scholarly journals Processes Governing Alkaline Groundwater Chemistry within a Fractured Rock (Ophiolitic Mélange) Aquifer Underlying a Seasonally Inhabited Headwater Area in the Aladağlar Range (Adana, Turkey)

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-21 ◽  
Author(s):  
Cüneyt Güler ◽  
Geoffrey D. Thyne ◽  
Hidayet Tağa ◽  
Ümit Yıldırım
Keyword(s):  
Fractured Rock ◽  
Groundwater Chemistry ◽  
Rock Interaction ◽  
Anthropogenic Inputs ◽  
Ophiolitic Mélange ◽  
Hydrochemical Data ◽  
Dug Wells ◽  
Geochemical Models ◽  
Interseasonal Variability ◽  
Alkaline Groundwater

The aim of this study was to investigate natural and anthropogenic processes governing the chemical composition of alkaline groundwater within a fractured rock (ophiolitic mélange) aquifer underlying a seasonally inhabited headwater area in the Aladağlar Range (Adana, Turkey). In this aquifer, spatiotemporal patterns of groundwater flow and chemistry were investigated during dry (October 2011) and wet (May 2012) seasons utilizing 25 shallow hand-dug wells. In addition, representative samples of snow, rock, and soil were collected and analyzed to constrain the PHREEQC inverse geochemical models used for simulating water-rock interaction (WRI) processes. Hydrochemistry of the aquifer shows a strong interseasonal variability where Mg–HCO3 and Mg–Ca–HCO3 water types are prevalent, reflecting the influence of ophiolitic and carbonate rocks on local groundwater chemistry. R-mode factor analysis of hydrochemical data hints at geochemical processes taking place in the groundwater system, that is, WRI involving Ca- and Si-bearing phases; WRI involving amorphous oxyhydroxides and clay minerals; WRI involving Mg-bearing phases; and atmospheric/anthropogenic inputs. Results from the PHREEQC modeling suggested that hydrogeochemical evolution is governed by weathering of primary minerals (calcite, chrysotile, forsterite, and chromite), precipitation of secondary minerals (dolomite, quartz, clinochlore, and Fe/Cr oxides), atmospheric/anthropogenic inputs (halite), and seasonal dilution from recharge.

scholarly journals COMPUTER CODES OF GEOCHEMICAL MODELING USED TO WATER-ROCK INTERACTION SIMPLE AND COMPLEX SYSTEMS

2019 ◽  
Vol 16 (32) ◽  
pp. 108-118
Author(s):  
Marcos Antônio KLUNK ◽  
Sudipta DASGUPTA ◽  
Mohuli DAS ◽  
Paulo Roberto WANDER
Keyword(s):  
Complex Systems ◽  
Geochemical Modeling ◽  
Chemical Properties ◽  
Coupled Transport ◽  
Burial History ◽  
Batch Mode ◽  
Data Set ◽  
Rock Interaction ◽  
Geochemical Reactions ◽  
Geochemical Models

The numerical modeling of transport and reaction was used for the understanding of the evolution of the diagenetic processes and their importance in the characterization and prediction of oil reservoir quality. Geochemical models are represented by numerical equations based on the physical-chemical properties of minerals. There are many software’s available in the market to simulate systems and geochemical reactions. The codes are divided into three distinct categories: coupled transport of reaction, modeling speciation, and batch mode according to the numerical method. Simple systems have clear connections between inputs and outputs. Complex systems have multiple factors that provide a probability distribution of data inputs that interact in specific functions. The outputs produced as a result are therefore impossible to predict with complete accuracy. Several research groups tried to develop numerical codes for geochemical modeling. The critical factors for the use of these systems are (i) verification of the simulation results with empirical data set and (ii) sensitivity analysis of these results, for the construction of general models which provide a predictive character. This last factor is particularly important as it establishes the qualitative and quantitative impact of each parameter in the simulations. Thus, with a complete numerical model diagenetic, it is possible to perform various simulations modifying one or the other parameter to test the sensitivity in the construction of these different geological scenarios. This set includes mineral composition and texture, the composition of fluids, paragenetic sequence, and burial history. This work brings fundamental concepts related to this topic as well as an analysis of commercial software available.

