Brine Evolution Research Articles

Geochemical evolution of the Dead Sea brine during the last glacial cycle from chemical compositions of interstitial soluble salts

The chemical evolution of the brines that filled the Dead Sea Basin during the final phase of the last interglacial and throughout the last glacial period is constructed from the temporal variations in the Na/Cl, Mg/Cl, Br/Cl, and Br/Mg ratios of soluble salts that extracted from cores that were drilled at the modern Dead Sea floor and from sediments of the last glacial Lisan Fm. that are exposed at the high terraces above the modern Dead Sea (covering the ∼ 100–13 ka period).The main observations are: (1) Variations in the Na/Cl ratios reflect processes of halite precipitation/dissolution during arid/wet periods in the drainage basin, respectively, and exchanges between the upper and the lower brines; (2) Ions of Na + and Cl-were supplied to the brines by the dissolution of halite from the Mount Sedom salt diapir, and of halite deposits, which precipitated in the lake during the hyper-arid periods of the last interglacial; (3) The upper brine of Lake Lisan was sensitive to the hydroclimatic conditions in the lake’s drainage basin, since being directly exposed to the atmosphere, and to variations in flows of freshwater and groundwater brines, which had distinct influence on its chemical record. At the same time, the lower brine was isolated from the surroundings, by the overlying brine and received chemical inputs only by restrict mixing between the brines which buffered the intensity of regional hydro-climatic events.Temporal patterns in the Na/Cl ratios indicate that between ∼ 100–30 ka, the deep brine evolved through a moderate but steady “enrichment” by Na + and Cl-ions due to continuous dissolution of halite by the upper brine of the lake. Towards the end of this period, between ∼ 43–30 ka, the Amiaz plain, a marginal basin, comprised a semi-isolated water-body that witnessed frequent episodes of halite precipitation/dissolution with temporal patterns that resemble millennial temperature (δ18O) variations in the Greenland ice core.Between ∼ 30–18 ka (MIS 2), when Lake Lisan reached its highest stands and maximumspatialexpansion, the soluble salts from the deepest basin and from the high sections of the Lisan Fm. indicate on centennial dissolution cycles of the Mount Sedom salt diapir that took place in the upper brine and sank down to the lower brine. During the ∼ 18–14 ka decline of the lake to its low levels of the Holocene, the elemental ratios reveal several episodes of enhanced supply of freshwater to the shrinking lake, causing intensified halite dissolution and supply of Na + and Cl- ions to the deep basin, setting the grounds for massive halite precipitation, which initiated after a sharp level decline at ∼ 14 ka.The long-term (∼100–13 ka) temporal pattern in the elemental ratios of the lower brine resembles global CO2concentrations and sea surface temperature trends, while the short-term fluctuations in the upper brine are correlated with short warm/cold cycles in the Greenland ice core δ18O data, indicating a strong impact of the global climate.

Hydrochemical Characteristics and Evolution of Underground Brine in Lop Nur, Northwestern China

AbstractLop Nur is located at the eastmost end of the Tarim Basin in Xinjiang, Northwestern China. This study reviews the hydrochemical characteristics and evolution of underground brine in Lop Nur, based on analytical data from 429 water samples (mainly brine). It is found that in the NE–SW direction, from the periphery to the Luobei sub‐depression, while the hydrochemical type varies from the sodium sulfate subtype (S) to the magnesium sulfate subtype (M), the corresponding brine in the phase diagram transfers from the thenardite phase (Then) area, through the bloedite phase (Blo), epsomite phase (Eps), picromerite phase (Picro), finally reaching the sylvite phase (Syl) area. As for the degree of evolution, the sequence is the periphery < Luobei horizontally and the overlying glauberite brine < the underlying clastic brine vertically. It is concluded that the oxygen and hydrogen isotopic compositions of the brine have evidently been affected through the effects of evaporation and altitude, as well as the changes in local water circulation in recent years. Boron and chloride isotopic compositions show that the glauberite brine is formed under more arid conditions than the clastic one. The strontium isotopic composition indicates that the Lop Nur brine primarily originates from surface water; however, deep recharge may also be involved in the evolution of the brine, according to previous noble gas studies. It is confirmed that the brine in Lop Nur has become enriched with potassium prior to halite precipitation over the full course of the salt lake's evolution. Based on chemical compositions of brine from drillhole LDK01 and previous lithological studies, the evolution of the salt lake can be divided into three stages and it is inferred that the brine in Lop Nur may have undergone at least two significant concentration‐dilution periods.

