Shallow Meteoric Water Research Articles

Controls of groundwater mineralization assessment in a mining catchment in the Upper West Region, Ghana: Insights from hydrochemistry, pollution indices of groundwater, and multivariate statistics

Natural and anthropogenic activities have proven to be the main sources of contaminants in groundwater. Hence, the need for continuous evaluation of the controlling factors of groundwater mineralization for monitoring purposes. The study assessed the controls of the groundwater mineralization in the Julie gold belt of the Upper West Region of Ghana using hydrochemistry, pollution index of groundwater (PIG), percentage of pollution index (PPI), factor analysis, and a multivariate linear regression model. TDS ​> ​HCO3− ​> ​NO3− ​> ​Ca2+ ​> ​Mg2+ ​> ​Na+ ​> ​Cl− ​> ​SO42− ​> ​K+ ​> ​CO32− ​> ​F− are the trends in the abundance of the hydrochemical parameters and are generally within WHO acceptable limits, with the exception of F− and NO3− contents in 5 and 32 communities, respectively. Waters containing Mg2+, Na+, HCO3−, and SO42− evolved into Mg–HCO3–Na–SO4. The PIG indicated pollution levels of 73.3% and 26.7% from mineral dissolution and agricultural activities, respectively, from the PPI values. From the indices, shallow meteoric water (r2 ​> ​1 values), factor analysis, and regression model approaches, anthropogenic activities, and mineral dissolution are the main controlling factors for the groundwater chemical composition in the area.

The formation mechanism of the Cona Woka rift in Eastern Himalaya and its influence on the Tethyan Himalayan polymetallic deposits revealed by magnetotelluric imaging

Located in the eastern Himalaya and surrounded by Yalaxiangbo dome, the Cona Woka rift may provide valuable information for the extensional mechanism of crust and distribution of the Tethyan Himalayan polymetallic deposits. Here, for the first time we obtain the three-dimensional electrical structure reaching a depth of approximately 45 km across the Cona Woka rift. Underneath the Cona Woka rift, the electrical model reveals the intersection between the deep electrically conductive body (effective conductivity value of 0.29 s/m, 10–45 km depth) and the shallow conductive layer (conductivity value of 0.3–1 s/m, <10 km depth). We propose that the tearing of Indian slab should have contributed to the partial melting of the crust. The upper and middle crust has a melt fraction of approximately 17–20 vol%, which may deform locally to form the Cona Woka rift. The Yalaxiangbo dome is also influenced by the local deformation of the crust. Moreover, the local deformation may drive the upward migration of the fluids along the rift zone to mix with the shallow meteoric water, especially in the intersection of the Cona Woka rift and the east-west trending faults, affecting the distribution of Tethyan Himalayan polymetallic deposits.

Assessing the geochemical processes controlling groundwater quality and their possible effect on human health in Patna, Bihar.

This research was conducted in the urban area of Patna region, the capital and largest city of Bihar, which is part of the Indo-Gangetic alluvium plain. This study aims to identify the sources and processes controlling groundwater's hydrochemical evolution in the Patna region's urban area. In this research, we evaluated the interplay between several measures of groundwater quality, the various possible causes of groundwater pollution, and the resulting health risks. Twenty groundwater samples were taken from various locations and examined to determine the water quality. The average EC of the groundwater in the investigated area was 728 ± 331.84 µS/cm, with a range of around 300-1700 µS/cm. Positive loadings were seen for total dissolved solids (TDS), electrical conductivity (EC), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), chloride (Cl-), and sulphate (SO42-) in principal component analysis (PCA), demonstrating that these variables accounted for 61.78% of the total variance. In the groundwater samples, the following main cations are the most prevalent such as Na+ > Ca2+ > Mg2+ > K+, while the dominant anions are HCO3- > Cl- > SO42-. The elevated HCO3- and Na+ ions indicate that carbonate mineral dissolution might affect the study area. The result demonstrated that 90% of samples fall into the Ca-Na-HCO3 type, remaining in the mixing zone. The presence of the NaHCO3 kind of water is suggestive of shallow meteoric water, which may have originated from the river Ganga that is located nearby. The results show that a multivariate statistical analysis and graphical plots successfully identify the parameters controlling groundwater quality. In accordance with guidelines for safe drinking water, the electrical conductivity and potassium ion concentrations in the groundwater samples are 5% higher than acceptable levels. People who take large amounts of salt replacements report feeling tight in the chest, vomiting, having diarrhoea, developing hyperkalaemia, having trouble breathing, and even experiencing heart failure.