scholarly journals HFSE‐REE Transfer Mechanisms During Metasomatism of a Late Miocene Peraluminous Granite Intruding a Carbonate Host (Campiglia Marittima, Tuscany)

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 682
Author(s):  
Paoli ◽  
Dini ◽  
Petrelli ◽  
Rocchi
Keyword(s):  
External Source ◽  
Magmatic Fluid ◽  
Chemical Components ◽  
Fluid Composition ◽  
Peraluminous Granite ◽  
Rock Interaction ◽  
Complete Replacement ◽  
Element Mobilization ◽  
Geochemical Models ◽  
Metasomatic Event

The different generations of calc‐silicate assemblages formed during sequential metasomatic events make the Campiglia Marittima magmatic–hydrothermal system a prominent case study to investigate the mobility of rare earth element (REE) and other trace elements. These mineralogical assemblages also provide information about the nature and source of metasomatizing fluids. Petrographic and geochemical investigations of granite, endoskarn, and exoskarn bodies provide evidence for the contribution of metasomatizing fluids from an external source. The granitic pluton underwent intense metasomatism during post‐magmatic fluid–rock interaction processes. The system was initially affected by a metasomatic event characterized by circulation of K‐rich and Ca(‐Mg)‐rich fluids. A potassic metasomatic event led to the complete replacement of magmatic biotite, plagioclase, and ilmenite, promoting major element mobilization and crystallization of K‐feldspar, phlogopite, chlorite, titanite, and rutile. The process resulted in significant gain of K, Rb, Ba, and Sr, accompanied by loss of Fe and Na, with metals such as Cu, Zn, Sn, W, and Tl showing significant mobility. Concurrently, the increasing fluid acidity, due to interaction with Ca‐rich fluids, resulted in a diffuse Ca‐metasomatism. During this stage, a wide variety of calc‐silicates formed (diopside, titanite, vesuvianite, garnet, and allanite), throughout the granite body, along granite joints, and at the carbonate–granite contact. In the following stage, Ca‐F‐rich fluids triggered the acidic metasomatism of accessory minerals and the mobilization of high-field-strength elements (HFSE) and REE. This stage is characterized by the exchange of major elements (Ti, Ca, Fe, Al) with HFSE and REE in the forming metasomatic minerals (i.e., titanite, vesuvianite) and the crystallization of HFSE‐REE minerals. Moreover, the observed textural disequilibrium of newly formed minerals (pseudomorphs, patchy zoning, dissolution/reprecipitation textures) suggests the evolution of metasomatizing fluids towards more acidic conditions at lower temperatures. In summary, the selective mobilization of chemical components was related to a shift in fluid composition, pH, and temperature. This study emphasizes the importance of relating field studies and petrographic observations to detailed mineral compositions, leading to the construction of litho‐geochemical models for element mobilization in crustal magmatic‐hydrothermal settings.

Modelling coupled processes in bentonite: recent results from the UK's contribution to the Äspö EBS Task Force

2012 ◽  
Vol 76 (8) ◽  
pp. 3033-3043 ◽  
Author(s):  
D. Holton ◽  
S. Baxter ◽  
A. R. Hoch
Keyword(s):  
Large Scale ◽  
Task Force ◽  
Fractured Rock ◽  
Coupled Processes ◽  
Spent Fuel ◽  
Rock Interaction ◽  
Waste Container ◽  
Buffer Material ◽  
The Uk

AbstractA range of potential concepts for the geological disposal of high level wastes and spent fuel are being studied and considered in the UK. These include concepts that use bentonite as a buffer material around the waste containers. The bentonite will be required to fulfil certain safety functions, the most important being (1) to protect the waste containers from detrimental thermal, hydraulic, mechanical and chemical processes; and (2) to retard the release of radionuclides from any waste container that fails. The bentonite should have a low permeability and a high sorption capacity.These safety functions could be challenged by certain features, events and processes (FEPs) that may occur during the evolution of the disposal system. A consideration of how these FEPs may affect the safety functions can be used to identify and to prioritize the important areas for research on bentonite. We identify these important areas (which include hydration of compacted bentonite, illitization and erosion of bentonite), and describe how they are being investigated in current international research on bentonite.The Äspö EBS Task Force is a collaborative international project designed to carry out research on bentonite. In 2011, the Nuclear Decommissioning Authority Radioactive Waste Management Directorate joined the EBS Task Force partly to benefit from its collective experience. The work of the EBS Task Force is split into two research subareas: (1) the THM subarea, which includes tasks to understand homogenization of bentonite as it resaturates, to investigate the hydraulic interaction between bentonite and fractured rock, and to model in situ experiments; and (2) the THC subarea, which includes tasks to investigate the issue of understanding transport through bentonite, and to model in situ experiments. In particular, the bentonite rock interaction experiment is a large-scale in situ experiment concerned with understanding groundwater exchange across bentonite rock interfaces, with the objective of establishing better understanding of bentonite wetting. In this paper, we describe our work to model the spatial and temporal resaturation of bentonite buffer in a fractured host rock.

