Brine contains cations such as K
+
, Ca
2+
, Na
+
, Mg
2+
, Li
+
, B
3+
, Rb
2+
, and Cs
2+
, as well as anions such as SO
4
2−
, Cl
−
, HCO
3
−
, CO
3
2−
, NO
3
−
, Br
−
, and I
−
, which are ...valuable elements. Brines are widely distributed in salt lakes in the world's three enormous plateaus and beyond and are classified into three types: sulfate-, chloride-, and carbonate-type brines. Sulfate-type brine forms in salt lakes, whereas carbonate-type brine results from magmatic and hydrothermal activity. Chloride-type brine forms in deep basins due to the reduction and transformation of buried brine. Li in brine plays a critical role in clean energy transitions, and K in brine is important for potash production. Recently, new techniques for extracting Li from brine have been developed, and the large-scale, comprehensive development pattern of brines has formed the basis for a recycling economic model, which contributes to the efficient use of brines for potash and Li
2
CO
3
development and CO
2
emission reduction. This article reviews the genesis of brines and highlights new utilization techniques, trends, and sustainable development.
Evidence for Quaternary climate change in East Africa has been derived from outcrops on land and lake cores and from marine dust, leaf wax, and pollen records. These data have previously been used to ...evaluate the impact of climate change on hominin evolution, but correlations have proved to be difficult, given poor data continuity and the great distances between marine cores and terrestrial basins where fossil evidence is located. Here, we present continental coring evidence for progressive aridification since about 575 thousand years before present (ka), based on Lake Magadi (Kenya) sediments. This long-term drying trend was interrupted by many wet–dry cycles, with the greatest variability developing during times of high eccentricity-modulated precession. Intense aridification apparent in the Magadi record took place between 525 and 400 ka, with relatively persistent arid conditions after 350 ka and through to the present. Arid conditions in the Magadi Basin coincide with the Mid-Brunhes Event and overlap with mammalian extinctions in the South Kenya Rift between 500 and 400 ka. The 525 to 400 ka arid phase developed in the South Kenya Rift between the period when the last Acheulean tools are reported (at about 500 ka) and before the appearance of Middle Stone Age artifacts (by about 320 ka). Our data suggest that increasing Middle- to Late-Pleistocene aridification and environmental variability may have been drivers in the physical and cultural evolution of Homo sapiens in East Africa.
Well‐dated lacustrine records are essential to establish the timing and drivers of regional hydroclimate change. Searles Basin, California, records the depositional history of a fluctuating ...saline‐alkaline lake in the terminal basin of the Owens River system draining the eastern Sierra Nevada. Here, we establish a U‐Th chronology for the ∼76‐m‐long SLAPP‐SLRS17 core collected in 2017 based on dating of evaporite minerals. Ninety‐eight dated samples comprising nine different minerals were evaluated based on stratigraphic, mineralogic, textural, chemical, and reproducibility criteria. After the application of these criteria, a total of 37 dated samples remained as constraints for the age model. A lack of dateable minerals between 145 and 110 ka left the age model unconstrained over the penultimate glacial termination (Termination II). We thus established a tie point between plant wax δD values in the core and a nearby speleothem δ18O record at the beginning of the Last Interglacial. We construct a Bayesian age model allowing stratigraphy to inform sedimentation rate inflections. We find that the >210 ka SLAPP‐SRLS17 record contains five major units that correspond with prior work. The new dating is broadly consistent with previous efforts but provides more precise age estimates and enables a detailed evaluation of evaporite depositional history. We also offer a substantial revision of the age of the Bottom Mud‐Mixed Layer contact, shifting it from ∼130 ka to 178 ± 3 ka. The new U‐Th chronology documents the timing of mud and salt layers and lays the foundation for climate reconstructions.
Plain Language Summary
Searles Lake, California, is currently a dry saltpan; however, in the past, it was a large and deep lake (>200 m). Lake levels have varied with changes in climate. These changes influenced the sediments deposited. Thus, changes in the lake sediments can be applied to understand the past environments of the region. Here, we developed a chronology for a 76‐m‐long sediment core using isotopic dating methods. The lake sediments contain many different minerals which can be dated. However, some of these minerals formed after the lake sediments were deposited and others have been chemically altered in the time since their formation. We developed criteria for the selection of samples that are the most likely to reflect the age of sediment deposition. We used the selected ages along with statistical modeling to determine the ages of the sediments with depth. We find that the core contains a record that spans over 200,000 years, including the last two glacial cycles. The age model presented here lays the foundation for the exploration of how past climate changes impacted water availability and vegetation in southeastern California.
