Next Issue
Volume 11, August
Previous Issue
Volume 11, June

Geosciences, Volume 11, Issue 7 (July 2021) – 37 articles

Cover Story (view full-size image): Fissure ridges consist of elongated travertine masses with an apical fissure that follows the long axis of the body. Two symmetrical or asymmetrical walls made up of bedded travertine typically dip away from the central fissure. The internal part of the fissure is often cut by a network of sealed fractures, almost parallel to the long axis of the ridge, filled by banded Ca-carbonate. These veins are developed within the fault zone and represent conduits feeding geothermal fluids. Fissure ridge analysis, in terms of geometry, age (using U/Th, U/Pb, and 14C geochronology), and geochemical properties, provides information about the structural features and timing of the fault system, and on the fluid path from depth to surface. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
Article
Vertical Land Motion as a Driver of Coastline Changes on a Deltaic System in the Colombian Caribbean
Geosciences 2021, 11(7), 300; https://doi.org/10.3390/geosciences11070300 - 20 Jul 2021
Cited by 2 | Viewed by 1029
Abstract
To face and properly mitigate coastal changes at a local level, it is necessary to recognize and characterize the specific processes affecting a coastline. Some of these processes are local (e.g., sediment starvation), while others are regional (e.g., relative sea-level change) or global [...] Read more.
To face and properly mitigate coastal changes at a local level, it is necessary to recognize and characterize the specific processes affecting a coastline. Some of these processes are local (e.g., sediment starvation), while others are regional (e.g., relative sea-level change) or global (e.g., eustatic sea-level rise). Long tide gauge records help establish sea-level trends for a region that accounts for global (eustatic, steric) and regional (isostatic) sea-level changes. Local sea-level changes are also the product of vertical land motion (VLM), varying depending on tectonic, sedimentological, and anthropogenic factors. We investigate the role of coastal land subsidence in the present-day dynamics of an abandoned delta in the Colombian Caribbean. Satellite images and synthetic aperture radar acquisitions are used to assess decadal-scale coastline changes and subsidence rates for the period 2007–2021. We found that subsidence rates are highly variable alongshore. Local subsidence rates of up to −1.0 cm/yr correspond with an area of erosion rates of up to −15 m/yr, but coastal erosion also occurs in sectors where subsidence was not detected. The results highlight that local coastline changes are influenced by multiple, interacting drivers, including sand supply, coastline orientation and engineering structures, and that subsidence alone does not explain the high rates of coastal erosion along the study area. By the end of the century, ongoing coastal erosion rates of up to −25 m/yr, annual rates of subsidence of about −1 cm/yr, and current trends of global sea-level rise are expected to increase flooding levels and jeopardize the existence of the deltaic barrier island. Full article
(This article belongs to the Special Issue Shoreline Dynamics and Beach Erosion)
Show Figures

Figure 1

Article
Stream Sediment Datasets and Geophysical Anomalies: A Recipe for Porphyry Copper Systems Identification—The Eastern Papuan Peninsula Experience
Geosciences 2021, 11(7), 299; https://doi.org/10.3390/geosciences11070299 - 20 Jul 2021
Viewed by 1460
Abstract
Airborne magnetic and radiometric datasets have, over the past few years, become powerful tools in the identification of porphyry systems which may host economic porphyry copper–gold–molybdenum ore bodies. Magnetisation contrasts with the unaltered host rocks, coupled with the elevated radiometric signature, compared to [...] Read more.
Airborne magnetic and radiometric datasets have, over the past few years, become powerful tools in the identification of porphyry systems which may host economic porphyry copper–gold–molybdenum ore bodies. Magnetisation contrasts with the unaltered host rocks, coupled with the elevated radiometric signature, compared to the host rock, makes identification of large-scale porphyry copper systems possible. Integrating these two different datasets with stream sediment data and other geochemical exploration methods results in a higher degree of confidence. Stream sediment data were analysed to see the distribution of copper and gold elements throughout the study area, located within the Eastern Papuan Peninsula of Papua New Guinea. Airborne geophysics data over the same area were also processed for magnetic and radiometric responses. The processing of the magnetic data revealed several magnetic anomalies related to concealed intrusive rock units, with associated radiometric signatures. The distribution of gold and copper anomalism was correlated with the geology and geophysical signatures. Results indicate varying degrees of correlation, with some areas showing a strong correlation between gold/copper occurrence and geophysical signatures, compared to other areas. Some factors that we believe impact the level of correlation may include tectonic history, volcanic cover, and weathering patterns. We recommend caution when applying multi-data exploration for porphyry copper systems. Full article
(This article belongs to the Special Issue The Geoscience of the Pacific Islands Region: Theory and Practice)
Show Figures

Figure 1

Article
Nature of Ore Fluid at the Sopokomil Zn-Pb Deposit, North Sumatra, Indonesia: Implications for Metal Transport and Sulfide Deposition
Geosciences 2021, 11(7), 298; https://doi.org/10.3390/geosciences11070298 - 19 Jul 2021
Cited by 1 | Viewed by 1170
Abstract
Little is known about the nature of ore fluid at the Sopokomil shale-hosted massive sulfide Zn-Pb deposit (North Sumatra, Indonesia). We therefore investigated its ore-fluid salinities, temperatures, densities, redox state, and pH using fluid inclusion microthermometry, sphalerite composition, and thermodynamic modelling. The fluid [...] Read more.
Little is known about the nature of ore fluid at the Sopokomil shale-hosted massive sulfide Zn-Pb deposit (North Sumatra, Indonesia). We therefore investigated its ore-fluid salinities, temperatures, densities, redox state, and pH using fluid inclusion microthermometry, sphalerite composition, and thermodynamic modelling. The fluid salinities and temperatures were ≈6 wt.% NaCl equiv and ≈165 °C, respectively, corresponding to an ore fluid less dense than seawater (≈0.96 g/mL). Sphalerite contains ≈9.9 mole% FeS in the stratiform ore and ≈3.4 mole% FeS in the feeder ore, suggesting a reduced fluid, which must have been acidic to be fertile. Such redox state and acidity invoke fluid dilution as the sulfide depositional mechanism. The bulk of the sulfides were precipitated in the early stage of mixing, within T = 165–155 °C. Key ingredients of sphalerite and galena at Sopokomil include (1) Zn that was primarily transported as ZnCl+, (2) Pb that predominantly occurred as PbCl2(aq), and (3) S that was largely supplied by marine sediment porewater. This study highlights the significance of a dramatic shift in thermal and chemical equilibrium induced by fluid dilution in the making of the first significant shale-hosted massive sulfide Zn-Pb deposit in Indonesia. Full article
Show Figures

