Residual brines and leachates are identified by Br?/Cl? ratios. Most of the brines are dissolution brines of Permian evaporites. New analyses show that the pattern of rare-earth elements and yttrium (REY) are closely linked to H and O isotope distribution. Thermal brines from deep wells and artesian wells indicate isotopically evaporated brines, which chemically interacted with their aquifer environment. Isotopes and rare-earth element patterns prove that cross flow exists, especially in the post-Rupelian aquifer. However, even at depths exceeding 2,000 m, interaquifer flow takes place. The rare-earth element pattern and H and O isotopes identify locally ascending brines. A large-scale lateral groundwater flow has to be assumed because all pre-Rupelian aquifer systems to a depth of at least 500 m are isotopically characterised by Recent or Pleistocene recharge conditions.  相似文献   

12.
The Salton Sea geothermal system (SSGS) is the site of active hydrothermal metamorphism and metallogenesis in the delta of the Colorado River, which partially fills the Salton Trough rift zone at the head of the Gulf of California. Growth of the delta across the rift has isolated the northern part of the Salton Trough since the Pleistocene, forming the evaporative Salton Sea basin whose sediments host the SSGS. More than 70 commercial geothermal wells, including a 3.2 km deep research borehole drilled as part of the Salton Sea Scientific Drilling Project (SSSDP), are yielding a wealth of new data from this system.Within the SSGS, active greenschist facies metamorphism is occuring at temperatures 365°C at only 2–3 km depth, by reaction of NaCaKFeMnCl brines with the deltaic and lacustrine Pilo-Pleistocene sediments. Two kinds of base metal ore mineralization occur at depth: stratabound diagenetic Fe sulfides, and epigenetic vertical veins containing FeZnCuPb sulfides and Fex oxides. The vein mineralization occurs as two types: an older, reduced carbonate-sulfide assemblage, and a modern, oxidized, silicate-hematite-sulfide assemblage. The earlier assemblage formed at temperatures up to 100°C higher than the ambient temperatures measured in the wells today, implying that cooler, oxidized fluids have displaced hot, reduced fluids.A sharp interface between shallow fluids containing <12 wt % TDS and deep hypersaline brines containing 15–27 wt % TDS exists in the SSGS. The deeper hypersaline brines are rich in base metals (Fe 1500 ppm, Mn 1000 ppm, Zn 500 ppm) whereas the overlying lower-salinity fluids contain less than 100 ppm each of Fe, Mn and Zn. The modern silicate-hematite-sulfide vein assemblage is precipitating where the two fluids appear to be mixing. The two fluid types also have distincty different δ18O and δD relations. The shallow lower-salinity fluids have only partially-exchanged oxygen with deltaic and lacustrine host rocls. The deep hypersaline brines have exchanged oxygen extensively at 250°C with the deltaic sediments. δD values of the hypersaline brines are typically lighter than either the lower-salinity fluids or the modern evaporating groundwaters occupying the Salton Trough, implying a different source for the original fluids.The high salinities of the geothermal brines are derived from a combination of evaporation of fossil lakewaters, groundwater dissolution of shallow lacustrine evaporites, and subsurface hydrothermal metamorphism of buried lacustrine evaporites. Episodic filling and desiccation of the closed Salton Sea basin has allowed cold saline brines to form and percolate down into the sedimentary section. In some wells anyhydrite meta-evaporites and interbedded solution collapse breccias occur at 1 km depth. The anyhydrite contains fluid inclusions that are saturated in halite at their homogenization temperatures of 300°C, recording the hydrothermal dissolution of bedded salt. Based on Sr and Pb isotopic data and whole-rock chemical data, the source of the metals in the hypersaline brines is from leaching of the host sediments. However, the origin of reduced S for ore mineralization remains an enigma. δ34S values for vein sulfides cluster uniformly around zero per mil, implying that an isotopically-homogeneous source of reduced sulfide exists in the brines. It is possible that the vein sulfides receive a constribution from a magmatic S source.Movement and mixing of brines of different chemistry and oxidation states play a major role in ore genesis. Our model envisages an early stage in which a deep brine pool accumulated at depth in the sedimentary section by partial section by partial evaporation of basin and dissolution of bedded salts. Intrusion of rift-related basaltic magma into the base of the sedimentary caused heatingand fracturing of the sediments, resulting in precipitation of the carbonate-sulfide veins during pore fluid expulsion. Heating also caused a diapir of the hypersaline brine to rise and displace colder, less saline, shallower pore fluids. This brine intrusion was accompanied by pervasive and extensive mineralization. As this diapir cooled it began to move downward, drawing in shallow, more oxidized fluids and causing the formation of the modern silicate-hematite-sulfide vein ore zone.  相似文献   

