Aquatic Geochemistry最新文献

The northeastern Sichuan Basin hosts deep brines with unusually high concentrations of potassium (K) and lithium (Li). This study examines deep brines abundant in K and Li in northeastern Sichuan Basin. Brine samples from Well ZK601 underwent comprehensive analysis for major elements, trace elements, and Sr isotopes. Lithium content in core samples correlated with regional brine reservoir features. Brine samples showed a salinity range of 354.6–363 g/L, with varying contents of Na⁺ (101–106 g/L), K⁺ (28.92–34.84 g/L), Cl⁻ (202.1–206 g/L), Br⁻ (2110–2980 mg/L), and Li⁺ (169.5–204.5 mg/L). The ⁸⁷Sr/⁸⁶Sr ratio in brine was 0.708324. Li notably increased post-green bean rock deposition in 71 core samples. The ratios are as follows: Br × 10³/Cl is 10.24, K × 10³/Cl is 169.13, nNa/nCl is 0.74, and SO₄ × 10³/Cl is 0.49. These brines likely originated from ancient seawater, evolving via rock interactions during burial, notably enriching K and Li through gypsum dehydration. Geochemical traits and Sr isotopes affirm ancient seawater origin, stressing continual water–rock interactions. The volcanic activity contributed significantly to lithium enrichment, consolidated during later burial stages. Brine reservoirs, mostly in formations like dolomite within the Jialingjiang Formation, associate closely with fractured zones. Structural traps define distribution, while fault systems govern enrichment. Accumulation mainly occurs in fractured zones, reflecting a mineralization model of seawater origins, metamorphism, filtration, and structural enrichment. In summary, our model outlines a transformation from seawater origins to structural controls enriching K and Li in deep brines in northeastern Sichuan Basin.

To deepen the comprehension of the geochemical behaviour of salt-forming elements (K, Li, B, Ca, Mg, Sr) and distribution patterns in the primary lithium-rich salt lake region of Qaidam Basin, 31 river and lake surface sediments from various hydrogeological settings spanning high mountain to terminal salt lake regions were gathered from the Nalenggele River, the primary feeder river of the lithium-rich salt lakes. Through sequential extraction procedure, we identified notable variances in the chemical speciation of elements across various hydrological environments. Excluding elements bound to the residual fraction, all other chemical speciation content of salt-forming elements show distinct regional variations, suggesting a predominant influence of evaporation and hydrodynamic and the inherent chemical properties of elements are also very important in determining their chemical speciation distribution characteristics. Meanwhile, we have found that in addition to being absorbed and fixed by secondary clay minerals, Li bound to Fe–Mn oxides may also play a crucial role in Li isotope fractionation from the river to the terminal salt lake brine and the precipitation of evaporation salt minerals could influence the B isotope fractionation to a certain extent. Furthermore, The Li and B lost to sediments during the migration process have potential utility and there is scope for enhanced exploitation in the future. Therefore, the results obtained from the sequential extraction procedure of sediments evidently serve as a valuable method for understanding the geochemical behaviour of salt-forming elements in the epigenetic environment.

Bromine (Br) is a vital chemical raw material primarily obtained from marine brine. The bromine/chlorine (Br/Cl) ratio serves as a crucial indicator for predicting marine potash mineralization in evaporites. As salinity increases, bromine gradually accumulates through evaporation in residual brine. During the process of brine evaporation to the potassium salt stage, the bromine content in the brine can exceed 1000 ppm. The marine brine sourced from the weathering crust reservoir at the top of the Ordovician Majiagou Formation in the Jingbian gas field, Ordos Basin, in northwestern China, displays an exceptionally high bromine content (averaging 1590 ppm), surpassing levels found in contemporary seawater. Based on analysis of major compositions, only brine evaporates to the gypsum stage. Despite extensive exploration in the region, large-scale potassium salt deposits have not been identified. This heightened concentration of bromine in low salinity brine suggests supplementation from additional organic bromine sources. The strata adjacent to the high-bromine oil field water in the Jingbian gas field, Ordos Basin, consist of the Ordovician marine evaporite strata of the Majiagou Formation and the overlying Carboniferous and Permian marine and continental deposits rich in fossil algae. Interactions between hydrocarbons and oilfield water contribute to the notable bromine anomaly observed in the Jingbian gas field in the Ordos Basin. Elevated bromine levels have also been noted in brine from various oil fields worldwide. Through an analysis of the major compositions of brines and bromine, this study will elucidate the reasons behind the presence of high bromine brines.