Figure 1

Article
Assessment of Seismic Bedrock in Deep Alluvial Plains. Case Studies from the Emilia-Romagna Plain
Geosciences 2021, 11(7), 297; https://doi.org/10.3390/geosciences11070297 - 18 Jul 2021
Cited by 2 | Viewed by 901
Abstract
The estimation of seismic shaking is essential for a realistic assessment of the local seismic hazard and the implementation of effective strategies for prevention and mitigation of the seismic risk. One of the most important aspects in the analysis of the site seismic [...] Read more.
The estimation of seismic shaking is essential for a realistic assessment of the local seismic hazard and the implementation of effective strategies for prevention and mitigation of the seismic risk. One of the most important aspects in the analysis of the site seismic assessment is the recognition of the seismic bedrock and its depth. Unfortunately, these data are not always easy to evaluate, especially in areas where the thickness of loose or poorly consolidated sediments is high. This article illustrates data and case studies from the Emilia-Romagna sector of the Po Plain, in order to provide examples and suggestions for the recognition of the seismic bedrock in alluvial and coastal areas characterised by significant thicknesses of unconsolidated sediments, using available data and not expensive geophysical surveys. The application of the proposed method indicates that the study area can be divided into four domains characterized by different depths of the seismic bedrock: the marginal or pede-Apennine belt, the high structural zones, the syncline/minor anticline zones, and the Po delta-coast zone. Full article
Show Figures

Figure 1

Review
Origin and Application of the Twinned Calcite Strain Gauge
Geosciences 2021, 11(7), 296; https://doi.org/10.3390/geosciences11070296 - 16 Jul 2021
Cited by 2 | Viewed by 939
Abstract
This paper is a personal account of the origin and development of the twinned-calcite strain gauge, its experimental verification, and its relationship to stress analysis. The method allows the calculation of the three-dimensional deviatoric strain tensor based on five or more twin sets. [...] Read more.
This paper is a personal account of the origin and development of the twinned-calcite strain gauge, its experimental verification, and its relationship to stress analysis. The method allows the calculation of the three-dimensional deviatoric strain tensor based on five or more twin sets. A minimum of about 25 twin sets should provide a reasonably accurate result for the magnitude and orientation of the strain tensor. The opposite-signed strain axis orientation is the most accurately located. Where one strain axis is appreciably different from the other two, that axis is generally within about 10° of the correct value. Experiments confirm a magnitude accuracy of 1% strain over the range of 1–12% axial shortening and that samples with more than 40% negative expected values imply multiple or rotational deformations. If two deformations are at a high angle to one another, the strain calculated from the positive and negative expected values separately provides a good estimate of both deformations. Most stress analysis techniques do not provide useful magnitudes, although most provide a good estimate of the principal strain axis directions. Stress analysis based on the number of twin sets per grain provides a better than order-of-magnitude approximation to the differential stress magnitude in a constant strain rate experiment. Full article
Show Figures

Figure 1

Article
Lithological and Geochemical Heterogeneity of the Organo-Mineral Matrix in Carbonate-Rich Shales
Geosciences 2021, 11(7), 295; https://doi.org/10.3390/geosciences11070295 - 16 Jul 2021
Cited by 2 | Viewed by 677
Abstract
The paper discusses the issues of interaction of the organic matter and the siliceous-carbonate mineral matrix in unconventional reservoirs of the Upper Devonian Domanik Formation of the Upper Kama Depression of the Volga-Ural Basin. The Domanik Formation is composed of organic-rich low-permeability rocks. [...] Read more.
The paper discusses the issues of interaction of the organic matter and the siliceous-carbonate mineral matrix in unconventional reservoirs of the Upper Devonian Domanik Formation of the Upper Kama Depression of the Volga-Ural Basin. The Domanik Formation is composed of organic-rich low-permeability rocks. Lithological and geochemical peculiarities of rocks were studied using light microscopy, X-ray diffraction analysis (XRD), scanning electronic microscopy (SEM), and evaporation method. Organic matter was examined by the Rock-Eval pyrolysis with quantitative and qualitative evaluation of generation potential and maturity degree. Integrated analysis of results of lithological and geochemical studies allowed identifying intervals in the studied section where organic matter can form a complex association with the siliceous-carbonate matrix. It was fixed experimentally that in some cases the mineral carbonate matrix and the organic matter form a one-whole high-molecular compound. The authors supposed that in the course of sedimentation, organic matter is immobilized into the structure of the mineral carbonate matrix. At the deposition and diagenesis stage, the carbonate matter interacts with acids of the organic matter and forms natural organo-mineral polymers. Special physicochemical properties of such organo-mineral associations shed new light onto the problems of producing from hard-to-develop nonconventional carbonate reservoirs and evaluating the associated risks. Full article
(This article belongs to the Special Issue Petrophysics and Geochemistry of Unconventional Reservoirs)
Show Figures

Figure 1

Article
Using Fission-Track Radiography Coupled with Scanning Electron Microscopy for Efficient Identification of Solid-Phase Uranium Mineralogy at a Former Uranium Pilot Mill (Grand Junction, Colorado)
Geosciences 2021, 11(7), 294; https://doi.org/10.3390/geosciences11070294 - 16 Jul 2021
Cited by 2 | Viewed by 918
Abstract
At a former uranium pilot mill in Grand Junction, Colorado, mine tailings and some subpile sediments were excavated to various depths to meet surface radiological standards, but residual solid-phase uranium below these excavation depths still occurs at concentrations above background. The combination of [...] Read more.
At a former uranium pilot mill in Grand Junction, Colorado, mine tailings and some subpile sediments were excavated to various depths to meet surface radiological standards, but residual solid-phase uranium below these excavation depths still occurs at concentrations above background. The combination of fission-track radiography and scanning electron microscope energy-dispersive X-ray spectroscopy (SEM-EDS) provides a uniquely efficient and quantitative way of determining mineralogic associations of uranium that can influence uranium mobility. After the creation of sample thin sections, a mica sheet is placed on those thin sections and irradiated in a nuclear research reactor. Decay of the irradiated uranium creates fission tracks that can be viewed with a microscope. The fission-track radiography images indicate thin section sample areas with elevated uranium that are focus areas for SEM-EDS work. EDS spectra provide quantitative elemental data that indicate the mineralogy of individual grains or grain coatings associated with the fission-track identification of elevated uranium. For the site in this study, the results indicated that uranium occurred (1) with coatings of aluminum–silicon (Al/Si) gel and gypsum, (2) dispersed in the unsaturated zone associated with evaporite-type salts, and (3) sorbed onto organic carbon. The Al/Si gel likely formed when low-pH waters were precipitated during calcite buffering, which in turn retained or precipitated trace amounts of Fe, As, U, V, Ca, and S. Understanding these mechanisms can help guide future laboratory and field-scale efforts in determining long-term uranium release rates to groundwater. Full article
(This article belongs to the Section Geochemistry)
Show Figures

