Rock Interaction Research Articles

The origin and water quality of spring systems in Monchique, Portugal: A focus on Long-Term sustainability and elevated sodium levels

Spring water systems in Monchique, SW Portugal, not only serve diverse local utilities–from thermal baths to bottled water–but also represent a microcosm of a global concern: elevated sodium levels in spring-sourced bottled waters. This research employs hydrogeochemical and isotopic analyses to investigate the origin, hierarchy and quality of the springs offering a new focus on elevated sodium concentrations, a known global cardiometabolic risk factor. The springs arise from a complex hydrogeological system formed by extensive faulting between argillaceous country-rocks and intruded Cretaceous syenites. Here we show that thermal springs with temperatures of 23–31 °C, have a groundwater age of 5000 years, indicative of extended water–rock interactions and recharge at elevations of 450 to 650 m revealing a hitherto unreported resilience in regional groundwater hydraulics. Conversely, cold springs recharging from 200 m to the area’s peak at 900 m follow shorter paths within the regolith influenced by shallow geological features. The study detects nitrate contamination from surface sources in the cold springs and relatively high sodium levels in the geothermal springs that approach or surpass guideline values. Elevated sodium is attributed, for the first time, to long-term interactions and cation exchange with Na-rich syenites, possibly intensified by heat-induced dissolution at depth. This study informs current perspectives on the long-term sustainability and public health implications of spring water systems. The ion chemistry and isotopic evidence suggest that thermal springs, due to their longer circulation times, are less vulnerable to climatic shifts compared to the more susceptible cold springs. While offering specific insights into the Monchique springs, the research has broad implications to similar high-sodium thermal springs across the Iberian Peninsula and potentially worldwide.

Cross-scale mechanical softening of Marcellus shale induced by CO2-water–rock interactions using nanoindentation and accurate grain-based modeling

Mechanical softening behaviors of shale in CO2-water–rock interaction are critical for shale gas exploitation and CO2 sequestration. This work investigated the cross-scale mechanical softening of shale triggered by CO2-water–rock interaction. Initially, the mechanical softening of shale following 30 d of exposure to CO2 and water was assessed at the rock-forming mineral scale using nanoindentation. The mechanical alterations of rock-forming minerals, including quartz, muscovite, chlorite, and kaolinite, were analyzed and compared. Subsequently, an accurate grain-based modeling (AGBM) was proposed to upscale the nanoindentation results. Numerical models were generated based on the real microstructure of shale derived from TESCAN integrated minerals analyzer (TIMA) digital images. Mechanical parameters of shale minerals determined by nanoindentation served as input material properties for AGBMs. Finally, numerical simulations of uniaxial compression tests were conducted to investigate the impact of mineral softening on the macroscopic Young’s modulus and uniaxial compressive strength (UCS) of shale. The results present direct evidence of shale mineral softening during CO2-water–rock interaction and explore its influence on the upscale mechanical properties of shale. This paper offers a microscopic perspective for comprehending CO2-water-shale interactions and contributes to the development of a cross-scale mechanical model for shale.

Influences of bedding angle and soaking time on the mechanical behaviour of silty mudstone: laboratory testing and theoretical modelling

Silty mudstone is highly susceptible to the influence of hot and humid environments, leading to the deterioration of its mechanical properties presenting a geohazard and even resulting in geological disasters. Accurately characterizing the effects of bedding and water–rock interaction on the mechanical behaviour of silty mudstone is a crucial prerequisite for the protection and reinforcement of silty mudstone slopes. To this end, uniaxial compression tests and Brazilian splitting tests were conducted to examine the mechanical properties of bedded silty mudstone. Based on the test results, the effects of bedding angle and soaking time on mechanical properties such as tensile strength, uniaxial compressive strength and elastic modulus of bedded silty mudstone were revealed. The test results showed that the tensile strength increased exponentially with increasing bedding angle. The observed split failure patterns of bedded silty mudstone encompassed splitting–pulling damage, shear damage and splitting damage. The uniaxial compressive strength of silty mudstone exhibited a U-shaped variation with an increase in bedding angle. The specimen with a bedding angle of 45° had the lowest uniaxial compressive strength at 7.64 MPa. Furthermore, the elastic modulus of silty mudstone was positively correlated with the bedding angle. The failure patterns of bedded silty mudstone under uniaxial compression included splitting-tension damage, shear-slip damage and splitting-shear damage. The saturated tensile strength, uniaxial compressive strength and elastic modulus of bedded silty mudstone exhibited an exponential decrease with increasing soaking time. The test data confirmed the applicability of the Jaeger equation to the uniaxial compressive strength of bedded silty mudstone. Subsequently, a modified Hoek–Brown failure criterion was derived by combining fracture mechanics theory and test results and introducing a softening factor. The parameters A , D and m in the above failure criterion decreased exponentially with increasing soaking time and an empirical Hoek–Brown failure criterion considering the soaking time was established. Compared with previous theoretical models, this model is more adaptable to the actual engineering situation, which results in more accurate calculations.

