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Barite (BaSO4) and celestite (SrSO4) are the end-members of a nearly ideal solid solution. Most of the exploitable deposits of celestite occur associated with evaporitic sediments which consist of gypsum (CaSO4·2H2O) or anhydrite (CaSO4). Barite, despite having a broader geological distribution is rarely present in these deposits. In this work, we present an experimental study of the interaction between gypsum crystals and aqueous solutions that bear Sr or Ba. This interaction leads to the development of dissolution-crystallization reactions that result in the pseudomorphic replacement of the gypsum crystals by aggregates of celestite or barite, respectively. The monitoring of both replacement reactions shows that they take place at very different rates. Millimeter-sized gypsum crystals in contact with a 0.5 M SrCl2 solution are completely replaced by celestite aggregates in less than 1 day. In contrast, only a thin barite rim replaces gypsum after seven days of interaction of the latter with a 0.5 M BaCl2 solution. We interpret that this marked difference in the kinetics of the two replacement reactions relates the different orientational relationship that exists between the crystals of the two replacing phases and the gypsum substrate. This influence is further modulated by the specific crystal habit of each secondary phase. Thus, the formation of a thin oriented layer of platy barite crystals effectively armors the gypsum surface and prevents its interaction with the Ba-bearing solution, thereby strongly hindering the progress of the replacement reaction. In contrast, the random orientation of celestite crystals with respect to gypsum guarantees that a significant volume of porosity contained in the celestite layer is interconnected, facilitating the continuous communication between the gypsum surface and the fluid phase and guaranteeing the progress of the gypsum-by-celestite replacement.

We have identified that diplonemids, an abundant group of marine planktonic protists, accumulate conspicuous amounts of Sr 2+ and Ba 2+ in the form of intracellular barite and celestite crystals, in concentrations that greatly exceed those of the most efficient Ba/Sr-accumulating organisms known to date. We propose that diplonemids are potential players in Ba 2+ /Sr 2+ cycling in the ocean and have possibly contributed to sedimentary rock formation over long geological periods. Barium and strontium are often used as proxies of marine productivity in palaeoceanographic reconstructions of global climate. However, long-searched biological drivers for such correlations remain unknown. Here, we report that taxa within one of the most abundant groups of marine planktonic protists, diplonemids (Euglenozoa), are potent accumulators of intracellular barite (BaSO 4 ), celestite (SrSO 4 ), and strontiobarite (Ba,Sr)SO 4 . In culture, Namystinia karyoxenos accumulates Ba 2+ and Sr 2+ 42,000 and 10,000 times higher than the surrounding medium, forming barite and celestite representing 90% of the dry weight, the greatest concentration in biomass known to date. As heterotrophs, diplonemids are not restricted to the photic zone, and they are widespread in the oceans in astonishing abundance and diversity, as their distribution correlates with environmental particulate barite and celestite, prevailing in the mesopelagic zone. We found diplonemid predators, the filter-feeding zooplankton that produces fecal pellets containing the undigested celestite from diplonemids, facilitating its deposition on the seafloor. To the best of our knowledge, evidence for diplonemid biomineralization presents the strongest explanation for the occurrence of particulate barite and celestite in the marine environment. Both structures of the crystals and their variable chemical compositions found in diplonemids fit the properties of environmentally sampled particulate barite and celestite. Finally, we propose that diplonemids, which emerged during the Neoproterozoic era, qualify as impactful players in Ba 2+ /Sr 2+ cycling in the ocean that has possibly contributed to sedimentary rock formation over long geological periods. IMPORTANCE We have identified that diplonemids, an abundant group of marine planktonic protists, accumulate conspicuous amounts of Sr 2+ and Ba 2+ in the form of intracellular barite and celestite crystals, in concentrations that greatly exceed those of the most efficient Ba/Sr-accumulating organisms known to date. We propose that diplonemids are potential players in Ba 2+ /Sr 2+ cycling in the ocean and have possibly contributed to sedimentary rock formation over long geological periods. These organisms emerged during the Neoproterozoic era (590 to 900 million years ago), prior to known coccolithophore carbonate biomineralization (~200 million years ago). Based on reported data, the distribution of diplonemids in the oceans is correlated with the occurrence of particulate barite and celestite. Finally, diplonemids may provide new insights into the long-questioned biogenic origin of particulate barite and celestite and bring more understanding of the observed spatial-temporal correlation of the minerals with marine productivity used in reconstructions of past global climate.