Advancing underground hydrogen storage (UHS) is essential for a sustainable, emission-free future, with its success highly contingent on the unique properties of each subsurface reservoir. To ensure optimal storage, detailed site assessments are required. One of the critical gaps in knowledge necessary for ensuring safe storage is geochemical redox reactions, especially those involving iron. These redox reactions are crucial as they influence hydrogen retention or loss in the subsurface environments. In this study, we have theoretically addressed hydrogen consumption via abiotic reduction of a Fe³⁺ oxide under different Fe²⁺ activities. Simulations indicate that in scenarios, where the initial hydrogen partial pressure is extremely low (around 10⁻⁵ bars), decreasing the activity of Fe²⁺ by a factor of 10 can lead to a marked decrease in the initial hydrogen pressure by a maximum factor of 1000 within a few years. Variations in Fe²⁺ activity can significantly influence abiotic hydrogen consumption only under very low hydrogen partial pressures. This is primarily due to enhanced dissolution of Fe³⁺ oxides. In comparison, in conditions where hydrogen partial pressure is higher (> 10⁻² bars), reduction of Fe³⁺ oxide can yield magnetite, resulting in a muted loss of hydrogen over time. The transition in the reduction behavior of Fe³⁺ oxide from a ‘dissolution-driven’ process to ‘magnetite crystallization,’ which also determines the fate of stored hydrogen, depends on initial hydrogen partial pressure. Our results demonstrate that low quantities of hydrogen can be maintained within typical storage cycles spanning less than a year, depending upon aqueous Fe content.

Hydromagnesite (HM for short) is a natural carbonate mineral that is widely distributed. It is a high-quality mineral raw material for preparing flame retardants, magnesium oxides, heavy/light basic magnesium carbonates, magnesium hydroxides, and other Mg products. The evaluation of HM resources is of great significance to the development and utilization of salt lake resources. Using remote sensing technology to observe HM resources in salt lake can overcome the shortcomings of traditional prospecting methods such as discontinuous spatial data, time and effort. In addition, spectral analysis is the basis of hyperspectral remote sensing, and more detailed analysis of the spectral characteristics of HM is still lacking; therefore, we measured the reflection spectral curve of HM samples in the area of Jiezechaka by ASD FieldSpec4 short-wave infrared spectrometer and determined the mineral composition and content of HM samples by X-ray diffraction. The analysis indicated three and seven absorption valleys with high and low absorption intensities, respectively, in the reflectance spectral curves of the HM samples in the Jiezechaka area. Then, on this basis, the Landsat8 OLI multispectral data and ZY1-02D AHSI hyperspectral data were used as the basic data of remote sensing inversion. As the ZY1-02D AHSI data have 166 bands, which is much more than Landsat8 OLI data, it has a stronger ability to characterize the spectral characteristics of HM and can better meet the requirements of remote sensing inversion. The end member spectra were selected based on PPI and SMACC methods, respectively. The HM information around Jiezechaka Salt Lake in Tibet was extracted by the mixture tuned matched filtering method, and the regional distribution map of HM was made. A confusion matrix operation was used to compare the determination results of the two types of data. Among them, based on Landsat8 data, PPI method was used to obtain end members, and the overall accuracy of HM extraction results was > 69%, and the kappa coefficient was 0.688. Based on Landsat8 data, SMACC method was used to obtain end members, and the overall accuracy of HM extraction results was > 67%, and the kappa coefficient was 0.667. Based on ZY1-02D AHSI data, PPI method was used to obtain end members, and the overall accuracy of HM extraction results was > 76%, and the kappa coefficient was 0.743. Based on ZY1-02D AHSI data, SMACC method was used to obtain end members, and the overall accuracy of HM extraction results was > 73%, and the kappa coefficient was 0.728. It shows that the end members selected by PPI method can better express HM information in the image. Finally, through the overlay analysis of the four results, we concluded that HM outcrops in the Jiezechaka area are mainly distributed in the northwestern and southeastern regions of the lake. This study provides a rapid assessment technique for measuring HM information from salt lakes.