Fluid–Melt–Rock Interaction during the Transition from Magmatism to HT-UHT-Granulite- and Amphibolite-Facies Metamorphism in the Ediacaran Adrar–Suttuf Metamafic Complex, NW Margin of the West African Craton (Southern Morocco)

Abstract Underplated mafic intrusions ponded at the base of the lower continental crust in extensional settings can experience ultra-high-temperature (UHT) granulite-facies metamorphism during tens of My due to slow cooling rates. These intrusions are also the source of heat and carbonic fluids for regional high-temperature (HT) granulite-facies metamorphism in the continental crust. This work analyses the fluid–melt–rock interaction processes that occurred during the magmatic to HT-UHT-granulite- and amphibolite-facies metamorphic evolution of high-grade mafic rocks from the Eastern Ediacaran Adrar–Suttuf Metamafic Complex (EASMC) of the Oulad Dlim Massif (West African Craton Margin, Southern Morocco). P–T conditions were determined using Ti-in-amphibole thermometry, two-pyroxene and amphibole–plagioclase thermobarometry, and phase diagram calculations. The thermobarometric study reveals the presence of tectonically juxtaposed lower- and mid-crustal blocks in EASMC that experienced decompression-cooling paths from, respectively, UHT and HT granulite-facies conditions at ca. 1.2 ± 0.28 GPa and 975 ± 50°C, and ca. 0.82 ± 0.15 GPa and 894 ± 50°C, to amphibole-facies conditions at ca. 0.28 ± 0.28 GPa and 787 ± 45°C (precision reported for the calibrations at 1 s level). An age for the magmatic to UHT granulite-facies metamorphic transition of 604 Ma was constrained from published SHRIMP Th–U–Pb zircon ages of the igneous protoliths. An amphibole 40Ar–39Ar cooling age of 499 ± 8 Ma (precision at 2 s level) was obtained for the lower-crustal blocks. Amphibole 40Ar–39Ar closure temperatures of 520–555°C were obtained for an age range of 604–499 Ma and an average constant cooling rate of 4.2°C/My, suggesting that the lower-crustal blocks cooled down to the greenschist–amphibolite facies transition in ca. 100 My. During the high-temperature stage, interstitial hydrous melts assisted textural maturation of the rock matrix and caused incongruent dissolution melting of olivine and pyroxenes, and, probably, development of An-rich spikes at the grain rims of plagioclase, and local segregation of pargasite into veins. Subsequent infiltration of reactive hydrous metamorphic fluids along mineral grain boundaries during cooling down to amphibolite-facies conditions promoted mineral replacements by coupled dissolution-precipitation mechanisms and metasomatism. Ubiquitous dolomite grains, with, in some cases, evidence for significant textural maturation, appear in the granoblastic aggregates of the high-grade mafic rocks. However, calculated phase relationships reveal that dolomite could not coexist with H2O–CO2 fluids at HT-UHT granulite- and low-medium P amphibolite-facies conditions. Therefore, it is proposed that it may have been generated from another CO2-bearing phase, such as an immiscible carbonatitic melt exsolved from the parental mafic magma, and preserved during cooling due to the prevalence of fluid-absent conditions in the granoblastic matrix containing dolomite. The lower-crustal mafic intrusions from EASMC can represent an example of a source of heat for granulitisation of the mid crust, but a sink for carbon due to the apparent stability of dolomite under fluid-absent conditions.

Representative High-Temperature Hydrothermal Activities in the Himalaya Geothermal Belt (HGB): A Review and Future Perspectives