Xinglong County is an important groundwater recharge area for the Beijing-Tianjin-Hebei region, northern China, as well as a potential area to develop strontium (Sr)-rich mineral water. Combining the regional hydrogeological setting and hydrochemical investigation associated with five surface-water samples and 72 groundwater samples, the source and the spatial variation of Sr2+, the processes of water–rock interaction, and the Sr2+ enrichment mechanism were elucidated. To reduce the uncertainty related to the potentially ambiguous interpretation of laboratory results, some leaching experiments were conducted. The results showed that the groundwater was mainly HCO3–Ca·Mg type, and the concentration of Sr2+ ranged from 0.04 to 6.2 mg/L. Groundwater with elevated Sr2+ concentration was mainly distributed in eastern and southern Xinglong County, where metamorphic rocks and intrusive rocks occur, while low Sr2+ groundwater (<0.2 mg/L) was found in the aquifers comprised of pure carbonate rocks. Further analysis revealed that high Sr2+ concentrations are not present in specific rocks but are closely related to minerals, mainly originating from the dissolution of celestite, gypsum, calcite and strontianite. In addition, the high level of Sr2+ in groundwater is greatly determined by hydrogeological setting. The relatively impermeable intrusive rocks and overlying carbonate rocks provide sufficient water storage space, where Sr-rich groundwater was formed during the process of long-term water–rock interaction. The concept of groundwater storage space is proposed to explore the mechanism of elevated Sr2+ concentration in groundwater from a new perspective. This study may provide support for the development and utilization of mineral water and water resources conservation.

Due to the special hydrogeological conditions in karst areas, groundwater responds quickly to rainfall. The covariation of ion concentrations and spring discharge can help better understand the hydrogeochemical process of groundwater occurring in the heterogeneous karst aquifers. In this study, high-resolution monitoring of groundwater discharge, hydrochemistry, and stable isotopes was conducted at the Qingjiangyuan (QJY), a spring of the Qingjiang watershed in Hubei, China. The purpose is to investigate the changes in hydrogeochemical processes and chemical weathering under the influence of rainfall. The dynamics of spring discharge indicate the presence of pipelines and fissures of different sizes. According to the spring discharge attenuation curves, there are at least three medium types in the aquifer, which account for 45.7%, 34.2%, and 20.1% of the total groundwater. Pearson correlation analysis shows that the main sources of the solute in the QJY are carbonate minerals (mainly calcite and dolomite), evaporites (mainly gypsum and sylvite), celestite, and strontianite. Anthropogenic activities have less impact on groundwater solutes. Although carbonate minerals dominate the hydrochemistry, the changes in hydrogeochemical behavior caused by rainfall may come from gypsum, which is supported by the ion concentrations. At the early rainfall stage, Ca 2+ concentration increased from 42.9 to 45.6 mg/L, followed by the SO 4 2− from 15.2 to 16.6 mg/L. When the discharge increased to the maximum (2320 L/s), Ca 2+ and SO 4 2− showed opposite trends, decreased to 39.7 mg/L and 10.4 mg/L, respectively. The results also suggest that carbonate rocks and evaporites have important roles in hydrochemistry. The contributions of these three end-members were quantified based on the law of mass conservation. The proportions of carbonate weathering and evaporite weathering were 83.4% (85.2–80.3%) and 11.6% (6.9–18.0%), respectively, and rain was 5.0% (0.1–10.4%). These results were integrated into a hydrogeological conceptual model that explains the hydrogeochemical processes, including rock weathering, piston, and dilution effects caused by rainfall. The proposed conceptual model helps to improve the understanding of hydrogeochemical processes and chemical weathering in karst areas.