Application of hierarchical cluster analysis and principal component analysis to identify compositional trends of brine in crystalline basements and sedimentary basins

The present study identifies distinct geochemical signatures of deep brines originating from crystalline basements and sedimentary basins. A corresponding conceptual hydrogeochemical model is developed outlining the evolution of crystalline and sedimentary brines. The combined application of Hierarchical Cluster Analysis and Principal Component Analysis allowed the identification of evolutionary trends of groundwater towards crystalline and sedimentary brines. Using 308 brine samples from the existing literature, eight chemical species were considered in the analysis: sodium, magnesium, potassium, calcium, strontium, chlorine, sulfate, and bromine, from which two salinity evolution pathways towards common Ca–Cl brines were derived: (1) the evolution of crystalline brines, which evolved from recharge water to brine through hydration of silicates, is described by the linear equation Ca = −1610 + 0.4*Cl; and (2) the evolution of sedimentary brines, which evolved from recharge water to brine through dissolution and precipitation of halite, is described by the linear equation Cl/Br = 103 + Na/Br. We also discuss differences in water isotopes, and in lithium and boron concentrations which directly reflect various temperature-dependent processes that control the evolution of sedimentary and crystalline brines. This leads to development of a discriminatory graphical tool using B/Br and Li/Br ratios, with crystalline brines having B/Br and Li/Br ratios below 0.01 and sedimentary brines above 0.01. Our results improve our understanding of deep crustal brine evolution through brine-rock interaction.

Mineralogical Investigation of Mg‐Sulfate at the Canaima Drill Site, Gale Crater, Mars

AbstractFor the first time on Mars, the crystalline magnesium‐sulfate mineral starkeyite (MgSO4‧4H2O) was definitively identified using the CheMin X‐ray diffraction instrument at Gale crater. At the Canaima drill site, starkeyite along with amorphous MgSO4‧nH2O are among the “polyhydrated Mg‐sulfates” interpreted in orbital reflectance spectra. Mg‐sulfates are good climate indicators as they are very responsive to changes in temperature and relative humidity. We hypothesize that, through evaporation, Mg‐sulfates formed at the end of brine evolution when ion concentrations became saturated and precipitated on the surface or near sub‐surface as either epsomite or meridianiite. These minerals were subsequently dehydrated later to starkeyite and amorphous MgSO4‧nH2O in response to a drier Mars. At Canaima, starkeyite is stable and would form during the warmer Mars summers. Due to very slow kinetics at the low Mars winter temperatures, starkeyite and amorphous MgSO4‧nH2O would be resistant to recrystallize to more hydrous forms and thus likely persist year‐round. During the course of analyses, starkeyite transforms into amorphous MgSO4‧nH2O inside the rover body due to the elevated temperature and greatly reduced relative humidity compared to the martian surface at the Canaima drill site. It is possible that crystalline sulfate minerals existed in earlier samples measured by CheMin but altered inside the rover before they could be analyzed. Starkeyite is most likely prevalent in the subsurface, whereas both starkeyite and amorphous MgSO4‧nH2O are likely present on the surface as starkeyite could partially transform into amorphous MgSO4‧nH2O due to direct solar heating.

The Study on the Genesis of Underground Brine in Laizhou Bay Based on Hydrochemical Data

The Laizhou Bay area contains a large amount of Quaternary brine resources, which have been gradually depleted by long-term high-intensity mining. The local brine genesis is still controversial, and the dominant theory of the evaporation of brine formation limits the exploration of brine resources to the land area, while the confirmation of freezing brine formation would greatly expand the brine storage range. In this research paper, the genesis of underground brines was analyzed based on the major ion concentrations of 62 samples of underground brines at different depths at 24 stations along the south coast of Laizhou Bay. The results show that the underground brines originated from seawater; however, their chemical components were changed during the evolution process after formation. The hydrogeochemical modeling results show that the mixing of seawater and fresh groundwater also affects the chemical composition of brines. The large-scale exploitation of brine resources in recent decades has also led to significant changes in the chemical composition of the underground brine in Laizhou Bay compared with the earlier period. The special geographic environment and the development of the brine chemical industry have led to the evolution of underground brines in Laizhou Bay being affected by a variety of factors, which makes the traditional analysis of brine genesis in this region not applicable. Furthermore, although evaporation and concentration are the dominant factors in the formation of brine, there is still a lack of evidence to rule out the existence of the freezing pathway.

Origin and evolution of deep lithium-rich brines in the southwest Jianghan Basin, central China: Evidence from hydrochemistry and stable isotopes