scholarly journals GIS-Hydrogeochemical Model of the Yaoundé Fractured Rock Aquifer, Cameroon: Aquifer Setting, Seasonal Variations in Groundwater-Rock Interaction and Water Quality

2019 ◽  
Vol 07 (05) ◽  
pp. 232-263
Author(s):  
Richard Ayuk II Akoachere ◽  
Omabgemi Omoloju Yaya ◽  
Sonia Ebot Egbe ◽  
Thomson Areakpoh Eyong ◽  
Bihmimihney Nelly Nji ◽  
...  
Keyword(s):  
Water Quality ◽  
Seasonal Variations ◽  
Fractured Rock ◽  
Rock Interaction ◽  
Fractured Rock Aquifer

scholarly journals Hydrochemical peculiarities and groundwater quality assessment of the Birimian and Tarkwaian aquifer systems in Bosome Freho District and Bekwai Municipality of the Ashanti Region, Ghana

2021 ◽  
Vol 80 (24) ◽  
Author(s):  
Louis Boansi Okofo ◽  
Nana Akyerefi Anderson ◽  
Kenneth Bedu-Addo ◽  
Ekua Afrakoma Armoo
Keyword(s):  
Carbonic Acid ◽  
Anthropogenic Activities ◽  
Water Discharge ◽  
Groundwater Chemistry ◽  
Discharge Zone ◽  
Statistical Tool ◽  
Natural Factor ◽  
Rock Interaction ◽  
Ashanti Region ◽  
Aquifer Systems

AbstractThe Birimian and Tarkwaian aquifer systems are the main sources of water supply for the Bosome Freho District and Bekwai Municipality inhabitants in the Ashanti region of Ghana. A hydrogeochemical assessment was carried out to ascertain the natural baseline chemistry of the groundwaters and the factors influencing groundwater chemistry in these two areas. A multivariate statistical tool consisting of principal component analysis (PCA) and hierarchical cluster analysis (HCA) together with hydrochemical graphical plots was applied on 64 groundwater samples. The Q–mode HCA results were used to explain the changes in groundwater chemistry along the flow paths where three spatial groundwater zones and water types were delineated. The first type consists of Ca–Mg–HCO3 freshwater (recharge zone), which transitions into Ca–Na–HCO3 or Na–Ca–HCO3 mixed waters (intermediate zone) and finally evolves to the third type of Na–Ca–Mg–HCO3–Cl water (discharge zone). The study also reveals that the natural process influencing water chemistry is groundwater–rock interaction from carbonate and silicate weathering/dissolution, aided by carbonic acid from precipitation and releases concentration of Na+, Ca2+, Mg2+, and HCO3− into the groundwaters significantly. The chloro-alkaline indices also reveal cation exchange as the principal natural factor that controls groundwater chemistry in the area. Inverse geochemical modelling shows the dissolution of primary minerals such as dolomite, plagioclase, halite, gypsum, and precipitation of calcite and chlorite along the groundwater flow path. Anthropogenic activities have little influence on groundwater chemistry. The quality of groundwater in the Bosome Freho District and Bekwai Municipality is suitable for irrigational use and drinking water consumption. The results obtained so far will contribute to research paucity in the study area and serve as a guide for decision-makers for improved water resources management.

scholarly journals Acoustic Emission Multi-Parameter Analysis of Dry and Saturated Sandstone with Cracks under Uniaxial Compression

