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We use the crystallinity of hydrated silica, represented by the 1.4 μm absorption position in orbiter spectroscopic data, as a proxy for the longevity of water–rock interaction in the Syrtis Major region. Geological maps and crater size–frequency distribution analyses are employed to contextualize mineral detections and estimate surface ages. Hydrated silica is detected within two distinct geological units: a younger “volcanic terrain” (vt) unit (∼2.4 Ga) and an older “highland terrain” (ht) unit (3.5–3.7 Ga). Hydrated silica in the vt unit typically has a band position <1.41 μm, consistent with amorphous opal‐A, suggesting these younger terrains have experienced limited interaction with water. In contrast, hydrated silica in the older highlands typically has a band position >1.41 μm, indicating opal‐CT, suggesting that these deposits have had more time to interact with water, while also producing accessory minerals such as kaolinite and Fe/Mg phyllosilicates. Plain Language Summary This study explores the interactions between water and rocks in a region on Mars known as Syrtis Major by investigating a mineral‐like substance called hydrated silica. The structure of hydrated silica helps us estimate the extent of water interaction and its effects on the rocks. We used satellite data to locate this mineral across Syrtis Major and infer its crystal structure. Furthermore, we developed detailed geological maps and estimated surface ages to understand the geological context. We found that hydrated silica is located in two different types of areas: (a) a younger volcanic region; and (b) an older highland region. In the younger volcanic areas, it appears that less crystalline hydrated silica formed by interaction with small amounts of water, possibly during later volcanic activity. In the older highlands, more crystalline hydrated silica likely interacted with water for a longer duration or in larger amounts. This information aligns with the idea that the older highlands experienced more extensive or long‐lasting interactions with water compared to the younger volcanic regions. It provides insights into different wet periods in Mars' past, aiding our understanding of the planet's geological history and the role water played in shaping its surface. Key Points We analyzed the crystallinity of hydrated silica in Syrtis Major to infer the extent and longevity of water–rock interaction Amorphous silica is found in young volcanic terrains within Nili and Meroe Paterae and more crystalline silica in the older highlands Older highland regions likely underwent a longer interaction with water compared to younger volcanic terrains

To improve our understanding of hydrothermal activity on the Yellowstone Plateau volcanic field, we collected and analyzed a large data set of δ2H, δ18O, and the 3H concentrations of circum‐neutral and alkaline waters. We find that (a) hot springs are fed by recharge throughout the volcanic plateau, likely focused through fractured, permeable tuff units. Previous work had stressed the need for light δ2H water recharge restricted to the northern part of the plateau or recharge during past cold periods. However, new data from the Y‐7 drill hole suggests that recharge is not restricted to a certain area or a cold period. (b) δ18O values of thermal waters in the geyser basins are shifted from the global meteoric water line by temperature‐dependent water‐rock reactions with higher subsurface temperatures resulting in a greater shift. (c) Large temporal variations in the isotopic composition of meteoric water recharge and small temporal variability in the isotopic composition of hot spring discharge implies that the volume of groundwater in, and around the Yellowstone caldera is substantially larger than the volume of annual water recharge. (d) Hot springs discharged through different rhyolitic units correlate with identifiable differences in δ2H and δ18O compositions, 3H concentrations, and water chemistry that imply equilibration at different temperatures and travel along different flow paths. (e) Based on measured 3H concentrations, we calculate that hot spring waters in the central part of the geyser basins mostly contain <2% post‐1950 meteoric water, whereas waters discharged at the basin margins contain larger fractions of post‐1950s meteoric water.