Lithium-rich brines from the upper Cretaceous and lower Eocene in the Jiangling depression, southwest Jianghan Basin were collected. In order to study the origin, evolution of the brines and the enrichment mechanism of lithium, the hydrochemical compositions and stable isotopes of the brines were tested and analyzed. The highest concentrations of potassium and lithium in the brine were 3.21 g/L and 97.85 mg/L, respectively. The brines of upper Cretaceous are mainly weakly acidic, while the lower Eocene brines are acid to alkalescent, and they are all Cl-Na type water. Compared with the ion trajectories of seawater evaporation, the brines showed enrichment of Cl, Ca, and Sr and depletion of Mg, which may be due to the dissolution of halite and water–rock interaction. The δD and δ18O compositions of the brines in both aquifers are similar, with δD values ranging from −51.4 to –33.0 ‰ and δ18O values ranging from −3.8 to 3.7 ‰. The data of δD and of δ18O indicate that the two aquifer brines originated from meteoric waters and experienced intense evaporation. The 87Sr/86Sr values (0.710144 to 0.712448) in the Upper Cretaceous brines are similar to the Paleocene sandstones, and the 87Sr/86Sr values (0.709982 to 0.710806) in the Lower Eocene brines are similar to the Paleocene anhydrite and glauberite. And the average content of lithium element in the upper Cretaceous brine is 54.38 mg/L, and the δ7Li values ranges from 10.2 to 14.1 ‰; the average content of lithium in lower Eocene brine is 23.81 mg/L, and the δ7Li values ranges from 17.7 to 21.9 ‰. The characteristics of 87Sr/86Sr and δ7Li indicate that the water–rock interaction between brine and silicate rock and the dissolution of halite lead to the enrichment of lithium in the brine of the two aquifers.

Metal budget and origin of aqueous brines depositing deep-seated Zn-Pb mineralization linked to hydrocarbon reservoirs, North German Basin

The origin, evolution, and interplay of brine and hydrocarbon fluid systems play a crucial role in the formation of deep sediment-hosted base metal ore deposits. Here we investigate ratios of halogens, noble gases, stable C and S isotopes, and metal budgets of aqueous brines, which deposited deep-seated and near-surface hydrothermal Zn-Pb mineralization hosted by Zechstein carbonates in the Lower Saxony Basin (North German Basin), by studies of fluid inclusions in sphalerite and quartz. Major and trace element geochemistry and noble gas isotopic signatures of brine inclusions revealed that the ore-forming fluids were highly reactive and experienced prolonged interactions with host rocks in the constricted, over-pressured metal source regions and consequently evolved from near-neutral, oxidized brines towards more reduced, acidic high-salinity brines. Quartz-hosted halite-saturated fluid inclusions with Th <200°C contain Zn and Pb concentrations up to ca. 9400 μg g-1 and 5200 μg g-1, respectively, and indicate the efficiency of metal scavenging processes. The interactions with Westphalian coals and Corg-rich shales influenced the redox state as well as the trace and critical element budget of the sphalerite-hosted fluid inclusions, with enrichment in Ge, Pd, Sb, Tl, Bi, and Ag. The salinities of metalliferous fluids originated primarily from seawater evaporation, however in addition a significant halite-dissolution component is present in the southern part of the Lower Saxony Basin. High concentrations of radiogenic noble gases and potassium in the sphalerite-hosted fluid inclusions are ascribed to strong interactions with the Paleozoic siliciclastic sedimentary pile and crystalline basement rocks. Reflux of the strongly modified, sulfur-poor, Zn-Pb-bearing acidic brines, proceeded via re-activated structurally controlled pathways into sour gas or gas-saturated brine pools in the Zechstein Ca2 carbonate unit. Here, mixing of the ascending metal-rich brines with H2S derived from thermochemical sulfate reduction (TSR), resulted in the deposition of deep-seated Zn-Pb ores in the Lower Saxony Basin. The overall timing of the Zn-Pb ore formation can be constrained to the Upper Cretaceous basin inversion.

Dolomite cement microstratigraphy: A record of brine evolution and ore precipitation mechanisms, upper Knox Group, Tennessee and Kentucky, USA

AbstractTrace element changes in fluids associated with ore-forming events in sedimentary basins may be recorded by contemporaneous cements, especially zoned carbonate minerals (microstratigraphy). Cement analysis using advanced mapping and analytical techniques including scanning electron microscopy cathodoluminescence (SEM-CL), charge contrast imaging, high-resolution X-ray computed tomography (XCT), and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) documents geochemical changes associated with Mississippi Valley–type mineralization in solution-collapse breccias of the Cambrian–Ordovician Knox Group (Tennessee and Kentucky, USA). Dolomite cement zonation coincident with changes in Fe and Mn can be observed with optical microscope CL in bands as narrow as 5 µm, whereas panchromatic SEM-CL reveals microfractures and cement subzones coincident with changes in La and Ce concentrations in bands as narrow as 0.1 µm. XCT scans image a high-density (Fe-rich) dolomite zone at the onset of late sulfide precipitation. The transition from pre-ore to ore-stage cementation is marked by increased Fe, Mn, Zn, Cd, Ga, Pb, and Sr and decreased La and Ce concentrations. Fine-scale metal depletion cycles during this transition may record metal precipitation from brine in response to the availability of reduced sulfur. Except for Fe and Mn, post-ore dolomite zones generally have low metal concentrations. Thus, dolomite microstratigraphy tracks systematic changes in brine metal concentrations modified by episodes of localized sulfide mineral precipitation.