Southern Tibet and western Yunnan are areas with an intensive distribution of high-temperature geothermal systems in China, as an important part of the Himalayan Geothermal Belt (HGB). In recent decades, China has conducted systematic research on high-temperature geothermal fields such as Yangbajing, Gudui, and Rehai. However, a comprehensive understanding has not yet been formed. The objective of this study was to enhance comprehension of the high-temperature geothermal system in the HGB and to elucidate the hydrogeochemical characteristics of geothermal fluids. This will facilitate the subsequent sustainable development and exploitation of domestic high-temperature hydrothermal geothermal resources. To this end, this study analysed geothermal spring and borehole data from the Yangbajing, Gudui, and Rehai geothermal fields. Based on previous research results, the source, evolution, and reservoir temperature characteristics of geothermal fluids are compared and summarised. The main high-temperature geothermal water in the geothermal field is derived from the deep Cl-Na geothermal fluid. Yangbajing’s and Gudui’s geothermal waters are primarily recharged by snow-melt water, while Rehai’s geothermal water is mainly recharged by local meteoric water. The average mixing ratios of magmatic water in the Yangbajing, Gudui, and Rehai geothermal fields are 17%, 21%, and 22%, respectively. The Yangbajing and Gudui geothermal fields have a relatively closed geological environment, resulting in a stronger water–rock interaction compared to the Rehai geothermal field. As geothermal water rises, it mixes with shallow cold water infiltration. The mixing ratios of cold water in the Yangbajing, Gudui, and Rehai geothermal fields are 60–70%, 40–50%, and 20–40%, respectively. Based on the solute geothermometer calculations, the maximum geothermal reservoir temperatures for Yangbajing, Gudui, and Rehai are 237 °C, 266 °C, and 282 °C, respectively. This study summarises and compares the hydrogeochemical characteristics of three typical high-temperature geothermal fields. The findings provide an important theoretical basis for the development of high-temperature geothermal resources in the Himalayan Geothermal Belt.

Strike‐slip fault zone architecture and its effect on fluid migration in deep‐seated strata: Insights from the Central Tarim Basin

AbstractThe internal fault architecture is crucial in assessing the significance of faults in fluid migration. The development of overlapping zones between segments and subsidiary structures is characteristic of a strike–slip faults. However, their internal architectures and roles in fluid migration are still poorly understood. The Tarim Basin's recently identified strike–slip faults imply that the petroleum resource is hosted in caves that were formed by subsequent dissolution after the formation of the fault zones in carbonate rocks, indicating that the internal fault architecture may be closely linked to the accumulation of petroleum. We investigated the architecture of the strike–slip fault zone using field, geochemical, seismic and well‐logging data. The results revealed that the strike–slip faults contain flower‐like structures in their vertical profiles and an en échelon and ‘X’ conjugate pattern in their horizontal slices. The fault core may become more complex because of the flower structure as fault breccia, slip surfaces, hydrothermal veins, dissolved pores and caves develop, and the damage zone contains multiple stages of fractures with high dip angles. Compared with ‘X’ pattern conjugate faults, NE‐trending strike–slip faults have a more developed and connected fault zone. The fault core acts as a fast conduit for fluid transport and experiences significant elemental losses, and the elemental variations in the damage zone may relate in long‐term and relatively lower‐level fluid–rock interactions. Three fault zone architecture models were created, namely, a releasing bend, a restraining bend and a single segment, and their controlling impacts on fluid migration were addressed accordingly. Our findings imply that fluid migration and accumulation are more favourable at the releasing bend than at the restraining bend and single segment.

Machine learning model for deep exploration: Utilizing short wavelength infrared (SWIR) of hydrothermal alteration minerals in the Qianchen gold deposit, Jiaodong Peninsula, Eastern China

The Jiaodong Peninsula in the eastern North China Craton is renowned globally as a major gold province. Notably, the Jiaojia orefield is an important gold-producing district in this region, and its depths are inferred to offer substantial prospecting potential, underscoring the need for innovative exploration tools to uncover concealed orebodies. The Qianchen gold deposit in the southern part of the Jiaojia orefield is characterized by the disseminated-stockwork-style orebodies at depths of ca. –1000 to –1800 m, with three mineralization stages, namely (I) pre-ore K-feldspar-quartz stage, (II) quartz-sericite-gold-polymetallic sulfide stage (main Au mineralization stage), and (III) post-ore quartz-calcite stage. Systematic short-wavelength infrared (SWIR) spectral analysis reveals that sericite group minerals developing in Stage II are the predominant and wide-distributed alteration minerals at Qianchen. Their spectral characteristics demonstrate a shift in the Al-OH absorption feature wavelength positions (Pos2200) to longer wavelengths (>2205 nm) within the orebodies. This shift is likely due to strong water–rock interactions leading to Fe and Mg substituting for Al in octahedral sites. Orthogonal partial least squares discriminant analysis (OPLS-DA) indicates that the H2O, OH, and FeOH spectral bands (Variable Importance in the Projection (VIP) ≥ 1) of sericite are crucial for distinguishing between gold ores and barren wall rocks. Additionally, Long Short-Term Memory (LSTM) models demonstrate that spectral data of sericite can be used to predict ore samples with an accuracy of 82 %, validated by receiver operating characteristic analysis (84 %), and blind test results demonstrate that the predicted grade closely aligns with the actual grade. Therefore, it is concluded that SWIR spectral characteristics of sericite group minerals can serve as an effective indicator for prospecting the Qianchen concealed gold mineralization. This study highlights the potential of coupling between machine learning and SWIR spectral data of alteration minerals to uncover the concealed lode gold mineralization.