The origin of methane in serpentinite-hosted hyperalkaline hot spring at Hakuba Happo, Japan: Radiocarbon, methane isotopologue and noble gas isotope approaches

Methane (CH4) associated with marine and terrestrial sites of serpentinization has been proposed to be abiotic in origin. However, the source of carbon and the depth and temperature of CH4 synthesis often remain inconclusive. We measured the radiocarbon (14C), bulk stable isotope ratios (δ13C and δD) and isotopologue abundance (Δ13CH3D) of CH4, and noble gas isotope composition of gas samples from two hyperalkaline geothermal wells (Happo #1 and Happo #3) at Hakuba Happo, Japan, to constrain the source of carbon and the CH4 generation processes. The CH4 samples from both sites were nearly 14C-free, whereas the carbonate precipitates inside the Happo #1 well contained 14C corresponding to 51 to 62 percent modern carbon, indicating that the majority of CH4 was not generated from the reduction of dissolved carbonate in the hot spring water. CH4 samples from Happo #1 and Happo #3 yielded Δ13CH3D-based apparent temperatures of 206−40+52°C and 323−85+143°C, respectively, which are much higher than the measured well water temperatures (∼50°C). Therefore, 14C and clumped isotopologue temperatures suggest that Hakuba Happo CH4 was generated below the depth where the shallow meteoric water circulated. The 3He/4He ratios were 4.10 and 4.47 Ratm for Happo #1 and Happo #3, respectively. The 3He/4He and 4He/20Ne ratios revealed that approximately 50% of He was of mantle origin, suggesting that the Hakuba Happo hot spring received volatiles, including CO2, from the mantle. However, the observed δ13CCH4 values (approximately −35‰) were significantly lower than those of typical mantle-derived carbon (–5‰), implying that mantle-derived CO2 is not the major carbon source for CH4 formation. High CH4 concentrations in the Hakuba Happo fluids, compared to those in hot springs in the area not associated with serpentinization, suggest that CH4 was generated from 13C-depleted fossil carbon sources and serpentinization-derived H2 at high temperatures (>200°C), and subsequently entrained into the cooler circulating meteoric water system.

Geochemical Properties of Heavy Oil in Central Sumatra Basin

Heavyoilcommonly occurs due to biodegradation, whichmade the lighter fractiondisappears and then leaves the heavier fraction. Heavy oil is characterized by asphaltic, solid, and viscous because it contains asphalthene. Chemically, heavy oils contain fewer hydrogen atoms than light oils. Bulk properties ofheavy oil in addition to having a specific gravity of less than 25° API gravity, high viscosity, and often contain (concentration) of heavy metals (vanadium, nickel) which is higher than light oil (normal oil). Geochemical analysis based on the gas chromatography (GC) chromatogram of heavy oil in the Central Sumatra Basin shows a different pattern. The chromatogram pattern eliminates the light molecular fractions of the compounds in biodegraded oil and tar sand/bitumen. According to their geochemical properties, there are 4 (four) types of heavy oil in the Central Sumatra Basin namely: Type l come from shallow reservoir, water wash, and full biodegradation/all alkane depleted); Type 2 come from shallow reservoir, meteoric water, and light biodegradation, only low molecular weight alkane depleted); Type 3 come from deep reservoir, vertical gravity segregation, decreased weight fraction, can be caused by oil conditions in thick reservoirs, covered by impermeable lithology and usually located on the edge of the field (flank). Type 4 which contains medium-heavy oil (27°API) and is difficult to produce.

Thermal springs and active fault network of the central Colca River basin, Western Cordillera, Peru