Origin and evolution of intercrystalline brine in the northern Qaidam Basin based on hydrochemistry and stable isotopes

The Kunteyi Basin, located in northern Qaidam, is known as a significant potash ore deposit in China. It is of great significance to study the origin of the potassium-rich intercrystalline brine to support the exploitation of potassium salts. In this study, the major ion concentrations and isotopic ratios (δ2H, δ18O, and δ11B) of intercrystalline brine were used to analyze the evolution of the brine. The results show that the intercrystalline brine has a much higher concentration of total dissolved solids compared with the oil-field brine. Most of the ions are enriched except Ca2+ and Br−. The value of δ2H and δ18O are much negative while the δ11B values are positive. The analysis of CNa/CCl, CBr/CCl, Cl/(Na + K + Mg) and isotopes ratios, indicate that (1) Atmospheric precipitation is the primary source of water in brine; (2) The salinity of the brine is mainly influenced by halite dissolution; (3) The study area was influenced by the deep hydrothermal fluids. The thermal water recharged the Pleistocene layer, reacted with polyhalite, and formed Mg- and K-rich brine. The solution rose along the channel formed by the Shuangqiquan Fault and was supplied to the shallow intercrystalline brine.

Hydrogeochemical and isotopic signatures elucidate deep subsurface hypersaline brine formation through radiolysis driven water-rock interaction

Geochemical and isotopic fluid signatures from a 2.9–3.2 km deep, 45–55 °C temperature, hypersaline brine from Moab Khotsong gold and uranium mine in the Witwatersrand Basin of South Africa were combined with radiolytic and water–rock isotopic exchange models to delineate brine evolution over geologic time, and to explore brine conditions for habitability. The Moab Khotsong brines were hypersaline (Ca-Na-Cl) with 215–246 g/L TDS, and Cl− concentrations up to 4 mol/L suggesting their position as a hypersaline end-member significantly more saline than any previously sampled Witwatersrand Basin fluids. The brines revealed low DIC (∼0.266–∼1.07 mmol/L) with high (∼8.49–∼23.6 mmol/L) DOC pools, and several reduced gaseous species (up to 46 % by volume H2) despite microoxic conditions (Eh = 135–161 mV). Alpha particle radiolysis of water to H2, H2O2, and O2 along with anhydrous-silicate-to-clay alteration reactions predicted 4 mol/L Cl− brine concentration and deuterium enrichment in the fracture waters over a period > 1.00 Ga, consistent with previously reported 40Ar noble gas-derived residence times of 1.20 Ga for this system. In addition, radiolytic production of 7–26 nmol/(L × yr) H2, 3–11 nmol/(L × yr) O2, and 1–8 nmol/(L × yr) H2O2 was predicted for 1–100μ g/g 238U dosage scenarios, supporting radiolysis as a significant source of H2 and oxidant species to deep brines over time that are available to a low biomass system (102–103 cells/mL). The host rock lithology was predominately Archaean quartzite, with minerals exposed on fracture surfaces that included calcite, pyrite, and chlorite. Signatures of δ18Ocalcite, δ13Ccalcite, Δ33Spyrite,δ34Spyrite and 87Sr/86Sr obtained from secondary ion mass spectrometry (SIMS) microanalyses suggest several discrete fluid events as the basin cooled from peak greenschist conditions to equilibrium with present-day brine temperatures. The brine physiochemistry, geochemistry, and cellular abundances were significantly different from those of a younger, shallower, low salinity dolomitic fluid in the same mine, and both were different from the mine service water. These results indicate the discovery of one of few long-isolated systems that supports subsurface brine formation via extended water–rock interaction, and an example of a subsurface brine system where abiotic geochemistry may support a low biomass microbial community.

Lithium and strontium isotopic systematics in the Nalenggele River catchment of Qaidam basin, China: Quantifying contributions to lithium brines and deciphering lithium behavior in hydrological processes

The salt lakes fed by the Nalenggele River in the Qaidam Basin, located on the northeastern Qinghai Tibetan Plateau (QTP), are major brine lithium reservoirs in China. The quantitative identifications of the Li sources and their dynamic behavior shed light on the formation mechanism of the brine Li deposits in closed-basin of arid regions. This study presents Li and Sr isotope ratios (δ7Li, 87Sr/86Sr) and other hydrogeochemical parameters for river waters, springs, spring river waters, shallow groundwaters, surface brines, and intercrystalline brines around the Nalenggele River Basin (NRB) and its adjacent small watersheds. The results indicate that the Nalenggele River water is a mixing product of hot springs and regional surface meltwater, and the source of dissolved Li in the NRB is mainly supplied by the hot springs. With multi-tracer models, it is confirmed that around 84.9 %−93.4 % of dissolved Li is provided by the Li-rich hot spring waters, which account for only 3–5 % of the total water input. Furthermore, the dissolved Li in the streams of different hydrological regions shows various isotopic fractionation behavior. In general, the lower average δ7Li values (average of +5.6 ‰) with more enriched Li with respect to Na in the waters of the piedmont Gobi region indicates a significant additional input of dissolved Li from bedrock and sediments. The second-stage alluvial fan of the NRB produces 7Li enrichments and Li-depleted waters (compared with Na), which can be explained by the adsorption of clay or Fe (Mn) oxide phases that fractionate Li isotopes. The highest average δ7Li values (+12.76 ‰) are observed when Li is not adsorbed by the scarce fine clastic sediments in the hypersaline environment of the salt lake region. It can be concluded that the continuous halite precipitation during the brine evolution not only causes the abnormal enrichment of Li in the brine (compared with Na) but also continuously sequesters the 6Li from the brines, resulting in a significant 7Li enrichment. Overall, these findings advance the understanding of the lithium sources of Li-rich brines and its enrichment and metallogenic process during water migration in hyper-arid regions and have crucial indicative significance for lithium cycling under a strong evaporation environment.