The Tataleng River (TTR), as an important tributary of the Da Qaidam Salt Lake (DQSL) and Xiao Qaidam Salt Lake (XQSL) in the Qaidam Basin (QB), has an exceptionally high B content. However, the solute sources and the provenance of B in the TTR are still unclear, which significantly hinders a deeper understanding of the source–sink processes of the boron deposits in the QB. In this study, water samples were collected from tributaries, mainstreams, mud volcanoes, hot springs, and rainwater in the TTR area. Through hydrochemical analysis, forward modeling, and B isotope geochemistry methods, combined with the previous research results, some findings were obtained. The hydrochemical type of TTR is Ca–Mg–Cl, and the major mechanism of controlling chemical composition is rock weathering. The solute sources in the TTR are mainly from dissolution of evaporites (75.9%), atmospheric precipitation (20.8%), and a minor contribution from carbonates (3.1%) and silicates weathering (0.6%). The higher B content (0.89–4.30 mg/L, mean = 2.13 mg/L) and lower δ¹¹B value (0.79‰–4.71‰, mean = 4.17‰) of the TTR indicate that the B sources are mainly from mixture of mud volcanic waters (56.19–199.98 mg/L, mean = 113.51 mg/L, − 1.26‰–2.22‰, mean = 0.85‰) in the upper reaches, and the deep groundwater near the Indosinian granite in the lower reaches. The significant difference in boron resources between the two lakes may be due to the enrichment of B in the late Pleistocene in the DQSL, which received exceptionally rich soluble B carried by the ancient TTR during an active tectonic period, while the weakening of tectonic activity and the diversion of the ancient TTR resulted in the supply of B with significantly reduced content to the XQSL. These results are helpful for a deeper understanding of the ore-forming mechanisms of the boron deposits in salt lake.

Mahai Basin (MH), located in the northern Qaidam Basin (QB), possesses abundant K-rich brine resources. The investigation on the origin of deep K-rich confined brine and the variations in K–Mg elements corresponding to the evolution in MH shed light on the significance of assessment and utilization of brine deposits. This study presents multiple isotopes (δ¹⁸O–δD, ⁸⁷Sr/⁸⁶Sr) and hydrochemical characteristics for various waters (including river water, surface brine, intercrystalline brine, confined brine and anticlinal brine) in the MH. Our findings corroborate that: (1) confined brine exhibits relatively high K⁺ (average value of 6.88 g/L) and low Ca²⁺–Sr²⁺ concentrations, compared to anticlinal brine, and its chemical composition resembles the evolution of Yuqia River in Ca–SO₄–HCO₃ diagram, suggesting that contemporary river water is the primary source of confined brine. (2) The δ¹⁸O–δD values of confined brine in MH ranged from − 17.80 to − 27.40‰ and 1.50 to 2.40‰, respectively, and fall on the right field of the local evaporation line, indicating successive evaporation and concentration processes. (3) The ⁸⁷Sr/⁸⁶Sr ratios (0.71142–0.71145) of confined brine fall between river water (0.71150–0.71183) and anticlinal brine (0.71135), combining with river water and confined brine which exhibit low Sr content, and further confirming the origin of confined brine is a mixture by river and anticlinal brine and much river recharge budget. (4) Considering the evolution of sedimentary facies (Dezongmahai Lake area as an example) and the gradual increase in K and Mg contents in MH, the enrichment of K and Mg exhibits a certain correlation with the evolution of MH. Notably, the brine in the northeast of the basin displays the highest levels of K and Mg, indicating that this region serves as the ultimate depositional center.

Brine groundwater in Quaternary salt lakes is widely exploited to extract potassium, lithium, and boron; the complex hydrogeological parameters of brine aquifers could cause significant difficulties in brine resource assessment and exploitation. However, the origin and porosity of brine aquifers remain unclear. This study presents an approach that utilizes geochemical indicator analysis with paleogeographic reconstruction to better assess porosity in salt lake aquifers. We identified 15 representative boreholes in Mahai Salt Lake, and the lithology, porosity, and chloride contents of their respective sediments, the pore porosity of each borehole in the study area ranges from 38.17 to 0.51%, the average chloride content of each borehole ranges from 26.63 to 38.74%, found that the vertical porosity fluctuations of halite deposits were significantly larger than those of detrital deposits, the sediments in the boreholes consisted predominantly of halite-containing debris or fine-debris-containing halite, reflecting the paleoenvironmental signatures of the salt lake. According to lithology and sedimentary environment, four brine aquifers were classified and the chloride and porosity distribution characteristics in the I–IV brine aquifers were further illustrated. Based on information of paleolake evolution in Qaidam Basin, we established a conceptual model to identify the impact factors for the porosity distribution pattern in the I–IV brine aquifers.