Thermal waters and vapor discharges (hot springs, geysers, solfataras, and fumaroles) are common phenomena in volcanic regions at active plate boundaries, and the Central Andes are no exception. The Colca River basin in S Peru is a highly diversified and complex thermal region with unresolved questions on the origin of thermal fluids, reservoir temperature, and connections with tectonic and/or volcanic activity. To answer these, we used hydrogeochemical analysis of 35 water samples from springs and geysers, together with isotopic (δ18O and δD) analysis, chemical and mineral studies of precipitates collected in the field around these outflows, and field observations. We aimed (1) to recognize the geochemistry of thermal waters and precipitates in the central part of the Colca River basin, (2) to identify fluid sources and their origin, (3) to estimate the temperature of a potential geothermal reservoir, and (4) to discuss the regional active tectonic and volcanic framework of this geothermal region and mutual relationships.Our results corroborate a heterogeneous and complex geothermal system in the central part of the Colca River basin, with contrasting hydrogeochemical and physical properties, variable isotope composition, different reservoir temperatures, and associated precipitates around thermal springs. Processes controlling water chemistry are closely related to the Ampato-Sabancaya magmatic chamber's activity and tectonic structures that allow complex interactions of meteoric waters with magmatic fluids and gases. With a considerable gradient of pressure owing to local relief and deep incision in the Colca Canyon, these processes led to the differentiation of the thermal waters into three main groups. (1) Chloride-rich, mainly sodium chloride, thermal waters are of meteoric origin but mature within the geothermal reservoir possibly fed by magma degassing. These waters' chemical and isotopic composition results from water-rock interaction and mixing with magmatic waters within the reservoir. These waters discharge at the bottom of the Colca Canyon and Valley, presenting a broad hydrogeochemical spectrum and highly variable mineral phases precipitating at the outflows. The reservoir temperature estimated for these waters ranges from 180 to 200 °C. The group of hottest springs and geysers at the bottom of the Colca Canyon waters are fully equilibrated, with the reservoir temperature ~ 240 °C. (2) Sulfate-rich waters are shallow meteoric waters heated by ascending gases that form an independent group referring to the local water circulation, often controlled by tectonic barriers. (3) Bicarbonate-rich waters are the intermediate meteoric waters, divided into two hydrochemical groups: waters partially equilibrated with reservoir rocks and more similar to chloride-rich waters or additionally enriched with SO4 and more similar to sulfate-rich waters.Studied thermal springs show a clear spatial correlation with active and seismogenic crustal W- to NW-tracing normal and strike-slip faults. These act as barriers to infiltrating meteoric waters, provide pathways to hydrothermal solutions and gases assisting in meteoric water heating, and yield passages for pressured by lithostatic load and heated waters to ascend to the surface.

Gas Leakage From Shallow Ponding Magma and Trapdoor Faulting at Sierra Negra Volcano (Isabela Island, Galápagos)

AbstractWe report on new volcanic gas composition results acquired in October 2017 at Minas de Azufre, a persistent fumarolic field topping the resurgent Sierra Negra caldera, in the Galápagos archipelago. Our results indicate that the Minas de Azufre fumaroles are moderately hydrous (52–64 mol.% H2O) and rich in CO2 (35–46 mol.%), with total sulfur (ST) being 21–35 times less abundant than CO2. SO2, the most abundant S species, is released at an average rate of 19 ± 9 tons/day. Using a volatile saturation model that provides the composition of magmatic gases at equilibrium with western Galápagos basaltic melt (48 wt. % SiO2) in the 400–0.1 MPa pressure range, we infer that Minas de Azufre fumarolic emissions consist of a mixture of (a) magma‐derived gases coexisting with a melt at ∼50–60 MPa and (b) shallow meteoric water. We thus propose that the fumaroles are supplied by outgassing of magma stored in a ∼2 km deep sill‐like reservoir underneath the caldera floor, and that the trapdoor fault system at the western margin of the resurgent caldera block acts as a preferential pathway for magmatic gas ascent and surface discharge. Our results thus suggest that, in contrast to the majority of the volcano‐hosted hydrothermal systems worldwide, Minas de Azufre releases a relatively pristine magmatic gas.

Tracking fluid mixing in epithermal deposits – Insights from in-situ δ18O and trace element composition of hydrothermal quartz from the giant Cerro de Pasco polymetallic deposit, Peru