Rift-induced structurally controlled hydrothermal barite veins in 1.6 Ga granite, Western Bastar Craton, Central India: Constraints from fluid inclusions, REE geochemistry, sulfur and strontium isotopes studies

Expressive granitic magmatism and a complex system of fault and shear zones are the main features associated with the crustal evolution and metallogeny in the Western Bastar Craton (WBC), Central India. The barite mineralization in WBC, Central India, occurs as veins and fracture fillings along faults are activated or reactivated as a consequence of rifting of – 1.5–1.6 Ga Pranhita-Godavari (PG) basin. The barite mineralization is hosted in ca. 1.6 Ga Mul granite of WBC. We present the first comprehensive, integrated field and laboratory studies approach using structural mapping, fluid inclusion, Sulfur, and Sr-Isotope geochemistry, mineral, and REE geochemistry to characterize barite mineralization ore-forming processes, a fluid source, and structural control. The host granite is intensely altered with evidence of hydrothermal mineralization in the form of silicification and hematitisation. Both sulfide-free (Brt-I) and sulfide-bearing (Brt-II) barites occur in the study area. Besides, barites with fluorite (Brt-III) were also observed in minor concentrations. The mineralization is associated with quartz-calcite vein, and the barite is accompanied by galena, pyrite, and chalcopyrite. Petrographic observations, fluid inclusion, and isotope data suggest a bimodal evolution of the mother brine viz. the oxidative source forms sulfide-free high-salinity brine and reductive low-salinity sulfide-bearing aqueous fluid formed by interaction with reducing agent causing hydrothermal barite mineralization in the study area. The source for the hydrotherms responsible for the formation of barite and galena in association with the quartz-barite vein is, in all probability, granitic magma. Incompatible elements like Ba, Pb and volatiles like S, preferentially concentrated in late magmatic hydrothermal fluids, got emplaced along the structurally weak zones in the interior of the granite pluton. The combined 87Sr/86Sr and δ34S‰ data suggest mixing fluids from diverse sources, including magmatic, marine, and crustal fluids. Low 87Sr/86Sr (<0.707) and high δ34S(>10‰) are indicative of alteration products of granite that were subsequently mixed with submarine hydrothermal fluid mobilized through the Mesoproterozoic PG rift system. This regional rifting event provided pathways for fluid flow and ore formation along faults/fracture systems (F2 and F3 fault systems) in the host Mul granite of WBC. The F2 fault system, sympathetic to the PG rift, is deep-seated and contains mainly barites of magmatic origin besides the minor marine signature. The F3 cross faults, developed across the gneissic foliation of TTG gneisses and charnockites, can be traced to the PG basin's younger marine sediments, host barites of dominantly marine signature.The Ba ± F mineralization in the study area is a perspective for regional exploration for REE-Ba-F in central India and elsewhere in a similar geological milieu. The epigenetic-submarine hydrothermal vein-type barite mineralization hosted in granite, WBC differs from Sedex, VMS, Carlin, or Orogenic type barite deposits, which has a great deal of replicability and suitability for future exploration targeting.

Hydrogeochemical characteristics and sources of mirabilite in the high saline system of Sabkha Oum El Khialate, Southern Tunisia

Using hydrogeochemical approaches and geochemical modeling, integrated with data from 83 samples, including brines and fresh water, the main factors controlling the evolution of brine in the Sabkha Oum El Khialate catchment area in southeastern Tunisia are determined. Samples with high total dissolved solids (TDS), in the continental saline depression, are consistently dominated by Na–SO4 and Na–SO4–Cl water types while Ca–SO4–HCO3 and Ca–HCO3–SO4–Cl are the dominated facies in the catchment area of the sabkha. The PHREEQC geochemical modeling using PITZER database shows that most samples of the saline depression are oversaturated with respect to (sulfate minerals) thenardite, bloedite, glauberite, gypsum, and mirabilite and undersaturated with respect to calcite, halite, and dolomite. The most important hydrogeochemical processes that affect brine evolution in the Sabkha along the flow path are evaporation, gypsum dissolution, and the cationic exchange on clay minerals.