Study on rock energy evolution and constitutive model under water–rock interaction

To explore the degradation in rock mechanical properties due to water–rock interactions and formulate a nonlinear damage constitutive model for the entire stress–strain curve of rocks, experiments involving saturated, dry-wet cycling, and uniaxial compression tests were conducted on granite and siltstone. Based on energy theory, the energy evolution of the rock throughout the testing process was scrutinized. The range of the compaction stage was identified through the analysis of the dissipation energy change curve. A nonlinear damage constitutive model for rocks subjected to water-rock interactions was then devised, drawing on concepts from statistical damage mechanics. The findings indicated a progressive reduction in uniaxial compressive strength and elastic modulus due to water–rock interactions, while the Poisson’s ratio was observed to increase. The energy density curve under these conditions delineated four distinct phases: compaction energy dissipation, linear energy accumulation, pre-peak gradient increase, and post-peak sudden change. The introduction of the unit elastic strain energy density metric underscored the deteriorating effects from an energy standpoint. A nonlinear damage constitutive model, incorporating the compaction stage based on a coupled damage variable, was formulated. The predictions of this model closely matched the empirical data, thereby affirming its validity. This model provides an enhanced depiction of rock deformation and failure mechanisms under the influence of water–rock interactions.

Assessment of Groundwater Quality Using the Pollution Index of Groundwater (PIG), Nitrate Pollution Index (NPI), Water Quality Index (WQI), Multivariate Statistical Analysis (MSA), and GIS Approaches: A Case Study of the Mnasra Region, Gharb Plain, Morocco

Groundwater, an invaluable resource crucial for irrigation and drinking purposes, significantly impacts human health and societal advancement. This study aims to evaluate the groundwater quality in the Mnasra region of the Gharb Plain, employing a comprehensive analysis of thirty samples collected from various locations, based on thirty-three physicochemical parameters. Utilizing tools like the Pollution Index of Groundwater (PIG), Nitrate Pollution Index (NPI), Water Quality Index (WQI), Irrigation Water Quality Index (IWQI), as well as Multivariate Statistical Approaches (MSA), and the Geographic Information System (GIS), this research identifies the sources of groundwater pollution. The results revealed Ca2+ dominance among cations and Cl− as the primary anion. The Piper and Gibbs diagrams illustrated the prevalent Ca2+-Cl− water type and the significance of water–rock interactions, respectively. The PIG values indicated that 86.66% of samples exhibited “Insignificant pollution”. NPI showed notable nitrate pollution (1.48 to 7.06), with 83.33% of samples rated “Good” for drinking based on the WQI. The IWQI revealed that 80% of samples were classified as “Excellent” and 16.66% as “Good”. Spatial analysis identified the eastern and southern sections as highly contaminated due to agricultural activities. These findings provide valuable insights for decision-makers to manage groundwater resources and promote sustainable water management in the Gharb region.

Carbonate dissolution enhances particulate iron sulfide mobilization during water-shale interaction

The interaction between shale and water in the environment can lead to the mobilization of micrometer-sized iron sulfide (pyrite) grains. Because these grains often contain high concentrations of toxic elements, including arsenic, this process can pose a significant hazard. While previous studies have suggested that calcite dissolution plays a major role in iron sulfide mobilization, the relationship between rock composition and the release of particulate matter is unclear. Here, we performed laboratory experiments that simulated water–rock interaction in the subsurface on 5 different shale formations: Eagle Ford, Marcellus, Mancos, and Barnett from the USA, and Ein Zeitim from Israel. We used high resolution imaging to evaluate the impact of a reactive fluid on the shale surface, and used image analysis software to determine the rate of iron sulfide grain mobilization. Comparison of the shale surfaces before and after the experiments showed that the dissolution of calcite cement had a major impact on sulfide mobilization: grains that were primarily surrounded by calcite cement were up to 85 times more likely to be mobilized than grains embedded in the shale matrix, which compromises a complex mixture of submicrometer-scale phases, including phyllosilicates, organics, and carbonates. By contrast, iron sulfide embedded in organic matter typically remained cemented in place. This suggests that while calcite dissolution is a crucial phase in facilitating iron sulfide detachment in shales, organic matter might act as an adhesive that suppresses particulate mobilization. However, the adhesive effect of organic matter is only likely to be of secondary importance. Overall, our results indicate that during hydraulic fracturing operations, which involve the injection of fluid into shales in the subsurface, formations with high levels of carbonate cement are more likely to release particulate iron sulfide, thereby reducing the quality of flowback water and potentially increasing treatment costs.