Ore precipitation in mineral deposits formed in the upper parts of a porphyry system, at shallow crustal level (< 1.5 km), such as epithermal Au-Ag-(Cu)-(As) and polymetallic deposits is often triggered by fluid cooling and/or mixing between fluids from different sources. Commonly, in such deposits, two main fluid sources are identified a deeply sourced magmatic fluid and a shallow meteoric water stored in a surficial aquifer. Oxygen and hydrogen isotope compositions of gangue and alteration minerals using conventional bulk isotopic methods support the existence of mixing between these two fluid types. However, bulk isotope analysis provides only limited information on the exact mixing mechanisms and on the changing proportions of the involved fluids. Due to their high spatial resolution, SIMS in-situ oxygen isotope and LA-ICP-MS trace element analyses, in transects across growth zones of single crystals are adequate tools to trace the dynamics of this fluid mixing. In this study, in-situ SIMS oxygen isotope and LA-ICP-MS trace element analyses were performed on 10 selected quartz crystals from the giant Cerro de Pasco porphyry-related epithermal polymetallic deposit in central Peru. The results, combined with previous microthermometric and LA-ICP-MS fluid inclusion studies on the same or equivalent crystals, allow quantifying and documenting the mixing between different types of fluids that formed the large Cerro de Pasco epithermal polymetallic deposit. The δ18Oquartz values range between 4‰ and 20‰ and display variations up to 11.5‰ inside single crystals that cannot be only, nor mainly ascribed to fluid temperature changes. Rather, these variations record variable mixing proportions of a rising moderate-salinity magmatic fluid with a δ18OH2O around 10‰ and a low-salinity fluid with a δ18OH2O between 0 and 4‰, the latter stored below the paleo-water table. Each analyzed quartz crystals also display important variation of their trace element content, with Al (43 to 2098 ppm), Li (0.7 to 18 ppm), Ge (1.1 to 24ppm) and Ti (0.8 to 10 ppm). These variations do not systematically correlate with oxygen isotope compositions. This suggests that quartz trace element content is controlled by a complex interplay of fluid composition, temperature, pressure, and growth rate. Application of published Ti-in-quartz geothermometers on quartz grains from which the precipitation temperature is well constrained by fluid inclusion microthermometry, shows that it can lead to overestimation or underestimation of precipitation temperatures by more than 50 °C.The obtained δ18Oquartz patterns measured along profiles in the studied quartz crystals, and less clearly the in-situ trace element compositions, reveal abrupt changes and suggest that mixing between magmatic and surface-derived low-salinity fluids was not a continuous process. It rather took place through the influx of multiple short-lived pulses of magmatic fluid into the surface-derived low-salinity fluid surface aquifer.

Stable isotope and anthropogenic tracer signature of waters in an Andean geothermal system

In the present study, we combined stable isotopes and anthropogenic tracers to investigate the origin, residence times, and evolution of thermal waters in the Lonquimay-Tolhuaca Volcanic Complex (LTVC) of the southern Chilean Andes. A total of 20 water samples from springs discharging at a broad range of temperatures (8–96 °C) were collected and analyzed for major ion geochemistry, stable isotope ratios (δ2H, δ18O, δ13CTDIC), dissolved chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6). In addition, we compiled all available data on the isotopic composition of precipitation in the region to derive the local meteoric water line. Coupled with a Rayleigh-fractionation model of precipitation, we provide constraints on the elevation at which infiltration and recharge to the system is produced. δ13CTDIC values are consistent with the bulk of dissolved inorganic carbon being derived from the addition of soil CO2 to an atmospheric source, while magma degassing and boiling processes are evidenced in samples discharging directly on the flanks of volcanoes. The isotopic composition of thermal water, once heated at depth, is further modified by CO2 degassing and carbonate precipitation during ascent. All geothermal samples contain low but detectable concentrations of CFC-11, CFC-12, CFC-113, and SF6, suggesting the addition of only a small fraction (2–22%) of modern meteoric water. The discharge temperature of naturally outflowing springs in the LTVC correlates directly with the age distribution of the water samples. This difference in residence times is attributed to the distinct subsurface circulation pathways of each water type—i.e., the shallow, diffuse flow of cold groundwater vs. the deep, focused circulation of thermal water along fault zones. Conduit flow along high vertical permeability networks allows hydrothermal fluid to remain relatively unmixed with shallow meteoric water during ascent. Data from this study confirm that fault-fracture meshes with different orientations exert a first order control on the residence times, ascent, and mixing rates of thermal waters in this segment of the Andean Cordillera, thus modulating their chemical and isotopic signature. Additionally, our results show that the combined use of conventional hydrogeochemical and isotopic data with environmental tracers, including anthropogenic CFCs and SF6, is a powerful tool to better understand the dynamics of geothermal systems.

Structural control on shallow hydrogeochemical processes at Caviahue-Copahue Volcanic Complex (CCVC), Argentina