A Comprehensive Methodology for Monitoring Evaporitic Mineral Precipitation and Hydrochemical Evolution of Saline Lakes: The Case of Lake Magadi Soda Brine (East African Rift Valley, Kenya).

Lake Magadi, East African Rift Valley, is a hyperalkaline and saline soda lake highly enriched in Na+, K+, CO32–, Cl–, HCO3–, and SiO2 and depleted in Ca2+ and Mg2+, where thick evaporite deposits and siliceous sediments have been forming for 100 000 years. The hydrogeochemistry and the evaporite deposits of soda lakes are subjects of growing interest in paleoclimatology, astrobiology, and planetary sciences. In Lake Magadi, different hydrates of sodium carbonate/bicarbonate and other saline minerals precipitate. The precipitation sequence of these minerals is a key for understanding the hydrochemical evolution, the paleoenvironmental conditions of ancient evaporite deposits, and industrial crystallization. However, accurate determination of the precipitation sequence of these minerals was challenging due to the dependency of the different hydrates on temperature, water activity, pH and pCO2, which could induce phase transformation and secondary mineral precipitation during sample handling. Here, we report a comprehensive methodology applied for monitoring the evaporitic mineral precipitation and hydrochemical evolution of Lake Magadi. Evaporation and mineral precipitations were monitored by using in situ video microscopy and synchrotron X-ray diffraction of acoustically levitated droplets. The mineral patterns were characterized by ex situ Raman spectroscopy, X-ray diffraction, and scanning electron microscopy. Experiments were coupled with thermodynamic models to understand the evaporation and precipitation-driven hydrochemical evolution of brines. Our results closely reproduced the mineral assemblages, patterns, and textural relations observed in the natural setting. Alkaline earth carbonates and fluorite were predicted to precipitate first followed by siliceous sediments. Among the salts, dendritic and acicular trona precipitate first via fractional crystallization—reminiscent of grasslike trona layers of Lake Magadi. Halite/villiaumite, thermonatrite, and sylvite precipitate sequentially after trona from residual brines depleted in HCO3–. The precipitation of these minerals between trona crystals resembles the precipitation process observed in the interstitial brines of the trona layers. Thermonatrite precipitation began after trona equilibrated with the residual brines due to the absence of excess CO2 input. We have shown that evaporation and mineral precipitation are the major drivers for the formation of hyperalkaline, saline, and SiO2-rich brines. The discrepancy between predicted and actual sulfate and phosphate ion concentrations implies the biological cycling of these ions. The combination of different in situ and ex situ methods and modeling is key to understanding the mineral phases, precipitation sequences, and textural relations of modern and ancient evaporite deposits. The synergy of these methods could be applicable in industrial crystallization and natural brines to reconstruct the hydrogeochemical and hydroclimatic conditions of soda lakes, evaporite settings, and potentially soda oceans of early Earth and extraterrestrial planets.

Experimental study on the influence of brine concentration on the dissociation characteristics of methane hydrate

Brine stimulation is a common method for assisting depressurization to produce hydrate, which significantly improves the efficiency of hydrate production. In this work, to study the influence of brine concentration on the natural gas hydrate production process, a novel cylindrical hydrate production simulation experimental device was established, and investigations of hydrate dissociation experiments induced by depressurization in conjunction with brine injection were carried out. The effects of different brine concentrations on the gas production rate and heat transfer during production were studied. The distribution, flow, and concentration evolution of brine during hydrate production were analyzed. Brine injection can significantly enhance cumulative gas production during the depressurization stage, increase the sensible heat for hydrate dissociation, enhance heat transfer between the hydrate reservoir and the environment during the recovery process, and significantly improve the gas production rate of hydrate. The increase in the gas production rate caused by brine injection mainly occurs at the end of the depressurization stage and the beginning of the constant pressure stage. The injected brine is mainly located in the middle and upper areas of the reactor. In the bottom area of the reactor, the hydrate has higher saturation and longer dissociation time, which is slightly affected by the injected brine. A higher hydrate saturation is not beneficial to brine injection and does not promote hydrate dissociation. Additionally, in the experiments with brine injection, the resistance decreases more obviously during the depressurization stage due to more hydrate dissociation. The resistance also shows that in the bottom area of the reactor, there is a higher hydrate saturation and a lower brine effect on hydrate.