Carbon neutrality has become a global common goal. CCUS, as one of the technologies to achieve carbon neutrality, has received widespread attention from academia and industry. After CO2 enters the formation, under the conditions of formation temperature and pressure, supercritical CO2, formation water, and rock components interact, which directly affects the oil and gas recovery and carbon sequestration efficiency. In this paper, the recent progress on CO2 water–rock interaction was reviewed from three aspects, including (i) the investigation methods of CO2 water–rock interaction; (ii) the variable changes of key minerals, pore structure, and physical properties; and (iii) the nomination of suitable reservoirs for CO2 geological sequestration. The review obtains the following three understandings: (1) Physical simulation and cross-time scale numerical simulation based on formation temperature and pressure conditions are important research methods for CO2 water–rock interaction. High-precision mineral-pore in situ comparison and physical property evolution evaluation are important development directions. (2) Sensitive minerals in CO2 water–rock interaction mainly include dolomite, calcite, anhydrite, feldspar, kaolinite, and chlorite. Due to the differences in simulated formation conditions or geological backgrounds, these minerals generally show the pattern of dissolution or precipitation or dissolution before precipitation. This differential evolution leads to complex changes in pore structure and physical properties. (3) To select the suitable reservoir for sequestration, it is necessary to confirm the sequestration potential of the reservoir and the later sequestration capacity, and then select the appropriate layer and well location to start CO2 injection. At the same time, these processes can be optimized by CO2 water–rock interaction research. This review aims to provide scientific guidance and technical support for shale oil recovery and carbon sequestration by introducing the mechanism of CO2 water–rock interaction, expounding the changes of key minerals, pore structure, and physical properties, and summarizing the sequestration scheme.

Natural radiogenic isotopes (primarily 87Sr/86Sr) from hot springs in the Upper Geyser Basin of the Yellowstone Plateau volcanic field and associated rocks were used to evaluate groundwater flow patterns, water‐rock reactions, and the extent of mixing between various groundwater sources. Thermal waters have very low uranium concentrations and 234U/238U activity ratios near 1.0, which limit their utility as tracers in this reducing setting. Thermal waters have higher Sr concentrations (<22 ng/g) and a wide range of 87Sr/86Sr values that vary both temporally at individual discharge sites and between adjacent springs, indicating that conduits tap different subsurface reservoirs to varying degrees. Sr from local rhyolites have 87Sr/86Sr compositions that bound the range of values observed in groundwater throughout the basin. Non‐boiling springs on the west flank of the basin discharge water with low 87Sr/86Sr consistent with flow through young volcanic rocks exposed at the surface. Boiling springs in the central basin have higher 87Sr/86Sr values reflecting interactions with older, more radiogenic volcanic rocks. Variability in upwelling thermal waters requires mixing with a low 87Sr/86Sr component derived from young lava or glacial sediments, or more likely, from deeper sources of hot groundwater circulating through buried Lava Creek Tuff having intermediate 87Sr/86Sr. Isotope data constrain basin‐wide output of thermal water to 110–140 kg·s−1. Results underscore the utility of radiogenic Sr isotopes as valuable tracers of hydrothermal flow patterns and improve the understanding of temperature‐dependent water‐rock reactions in one of the largest continental hydrothermal systems on Earth. Plain Language Summary Radiogenic isotopes of strontium (87Sr/86Sr) vary widely in rocks and the waters that interact with them. We use 87Sr/86Sr in waters from hot springs in the Upper Geyser Basin of the Yellowstone Plateau volcanic field to help define patterns of groundwater flow through subsurface volcanic rocks. Lava flows and tuffs adjacent to and underlying the basin have different 87Sr/86Sr compositions reflecting different crustal and mantle components incorporated during rhyolite generation. Groundwater interacting with those rocks inherits their 87Sr/86Sr signature, which can then be used to trace subsurface flowpaths. Modern and past hot springs along the basin margin discharge water having low 87Sr/86Sr values that indicate groundwater was restricted to shallow flowpaths through younger volcanic rocks. Hot springs in the central basin have compositions reflecting mixing between groundwater flowing through deeper and older, high‐87Sr/86Sr volcanic rocks and groundwater having lower 87Sr/86Sr values. The low‐87Sr/86Sr component could be derived from shallow sources (young volcanic rocks or glacial sediments) or from more‐deeply buried tuff associated with the most recent collapse of the Yellowstone caldera. The data presented here provide a means of tracing hydrothermal flow patterns in complex volcanic environments and improve the understanding of hydrothermal activity in one of the largest active continental magmatic systems on Earth. Key Points Water from hot springs in the Upper Geyser Basin has 87Sr/86Sr derived from volcanic rocks flanking and underlying the basin Variable 87Sr/86Sr in water from springs in proximity and over time reflect mixing between groundwater in distinct rock reservoirs Reducing conditions along flowpaths yield groundwater with low U concentrations and 234U/238U activities near 1.0