The Caviahue-Copahue Volcanic Complex (CCVC) hosts one of Argentina's most important geothermal systems. To provide new insights into origin, circulation, and residence time of fluids, the chemical and isotopic composition (3He/4He, δ2H-δ18O in H2O; δ13C-δ18O in CO2; 87Sr/86Sr) of thermal waters was measured together with the 3H and 14C activities. Water samples were collected from hot springs (LM, TC, LMM, CB and AF) representing the five major thermal zones of the CCVC and assumed to be steam-heated meteoric waters, and a well condensate (COP-2). The LMM, CB, and AF chemical composition and 87Sr/86Sr ratios show that water chemistry is acquired locally from exchange with volcanic rocks (Sr, SiO2, among others) and from steam (H2S). Two surface geothermal manifestations (LM and TC), along with the well condensate, COP-2, contain a higher contribution of deep-originating fluids, with 87Sr/86Sr indicating possible contribution from deep-seated granitoids or sediments from the underlying basement. Radiocarbon-based residence times indicate ages ranging between 13,540 and 17,520 yrs. BP, representing the minimum age for the geothermal reservoir waters. Tritium is mainly absent in hot spring waters except for LMM and CB where the activity is close to the detection limit. This indicates a minimum age older than 70 yrs. for the water circulating in the shallow circuit. This result suggests that shallow meteoric water have a more complex and/or deeper circuit, resulting in older residence times. Helium isotopes in the CCVC span a wide range, from a pure mantle-derived value, of 8.35Ra, to a more crustal radiogenic signature, of 4.6Ra. The spatial variation is explained by associating the geochemical data with the geological context, which includes the distribution of fault-fracture meshes and different sources of magmatic volatiles underlying the Copahue volcano. The first order control on helium isotope signatures observed in this study seems to be dominated by the degree of crustal assimilation of the magmatic sources, which is in turn controlled by the local arrays of faults.

Feature, genetic model and distribution of calcareous insulating layers in marine strata of western Pearl River Mouth basin in north of South China Sea

We have systematically investigated the feature, genetic model and distribution of calcareous insulating layers in marine strata of the I oil group in member 2 of Zhujiang formation (ZJ2I oil formation), western Pearl River Mouth basin (PRMB) in the north of the South China Sea by using data such as cores, thin sections, X-ray diffraction of whole-rock, and calcite cement carbon and oxygen isotopes. The lithology of the calcareous insulating layers in the study area is mainly composed of the terrigenous clastic bioclastic limestone and a small amount of fine-grained calcareous sandstone. On this basis, two genetic models of calcareous insulating layers are established, including the evaporation seawater genetic model and shallow burial meteoric water genetic model. The calcareous insulating layers of the evaporation seawater genetic model developed in the foreshore subfacies, mainly at the top of the 1–1 strata and 1–3 strata. The calcareous insulating layers of the shallow burial meteoric water genetic model developed in the backshore subfacies, primarily in the 1–2 strata.

Appraisal of Groundwater Quality with Human Health Risk Assessment in Parts of Indo-Gangetic Alluvial Plain, North India.

Groundwater contamination in the Indo-Gangetic alluvial plain has reportedly been affected by various factors, such as mineral dissolution, overexploitation, precipitation, and ion exchange. This study was designed to interpret the hydrochemical fluctuations in the groundwater sources of a rural area in Raebareli district. Groundwater is slightly alkaline and affected by the issues of fluoride, salinity, hardness, and nitrate. The Pollution Index of Groundwater significantly categorize 57% and 79% of the samples under the "insignificant pollution" category during pre-monsoon and post-monsoon periods. The Health risk assessment indicated the high susceptibility of children toward health risks. It also indicated that fluoride had greater impact than nitrate in the study area. The multivariate statistical analysis indicates that anthropogenic activities, such as agricultural practices, including excessive fertilizer application and improper domestic and cattle waste management, are probable causes of groundwater contamination through NO3-, Cl-, Na+, and K+. Furthermore, the base exchange index classified 71.43% samples in pre-monsoon and 78.57% in post-monsoon as Na-HCO3 type. The meteoric genesis index suggested that 78.57% and 85.71% of the samples belong to shallow meteoric water percolation type during pre- and post-monsoon periods, respectively. The Piper plots revealed that HCO3-Ca·Mg and SO4·Cl-Na + K type are the prominent facies in the area, with dominance of alkalis and weak acids. According to Gibbs plot, majority of the samples fall under "rock dominance" suggesting that "rock-water" interaction was the dominant natural process controlling the groundwater chemistry.