This paper confirms the regularities of the formation of increased concentrations of strontium (Sr) in fresh groundwater used for drinking water supply, depending on the time they are residen in the carbonate deposits of the aquifer. On average, every thousand years, the Sr concentration increases by 2.1–3.5 mg L−1. In addition, high strontium content is positively correlated with altitude and well depth and negatively correlated with redox conditions in the aquifer. Large relief elevations are associated with the development of marginal moraine deposits from the Last Glacial Period composed predominantly of clay, which contributes to a decrease in water exchange. The high Sr content is associated with the dissolution of significant formations of celestite and strontianite, up to their ore occurrences. For this reason, the saturation indices (SIs) for celestite and strontianite correlate with TDS and rise to − 1.42 and 2.05, respectively. Low Sr values do not correlate with the residence time of groundwater in the aquifer or the depth of wells and tend to depressions in the relief, with a virtual absence of overlying sediments and positive Eh values, which indicates an active water exchange. The low level of Sr is associated with the dissolution of gypsum, calcite, and dolomite containing strontium as an impurity. This causes the SIs for gypsum, calcite, and dolomite to correlate with TDS, while for celestite and strontianite, the SI drops to − 5.02 and − 0.92, respectively. The established patterns make it possible to more reasonably choose places for the construction of water wells to obtain drinking water of standard quality.

The Middle-Jurassic Opalinus Clay is the foreseen host rock for radioactive waste disposal in central northern Switzerland. An extensive drilling campaign aiming to characterize the argillaceous formation resulted in a comprehensive drill core data set. The rheologically weak Opalinus Clay is only mildly deformed compared to the over- and underlying rock units but shows a variety of natural fractures. While these structures are hydraulically indistinguishable from macroscopically non-deformed Opalinus Clay today, their analysis allows for a better understanding of the deformation behaviour in the geological past. Here, we present an overview of the different fracture and fault types recorded in the Opalinus Clay and a detailed microstructural characterization of veins—natural dilational fractures healed by secondary calcite and celestite mineralizations. Macroscopic drill core analysis revealed five different natural fracture types that encompass tension gashes of various orientations with respect to bedding and small-scale faults with displacements typically not exceeding the drill core diameter. The occurrence of different fault types generally fits well with the local tectonic setting of the different drilling sites and with respect to the neighbouring regional fault zones. The microstructural investigations of the various vein types revealed their often polyphase character. Fibrous bedding-parallel veins of presumable early age were found to be overprinted by secondary slickenfibres. The polyphase nature of fibrous bedding parallel veins and slickenfibres is supported by differing elemental compositions, pointing towards repeated fracturing and mineralization events. Direct dating of vein calcites with U–Pb was unsuccessful. Nevertheless, age constraints can be inferred from structural orientations and fault slip kinematics. Accordingly, some of the veins already formed during sediment compaction in Mesozoic times, others possibly relate to Early Cenozoic foreland uplift. The youngest veins are most likely related to Late Cenozoic regional tectonic events, such as the Jura fold-and-thrust belt to the south and the Hegau-Lake Constance Graben to the northeast of the study area. During these latest tectonic events, previously formed veins acted as rheologically stiff discontinuities in the otherwise comparably weak Opalinus Clay along which deformation of the rock formation was re-localized.

The onset of scaling in oil pipelines can halt or drastically reduce oil production, causing huge financial losses and delays. Current methods used to monitor scaling can take weeks, while the scaling process only takes few hours. The proposed sensor is designed for online monitoring of strontium ions concentration in seawater as an early scaling indicator. The sensor operates in the GHz range by probing the shift in the resonance frequency due to changes in the ionic concentrations of the medium. The results show selective sensitivity to changes in the strontium ions concentration even in the presence of many other ions found in seawater. The measured sensitivity is found to be stable and linear with a detection level of better than 0.08% (0.042 mol/L) of strontium ions in seawater. This work demonstrates a robust GHz sensor for strontium sulfate scale monitoring and early detection, which could be used in the oil industry to prevent huge production losses. These results could also be extended further to target the monitoring of other ions in different industrial sectors.