CO2–water–rock interactions have an important impact on the stability and integrity of the caprock in CO2 geological storage projects. The injected CO2 in the reservoir enters the caprock via different mechanisms, leading to either the dissolution or precipitation of minerals. The mineral alterations change the porosity, permeability, and mechanical properties of the caprock, affecting its sealing capability. To evaluate the sealing effectiveness of overlying caprock and identify the influencing factors, numerical simulations and experiments were carried out on the mudstone Dongying Formation in Dezhou, China. Based on high-temperature and high-pressure autoclave experiments, batch reaction simulations were performed to obtain some key kinetic parameters for mineral dissolution/precipitation. Then, they were applied to the following simulation. The simulation results indicate that gaseous CO2 has migrated 7 m in the caprock, while dissolved CO2 migrated to the top of the caprock. Calcite is the dominant mineral within 1 m of the bottom of the caprock. The dissolution of calcite increases the porosity from 0.0625 to 0.4, but the overall porosity of the caprock decreases, with a minimum of 0.054, mainly due to the precipitation of montmorillonite and K-feldspar. A sensitivity analysis of the factors affecting the sealing performance of the caprock considered the changes in sealing performance under different reservoir sealing conditions. Sensitivity analysis of the factors affecting the sealing performance of the caprock indicates that the difference in pressure between reservoir and caprock affects the range of CO2 transport and the degree of mineral reaction, and the sealing of the caprock increases with the difference in pressure. Increasing the initial reservoir gas saturation can weaken the caprock’s self-sealing behavior but shorten the migration distance of CO2 within the caprock. When the content is lower than 2%, the presence of chlorite improves the sealing performance of the caprock and does not increase with further chlorite content. This study elucidates the factors that affect the sealing ability of the caprock, providing a theoretical basis for the selection and safety evaluation of CO2 geological storage sites.

Large amounts of anthropogenic CO2 in the atmosphere are taken up when the ocean alters the seawater carbonate system, which could have a significant impact on carbonate-rich sediments. Coral reef limestone is a special biogenic carbonate, which is mainly composed of calcium carbonate. When carbonate-rich rocks are brought into contact with a CO2 weak acid solution, they will be dissolved, which may affect the physical and mechanical properties of the rock. In this paper, the physical and chemical interactions between CO2, seawater and the framework structure reef limestone were studied based on an experiment conducted in a hydrothermal reactor. The solution was analyzed for dissolved Ca2+ concentration during the reaction, and the rock mass, effective volume (except for the volume of open pores), permeability, images from electron microscopy and X-ray microtomography were contrasted before and after immersion. The uniaxial compressive and tensile strength tests were conducted, respectively, to clarify the mechanical response of the rock after the reaction. The results indicate that dissolution occurred during the reaction, and the calcium ions of the solution were increased. The physical properties of the rock were changed, and the permeability significantly increased. Because the rocks were soaked for only 15 days, the total cumulative amount of calcium carbonate dissolved was less, and the mechanical properties were not affected.

This study investigates the hydrochemistry of the Mandi Baha-Ud-Din district, which is an important part of the Jhelum Basin. The study area is highly populated with low facilities in the provision of clean drinking water. A Geographic Information System (GIS) was used to map the spatial variability of different physicochemical parameters. A total of 59 analysed groundwater samples indicated that the ionic concentration was in the order of Na+ > Ca2+ > Mg2+ > K+ for major cations and HCO3− > SO42− > Cl− > NO3− > F− > CO32− for anions. Traces of arsenic and other toxic elements were found in the vicinity of the industrial zone, but they are well below the designated thresholds. The bivariate Gibbs diagram illustrates that 75–80% of samples fall in the rock-water interaction zone, and the rest of the samples lie in the rock-water interaction and evaporation processes. Piper’s plot revealed that seven samples were dominated by alkaline earth metals, seven samples showed the nature of alkalies, and the rest of the samples showed mixed character. Final water quality index (82) shows that the water quality is generally “good”, per the NSFWQI classification. This paper illustrates hydrochemical facies along with a natural mechanism controlling overall water chemistry.