Multistage genesis of the late Cretaceous manganese karst-hosted Tasdremt deposit (High Atlas, Morocco)

The eastern part of the Souss Basin (Morocco) contains several Mn deposits in the Tasdremt district. Three Mn orebodies occur within the Cenomanian-Turonian dolostones and the Senonian (Coniacian to Maastrichtian) detrital series, the main orebody being located at the boundary between them. The Mn ores consist of coronadite group minerals, mostly coronadite and hollandite, in a karstified dolostone. New field observations, petrographic analyses, and geochemical data define the Tasdremt deposits as a karst-hosted accumulation (11–60 wt.% Mn), particularly enriched in Ba (1.5–8.2 wt.%) and Pb (1.0–5.0 wt.%) with poor contaminations in Al, Fe, and P. This study shows that the ore-forming process is similar to that occurring in the Imini C3 level, located ~ 100 km to the north-east. Such similarities with the high-grade pyrolusite-bearing ore suggest that the Tasdremt deposit is a lateral equivalent of the Imini deposits. However, the scarcity of pyrolusite in Tasdremt results in lower Mn grades, the Tasdremt ores being considered an aborted/incomplete system in comparison with the Imini deposits. 40Ar/39Ar geochronology of K-bearing Mn oxides yields late Cretaceous ages, defining three phases at ~ 91.5 Ma, ~ 77.5–82 Ma, and ~ 65–67 Ma. Although the source of metals remains hypothetical, mineralizing fluids were carried by O2-free groundwater that mixed with O2-rich shallow meteoric waters at the Tasdremt depositional site. The dissolution of the host dolostones and the karst environment have provided suitable conditions for the precipitation of Mn oxides, causing the coeval increase of pH and Eh, respectively. The Early Atlasic deformation during the Late Cretaceous is associated with mineralization events and was responsible for creation of low stand reliefs from Tasdremt to Imini. This period enabled karstification and mineralization. Connecting the Tasdremt deposits to other African Mn deposits is difficult since the latter consist of laterite resting above Paleoproterozoic Mn protores, and consequently formed under different conditions from karst-hosted deposits. It is likely that other Mn occurrences formed along the Atlas belt in similar settings.

Hydrogeochemical Assessment of Groundwater for Drinking and Agricultural Use: A Case Study of Rural Areas of Alwar, Rajasthan.

Groundwater contributes substantially to the development of arid and semi-arid regions around the globe. The present study integrates groundwater quality and its suitability for drinking and irrigation around Alwar city of Rajasthan state, where agriculture is the major land use. The application for drinking was assessed by comparing the observed value with prescribed standards of WHO. Groundwater was found suitable for drinking at most of the locations. The suitability of groundwater for irrigation was determined by calculating ion-based ratios and comparing them against the suggested ratios and indices for agricultural quality. Suitability for irrigation was assessed against electrical conductivity (EC), percentage sodium (%Na), residual Na2CO3 (RSC), per cent soluble sodium (SSP), sodium adsorption ratio (SAR), Mg hazard and permeability index (PI) etc., and the quality was compromised for EC, %Na and Mg Hz. Since the soil was sandy, the groundwater was found suitable for irrigation over long-term use, with the only problem of magnesium hazard. Based on the different ratios of anions and cations, silicate weathering was observed to be regulating groundwater chemistry, and the groundwater belonged to mixed CaMgCl and CaHCO3- type based on Piper's classification and relative abundance of ions. Further, meteoric genesis classification showed that the groundwater in the study region had direct base exchange and shallow meteoric water percolation. Presence of kaolinite and quartz minerals in soil confirmed that silicate weathering is the major process controlling groundwater chemistry.

Geochemistry of gas and water discharge from the magmatic-hydrothermal system of Guallatiri volcano, northern Chile

This work presents the first chemical and isotopic (δ13C-CO2, δ13C-CH4, 3He, 4He, 20Ne, 40Ar, 36Ar, δ18O, and δD) data for fluid discharges from Guallatiri volcano, a remote and massive stratovolcano, which is considered as the second most active volcano of the Central Volcanic Zone (CVZ) in northern Chile. Fumarolic gases had outlet temperatures of between 80.2 and 265 °C, and showed a significant magmatic fluid contribution marked by the occurrence of SO2, HCl, and HF that are partially scrubbed by a hydrothermal aquifer. The helium isotope ratios (< 3.2) were relatively low compared to those of other active volcanoes in CVZ, possibly due to contamination of the magmatic source by 4He-rich crust and/or crustal fluid addition to the hydrothermal reservoir. Geothermometry in the H2O-CO2-CO-H2-CH4 system suggests equilibrium temperatures of up to 320 °C attained in a vapor phase at redox conditions intermediate between those typical of hydrothermal and magmatic environments. Thermal springs located 12 km northwest of the volcano’s summit had outlet temperatures of up to 50.1 °C, neutral to slightly basic pH, and a sodium bicarbonate composition, typical of distal fluid discharges in volcanic systems. Cold springs at the base of the volcanic edifice, showing a calcium sulfate composition, were likely produced by interaction of shallow meteoric water with CO2- and H2S-rich gases. A geochemical conceptual model was constructed to graphically represent these results, which can be used as an indication for future geochemical monitoring and volcanic hazard assessment.