Figure 1

Article
Photogrammetric Prediction of Rock Fracture Properties and Validation with Metric Shear Tests
Geosciences 2021, 11(7), 293; https://doi.org/10.3390/geosciences11070293 - 15 Jul 2021
Cited by 3 | Viewed by 736
Abstract
An accurate understanding of jointed rock mass behavior is important in many applications ranging from deep geological disposal of nuclear waste, to deep mining, and to urban geoengineering projects. The roughness of rock fractures and the matching of the fracture surfaces are the [...] Read more.
An accurate understanding of jointed rock mass behavior is important in many applications ranging from deep geological disposal of nuclear waste, to deep mining, and to urban geoengineering projects. The roughness of rock fractures and the matching of the fracture surfaces are the key contributors to the shear strength of rock fractures. In this research, push shear tests with three normal stress levels of 3.6, 6.0, and 8.5 kPa were conducted on two granite samples with artificially induced well-matching tensile fractures with sizes of 500 mm × 250 mm and 1000 mm × 500 mm. The large sample reached on average a −60% weaker peak shear stress than the medium-sized sample, and a strong negative scale effect was observed in the peak shear strength. The roughness of the surfaces was measured using a profilometer and photogrammetry. The scale-corrected profilometer-based method (joint roughness coefficient, JRC) underestimates the peak friction angle for the medium-sized slabs by −27% for the medium sample and −9% for the large sample. The photogrammetry-based (Z2) method produces an estimate with −7% (medium) and + 12% (large) errors. The photogrammetry-based Z2 is an objective method that consistently produces usable estimates for the JRC and peak friction angle. Full article
Show Figures

Figure 1

Article
Laboratory Investigation of Hydraulic Fracture Behavior of Unconventional Reservoir Rocks
Geosciences 2021, 11(7), 292; https://doi.org/10.3390/geosciences11070292 - 15 Jul 2021
Cited by 5 | Viewed by 845
Abstract
The heterogeneity of the rock fabric is a significant factor influencing the initiation and propagation of a hydraulic fracture (HF). This paper presents a laboratory study of HF created in six shale-like core samples provided by RITEK LLC collected from the same well, [...] Read more.
The heterogeneity of the rock fabric is a significant factor influencing the initiation and propagation of a hydraulic fracture (HF). This paper presents a laboratory study of HF created in six shale-like core samples provided by RITEK LLC collected from the same well, but at different depths. For each tested sample, we determined the breakdown pressure, the HF growth rate, and the expansion of the sample at the moment when the HF reaches the sample surface. Correlations were established between the HF parameters and the geomechanical characteristics of the studied samples, and deviations from the general relationships were explained by the influence of the rock matrix. The analysis of the moment tensor inversion of radiated acoustic emission (AE) signals allows us to separate AE signals with a dominant shear component from the signals with a significant tensile component. The direction of microcrack opening was determined, which is in good agreement with the results of the post-test X-ray CT analysis of the created HF. Thus, it has been shown that a combination of several independent laboratory techniques allows one to reliably determine the parameters that can be used for verification of hydraulic fracturing models. Full article
(This article belongs to the Special Issue Petrophysics and Geochemistry of Unconventional Reservoirs)
Show Figures

Figure 1

Review
Biopolymers as Green Binders for Soil Improvement in Geotechnical Applications: A Review
Geosciences 2021, 11(7), 291; https://doi.org/10.3390/geosciences11070291 - 15 Jul 2021
Cited by 8 | Viewed by 1618
Abstract
Soil improvement using biopolymers has attracted considerable attention in recent years, with the aim to reduce the harmful environmental effects of traditional materials, such as cement. This paper aims to provide a review on the environmental assessment of using biopolymers as binders in [...] Read more.
Soil improvement using biopolymers has attracted considerable attention in recent years, with the aim to reduce the harmful environmental effects of traditional materials, such as cement. This paper aims to provide a review on the environmental assessment of using biopolymers as binders in soil improvement, biopolymer-treated soil characteristics, as well as the most important factors affecting the behavior of the treated soil. In more detail, environmental benefits and concerns about the use of biopolymers in soil improvement as well as biopolymer–soil interaction are discussed. Various geotechnical properties are evaluated and compared, including the unconfined compressive strength, shear strength, erosion resistance, physical properties, and durability of biopolymer-treated soils. The influential factors and soil and environmental conditions affecting various geotechnical characteristics of biopolymer-treated soils are also discussed. These factors include biopolymer concentration in the biopolymer–soil mixture, moisture condition, temperature, and dehydration time. Potential opportunities for biopolymers in geotechnical engineering and the challenges are also presented. Full article
(This article belongs to the Special Issue Soil-Structure Interaction)
Show Figures

Figure 1

Article
The Hydrothermal Vent Field at the Eastern Edge of the Hellenic Volcanic Arc: The Avyssos Caldera (Nisyros)
Geosciences 2021, 11(7), 290; https://doi.org/10.3390/geosciences11070290 - 13 Jul 2021
Viewed by 1264
Abstract
Almost three-quarters of known volcanic activity on Earth occurs in underwater locations. The presence of active hydrothermal vent fields in such environments is a potential natural hazard for the environment, society, and economy. Despite its importance for risk assessment and risk mitigation, the [...] Read more.
Almost three-quarters of known volcanic activity on Earth occurs in underwater locations. The presence of active hydrothermal vent fields in such environments is a potential natural hazard for the environment, society, and economy. Despite its importance for risk assessment and risk mitigation, the monitoring of volcanic activity is impeded by the remoteness and the extreme conditions of many underwater volcanoes. The morphology and the activity of the submarine caldera, Avyssos, at the northern part of Nisyros volcano in the South Aegean Sea (Greece), were studied using a remotely operated underwater vehicle. The recorded time series of temperature and conductivity over the submarine volcano have been analyzed in terms of the Generalized Moments Method. This type of analysis can be used as an indicator for the state of activity of a submarine volcano. Here, we expand the work conducted for the first time in 2018. We present the findings of the geological exploration and the mathematical analysis, obtained from the data collected in October 2010. The temperature and conductivity time series show minor fluctuations in a rather stable environment. Based on these results, the impact of developing appropriate mechanisms and policies to avoid the associated natural hazard is expected to be important. Full article
(This article belongs to the Special Issue Present and Past Submarine Volcanic Activity)
Show Figures