Origin and evolution of Sr-enriched hydrothermal brines: Insights from vein mineralization of Lower Triassic marine carbonates in the Eastern Sichuan Basin, South China

This paper focuses on celestite-carbonate-cemented veins that developed in the Jialingjiang Formation of the Lower Triassic carbonates from the Libixia anticline in eastern Sichuan Basin, China. Comparative petrography and geochemistry of the host rock and vein minerals provide clues to the nature, origin, and evolution of the vein-cementing fluids. The host rocks are composed mainly of micrite dolomite which yields δ18O, δ13C and 87Sr/86Sr ratios close to the values that characterize contemporaneous seawater. Two generations of vein-mineralization were recognized based on textural relationships, fluid inclusion data and isotope geochemistry. The early generation is dominated by celestite and saddle dolomite, formed from hypersaline, Sr-enriched, hydrothermal fluids. The later generation is represented by calcites, precipitated from less saline fluids at lower temperatures. The 87Sr/86Sr ratios of vein dolomite and celestite vary from 0.7076 to 0.7081, significantly lower than those of host carbonate counterparts (0.7078 to 0.7081; average 0.7080). This isotopic discrepancy suggests that the majority of Sr was sourced from deeper sequences of the lower Triassic carbonates, probably associated with thermochemical sulfate reduction for Sr accumulation. It is argued that the fracture systems associated with the Huayingshan fault provided the heat source and served as conduits for migration of hydrothermal fluids through several hundred meters, and the final mineralization occurred as a result of mixture of Sr-enriched brines with sulfate-bearing solutions. The large celestite ore bodies in the studied area are proposed to form related partially to these hydrothermal fluids.

Mineral Precipitations and Hydrochemical Evolution of Brines in Graduation Towers

The purpose of this study is to examine hydrochemical changes of saline groundwater and precipitation of mineral phases during evaporative graduation processes. Therefore, concentrated brines and mineral precipitates were sampled at four graduation towers with differing evaporation approaches. Solid phase compositions were qualitatively and quantitatively analysed. Hydrochemistry changes of dissolved ion concentrations during successive evaporation was assessed by comparing natural with concentrated brines. PHREEQC was used to simulate sequence and quantity of mineral precipitates. Finally, a prognosis for expected precipitations of a newly built graduation tower was made using PHREEQC modelling. The identified mineral phases included calcite, aragonite, gypsum and halite in varying proportions. Concentrations of all investigated ions (except bicarbonate) increase, eventually leading to supersaturation and sequential precipitation of evaporite minerals. Modelled saturation indices show that calcite is the first and halite is one of the last precipitating phases at all sites. Further calculated precipitates include the carbonates dolomite, siderite and strontianite; manganese oxide and hematite; and the sulphates baryte, celestine and gypsum which precipitate depending on local hydrogeochemistry and graduation conditions. Calculated precipitation quantities reach a maximum of 48.6 g/L of applied natural brine at an evaporation grade of 90%. After 25 years, the total expected mass of precipitates at the new graduation tower is about 34.4 t for a graduation process up to a salt content of 19%, and about 356 t for a permanent evaporation grade of 90%. • Except for bicarbonate, concentrations of all ions increase to different degrees. • Mineral precipitations are composed of calcite, aragonite, gypsum and halite. • Modelled precipitation sequence: carbonates, sulphates, chlorides. • Modelled precipitation amounts: max. 48.6 g/L for natural brine at 90% evaporation. • 25 y precipitation forecast for new graduation tower: max. 356 t at 90% evaporation.

Searles Lake evaporite sequences: Indicators of late Pleistocene/Holocene lake temperatures, brine evolution, and pCO2

Abstract Searles Lake, California, was a saline-alkaline lake that deposited &amp;gt;25 non-clastic minerals that record the history of lake chemistry and regional climate. Here, the mineralogy and petrography from the late Pleistocene/Holocene (32–6 ka) portion of a new Searles Lake sediment core, SLAPP-SRLS17, is combined with thermodynamic models to determine the geochemical and paleoclimate conditions required to produce the observed mineral phases, sequences, and abundances. The models reveal that the primary precipitates formed by open system (i.e., fractional crystallization), whereas the early diagenetic salts formed by salinity-driven closed system back-reactions (i.e., equilibrium crystallization). For core SLAPP-SRLS17, the defining evaporite sequence trona → burkeite → halite indicates brine temperatures within a 20–29 °C range, implying thermally insulating lake depths &amp;gt;10 m during salt deposition. Evaporite phases reflect lake water pCO2 consistent with contemporaneous atmospheric values of ∼190–270 ppmv. However, anomalous layers of nahcolite and thenardite indicate pulses of pCO2 &amp;gt; 700–800 ppm, likely due to variable CO2 injection along faults. Core sedimentology indicates that Searles Lake was continuously perennial between 32 ka and 6 ka such that evaporite units reflect periods of net evaporation but never complete desiccation. Model simulations indicate that cycles of partial evaporation and dilution strongly influence long-term brine evolution by amassing certain species, particularly Cl–, that only occur in late-stage soluble salts. A model incorporating long-term brine dynamics corrects previous mass-balance anomalies and shows that the late Pleistocene/Holocene (32–6 ka) salts are partially inherited from the solutes introduced into earlier lakes going back at least 150 ka.