13.
During the Cenozoic numerous shallow epicontinental evaporite basins formed due to tectonic movements in the Northern Province of the Central Iran Tectonic Zone (the Great Kavir Basin). During the Miocene, due to sea‐level fluctuations, thick sequences of evaporites and carbonates accumulated in these basins that subsequently were overlain by continental red beds. Development of halite evaporites with substantial thickness in this area implies inflow of seawater along the narrow continental rift axis. The early ocean basin development was initiated in Early Eocene time and continued up to the Middle Miocene in the isolated failed rift arms. Competition between marine and non‐marine environments, at the edge of the encroaching sea, produced several sequences of both abrupt and gradual transition from continental wadi sediments to marginal marine evaporites in the studied area. These evaporites show well‐preserved textures indicative of relatively shallow‐brine pools. The high Br content of these evaporites indicates marine‐derived parent brines that were under the sporadic influence of freshening by meteoric water or replenishing seawater. However, the association of hopper and cornet textures denotes stratified brine that filled a relatively large pool and prevented rapid variations in the Br profile. Unstable basin conditions that triggered modification of parent brine chemistry prevailed in this basin and caused variable distribution patterns for different elements in the chloride units. The presence of sylvite and the absence of Mg‐sulphate/chlorides in the paragenetic sequence indicate SO4−depleted parent brine in the studied sequence. Petrographic examinations along with geochemical analyses on these potash‐bearing halites reveal parental brines which were a mixture of seawater and CaCl2‐rich brines. The source of CaCl2‐rich brines is ascribed to the presence of local rift systems in the Great Kavir Basin up to the end of the Early Miocene. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

14.
Natural gas from the Zhaolanzhuang field of the Jizhong Superdepression, Bohai Bay Basin contains the highest proportions of H2S (40–92%) among the sour gases encountered in China. The gas payzones include the Eocene–Oligocene Kongdian Formation (Ek) and the Es4 member of the Shahejie Formation. The sedimentary sequence consists of halite, anhydrite, carbonate, sandstone and shale interbeds deposited in the evaporative brackish water lacustrine – salt lake setting. In the deepest part of the Jinxian sag, the total thickness of evaporites is more than 1000 m, of which halite accounts for over 40%. Various organic-rich mudstones intercalated with the evaporites are currently within the conventional hydrocarbon window (with a depth of 2500–3500 m), and likely the source for the oil and sour gas in the Zhaolanzhuang field. The temperatures of the gas reservoirs range from 75 to 100 °C, too low for significant thermochemical sulfate reduction. The co-occurrence of abundant elemental sulfur with the sour gas and the δ34S values of the various sulfur-containing compounds indicate that the H2S gases were most likely derived from much deeper source kitchens where significant thermochemical sulfate reduction has occurred.  相似文献   

15.
The Baiyu Mountain area has the most shortage of water in the Ordos Basin of China. The majority of the groundwater is in the Luohe water-bearing formation, which is characterized by high total dissolved solids (TDS). The concentration of TDS can be as high as 10.45 g/l, which makes the water unsuitable for either potable or irrigation purpose. The dominant ions in the groundwater are SO2–4·Cl–. The maximum concentrations of SO2–4 and Cl– are 3,170 and 3,830 mg/l, respectively. The areas with low TDS groundwater are in Jingbian and Zhidan counties. However, nitrogen pollution caused by human and agriculture activities is a significant threat to the protection of fresh water in these counties.  相似文献   