Figure 1

Article
Geomorphological Approach to Cliff Instability in Volcanic Slopes: A Case Study from the Gulf of Naples (Southern Italy)
Geosciences 2021, 11(7), 289; https://doi.org/10.3390/geosciences11070289 - 12 Jul 2021
Cited by 2 | Viewed by 992
Abstract
This paper deals with the problem of cliff stability and proposes a geomorphological zonation of a cliff using a sector of the Posillipo promontory (named the Coroglio-Trentaremi sea cliff, Italy), in the Campi Flegrei coastal area, as a case study. A detailed geological [...] Read more.
This paper deals with the problem of cliff stability and proposes a geomorphological zonation of a cliff using a sector of the Posillipo promontory (named the Coroglio-Trentaremi sea cliff, Italy), in the Campi Flegrei coastal area, as a case study. A detailed geological and geomorphological analysis was carried out, by combining field work with analysis of detailed scale topographic maps, orthophoto, and stratigraphical data from deep boreholes. Field and borehole data, together with structural data collected in seven different stations along the cliff, allowed us to derive six geological cross-sections and to reconstruct the complex stratigraphical and structural setting of the cliff. Geomorphological analysis focused on the detection of the main geomorphological factors predisposing to cliff instability. We selected the most significant factors and divided them into two groups: factors influencing landslide intensity and factors influencing cliff instability. Then, by means of a heuristic approach, we constructed a matrix that was used to derive a map showing the geomorphological zonation of the sea cliff. This map may enable to development of a reliable scenario of cliff instability and consequent retreat, which may be useful either to plan intervention works in the most critical areas or to organize prevention plans aimed at risk mitigation. Full article
(This article belongs to the Special Issue Shoreline Dynamics and Beach Erosion)
Show Figures

Figure 1

Article
Microfacies and Depositional Conditions of Jurassic to Eocene Carbonates: Implication on Ionian Basin Evolution
Geosciences 2021, 11(7), 288; https://doi.org/10.3390/geosciences11070288 - 09 Jul 2021
Cited by 3 | Viewed by 1102
Abstract
In order to decipher the paleo-depositional environments, during the Late Jurassic to Early Eocene syn-rift stage, at the margins of the Ionian basin, two different areas with exposed long sequences have been selected, Kastos Island (external margin) and Araxos peninsula (internal margin), and [...] Read more.
In order to decipher the paleo-depositional environments, during the Late Jurassic to Early Eocene syn-rift stage, at the margins of the Ionian basin, two different areas with exposed long sequences have been selected, Kastos Island (external margin) and Araxos peninsula (internal margin), and were examined by means of microfacies analysis and biostratigraphy. On Kastos Island, based on lithological and sedimentological features, the following depositional environments have been recognized: an open marine/restricted environment prevailed during the Early Jurassic (“Pantokrator” limestones), changing upwards into deep-sea and slope environments during the Late Jurassic and Early Cretaceous (Vigla limestones). The Upper Cretaceous (Senonian limestones) is characterized by a slope environment, whereas during the Paleogene, deep-sea and toe of slope conditions prevailed. In Araxos peninsula, Lower Cretaceous deposits (“Vigla” limestones) were accumulated in a deep-sea environment; Upper Cretaceous ones (Senonian limestones) were deposited in slope or toe of slope conditions. Paleocene limestones correspond to a deep-sea environment. In Araxos peninsula, changes occurred during the Cretaceous, whereas on Kastos Island, they occurred during the Paleocene/Eocene, related to different stages of tectonic activity in the Ionian basin from east to west. Full article
Show Figures

Figure 1

Article
Seismic Vulnerability Assessment and Simplified Empirical Formulation for Predicting the Vibration Periods of Structural Units in Aggregate Configuration
Geosciences 2021, 11(7), 287; https://doi.org/10.3390/geosciences11070287 - 09 Jul 2021
Cited by 5 | Viewed by 650
Abstract
The present research aims at investigating the vibration period of structural units (SUs) of a typical masonry aggregate located in the historical center of Mirandola, a municipality in the province of Modena. The clustered building consists of eighteen SUs mutually interconnected to each [...] Read more.
The present research aims at investigating the vibration period of structural units (SUs) of a typical masonry aggregate located in the historical center of Mirandola, a municipality in the province of Modena. The clustered building consists of eighteen SUs mutually interconnected to each other, which are characterized by solid brick walls and deformable floors. First of all, non-linear static analyses are performed by adopting the 3Muri software focusing on two distinct modelling techniques concerning the analyzed SUs in isolated and clustered configurations. Congruently to the procedure adopted, in order to evaluate a reliable seismic structural response of the SUs arranged in aggregate conditions, the contribution in terms of stiffness and mass derived from adjacent buildings is considered. The analysis results are represented in terms of risk factor, stiffness, and ductility. Secondly, the eigenvalue analysis is faithfully developed to identify the main vibration modes of the investigated SUs by proposing an empirical formulation, that allows for predicting the vibration period of structural units placed in aggregate configuration starting from the corresponding isolated ones. Finally, fragility functions are derived for both the heading and intermediate SUs to point out the expected damages under earthquakes with different intensities. Full article
Show Figures

Figure 1

Review
Physics of Space Weather Phenomena: A Review
Geosciences 2021, 11(7), 286; https://doi.org/10.3390/geosciences11070286 - 08 Jul 2021
Cited by 3 | Viewed by 1151
Abstract
In the last few decades, solar activity has been diminishing, and so space weather studies need to be revisited with more attention. The physical processes involved in dealing with various space weather parameters have presented a challenge to the scientific community, with a [...] Read more.
In the last few decades, solar activity has been diminishing, and so space weather studies need to be revisited with more attention. The physical processes involved in dealing with various space weather parameters have presented a challenge to the scientific community, with a threat of having a serious impact on modern society and humankind. In the present paper, we have reviewed various aspects of space weather and its present understanding. The Sun and the Earth are the two major elements of space weather, so the solar and the terrestrial perspectives are discussed in detail. A variety of space weather effects and their societal as well as anthropogenic aspects are discussed. The impact of space weather on the terrestrial climate is discussed briefly. A few tools (models) to explain the dynamical space environment and its effects, incorporating real-time data for forecasting space weather, are also summarized. The physical relation of the Earth’s changing climate with various long-term changes in the space environment have provided clues to the short-term/long-term changes. A summary and some unanswered questions are presented in the final section. Full article
(This article belongs to the Special Issue Latest Advances in Space Weather Research)
Show Figures