Characterization of lithium cycling in the Salar De Olaroz, Central Andes, using a geochemical and isotopic approach

The Salar de Olaroz is one of the main Li operations in Argentina. In order to identify sources and to understand the dynamics of Li in this salt pan, chemical and isotopic analysis (δ7Li and 87Sr/86Sr) of brines, thermal and river waters, as well as ignimbrites and sediments that outcrop in the basin were performed. The Li concentrations in shallow brines (i.e., ∼0.6 m below surface) range from 260 to 890 mg L−1 (average = 841 mg L−1, n = 16), while in deep brines (i.e, 200–450 m b.s.) concentrations are higher (average = 993 mg L−1, n = 16) and range from 690 to 1490 approximately. δ7Li values range from +5.9 to +7.2 ‰ and from +8.1 to +10.2 ‰ in shallow and deep brines respectively, while δ7Li values of the regional rocks and sediments vary between -13.8 and +0.5‰. The 87Sr/86Sr values indicate that the chemical composition of brines in Olaroz is the result of mixing between solutes that are originated from bedrock weathering by shallow meteoric water and water that has a hydrothermal contribution. Due to evaporation, Li concentrations in shallow brines increase by two or three orders of magnitude when compared with the values determined in the main tributaries and in the discharge of thermal waters. This process does not produce measurable isotopic fractionation of Li, thus the isotopic signature of shallow brines and halite crystals in contact with these waters are similar. As brine density increases, water descends through layers of silt and as the brine ages at depth, the formation of secondary minerals enhance the preferential adsorption of 6Li onto clay minerals and Fe (hydr)oxides resulting in higher δ7Li values in deep brines. Nevertheless, Li concentrations remain nearly constant or slightly increase with depth, which suggests that the removal of this element from the water due to adsorption is offset by Li contributions derived from processes that do not produce any isotopic fractionation. Two processes may account for this in the study system: 1) the mixing with ancient Li-rich fluids trapped in the deeper evaporitic layers that preserved the isotopic signature of their contemporaneous brines; and 2) the release of loosely- bound Li from the exchangeable sites of smectites that compose the clastic fraction of the salt flat sediments as they acquire a more crystalline nature over time. Consequently, it is expected that sediments accumulated below the salt crust may provide an important additional reservoir of Li to the brine, but further experimental studies will be necessary to investigate the mechanisms that control the partition of Li between the aqueous and solid phases and its isotopic fractionation in extremely arid and saline environments.

Groundwater property and composition variability under long-term irrigated area of Wonji Plain, Ethiopia

Abstract Wonji Shoa Sugar Estate (WSSE), located in the flood plain of the Awash River (Ethiopia), has been under long-term (&gt;60 years) irrigation, industrial activities and agro-chemical usage. In this study, the hydrochemical properties of groundwater bodies available at WSSE have been characterized for quality compositions. Water samples were collected from groundwater monitoring piezometers distributed in the sugarcane plantation and then analysed for physico-chemical quality parameters (pH, EC, major cations and anions) following standard procedures. Other chemical indices (e.g., total dissolved solids (TDS), total hardness (TH), magnesium absorption ratio (MAR), base exchange (r1), meteoric genesis (r2)) were derived from the measured water quality parameters. The compositional variability and groundwater classification has been presented using the Box and Piper plots. The potential sources of minerals were suggested for each of the considered water sources based on their quality characteristics. Both trilinear Piper plot and meteoric genesis index revealed that groundwater of the area is shallow meteoric water percolation type with a changing of hydrochemical facies and mixing trend. Groundwater of the area, is group 1 (Ca-Mg-HCO3) type, with no dominant cations and HCO3 are the dominant anions. Overall, the study result elucidates that the chemical composition of GW of the area showed spatial variability depending upon the variations in hydrochemical inputs from natural processes and/or anthropogenic activities within the region. The local anthropogenic processes could be discharges from sugar factory, domestic sewage and agricultural activities.