16.
Ikaite is a rare form of carbonate – calciumcarbonate hexahydrate (CaCO3·6H2O) and isthe precursor to thinolites. Metastable 'ikaite'crystals, discovered in unconsolidated marinesediments in the King George Basin in the BransfieldStrait, Antarctica, are related to diageneticremineralization reactions of organic matter. StableC, O, and H-isotopes track the response of ikaitecrystals, during growth, to changing interstitialfluid conditions as a result of bacterial sulphatereduction and methanogenesis. Ikaites form inpreference over calcite or aragonite at the prevailingsurface sediment conditions of -1.6 °C and 200bar in the King George Basin.The calcareous tufa towers of the terrestrial,hypersaline Mono Lake of northern California areCaCO3-precipitates formed by the influx ofsubmerged springs of calcium-rich freshwaters enteringthe alkaline lake (CO2 = 0.5 m, pH =9.8). Under current climatic conditions the mineralcalcite precipitates, but during the colder Tiogaglacial period of Late Wisconsian age (12,000 to 9,000years BP), and possibly present day during the winterseason, the monoclinic calcium carbonate hexahydrate(ikaite) was the dominant phase formed. Thesepaleo-ikaites have since recrystallized to form thecalcitic pseudomorph 'thinolites'. They are foundelsewhere in recent and ancient sediments of polarregions, e.g., as 'glendonites'. The environmentaloccurrence of ikaites and their pseudomorphs deem themas potential paleoclimatic indicators of coldenvironments. The larger crystals are typicallyrestricted to colder, deeper organic-rich sediments orin moderately evaporitic basins. In these cases, theikaite formation and decomposition may be influencedby additives such as phosphate or amino acids.  相似文献   

17.
Fluid inclusions trapped in ancient evaporites can contain a community of halophilic prokaryotes and eukaryotes that inhabited the surface brines from which the minerals formed. Entombed in the fluid inclusions in evaporites, some of these halophilic microbes remain viable for at least tens of thousands of years and possibly for hundreds of millions of years, even under high salinity, low oxygen, high radiation, low nutrient concentration. This review presents the scientific history of discovery, isolation, and culture of ancient halophilic microbes in halite fluid inclusions. We elucidated the controversy associated with the ancient halophilic microbes between geologists and geomicrobiologists. Major concerns and future perspectives on halophiles research were proposed. We emphasized that lithofacies analysis and depositional environment determination on evaporites are prerequisites before any microbiological survey, and rigorous biological protocol must be obeyed at all retrieval procedures for ancient microorganisms. We suggested that future study related to ancient halophilic microbes should focus on other evaporites such as gypsum, glauberite, and trona, characterize and identify older halophiles; clarify metabolic mechanism for longevity of ancient microorganisms.  相似文献   

18.
A seismic refraction/wide-angle reflection experiment was undertaken in the Levant Basin, eastern Mediterranean. Two roughly east–west profiles extend from the continental shelf of Israel toward the Levant Basin. The northern profile crosses the Eratosthenes Seamount and the southern profile crosses several distinct magnetic anomalies. The marine operation used 16 ocean bottom seismometers deployed along the profiles with an air gun array and explosive charges as energy sources. The results of this study strongly suggest the existence of oceanic crust under portions of the Levant Basin and continental crust under the Eratosthenes Seamount. The seismic refraction data also indicate a large sedimentary sequence, 10–14 km thick, in the Levant Basin and below the Levant continental margin. Assuming the crust is of Cretaceous age, this gives a fairly high sedimentation rate. The sequence can be divided into several units. A prominent unit is the 4.2 km/s layer, which is probably composed of the Messinian evaporites. Overlying the evaporitic layer are layers composed of Plio–Pleistocene sediments, whose velocity is 2.0 km/s. The refraction profiles and gravity and magnetic models indicate that a transition from a two layer continental to a single-layer oceanic crust takes place along the Levant margin. The transition in the structure along the southern profile is located beyond the continental margin and it is quite gradual. The northern profile, north of the Carmel structure, presents a different structure. The continental crust is much thinner there and the transition in the crustal structure is more rapid. The crustal thinning begins under western Galilee and terminates at the continental slope. The results of the present study indicate that the Levant Basin is composed of distinct crustal units and that the Levant continental margin is divided into at least two provinces of different crustal structure.  相似文献   