Figure 1

Article
Distributed Fiber Optic Strain Sensing for Geomechanical Monitoring: Insights from Field Measurements of Ground Surface Deformation
Geosciences 2021, 11(7), 285; https://doi.org/10.3390/geosciences11070285 - 08 Jul 2021
Viewed by 1208
Abstract
In recent years, distributed fiber optic strain sensing (DFOSS) technology has demonstrated a solution for continuous deformation monitoring from subsurface to surface along the wellbore. In this study, we installed a single-mode optical fiber cable in a shallow trench to establish an effective [...] Read more.
In recent years, distributed fiber optic strain sensing (DFOSS) technology has demonstrated a solution for continuous deformation monitoring from subsurface to surface along the wellbore. In this study, we installed a single-mode optical fiber cable in a shallow trench to establish an effective technique for ground surface deformation mapping. We conducted three experimental field tests (iron plate load, water tank filling up load, and airbag inflation) in order to confirm the strain sensitivity of DFOSS for static loads, dynamic overload, excavation, subsidence, and uplift. This paper also presents two installation methods to couple the fiber cable with the ground under various environmental conditions; here, the fiber cable was installed in a shallow trench with one part buried in the soil and another part covered with cement. Our results suggest that covering the cable with cement is a practical approach for installing a fiber cable for ground surface deformation monitoring. By combining this approach with wellbore DFOSS, accurate surface–subsurface deformation measurements can be obtained for three-dimensional geomechanical monitoring of CO2 storage and oil and gas fields in the future. Full article
(This article belongs to the Special Issue Mechanical Integrity of CO2 Storage Sites)
Show Figures

Figure 1

Article
Geologist in the Loop: A Hybrid Intelligence Model for Identifying Geological Boundaries from Augmented Ground Penetrating Radar
Geosciences 2021, 11(7), 284; https://doi.org/10.3390/geosciences11070284 - 08 Jul 2021
Cited by 1 | Viewed by 1179
Abstract
Common industry practice means that geological or stratigraphic boundaries are estimated from exploration drill holes. While exploration holes provide opportunities for accurate data at a high resolution down the hole, their acquisition is cost-intensive, which can result in the number of holes drilled [...] Read more.
Common industry practice means that geological or stratigraphic boundaries are estimated from exploration drill holes. While exploration holes provide opportunities for accurate data at a high resolution down the hole, their acquisition is cost-intensive, which can result in the number of holes drilled being reduced. In contrast, sampling with ground-penetrating radar (GPR) is cost-effective, non-destructive, and compact, allowing for denser, continuous data acquisition. One challenge with GPR data is the subjectivity and challenges associated with interpretation. This research presents a hybrid model of geologist and machine learning for the identification of geological boundaries in a lateritic deposit. This model allows for an auditable, probabilistic representation of geologists’ interpretations and can feed into exploration planning and optimising drill campaigns in terms of the density and location of holes. Full article
(This article belongs to the Special Issue Advances and Applications in Computational Geosciences)
Show Figures

Figure 1

Article
Spatial Relationships between Pockmarks and Sub-Seabed Gas in Fjordic Settings: Evidence from Loch Linnhe, West Scotland
Geosciences 2021, 11(7), 283; https://doi.org/10.3390/geosciences11070283 - 07 Jul 2021
Viewed by 781
Abstract
Sub-seabed gas is commonly associated with seabed depressions known as pockmarks—the main venting sites for hydrocarbon gases to enter the water column. Sub-seabed gas accumulations are characterized by acoustically turbid or opaque zones in seismic reflection profiles, taking the form of gas blankets, [...] Read more.
Sub-seabed gas is commonly associated with seabed depressions known as pockmarks—the main venting sites for hydrocarbon gases to enter the water column. Sub-seabed gas accumulations are characterized by acoustically turbid or opaque zones in seismic reflection profiles, taking the form of gas blankets, curtains or plumes. How the migration of sub-seabed gas relates to the origin and distribution of pockmarks in nearshore and fjordic settings is not well understood. Using marine geophysical data from Loch Linnhe, a Scottish fjord, we show that shallow sub-seabed gas occurs predominantly within glaciomarine facies either as widespread blankets in basins or as isolated pockets. We use geospatial ‘hot-spot’ analysis conducted in ArcGIS to identify clusters of pockmarks and acoustic (sub-seabed) profile interpretation to identify the depth to gas front across the fjord. By combining these analyses, we find that the gas below most pockmarks in Loch Linnhe is between 1.4 m and 20 m deep. We anticipate that this work will help to understand the fate and mobility of sedimentary carbon in fjordic (marine) settings and advise offshore industry on the potential hazards posed by pockmarked seafloor regions even in nearshore settings. Full article
Show Figures

Figure 1

Article
Data-Driven Modelling of Water Table Oscillations for a Porous Aquifer Occasionally Flowing under Pressure
Geosciences 2021, 11(7), 282; https://doi.org/10.3390/geosciences11070282 - 07 Jul 2021
Viewed by 596
Abstract
Modelling of shallow porous aquifers in scenarios where boundary conditions change over time can be a difficult task. In particular, this is true when data modelling is pursued, i.e., models are directly constructed by measured data. In fact, data contain not only the [...] Read more.
Modelling of shallow porous aquifers in scenarios where boundary conditions change over time can be a difficult task. In particular, this is true when data modelling is pursued, i.e., models are directly constructed by measured data. In fact, data contain not only the information related to the physical phenomenon under investigation, but also the effects of time-varying boundary conditions, which work as a disturbance. This undesired component conditions the training of data-driven models, as they are fitted by models, which can produce predictions diverging from measured data. Here, a very shallow porous aquifer is modelled in terms of its response to water table to precipitation. The aquifer is characterized by the presence of a low permeability silty top layer covering the lower sandy strata, where the aquifer normally flows. Therefore, when the piezometric level increases up to the low permeability layer, the aquifer changes its behavior from phreatic to confined. This determines the changing boundary condition, which makes the response of the aquifer to rain precipitations complex, as it is related to a two-fold condition: confined or phreatic. The aquifer here is investigated by two machine learning approaches, the earlier based on an evolutionary modeling, and the latter based on artificial neural networks. Evolutionary modeling returned explicit equations with a fitness efficiency up to 0.8 for 1 month for predictions and 0.48 for simulations, while neural networks arrived at 0.85 and 0.28, respectively. The aim of this study is to get an explicit model of the response of the piezometric heights of the aquifer to the precipitations, which is useful for planning the use of groundwater resources. Full article
(This article belongs to the Section Hydrogeology)
Show Figures