The protection of water resource has been the significant mission globally. Hydrochemical compositions and recharge source are the critical tools to analyze the water quality. In this study, 18 surface water and 5 groundwater samples were collected along the Xiongqu and Sequ rivers in the northern Longzi county of southern Tibet. The combination of factor analysis, correlation of major ions, geochemical modeling, and D–O–Sr isotopes were employed to clarify the hydrochemical compositions and recharge source. The concentration of major ions followed the abundance order of > > Cl for anions and Ca > Mg > Na > K for cations. Ca–HCO and Ca–SO types were identified for groundwater and surface water. Based on ratios of major ions and geochemical modeling, it is proposed that the dissolutions of gypsum, calcite, and dolomite controlled the hydrochemical compositions. D–O isotopes indicated a meteoric origin for surface water and groundwater, with the recharge elevation of 2,519–3,731 m. The Sr/ Sr ratios of groundwater and surface water were compatible with those of sulfate and carbonate minerals, revealing the main type of minerals interacting with water. The achievements of this study can provide a vital reference for groundwater utilization and protection in the Longzi county and adjacent areas in the Tibet.

The Krafla geothermal system is located in Iceland's northeastern neovolcanic zone, within the Krafla central volcanic complex. Geothermal fluids are superheated steam closest to the magma heat source, two‐phase at higher depths, and sub‐boiling at the shallowest depths. Hydrogen isotope ratios of geothermal fluids range from −87‰, equivalent to local meteoric water, to −94‰. These fluids are enriched in 18O relative to the global meteoric line by +0.5–3.2‰. Calculated vapor fractions of the fluids are 0.0–0.5 wt% (~0–16% by volume) in the northwestern portion of the geothermal system and increase towards the southeast, up to 5.4 wt% (~57% by volume). Hydrothermal epidote sampled from 900 to 2500 m depth has δD values from −127 to −108‰, and δ18O from −13.0 to −9.6‰. Fluids in equilibrium with epidote have isotope compositions similar to those calculated for the vapor phase of two‐phase aquifer fluids. We interpret the large range in δDEPIDOTE and δ18OEPIDOTE across the system and within individual wells (up to 7‰ and 3.3‰, respectively) to result from variable mixing of shallow sub‐boiling groundwater with condensates of vapor rising from a deeper two‐phase reservoir. The data suggest that meteoric waters derived from a single source in the northwest are separated into the shallow sub‐boiling reservoir, and deeper two‐phase reservoir. Interaction between these reservoirs occurs by channelized vertical flow of vapor along fractures, and input of magmatic volatiles further alters fluid chemistry in some wells. Isotopic compositions of hydrothermal epidote reflect local equilibrium with fluids formed by mixtures of shallow water, deep vapor condensates, and magmatic volatiles, whose ionic strength is subsequently derived from dissolution of basalt host rock. This study illustrates the benefits of combining phase segregation effects in two‐phase systems during analysis of wellhead fluid data with stable isotope values of hydrous alteration minerals when evaluating the complex hydrogeology of volcano‐hosted geothermal systems. Geothermal fluids in the Krafla geothermal system, northeast Iceland, have been characterized using oxygen and hydrogen isotopes, CO2 content, vapor content and temperature, and compared with hydrogen and oxygen isotope compositions of fluids that would be in equilibrium with hydrothermal epidote sampled from producing geothermal wells. We propose that vapor, rising from a two‐phase aquifer close to the magma heat source, variably mixes with the primary producing aquifer at ~1000 m depth, producing the observed heterogeneity in fluid properties across the geothermal system.