Achieving net-zero carbon emissions, this study introduces a sustainable pathway for reducing strontium sulfate (SrSO4) and celestite ore to strontium sulfide (SrS) using biofuels (biomethane, bioethanol) derived from agro-industrial waste and green hydrogen. Traditional SrSO4 reduction methods, which rely on fossil-derived reductants like coal and operate at energy-intensive temperatures (1100–1200 °C), generate significant greenhouse gases and toxic byproducts, highlighting the need for eco-friendly alternatives. Experimental results demonstrate that bioethanol outperformed other reductants, achieving 97% conversion of synthetic SrSO4 at 950 °C within 24 min and 74% conversion of natural celestite ore over 6 h. Remarkably, this bioethanol-driven process matches the energy efficiency of the conventional black ash method while enabling carbon neutrality through renewable feedstock utilization, reducing CO2 emissions by 30–50%. By valorizing agro-industrial waste streams, this strategy advances circular economy principles and aligns with Mexico’s national agenda for sustainable industrial practices, including its commitment to decarbonizing heavy industries. This study contributes to sustainable development goals and offers a scalable solution for decarbonizing strontium compound production in the chemical industry.

Geothermal installations often face operational challenges related to scaling which can lead to loss in production, downtime, and an increase in operational costs. To accurately assess and minimize the risks associated with scaling, it is crucial to understand the interplay between geothermal brine composition, operating conditions, and pipe materials. The accuracy of scaling predictive models can be impacted by uncertainties in the brine composition, stemming from sub-optimal sampling of geothermal fluid, inhibitor addition, or measurement imprecision. These uncertainties can be further increased for fluid at extreme conditions especially high salinity and temperature. This paper describes a comprehensive method to determine operational control strategies to minimize the scaling considering brine composition uncertainties. The proposed modelling framework to demonstrate the optimization under uncertainty workflow consists of a multiphase flow solver coupled with a geochemistry model and an uncertainty quantification workflow to locally estimate the probability of precipitation potential, including its impact on the hydraulic efficiency of the geothermal plant by increasing the roughness and/or decreasing the diameter of the casings and pipelines. For plant operation optimization, a robust control problem is formulated with scenarios which are generated based on uncertainties in brine composition using an exhaustive search method. The modelling and optimization workflow was demonstrated in a geothermal case study dealing with barite and celestite scaling in a heat exchanger. The results showed the additional insights in the potential impact of brine composition uncertainties (aleatoric uncertainties) in scaling potential and precipitation location. Comparing the outcome of optimization problem for the deterministic and fluid composition uncertainties, a change of up to 2.5% in the temperature control settings was observed to achieve the optimal coefficient of performance.

Sedimentary rocks of the Upper Cretaceous, Middle Miocene, Plio-Pleistocene, and Quaternary periods are present in the Red Sea coastal plain from south of El Quseir to Marsa Alam, and they are dispersed over Late Proterozoic basement rocks. The zinc and lead ores intercalated with celestite in Wadi Essel are dispersed throughout the adjacent rocks and intense in Middle Miocene sedimentary strata in clastic rocks. This work studied the fluid inclusions hosted in the celestite, which is in close to the lead–zinc mineralization, to measure the microthermometric parameters giving knowledge about the nature, composition and the condition of formation of celestite as well as lead- zinc mineralization. The fluid inclusions study for the celestite revealed that this celestite deposited from saline water (up to 9.054 wt% NaCl eq.) with density up to 1.045 g/cm 3 and the deposition of the celestite probably took place at temperatures between 50 and 75 °C for Wadi Essel celestite as well as accompanying lead–zinc sulphide, which considered as Mississippi valley type (MVT) Pb–Zn deposits.