Figure 1

Article
Structure and Composition of Basement and Sedimentary Cover in the Southwestern Part of the Siljan Ring, Central Sweden: New Data from the C-C-1 Drill Core
Geosciences 2021, 11(7), 281; https://doi.org/10.3390/geosciences11070281 - 03 Jul 2021
Viewed by 901
Abstract
The results from the geological and geophysical investigations of the Siljan Ring impact structure (central Sweden) have shown that the Paleozoic sedimentary succession and the Precambrian basement were strongly affected by complex deformational processes. Studies of a new drill core from the C-C-1 [...] Read more.
The results from the geological and geophysical investigations of the Siljan Ring impact structure (central Sweden) have shown that the Paleozoic sedimentary succession and the Precambrian basement were strongly affected by complex deformational processes. Studies of a new drill core from the C-C-1 well provide valuable additional information necessary for the reconstruction of the geological setting in the southwestern part of the Siljan Ring. It was found that the contact between the basement and the sedimentary cover is tectonic, not normal sedimentary, in origin. The basement interval comprises Precambrian metavolcanic and metasedimentary rocks with a single mafic intrusion (gabbro-dolerite) in the upper part. The rocks have only been partially metamorphosed. The intercalation of calcareous mudstones, skeletal wackstones, and black shales in the sedimentary cover interval is not consistent with the regional lithostratigraphy scheme. Thus, more likely that the sedimentary sequence is not complete as a result of tectonic displacements, and a significant part of the Lower and Middle Ordovician succession is missing. The Post-Proterozoic tectonic reactivation and impact event also caused the formation of four types of fracture. The third type of fracture is accompanied by cataclastic zones and probably have an impact-related nature. In the highly fractured basement rocks, a dissolution along the second type of fracture has resulted in the development of open vugs. Open vugs and microporosity in cataclastic zones have been considered to be an effective storage space for hydrocarbons. Full article
Show Figures

Graphical abstract

Article
Multiscale Characterization of Fracture Patterns: A Case Study of the Noble Hills Range (Death Valley, CA, USA), Application to Geothermal Reservoirs
Geosciences 2021, 11(7), 280; https://doi.org/10.3390/geosciences11070280 - 03 Jul 2021
Cited by 8 | Viewed by 1024
Abstract
In the basement fractured reservoirs, geometric parameters of fractures constitute the main properties for modeling and prediction of reservoir behavior and then fluid flow. This study aims to propose geometric description and quantify the multiscale network organization and its effect on connectivity using [...] Read more.
In the basement fractured reservoirs, geometric parameters of fractures constitute the main properties for modeling and prediction of reservoir behavior and then fluid flow. This study aims to propose geometric description and quantify the multiscale network organization and its effect on connectivity using a wide-ranging scale analysis and orders scale classification. This work takes place in the Noble Hills (NH) range, located in the Death Valley (DV, USA). The statistical analyses were performed from regional maps to thin sections. The combination of the length datasets has led to compute a power law exponent around −2, meaning that the connectivity is ruled by the small and the large fractures. Three domains have been highlighted in the NH: (1) domain A is characterized by a dominance of the NW/SE direction at the fourth order scale; (2) domain B is characterized by a dominance of the E/W and the NW/SE directions at respectively the fourth and third order scales; (3) domain C is also marked by the E/W direction dominance followed by the NW/SE direction respectively at the fourth and third order scale. The numerical simulations should consider that the orientation depends on scale observation, while the length is independent of scale observation. Full article
Show Figures

Figure 1

Article
Geochemistry of Pyritic Mudstones from the Singa Formation, Malaysia: Insights into Gold Potential, Source of Sulfur and Organic Matter
Geosciences 2021, 11(7), 279; https://doi.org/10.3390/geosciences11070279 - 02 Jul 2021
Viewed by 757
Abstract
Major trace element analyses, including pyrite chemistry of pyritic mudstones of shallow-marine Singa Formation of Pennsylvanian–Early Permian age have been carried out to assess gold potential, the source of sulfur and organic matter. Regionally, Singa Formation spatially correlates with the Bohorok Formation (Sumatra, [...] Read more.
Major trace element analyses, including pyrite chemistry of pyritic mudstones of shallow-marine Singa Formation of Pennsylvanian–Early Permian age have been carried out to assess gold potential, the source of sulfur and organic matter. Regionally, Singa Formation spatially correlates with the Bohorok Formation (Sumatra, Indonesia), the Kaeng Krachang group (Thailand), and the Lebyin group (Burma or Myanmar). In Southeast Asia, this formation is important because it has a record of glacial processes that occurred along the northern margin of Gondwana in the Late Paleozoic age. This study has revealed that mudstones of the Singa Formation, which contain lonestones of glacial origin, deposited under suboxic–oxic conditions in shallow marine environment during Pennsylvanian–Early Permian time. The black mudstones contain total organic carbon which ranges from 0.1 to 0.7 wt.%, and gold content varying from 40 to 62 ppb, making them gold source rocks. This study has revealed diagenetic gold presence in the early pyrite generations (pyrites 1, 2, and 3) in these mudstones with gold content ranging up to 1.6 ppm Au which is indicative of early enrichment of gold. Conversely, late generations of pyrite (pyrites 4, 5, and 6) in these mudstones record low gold content up to 0.5 ppm Au. The δ34S values for pyrite grains range from −24.6‰ to +6.2‰ likely indicate a combination of magmatic and biogenic source of sulfur. Organic carbon isotope composition of the pebbly mudstone samples shows a wide range from −23.9‰ to −5.8‰ indicating a mixed terrestrial and marine source. Full article
Show Figures