Hydrogeochemical assessment of groundwater quality in parts of the Hindon River basin, Ghaziabad, India: implications for domestic and irrigation purposes

The present study confers the hydrogeochemical characteristics and groundwater quality assessment for drinking and irrigational purposes. Most of the population depends on groundwater for their daily needs especially for drinking, irrigation, and industrial purposes. For this reason, total seventy-two groundwater samples have been collected from different parts of Ghaziabad district for the pre- and post-monsoon in the year 2016 and analyzed for water quality parameters such as pH, electrical conductivity, total dissolved solids, total hardness, bicarbonate (HCO3−), carbonate (CO32−), chloride (Cl−), sulphate (SO42−), fluoride (F−), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), and potassium (K+). Results show that the water samples of the study area are generally hard to very hard and slightly acidic to alkaline in nature. Results also suggest that chloride (Cl−) ions dominate over SO42− ions, whereas HCO3− ions dominate over Cl− and SO42− in the studied groundwater samples during the pre- and post-monsoon periods. The Piper trilinear diagram of groundwater shows that dominant facies is Na+–HCO3− type in both the monsoon periods. The nitrate concentration in the groundwater samples varies from 22 to 293 mg/l in the pre-monsoon, of which 83% of groundwater samples are not recommended for drinking with reference to the concentration of nitrate. Base-exchange indices classified 89% and 11% of the water sources as the Na-HCO3 type and Na-SO4 during the pre- and post-monsoon seasons, respectively. According to the meteoric genesis indices, 89% and 11% of the water sources as shallow meteoric water percolation and deep meteoric water percolation type during the pre- and post-monsoon periods, respectively. Furthermore, most of the groundwater samples are found mainly influenced by rock dominance according to Gibbs diagram plots.

Hydrochemical characteristics of groundwater and surface water for domestic and irrigation purposes in Vea catchment, Northern Ghana

The Vea catchment, mainly underlain by crystalline basement rocks, is located in Northern Ghana. Hydrogeochemical studies were carried out in this area with the objective of identifying the geochemical processes influencing water quality and suitability of surface and groundwater for agricultural and domestic uses. Sixty-one groundwater and four surface water samples were collected from boreholes, dams and rivers and analysed for Ca2+, Mg2+, Na+, K+, HCO3 −, Cl−, and SO4 2−, Fetot, PO4 3−, Mntot, NH4 +, NO3 −, NO2 −. In addition, pH, total dissolved solids, electrical conductivity, total hardness, turbidity, colour, salinity and dissolved oxygen were analysed. Chloro-alkaline indices 1 and 2, and characterization of weathering processes suggest that the chemistry of groundwater is dominated by the interaction between water and rocks. Cation exchange and silicate weathering are the dominant processes controlling the chemical composition of the groundwater in the area studied. Mineral saturation indices indicate the presence of at least three groups of groundwater in the Vea catchment with respect to residence time. The meteoric genesis index suggests that 86% of the water samples belong to the shallow meteoric water percolation type. The findings further suggest that the groundwater and surface water in the basin studied are mainly Ca–Mg–HCO3 water type, regardless of the geology. Compared to the water quality guidelines of WHO, the study results on sodium absorption ratio, sodium percentage, magnesium hazard, permeability index and residual sodium carbonate indicate that groundwater and surface water in the Vea catchment are generally suitable for drinking and irrigation purposes.

Hydrogeochemical assessment of Moradabad city, an important industrial town of Uttar Pradesh, India

An attempt has been made to understand the hydrochemistry of Moradabad city, a major industrial town of western Uttar Pradesh. For this purpose a total of 188 samples for both the seasons (pre- and post-monsoon of 2012 and 2013) were collected and analyzed for major cations (Na+, K+, Ca2+ and Mg2+) and anions (Cl−, HCO3 −, SO4 −, NO3 − and F−) and 14 samples collected in 2013 were analyzed for trace elements. The groundwater is slightly acidic to alkaline in nature and moderately hard to very hard. Elevated concentration of most of the major ions and trace elements is observed in the area. On the basis of Piper Trilinear plot groundwater has been identified as Na–Cl–SO4 type in pre-monsoon and Na–HCO3 type in post-monsoon season. Base-exchange indices along with meteoric genesis indices demonstrate that groundwater in all the four seasons belong to alkali bicarbonate type and are of shallow meteoric water percolation type. The concentration of the trace elements like (Al, Fe, Se and As) is higher than the permissible limits. Correlation of SiO2 with Cl and TDS was done to assess the processes responsible for altering the groundwater chemistry. Water quality index maps show that the groundwater in the north eastern and central parts of the study area is unsuitable for drinking purpose. A comparison of spatial distribution of EC and Cl with those of WQI depicts a strong correlation. The study, thus, suggests the poor groundwater quality of Moradabad city. Urban sprawl, population explosion, industrial expansion heavily affected the water quality of the study area.