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1959 ◽  
Author(s):  
Hongru Li ◽  
Rongxi Shen ◽  
Dexing Li ◽  
Haishan Jia ◽  
Taixun Li ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Fractured Rock ◽  
Rock Fracture ◽  
Failure Process ◽  
Parameter Analysis ◽  
Small Scale ◽  
Rock Interaction ◽  
Secondary Cracks ◽  
Ae Signals

In order to study the mechanics and acoustic emission (AE) characteristics of fractured rock under water-rock interaction, dried and saturated sandstone samples with prefabricated double parallel cracks were prepared. Then, uniaxial compression experiments were performed to obtain their AE signals and crack propagation images. The results show that water reduces the strength and fracture toughness of fractured sandstone and enhances plasticity. After saturation, the samples start to crack earlier; the cracks grow slowly; the failure mode is transformed from shear failure along the prefabricated cracks to combined shear and tensile failure; more secondary cracks are produced. The saturated samples release less elastic energy and weaker AE signals in the whole failure process. However, their AE precursor information is more obvious and advanced, and their AE sources are more widely distributed. Compared with dry specimens, the AE frequencies of saturated specimens in the early stage of loading are distributed in a lower frequency domain. Besides, the saturated samples release less complex AE signals which are dominated by small-scale signals with weaker multi-fractal characteristics. After discussion and analysis, it is pointed out that this may be because water makes rock prone to inter-granular fracture rather than trans-granular fracture. The water lubrication also may reduce the amplitude of middle-frequency band signals produced by the friction on the fracture surface. Multi-fractal parameters can provide more abundant precursory information for rock fracture. This is of great significance to the stability of water-bearing fractured rock mass and its monitoring, and is conducive to the safe exploitation of deep energy.

scholarly journals Evolution of groundwater chemistry in coastal aquifers of the Northern Dvina basin (NW Russia)

2019 ◽  
Vol 98 ◽  
pp. 07016
Author(s):  
Alexander Malov
Keyword(s):  
Fresh Water ◽  
Coastal Aquifers ◽  
Salt Water ◽  
Groundwater Chemistry ◽  
Rock Interaction ◽  
Calcite Dissolution ◽  
Alkaline Earth Elements ◽  
Northern Dvina Basin ◽  
Hydrolysis Of ◽  
Water Rock Interaction

The specific objective of the study is to clarify the sources and characteristics of groundwater chemistry in coastal aquifers of the Northern Dvina basin. It has been established that the chemical composition of fresh water evolves in the direction (Ca-Mg-HCO3) - (Na-HCO3) - (Na-Cl). It is due to successive replacement of the process of calcite dissolution in the recharge area on the watershed i) by the process of hydrolysis of sodium aluminosilicates in the transit zone and ii) by the processes of mixing fresh water with salt water and brines, cation exchange of alkaline earth elements with alkaline elements and dissolution of gypsum near discharge areas at the seashore and in paleovalleys. In the brackish and salty waters the Na/Ca ratio is reduced to 1-4. This indicates that in the aquifers there are other sources of Ca, in addition to the dissolution of gypsum. The most probable process is the hydrolysis of Ca-aluminosilicates, which indicates a significant time of water-rock interaction. The “brackish1” water with TDS 5-6 g·L-1, is particularly distinguished by the degree of modification due to water-rock interaction.

Predictions of the wetting of bentonite emplaced in a crystalline rock based on generic site characterization data

2018 ◽  
Vol 482 (1) ◽  
pp. 285-300 ◽  
Author(s):  
S. Baxter ◽  
D. Holton ◽  
S. Williams ◽  
S. Thompson
Keyword(s):  
Host Rock ◽  
Fractured Rock ◽  
Crystalline Rock ◽  
Spent Fuel ◽  
Rock Interaction ◽  
Buffer Material ◽  
Fracture Transmissivity ◽  
Interaction Experiment