Figure 1

Review
Fissure Ridges: A Reappraisal of Faulting and Travertine Deposition (Travitonics)
Geosciences 2021, 11(7), 278; https://doi.org/10.3390/geosciences11070278 - 30 Jun 2021
Cited by 5 | Viewed by 977
Abstract
The mechanical discontinuities in the upper crust (i.e., faults and related fractures) lead to the uprising of geothermal fluids to the Earth’s surface. If fluids are enriched in Ca2+ and HCO3-, masses of CaCO3 (i.e., travertine deposits) can [...] Read more.
The mechanical discontinuities in the upper crust (i.e., faults and related fractures) lead to the uprising of geothermal fluids to the Earth’s surface. If fluids are enriched in Ca2+ and HCO3-, masses of CaCO3 (i.e., travertine deposits) can form mainly due to the CO2 leakage from the thermal waters. Among other things, fissure-ridge-type deposits are peculiar travertine bodies made of bedded carbonate that gently to steeply dip away from the apical part where a central fissure is located, corresponding to the fracture trace intersecting the substratum; these morpho-tectonic features are the most useful deposits for tectonic and paleoseismological investigation, as their development is contemporaneous with the activity of faults leading to the enhancement of permeability that serves to guarantee the circulation of fluids and their emergence. Therefore, the fissure ridge architecture sheds light on the interplay among fault activity, travertine deposition, and ridge evolution, providing key geo-chronologic constraints due to the fact that travertine can be dated by different radiometric methods. In recent years, studies dealing with travertine fissure ridges have been considerably improved to provide a large amount of information. In this paper, we report the state of the art of knowledge on this topic refining the literature data as well as adding original data, mainly focusing on the fissure ridge morphology, internal architecture, depositional facies, growth mechanisms, tectonic setting in which the fissure ridges develop, and advantages of using the fissure ridges for neotectonic and seismotectonic studies. Full article
(This article belongs to the Section Sedimentology, Stratigraphy and Palaeontology)
Show Figures

Figure 1

Article
Study of Organic Matter of Unconventional Reservoirs by IR Spectroscopy and IR Microscopy
Geosciences 2021, 11(7), 277; https://doi.org/10.3390/geosciences11070277 - 30 Jun 2021
Cited by 2 | Viewed by 873
Abstract
The study of organic matter content and composition in source rocks using the methods of organic geochemistry is an important part of unconventional reservoir characterization. The aim of this work was the structural group analysis of organic matter directly in the source rock [...] Read more.
The study of organic matter content and composition in source rocks using the methods of organic geochemistry is an important part of unconventional reservoir characterization. The aim of this work was the structural group analysis of organic matter directly in the source rock in combination with a quantitative assessment and surface distribution analysis of the rock sample by FTIR spectroscopy and FTIR microscopy. We have developed new experimental procedures for semi-quantitative assessment of the organic matter content, composition and distribution in the source rocks and applied these procedures for the study of the samples from the Bazhenov shale formation (West Siberia, Russia). The results have been verified using the data from the study of organic matter obtained by Rock-Eval pyrolysis and differential thermal analysis. The obtained results demonstrate the prospects of FTIR spectroscopy and FTIR microscopy application for non-destructive and express analysis of the chemical structure and distribution of organic matter in rocks. Full article
(This article belongs to the Special Issue Petrophysics and Geochemistry of Unconventional Reservoirs)
Show Figures

Figure 1

Article
Mechanical Influence of Inherited Folds in Thrust Development: A Case Study from the Variscan Fold-and-Thrust Belt in SW Sardinia (Italy)
Geosciences 2021, 11(7), 276; https://doi.org/10.3390/geosciences11070276 - 30 Jun 2021
Cited by 1 | Viewed by 806
Abstract
Fold-and-thrust belts have a high variability of structural styles, whose investigation provides continuous updates of the predictive models that try to better approximate the geometries recognized in the field. The majority of studies are focused on the geometry and development of folds and [...] Read more.
Fold-and-thrust belts have a high variability of structural styles, whose investigation provides continuous updates of the predictive models that try to better approximate the geometries recognized in the field. The majority of studies are focused on the geometry and development of folds and thrust surfaces and the amount of displacement, taking into account the role played by the involved stratigraphic succession assumed as a layer cake. We present a case study from the external zone of the Variscan fold-and-thrust belt in SW Sardinia, where it was possible to investigate the lateral and vertical variations of the mechanical properties of the involved succession, how they related to previous folding, control thrust geometry, and kinematics. In this case, the superposition of two fold systems acted as a buttress that induced extensive back-thrusting. We found that there is a close connection between the attitude of the bedding and the geometry of back thrust surfaces, shear strength during thrust propagation, and variation in the shortening amount, depending on which part of the folds were cut across. The folding-related mechanical anisotropy also seems to have induced a ductile deformation in the footwall of back-thrusts. Although the case study considers the development of back-thrust, the relations between thrust and not-layer cake geometries could also be applied to fore-thrust development. Full article
Show Figures

Figure 1

Article
System Identification of Mosques Resting on Soft Soil. The Case of the Suleiman Mosque in the Medieval City of Rhodes, Greece
Geosciences 2021, 11(7), 275; https://doi.org/10.3390/geosciences11070275 - 30 Jun 2021
Cited by 1 | Viewed by 771
Abstract
The present study focuses on the dynamic system identification of the Suleiman Mosque minaret in the medieval city of Rhodes, Greece. Suleiman Mosque was built in 1522 at the site of the destroyed Christian Church of the Apostles. First, we performed sets of [...] Read more.
The present study focuses on the dynamic system identification of the Suleiman Mosque minaret in the medieval city of Rhodes, Greece. Suleiman Mosque was built in 1522 at the site of the destroyed Christian Church of the Apostles. First, we performed sets of ambient vibration measurements at the minaret of the monument. Based on these data, we calculated the eigenproperties of the minaret. Next, we modeled the monument in three dimensions, using the finite element method. Six numerical models were considered. Model Ι is the simplest one (isolated, fixed base minaret). Model VI is the most complicated one (simulation of the whole mosque also considering soil–structure interaction and foundation flexibility). The calculated predominant periods and mode shapes of Models I–VI are validated against the microtremor field measurements, recorded on the minaret’s two floors and ground level. We elaborate on the reliability of finite element models for earthquake response evaluation, considering soil–structure interaction and foundation flexibility on the mode shape eigenfrequencies. Additionally, we discuss the seismic response of the minaret compared to the whole monument. We observed no significant difference in the first two modes of response, implying that the minaret’s dynamic behavior is slightly affected by the entire mosque’s presence. Full article
(This article belongs to the Special Issue Numerical Modeling in Geotechnical Engineering)
Show Figures