Hydrodynamic processes in designing diamond drilling tools

Relevance. The rational choice of drilling tools is one of the components of a positive result of exploration, mining, drilling operations. The function of a complex solution of problems arising when drilling wells is assigned to a modern drilling tool. Today there is a great variety of designs of rock cutting drilling tools. However, scientific achievements in improving the material and technical production base contribute to the development of drilling technology and creation of new, more efficient tool designs. The most promising and effective in various mining conditions is a diamond drilling tool. During the operation of such a tool, flushing fluid circulation is of great importance, especially in the bottomhole zone of the well being constructed. When designing the structures of a diamond rock cutting tool, it is necessary to take into account not only the strength, cutting, and stabilizing properties, but also the possibility of an effective fluid flow in its circulation system, i.e. without flow energy consumption to overcome resistance, with sufficient capacity for cuttings removal and the necessary level of cooling, lubrication and implementation of other functions of the flushing fluid, which contribute to improving drilling results. At the same time, modern methods of designing a drilling tool should take into account the influence of the drilling fluid, its properties, and the nature of the flow on the rock destruction mechanism, i. e. require a thorough study of the nature of the fluid flow in the contact zone of the tool cutters with the rock. The article proposes the position of considering the design of a diamond drilling tool cutting surface from the point of view of the influence of hydrodynamic processes on the nature of cutters rock interaction. The results of the study of both the author herself and well-known world manufacturers of diamond drilling tools are given as arguments. Aim. To study the influence of the design features of the existing diamond drilling tool on the nature of the fluid flow in the bottomhole zone of the well during drilling. Objects. Designs of diamond drilling tools, hydrodynamic processes associated with drilling. Methods. Analytical method, computer simulation method. Results. Differences in fluid circulation in certain types of diamond drilling tools are determined. The zones of the diamond rock-cutting tool are distinguished. They differ in the nature of the fluid flow. Directions for reducing hydraulic resistance in the bottomhole zone of the well due to changes in the design features of the drilling tool were established.

The Hydrogeochemistry of and Earthquake-Related Chemical Variations in the Springs along the Eastern Kunlun Fault Zone, China

The Eastern Kunlun Fault (EKF) is situated in an area with a history of significant seismic events, yet it has witnessed a dearth of major earthquakes in recent years. This study conducted a detailed analysis of the hydrogeochemical characteristics of the springs in the EKF and their temporal variation, aiming to address the gaps in the research on the hydrogeochemistry in the region and to investigate the changes in water chemistry during the seismogenic process. In this study, the main elements, trace elements, hydrogen isotopes, oxygen isotopes, and strontium isotopes of 23 springs in the EKF were analyzed. The results indicated that the groundwater recharge in the eastern part of the Eastern Kunlun Fault Zone mainly originates from atmospheric precipitation, as supported by its isotopic characteristics. The spring water is immature, showing weak water–rock interactions. A hydrochemical analysis classified the springs into 11 main types, reflecting varying degrees of water–rock interaction. Based on measurements using quartz geothermometers, the estimated geothermal reservoir temperatures ranged from 39.6 to 120.3 °C, with circulation depths of 1.3 to 3.8 km. By means of regularly monitoring three selected springs, this study also explored the relationship between earthquakes and hot spring chemical variations. Finally, a conceptual model of hydrogeochemistry was proposed to describe the groundwater circulation in the study area.

The microbiota characterizing huge carbonatic moonmilk structures and its correlation with preserved organic matter

BackgroundMoonmilk represents complex secondary structures and model systems to investigate the interaction between microorganisms and carbonatic rocks. Grotta Nera is characterized by numerous moonmilk speleothems of exceptional size hanging from the ceiling, reaching over two meters in length. In this work we combined microbiological analyses with analytical pyrolysis and carbon stable isotope data to determine the molecular composition of these complex moonmilk structures as well as the composition of the associated microbiota.ResultsThree moonmilk structures were dissected into the apical, lateral, and core parts, which shared similar values of microbial abundance, richness, and carbon isotopes but different water content, microbiota composition, and organic matter. Moonmilk parts/niches showed higher values of microbial biomass and biodiversity compared to the bedrock (not showing moonmilk development signs) and the waters (collected below dripping moonmilk), indicating the presence of more complex microbial communities linked to carbonate rock interactions and biomineralization processes. Although each moonmilk niche was characterized by a specific microbiota as well as a distinct organic carbon profile, statistical analyses clustered the samples in two main groups, one including the moonmilk lateral part and the bedrock and the other including the core and apical parts of the speleothem. The organic matter profile of both these groups showed two well-differentiated organic carbon groups, one from cave microbial activity and the other from the leaching of vascular plant litter above the cave. Correlation between organic matter composition and microbial taxa in the different moonmilk niches were found, linking the presence of condensed organic compounds in the apical part with the orders Nitrospirales and Nitrosopumilales, while different taxa were correlated with aromatic, lignin, and polysaccharides in the moonmilk core. These findings are in line with the metabolic potential of these microbial taxa suggesting how the molecular composition of the preserved organic matter drives the microbiota colonizing the different moonmilk niches. Furthermore, distinct bacterial and archaeal taxa known to be involved in the metabolism of inorganic nitrogen and C1 gases (CO2 and CH4) (Nitrospira, Nitrosopumilaceae, Nitrosomonadaceae, Nitrosococcaceae, and novel taxa of Methylomirabilota and Methanomassiliicoccales) were enriched in the core and apical parts of the moonmilk, probably in association with their contribution to biogeochemical cycles in Grotta Nera ecosystem and moonmilk development.ConclusionsThe moonmilk deposits can be divided into diverse niches following oxygen and water gradients, which are characterized by specific microbial taxa and organic matter composition originating from microbial activities or deriving from soil and vegetation above the cave. The metabolic capacities allowing the biodegradation of complex polymers from the vegetation above the cave and the use of inorganic nitrogen and atmospheric gases might have fueled the development of complex microbial communities that, by interacting with the carbonatic rock, led to the formation of these massive moonmilk speleothems in Grotta Nera.