Insights into salty metamorphic fluid evolution from scapolite in the Trans-North China Orogen: Implication for ore genesis

Scapolite is abundant in medium to high grade metamorphic rocks with evaporitic calc-silicate bulk compositions, and because it can be Cl− and SO42− rich, is able to provide a unique view into the evolution of deep brines during orogenic cycles. In the Zhongtiao Mountains, part of the Trans-North China Orogen (TNCO), scapolite occurs in two distinct mineralogical associations; scapolite-I in carbonate-bearing biotite schist and scapolite-II in amphibolites. Initially, metamorphic Cl-rich scapolite-I formed in the schist at low fluid-rock ratio and peak pressure (meionite content = 32–37%, Cl = 2.34–2.75 wt.%). This observation, together with high molar Cl/Br ratios (Cl/Br = 973–2236), implies a halite-bearing evaporitic protolith. During a second stage of scapolite formation in the calc-silicates, rims overgrew scapolite-I with distinct compositions (Me% = 31–32, Cl = 2.64–3.0 wt.%, Cl/Br = 408–892). The lower molar Cl/Br ratios in scapolite-I rims imply that the later fluid was distinctly different to the earlier metamorphic fluid, and may have evolved through a stage of halite saturation induced by phase separation. Halite saturation would drive Br enrichment in the remaining fluid because Cl is preferentially sequestered in halite. Also at this time, amphibolites were subjected to intense open system fluid-rock interactions resulting in formation of scapolite-II (Me% = 30–32, Cl = 2.74–2.97 wt.%, Cl/Br = 291–1426), similar to that of the scapolite-I. S6+/∑S ratios in scapolite obtained via synchrotron XANES indicate that equilibration between fluid and scapolite would buffer the fluid to oxidized conditions, with oxygen fugacity (log fO2) beyond −15. The scapolitic rocks in this region were thus able to play a key role in controlling the salinity and oxidation state of the deep metamorphic fluid, thereby creating enhanced potential for scavenging of a range of metals within the metamorphic terrane and promoting syn-orogenic hydrothermal ore formation.

Effects of lithological and evolutionary processes on geochemical changes of Shahrokht-Yazdan Playa brines (east of Iran-west of Afghanistan)

The Shahrokht-Yazdan Playa is a sedimentary inland basin in the east of Iran and west of Afghanistan. It covers an area of 212.5 km2, lying 135 km northeast of Qayen at a border region known as Shahrokht. Some parts of the playa have stretched into Afghanistan (Yazdan area). In this playa, water level is controlled by the amount of rainfall, evaporation and groundwater recharge. To study the brine’s origin and evolution, some 95 water samples with specified intervals of 1 km were taken. The geochemistry of the brines was undertaken using the ICP-MS method and X-ray diffraction analysis on the sediments, the ionic concentrations of brine and mineralogical composition of sediments were identified. Major cations, as per their abundance, are sodium, calcium, magnesium and potassium and anions are chloride, sulphate and hydrogen carbonate, respectively. The results showed that the sediments of the lake’s bed were composed of chemical (evaporite) and clastic minerals (quartz, feldspar, muscovite and some clay minerals). Dominant evaporite minerals in sediments are gypsum, halite, calcite and dolomite while the minor mineral is clinochlore. Careful examination of surface samples indicates that carbonate and sulphate minerals deposited in the margins and minerals such as halite deposited as highly soluble in the centre of the playa. Chemical analyses of inflow water indicate that water has a molar ratio of $$ {\mathrm{Ca}}^{2+}>{\mathrm{CO}}_3^{2-} $$ , Cl−+ $$ {\mathrm{SO}}_4^{2-}>{\mathrm{HCO}}_3^{-},\kern0.5em {\mathrm{HCO}}_3^{-}\ll {\mathrm{Ca}}^{2+}+{\mathrm{Mg}}^{2+} $$ and is following the same second geochemical path (II) as that of Saline Valley and Dead Valley brine lakes on the brine evolution flow diagram. The inflow water to the basin is of the Na+-(Ca2+)-(Mg2+) $$ {\mathrm{SO}}_4^{2-} $$ -Cl−-( $$ {\mathrm{CO}}_3^{2-} $$ ) type which changes into Na+-Cl−- $$ {\mathrm{SO}}_4^{2-} $$ type during the geochemical evolution and deposition of evaporate minerals. In order to investigate the origin of major ions in the brine, the groundwater of the surrounding desert, which is the only supplier of ions to this area, was studied. The relationships between groundwater and regional brine were investigated. The study of the chemical changes of the brines in relation to the sedimentation of evaporite minerals indicates marked evolution of the brines in Shahrokht-Yazdan Playa to in so far as the formation of chloride minerals and type brines Na+-Cl−- $$ {\mathrm{SO}}_4^{2-} $$ occurred. The study of correlational relations with the help of SPSS software also shows the formation of carbonate and sulphate minerals in this playa and the saturation of brine from chloride.