AbstractA geological disposal facility (GDF) is the widely accepted long-term solution for the management of higher-activity radioactive waste. It consists of an engineered facility constructed in a suitable host rock. The facility is designed to inhibit the release of radioactivity by using a system consisting of engineered and natural barriers. The engineered barriers include the wasteform, used to immobilize the waste, the waste disposal container and any buffer material used to protect the container. The natural barrier includes the rocks in which the facility is constructed. The careful design of this multi-barrier system enables the harmful effects of the radioactivity on humans and biota in the surface environment to be reduced to safe levels.Bentonite is an important buffer material used as a component of a multi-barrier disposal system. For example, compacted bentonite rings and blocks are used to protect the copper container, used for the disposal of spent fuel, in the KBS-3 disposal system. As the bentonite saturates, through contact with groundwater from the host rock, it swells and provides a low hydraulic conductivity barrier, enabling the container to be protected from deleterious processes, such as corrosion. The characteristic swelling behaviour of bentonite is due to the presence of significant quantities of sodium montmorillonite.Recently, there have been detailed in situ experiments designed to understand how bentonite performs under natural conditions. One such experiment is the Buffer–Rock Interaction Experiment (BRIE), performed at the Äspö Hard Rock Laboratory near Oskarshamn in the SE of Sweden. This experiment is designed to further understand the wetting of bentonite from the groundwater flow in a fractured granite host rock.In this paper, the observations from the BRIE are explained using an integrated model that is able to describe the saturation of bentonite emplaced in a heterogeneous fractured rock. It provides a framework to understand the key processes in both the rock and bentonite. The predictive capability of these models was investigated within the context of uncertainties in the data and the consequence for predictions of the wetting of emplaced bentonite. For example, to predict the wetting of emplaced bentonite requires an understanding of the distribution of fracture transmissivity intersecting the bentonite. A consequence of these findings is that the characterization of the fractured rock local to the bentonite is critical to understanding the subsequent wetting profiles. In particular, prediction of the time taken to achieve full saturation of bentonite using a simplified equivalent homogeneous description of the fractured host rock will tend to be too short.

scholarly journals Hydrochemical Characteristics and Water Quality of Groundwater in the Thick Loess Deposits

2021 ◽  
Author(s):  
Shujian Li ◽  
He Su ◽  
Zhi Li
Keyword(s):  
Water Quality ◽  
Hierarchical Cluster ◽  
Dry Season ◽  
Groundwater Chemistry ◽  
Mineral Dissolution ◽  
Multiple Sources ◽  
Flood Season ◽  
Anthropogenic Inputs ◽  
Groundwater Samples ◽  
Loess Deposits

Abstract Water quality and quantity should be paid more attentions for regions with arid climate and thick vadose zones since the limited groundwater cannot be replenished rapidly once polluted. This study focused on the Loess Plateau of China to investigate the geochemical mechanism affecting groundwater chemistry and to calculate contribution rates of multiple sources to groundwater solutes. We employed multiple methods (diagrams, bivariate analyses, hierarchical cluster analysis (HCA), sodium adsorption ratio (SAR), water quality index (WQI), correlation analysis, forward simulation) for the above purposes. We collected 64 groundwater samples in the thick loess deposits in June 2018 (flood season) and April 2019 (dry season). The average concentrations of cation were in the order of Ca2+ > Na+ > Mg2+ > K+ in the flood season, and Na+ > Ca2+ > Mg2+ > K+ in the dry season. The order of anions contents in the flood season and the dry season was HCO3− > SO42− > Cl− > NO3−. The major hydrochemical facies were Ca-HCO3 and Ca·Mg-HCO3 in the flood season, and Na·Ca-HCO3·SO4 and Na-HCO3 in the dry season, respectively. Most of the groundwater (95% in the flood season and 96% in the dry season) was suitable for drinking, and overall water quality (except samples F28 and D13) was acceptable for irrigation. Mineral dissolution and cation exchange were important natural processes affecting groundwater chemistry. A forward model showed that the contribution of atmospheric input, anthropogenic input, evaporite dissolution, silicate weathering and carbonate weathering to solutes in groundwater was 2.3 ± 1.5%, 5.0 ± 7.1%, 19.3 ± 21.4%, 42.8 ± 27.3% and 30.6 ± 27.1% in the flood season, and 9.1 ± 6.4%, 3.4 ± 5.2%, 20.3 ± 15.9, 56.6 ± 23.2%, and 10.7 ± 15.4% in the dry season, respectively. Although the overall contribution of anthropogenic inputs was minor, it was the dominant source of solutes for some groundwater samples. This study provides fundamental information for water management in arid areas.

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