Key Points
>200 ka‐long sediment record of southwestern North American paleoenvironment
Establishes general criteria for selection of evaporite minerals for U‐Th dating
Explores a wide range of parameters for Bayesian age‐depth modeling
Diagenetic-hydrothermal brines, here called “hydrothermal Ca-Cl brines,” have compositions that reflect interactions between groundwaters and rocks or sediments at elevated temperatures. Hydrothermal ...Ca-Cl brines reach the surface by convection-driven or topographically driven circulation, and discharge as springs or seeps along fault zones to become important inflow waters in many tectonically active closed basins. Case studies from (1) Qaidam Basin, China, (2) Death Valley, California, (3) Salar de Atacama, Chile, and (4) Bristol Dry Lake, California illustrate that hydrothermal Ca-Cl inflow waters have influenced brine evolution in terms of major ion chemistries and mineral precipitation sequences. All four basins are tectonically active; three (Death Valley, Salar de Atacama, and Qaidam Basin) have well-documented Ca-Cl spring inflow and Holocene faulting. Bristol Dry Lake has young volcanic deposits and Salar de Atacama has an active stratovolcano on its eastern margin, indicating subsurface magma bodies. A midcrustal magma chamber has been identified in southern Death Valley. Volcanism and faulting in these closed basins provides the heat source for hydrothermal-diagenetic processes and the energy and pathways to deliver these waters to the surface.
Systematic changes in the chemistry of evaporated seawater contained in primary fluid inclusions in marine halites indicate that seawater chemistry has fluctuated during the Phanerozoic. The ...fluctuations are in phase with oscillations in seafloor spreading rates, volcanism, global sea level, and the primary mineralogies of marine limestones and evaporites. The data suggest that seawater had high Mg2+/Ca2+ratios (>2.5) and relatively high Na+concentrations during the Late Precambrian 544 to 543 million years ago (Ma), Permian (258 to 251 Ma), and Tertiary through the present (40 to 0 Ma), when aragonite and MgSO4salts were the dominant marine precipitates. Conversely, seawater had low Mg2+/Ca2+ratios (<2.3) and relatively low Na+concentrations during the Cambrian (540 to 520 Ma), Silurian (440 to 418 Ma), and Cretaceous (124 to 94 Ma), when calcite was the dominant nonskeletal carbonate and K-, Mg-, and Ca-bearing chloride salts, were the only potash evaporites.
Bicarbonate-rich source waters were needed to form the largest sodium carbonate evaporite deposits in the geologic record, the early and middle Eocene Green River trona (NaHCO3·Na2CO3·2H2O) in the ...Bridger basin, Wyoming, and nahcolite (NaHCO3) in the Piceance Creek basin, Colorado. Large modern and Pleistocene trona deposits are associated with magmatic activity and Na+-HCO3−-rich hydrothermal inflow waters, either within the depositional basin (Lake Magadi, Kenya) or at great distances (Searles Lake, California). No evidence exists for magmatic sources of CO2 near the Green River Formation. Several regional volcanic centers were active 300km or more to the north, but drainage reconstructions show that waters from these areas did not discharge into the Green River Formation lakes during evaporite deposition. Alternatively, Na+-HCO3−-rich waters could have drained northwestward from the Colorado Mineral belt to the Bridger basin via the proposed Aspen River. A river originating in the Colorado Mineral belt (Sawatch uplift) could also have provided source waters to the Piceance Creek basin. Field evidence, however, has not yet documented these flow paths, and specific Eocene volcanic centers and hydrothermal source areas have yet to be identified.
Other explanations for the elevated alkalinities needed to form thick sodium carbonate evaporites include accelerated silicate mineral weathering rates during a period of high atmospheric pCO2 and Eocene warmth. Amplified chemical weathering may explain the cluster of sodium carbonate evaporites in the USA and China that are Eocene in age. Another possible source of alkalinity to the Green River lakes is fault-controlled upward migration of a deep sedimentary source of CO2. The large amount of organic matter preserved in the evaporitic Wilkins Peak and Parachute Creek Members raises the possibility that decay of organic matter in Green River lakes could have added sufficient CO2 and alkalinity to produce waters capable of precipitating trona and nahcolite, although such degradation of organic matter has not created hyperalkalinity in modern lakes.
Quantification of the atmospheric concentration of CO2 (CO2atm) during warm periods of Earth's history is important because burning of fossil fuels may produce future CO2atm approaching 1000 parts ...per million by volume (ppm). The early Eocene (approximately 56 to 49 million years ago) had the highest prolonged global temperatures of the past 65 million years. High Eocene CO2atm is established from sodium carbonate minerals formed in saline lakes and preserved in the Green River Formation, western United States. Coprecipitation of nahcolite (NaHCO3) and halite (NaCl) from surface waters in contact with the atmosphere indicates CO2atm > 1125 ppm (four times preindustrial concentrations), which confirms that high CO2atm coincided with Eocene warmth.
Secular variations in the major ion chemistry and isotopic composition of seawater on multimillion-year time scales are well documented, but the causes of these changes are debated. Fluid inclusions ...in marine halite indicate that the Li concentration in seawater Li
declined sevenfold over the past 150 million years (Ma) from ~184 μmol/kg H
O at 150 Ma ago to 27 μmol/kg H
O today. Modeling of the lithium geochemical cycle shows that the decrease in Li
was controlled chiefly by long-term decreases in ocean crust production rates and mid-ocean ridge and ridge flank hydrothermal fluxes without requiring changes in continental weathering fluxes. The decrease in Li
parallels the 150 Ma increase in seawater Mg
/Ca
and
Sr/
Sr, and the change from calcite to aragonite seas, KCl to MgSO
evaporites, and greenhouse to icehouse climates, all of which point to the importance of plate tectonic activity in regulating the composition of Earth's hydrosphere and atmosphere.
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