Mineral chemistry and melt evolution of the mantle wedge peridotites in the Late Cretaceous Zagros Belt ophiolites (Iran): clues for the subduction initiation-induced forearc magmatism

We investigate in this paper mineral compositions and geochemical evolution of the mantle wedge peridotites preserved in the Late Cretaceous Zagros ophiolites of SW Iran. Mantle peridotites above subduction zones commonly experience distinct melting, depletion and refertilization processes as a result of the circulation of fluids derived from subducting slabs and flux melting. Our results reveal that the mantle wedge peridotites in the Zagros ophiolites are characterized mainly by residual and impregnated types. Residual peridotites resulted from early depletion and later refertilization processes, whereas impregnated peridotites developed due to episodic melt impregnations within and across the mantle. Mg#s and NiO contents, spinel Cr#, Mg#, and TiO 2 in olivines, Mg# and Al 2 O 3 contents of orthopyroxenes, and Mg#, TiO 2 and Al 2 O 3 contents in clinopyroxenes of dunites, harzburgites and lherzolites indicate the significant role of re-equilibration processes among different mineral phases and interactions with basaltic melts percolating within the host peridotites. The observed geochemical variations in the mineral chemistry of the Zagros peridotites reflect changes in magma chemistry and fluctuations in the degree of melt extraction and melt–rock interactions within the mantle peridotites. However, our data suggest that Mg–Fe distribution in the spinels of some dunites and harzburgites might also have resulted from subsolidus redistribution and exchange with surrounding olivine grains. Spinel and clinopyroxene phases in gabbroic rocks and ultramafic cumulates within the Zagros ophiolites also show significant variations in their compositions, suggesting that their magmas evolved from MORB-like to IAT, calc–alkaline and boninite suites, typical of subduction initiation-generated melts. Hence, the Zagros ophiolites present a case study of time-progressive melt evolution of the forearc oceanic lithosphere. Supplementary material: Datasets of the mineral chemistry and melt evolution of the mantle wedge peridotites in the Late Cretaceous Zagros Belt ophiolites (Iran) are available in tabular and figurative form at https://doi.org/10.6084/m9.figshare.c.7093528 . Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists

Permeability Effect and Nonlinear Coupling Characteristics of Rock–Soil Interaction with Water

The seepage effect of rock and soil in the process of encountering water follows a nonlinear coupling law between water and rock. According to the permeability of rock and soil during softening with water, changes in particles in rock and soil are related to permeability mechanisms. Based on the assumption of connection between particles in rock and soil, changes in particles before and after water infiltration, the mechanism of water–rock interaction, and the damage to rock and soil are analyzed herein. Combined with fractal theory and percolation theory, the random failure characteristics and nonlinear behavior of water in rock and soil are studied. At the same time, with the help of Fluent 17.0 software, the seepage process of rock samples in water is numerically simulated and analyzed. Taking the permeability coefficient of rock samples, the mass flow rate of water, and the internal pore water pressure of rock samples as tracking objects, it is found that there are obvious nonlinear characteristics in the process of water–rock interaction. The seepage–stress coupling between water and rock forms negative resistance to water seepage. The water infiltration is a slow and then accelerated process and tends to be stable. Research has shown that the coupling effect of seepage between water and rock increases the damage inside the rock and soil, and its permeability fluctuates randomly at different time steps. This feature is a common manifestation of fractal properties and percolation within rock and soil particles. At the same time, there is a non-equilibrium variation law of pore water pressure inside the rock and soil. This leads to a continuous strengthening of the seepage effect, reaching a stable state. The results of this study are crucial. It not only reveals the mechanism of interaction between water and rock but also correlates the degree of internal damage in rock and soil based on the seepage characteristics between water and rock. The conclusions can provide some reference value for relevant construction methods in the analysis of the formation of water flow characteristics, the prevention of rock slope seepage disasters, and the control of water inrush in tunnel excavation.