19.
The chemical and isotopic characteristics (oxygen, hydrogen, and strontium) of spring waters and isotopic compositions of helium (He) and neon (Ne) in gases escaping from spring waters in the Lanping–Simao Basin are studied. A total of twenty-one spring water samples (twelve hot springs, four cold springs, and five saline springs) and eleven gas samples were collected from the study area, including one spring and one gas sample from northern Laos. It is found that saline spring waters in the study area are of chloride type, cold spring waters are of carbonate type or sulfate type, and hot spring waters are of various types. High total dissolved solids levels in saline springs are significantly related to Upper Cretaceous–Paleocene salt-bearing strata. On the basis of hydrochemical geothermometry, the reservoir temperatures (Tr) for hot springs, cold springs, and saline springs are 65.5–144.1, 37.8–64.4, and 65.1–109.0 °C, respectively, and the circulation depths of saline springs are much larger than those of hot and cold springs. The oxygen and hydrogen isotopic compositions of springs in the Lanping–Simao Basin and northern Laos are primarily controlled by meteoric waters with obvious latitude and altitude effects, and are also influenced by δ18O exchange to some extent. Most Sr2+ in spring waters of the study area is derived from varied sources (carbonate, evaporite, and silicate mineral dissolution), and the Sr isotopic compositions are greatly influenced by volcanic rocks. Wide distribution of crust-derived He in the Lanping–Simao Basin and northern Laos reveal that faults in these areas may not descend to the upper mantle. It is concluded that water circulation in the study area may be limited above the upper mantle, while saline springs may originate from the Upper Cretaceous–Paleocene evaporites. Hydrochemical characteristics demonstrate affinities among the Lanping–Simao Basin, northern Laos, and Yanjing, eastern Tibet, while disaffinities are observed between these areas and Tengchong on the basis of the hydrochemical characteristics and noble gas isotopic compositions.  相似文献   

20.
Hydrochemistry of groundwater in Chithar Basin, Tamil Nadu, India was used to assess the quality of groundwater for determining its suitability for drinking and agricultural purposes. Physical and chemical parameters of groundwater such as electrical conductivity, pH, total dissolved solids (TDS), Na+, K+, Ca2+, Mg2+, Cl–, HCO3–, CO32–, SO42–, NO–3, F–, B– and SiO2 were determined. Concentrations of the chemical constituents in groundwater vary spatially and temporarily. Interpretation of analytical data shows that mixed Ca–Mg–Cl, Ca–Cl and Na–Cl are the dominant hydrochemical facies in the study area. Alkali earths (Ca2+, Mg2+) and strong acids (Cl–, SO42–) are slightly dominating over alkalis (Na+, K+) and weak acids (HCO3–, CO32–). The abundance of the major ions is as follows: Na+ Ca2+ Mg2+ > K+ = Cl– > HCO3–> SO42– > NO3– > CO32– . Groundwater in the area is generally hard, fresh to brackish, high to very high saline and low alkaline in nature. High total hardness and TDS in a few places identify the unsuitability of groundwater for drinking and irrigation. Such areas require special care to provide adequate drainage and introduce alternative salt tolerance cropping. Fluoride and boron are within the permissible limits for human consumption and crops as per the international standards.  相似文献   

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