Figure 1

Article
Capillary Barriers during Rainfall Events in Pyroclastic Deposits of the Vesuvian Area
Geosciences 2021, 11(7), 274; https://doi.org/10.3390/geosciences11070274 - 29 Jun 2021
Cited by 1 | Viewed by 729
Abstract
In the present paper, the capillary barrier formation at the interface between soil layers, which is characterized by textural discontinuities, has been analyzed. This mechanism has been investigated by means of a finite element model of a two-layer soil stratification. The two considered [...] Read more.
In the present paper, the capillary barrier formation at the interface between soil layers, which is characterized by textural discontinuities, has been analyzed. This mechanism has been investigated by means of a finite element model of a two-layer soil stratification. The two considered formations, belonging to the pyroclastic succession of the “Pomici di Base” Plinian eruption (22 ka, Santacroce et al., 2008) of the Somma–Vesuvius volcano, are affected by shallow instability phenomena likely caused by progressive saturation during the rainfall events. This mechanism could be compatible with the formation of capillary barriers at the interface between layers of different grain size distributions during infiltration. One-dimensional infiltration into the stratified soil was parametrically simulated considering rainfall events of increasing intensity and duration. The variations in the suction and degree of saturation over time allowed for the evaluation of stability variations in the layers, which were assumed as part of stratified unsaturated infinite slopes. Full article
(This article belongs to the Special Issue Natural and Artificial Unsaturated Soil Slopes)
Show Figures

Figure 1

Article
Sedimentology and Stratigraphy of an Upper Permian Sedimentary Succession: Northern Sydney Basin, Southeastern Australia
Geosciences 2021, 11(7), 273; https://doi.org/10.3390/geosciences11070273 - 29 Jun 2021
Cited by 2 | Viewed by 958
Abstract
This study integrates sedimentological and stratigraphic insights into the Upper Permian sedimentary rocks of the Wittingham, Tomago and Newcastle Coal Measures in the Northern Sydney Basin, Australia. Facies analysis documented fifteen facies that belong to seven facies associations. These facies associations correspond to [...] Read more.
This study integrates sedimentological and stratigraphic insights into the Upper Permian sedimentary rocks of the Wittingham, Tomago and Newcastle Coal Measures in the Northern Sydney Basin, Australia. Facies analysis documented fifteen facies that belong to seven facies associations. These facies associations correspond to different depositional environments and sub-environments including prodelta, delta-front, upper, lower delta-plain and fluvial. The stratigraphic development points to a shallowing upward trend and is reflected with fluvial deposits sitting on top of the deltaic deposits. The fluvio-deltaic contact is represented by an unconformity and displays an upward increase in sediment caliber. The delta front is mainly controlled by wave, storms- and/or river currents, even though the contribution of tides also occurs in the form of sedimentary structures that suggest tidal influence. In contrast, prodelta and delta-plain are significantly modulated by tidal currents. The impact of tides in the delta plain is fading away upward and therefore, the upper delta plain is much less impacted compared to the lower delta plain. The low abundance of wave ripples suggests that the wave action was not very important in the delta plain. Steep topographic gradients and increased sediment input are suggested, based on the limited or absent evidence of tides in the fluvial realm, related to the growing New England Orogen. In sequence stratigraphic terms, the deltaic system accumulated during highstand normal regression, while the deposition of the overlying fluvial system occurred during lowstand normal regression. The two systems are separated by a subaerial unconformity developed during an intervening forced regression. Short periods of transgression are inferred from the presence of higher frequency cycles in the delta-front. Full article
Show Figures

Figure 1

Article
Distribution of Holocene Marine Mud and Its Relation to Damage from the 1923 Earthquake Disaster in the Tokyo Metropolitan Area, Japan
Geosciences 2021, 11(7), 272; https://doi.org/10.3390/geosciences11070272 - 28 Jun 2021
Viewed by 1033
Abstract
Tokyo, which is located near the boundary between the North American and Philippine Sea plates, has been frequently struck by large earthquakes throughout the Holocene. The 1923 Taisho Kanto Earthquake is a rare historical earthquake that can be reconstructed in detail because abundant [...] Read more.
Tokyo, which is located near the boundary between the North American and Philippine Sea plates, has been frequently struck by large earthquakes throughout the Holocene. The 1923 Taisho Kanto Earthquake is a rare historical earthquake that can be reconstructed in detail because abundant datasets were collected by investigations performed just after the earthquake. We examined 13,000 borehole logs from the Tokyo and Nakagawa lowlands to clarify the distribution and thickness of incised-valley fills and soft marine mud that had accumulated since the Last Glacial Maximum (LGM) on a grid with a resolution of 150 m × 150 m. We compared these datasets with the distribution of wooden house damage ratios caused by the Taisho Kanto Earthquake. Our results showed that the thickness of the soft mud, but not that of the incised-valley fills, was strongly correlated with the wooden house damage ratio. The mud content was >60%, water content was >30%, and S-wave velocity was ca. 100 m/s in the soft Holocene marine mud. The wooden house damage ratio was highest where the soft mud thickness was 20 m, because in those areas, both the soft mud and the wooden houses resonated with a natural period of ca. 1 s. Full article
Show Figures

Figure 1

Article
Scaling in a Geothermal Heat Exchanger at Soultz-Sous-Forêts (Upper Rhine Graben, France): A XRD and SEM-EDS Characterization of Sulfide Precipitates
Geosciences 2021, 11(7), 271; https://doi.org/10.3390/geosciences11070271 - 28 Jun 2021
Cited by 3 | Viewed by 1107
Abstract
The Soultz-Sous-Forêts geothermal site (France) operates three deep wells for electricity production. During operation, scales precipitate within the surface installation as (Ba, Sr) sulfate and (Pb, As, Sb) sulfide types. Scales have an impact on lowering energy production and inducing specific waste management [...] Read more.
The Soultz-Sous-Forêts geothermal site (France) operates three deep wells for electricity production. During operation, scales precipitate within the surface installation as (Ba, Sr) sulfate and (Pb, As, Sb) sulfide types. Scales have an impact on lowering energy production and inducing specific waste management issues. Thus scaling needs to be reduced for which a thorough characterization of the scales has to be performed. The geothermal brine is produced at 160 °C and reinjected at 70 °C during normal operation. In the frame of the H2020 MEET project, a small heat exchanger was tested in order to allow higher energy production, by reinjecting the geothermal fluid at 40 °C. Samples of scales were analyzed by XRD and SEM-EDS, highlighting that mostly galena precipitates and shows various crystal shapes. These shapes can be related to the turbulence of the flow and the speed of crystal growth. Where the flow is turbulent (entrance, water box, exit), crystals grow quickly and mainly show dendritic shape. In the tubes, where the flow is laminar, crystals grow more slowly and some of them are characterized by well-developed faces leading to cubes and derived shapes. The major consequence of the temperature decrease is the increased scaling phenomenon. Full article
Show Figures

Figure 1

Previous Issue
Next Issue
Back to TopTop