Metasomatism of the continental crust and its impact on surface uplift: Insights from reactive‐transport modelling

AbstractHigh‐elevation, low‐relief continental plateaus are major topographic features and profoundly influence atmospheric circulation, sediment transport and storage, and biodiversity. Although orogenic surface‐uplift mechanisms for modern continental plateaus near known plate margins like Tibet are well‐characterized, they cannot account for examples in intracontinental settings like the Colorado Plateau. In contrast to canonical plate‐tectonic uplift mechanisms, broad‐scale hydration‐induced metasomatism of the lower crust has been suggested to reduce its density and increase its buoyancy sufficiently to contribute to isostatic uplift. However, the relationships between key petrophysical properties in these environments are not fully quantified, which limits application of this model. Here, we develop a series of petrological models that describe the petrological and topographic effects of fluid–rock interaction in non‐deforming continental crust of varying composition. We apply an open‐system petrological modelling framework that utilizes reactive‐transport calculations to determine the spatial and temporal scales over which mineralogic transformations take place compared with the magnitude of infiltration of aqueous fluids derived from devolatilization of subducting oceanic lithosphere. The buoyancy effect of hydration‐induced de‐densification is most significant for metabasic lower crust, intermediate for metapelitic crust, and minimal for granodioritic crust. We apply these results to a case study of the ~2 km‐high Colorado Plateau and demonstrate that under ideal conditions, hydration of its lower–middle crust by infiltrating aqueous fluids released by the Farallon slab during Cenozoic low‐angle subduction could have uplifted the plateau surface by a maximum of ~1 km over 16 Myr. However, realistically, although hydration likely has a measurable effect on surface tectonics, the uplift of orogenic plateaus is likely dominantly controlled by other factors, such as lithospheric delamination.

Geochemical and Isotopic Characteristics of the Emir Geothermal Waters in Kula Area, Western Anatolia

In this study, we investigate chemical and isotopic characteristics of thermal waters of the Emir geothermal field in the Kula region, which hosts the youngest volcanism in Turkey. Studied thermal waters with temperature and electrical conductivity values of 21–63 °C and 3840 to 5210 μS/cm are of Na–HCO3 type and have neutral character. δ18O and δD of thermal waters are − 9.40 to − 8.41‰ and − 64.16 to − 56.38‰ (VSMOW) and indicate a meteoric source with local recharge. Tritium values of thermal waters in the Emir geothermal field are mostly < 1 TU signifying a deep circulation. Positive δ13C values (1.32–4.46‰ VPDB) imply that carbon is derived dominantly from marine limestone and dominantly from endogenic CO2. δ18O and δ34S of dissolved sulfate yield that marine limestone is the source of sulfur in thermal waters, which are partly affected by sulfide oxidation and bacterial reduction processes. At discharge temperatures, Emir thermal waters are oversaturated with respect to albite, aragonite, calcite, α-cristobalite, dolomite, gibbsite, illite, K-feldspar, kaolinite, muscovite and quartz but undersaturated for anhydrite and wairakite. The activity diagrams suggest that high Na+ and K+ concentrations in waters are attributed to dissolution of muscovite, K-feldspar and albite. Chemical and isotopic compositions of the Emir thermal waters are controlled by a combination of processes including water–rock interaction, dissolution/precipitation and ion exchange. Various chemical and isotopic geothermometers applied to the thermal waters yielded reservoir temperatures in the range of 80–125 °C. Paleo-temperatures estimated from δ18O values of travertines and thermal waters (isotope fractionation) are consistent with modern discharge temperatures.

Fingerprinting dissolved organic compounds: a potential tool for identifying the surface infiltration environments of meteoric groundwaters

Current methods for tracing decades-old groundwaters rely on isotope geochemistry to determine groundwater age and altitude at the point of infiltration. Temporal and spatial variability in atmospheric conditions, and water–rock interactions, can make the interpretation of isotopes uncertain. Here, we propose a new method of groundwater tracing based on the fingerprinting of natural dissolved organics. We present our initial findings from the Grimsel Test Site in Switzerland, located within a fractured granite. Using 2D gas chromatography, we derive detailed organic fingerprints from surface soils at several locations and show that different soils produce distinctly different dissolved organic signatures. We then compare the soils with groundwater and lake water using a non-targeted approach employing principal component analysis and hierarchical cluster analysis. Our analysis finds three statistically significant clusters. Most groundwaters are clustered with the lake-water samples but two are clustered with soil from the highest altitude surface sampling location. We hypothesize that for samples to form a significant cluster, they must have been derived from a common environment, with a unique combination of organic compounds. For groundwaters to cluster with soil samples or lake water, we theorize there must be a hydraulic connection between the type of infiltration environment and the groundwater sampling locations within each cluster. Our research demonstrates that organic molecules derived from the surface environment can be used to discriminate near-surface environment(s) through which meteoric groundwater has infiltrated. Organic fingerprinting could prove a powerful tool for improved understanding of groundwater flow systems, particularly when combined with other complementary techniques. Supplementary material : Compound alignment data set and supplementary tables are available at https://doi.org/10.6084/m9.figshare.c.7129987 Thematic collection: This article is part of the Sustainable geological disposal and containment of radioactive waste collection available at: https://www.lyellcollection.org/topic/collections/radioactive

Kinetics mechanism of pore pressure effect on CO2-water-rock interactions: An experimental study

Carbon capture, utilization and storage (CCUS) is an effective technology to reduce carbon dioxide (CO2) content in atmosphere, while due to the insufficient mastery of deterioration laws of reservoir rocks caused by CO2, the extensive application of carbon storage projects is hindered by the leakage risk. Therefore, it was aimed to study the kinetics mechanism of pore water pressure on CO2-water–rock interactions. First, the pressure effect on water–rock interactions was studied to obtain the relationship between ratio of solid–liquid contact area Ψ and pore pressure, and the controlling mechanism of Ψ on reaction rate ri was verified. On this basis, the pressure effect on CO2-water–rock interactions was further studied. Considering the effects on Ψ and solution acidity, the original CO2-applicable kinetics equation was modified to reduce the error of calculating reaction rate by 33.60% on average. Meanwhile, a forecast method was proposed for the reaction rate under different pressure conditions, and the average calculation error was 41.00% lower than that of original kinetics equation. After verifying the accuracy of these two theoretical methods to calculate reaction rate, the reliability to calculate porosity evolution process was further verified, and the calculation errors could be reduced by 29.52% and 31.81%, respectively.

Using internal standards in time-resolved X-ray micro-computed tomography to quantify grain-scale developments in solid-state mineral reactions

Abstract. X-ray computed tomography has established itself as a crucial tool in the analysis of rock materials, providing the ability to visualise intricate 3D microstructures and capture quantitative information about internal phenomena such as structural damage, mineral reactions, and fluid–rock interactions. The efficacy of this tool, however, depends significantly on the precision of image segmentation, a process that has seen varied results across different methodologies, ranging from simple histogram thresholding to more complex machine learning and deep-learning strategies. The irregularity in these segmentation outcomes raises concerns about the reproducibility of the results, a challenge that we aim to address in this work. In our study, we employ the mass balance of a metamorphic reaction as an internal standard to verify segmentation accuracy and shed light on the advantages of deep-learning approaches, particularly their capacity to efficiently process expansive datasets. Our methodology utilises deep learning to achieve accurate segmentation of time-resolved volumetric images of the gypsum dehydration reaction, a process that traditional segmentation techniques have struggled with due to poor contrast between reactants and products. We utilise a 2D U-net architecture for segmentation and introduce machine-learning-obtained labelled data (specifically, from random forest classification) as an innovative solution to the limitations of training data obtained from imaging. The deep-learning algorithm we developed has demonstrated remarkable resilience, consistently segmenting volume phases across all experiments. Furthermore, our trained neural network exhibits impressively short run times on a standard workstation equipped with a graphic processing unit (GPU). To evaluate the precision of our workflow, we compared the theoretical and measured molar evolution of gypsum to bassanite during dehydration. The errors between the predicted and segmented volumes in all time series experiments fell within the 2 % confidence intervals of the theoretical curves, affirming the accuracy of our methodology. We also compared the results obtained by the proposed method with standard segmentation methods and found a significant improvement in precision and accuracy of segmented volumes. This makes the segmented computed tomography images suited for extracting quantitative data, such as variations in mineral growth rate and pore size during the reaction. In this work, we introduce a distinctive approach by using an internal standard to validate the accuracy of a segmentation model, demonstrating its potential as a robust and reliable method for image segmentation in this field. This ability to measure the volumetric evolution during a reaction with precision paves the way for advanced modelling and verification of the physical properties of rock materials, particularly those involved in tectono-metamorphic processes. Our work underscores the promise of deep-learning approaches in elevating the quality and reproducibility of research in the geosciences.