Evaporite Deposits Research Articles

Delineation of sinkhole in evaporite deposits using electrical resistivity survey: a case study of southern Kohat Plateau, Pakistan

Vertical electrical sounding (VES) is a non-destructive geophysical technique which provides fast subsurface lithological investigations and it is widely used in exploration of water, mineral resources, and its characterization. The present study work has been focused on subsurface imaging over evaporite deposits in Bahadarkhel area, Karak, Pakistan where multiple VES points along three profile lines have been acquired using Schlumberger electrode configuration to delineate subsurface lithology and structure of the area. The VES curves have been modeled and interpreted which resulted in true resistivities, depths, and thicknesses of layers. These VES points have been stacked along their respective profile lines for pseudosections and resistivity cross section preparation. Five distinct geoelectrical units have been identified depending upon their true resistivity values. Iso-resistivity 3D surfaces at 30 m and 60 m depths have been generated using the interpreted data which exhibits salt diapiric structure and dissolution of salt at depth by the action of infiltrating water from nearby ephemeral stream. Dar-zarrouk parameter calculations yield transverse resistance, longitudinal conductance, and anisotropy maps which infer that the area is mostly covered with rock salt and the presence of clay beds and calcareous sediments increases the resistivity values.

High-resolution chemostratigraphy in carbonate mudstones: Salina A-1 carbonate (Silurian), Michigan Basin, U.S.A.

Portable Energy-Dispersive X-Ray Fluorescence spectrometry (PXRF) is routinely used to identify stratigraphic variations in the elemental chemistry of fine-grained siliciclastics. The application of this approach in carbonates is limited, however. In this study, over 9000 PXRF analyses from nine drill cores are used to document cm-scale variations in the carbonate mudstones of the A-1 Carbonate (Silurian) in the Michigan Basin. High-resolution elemental data are integrated with petrographic and mineralogical observations to evaluate the extent to which: (i) basin-center mudstones in the A-1 Carbonate (A-1C) have spatially correlative elemental signatures (i.e. chemofacies), and (ii) elemental variations reflect temporal changes in relative sea-level and sedimentation.Spatially correlative variations in concentrations less than 5 wt% of Si, Al, K, and S are observed throughout the A-1C. Higher concentrations of Si, Al, and K are associated with more abundant siliciclastic minerals as determined petrographically and with x-ray diffraction, and are thus interpreted to reflect intensification of siliciclastic sedimentation caused by relative sea-level fall. Associated S increases reflect a higher abundance of anhydrite, which is interpreted as diagenetically altered gypsum deposited during periods of low relative sea-level. Chemofacies successions for siliciclastic and evaporite proxy elements indicate four transgressive-regressive cycles. Collectively, these data show that variations in the minor, non-carbonate sediment fraction within the A-1C are regionally correlative suggesting that siliciclastic and evaporite deposition responded in tandem to basin-wide controls on sedimentation. The observed relationship between siliciclastics and evaporites further exemplifies the broader utility of quantifying the elemental signatures and non-carbonate mineral compositions in carbonate-dominated strata to constrain sequence stratigraphic interpretations. These findings add to a growing body of work that demonstrates the utility of PXRF to generate reliable geochemical data sets and highlights the importance of integrating elemental and mineral data in sedimentological interpretations.

Negative emissions using Mg sourced from desalination brine or natural evaporite deposits

We establish a profitable negative emissions technology that converts desalination brine or salt deposits into saleable products while concurrently mineralizing atmospheric CO2 as Mg-carbonates. The process produces water, gypsum, salt, potash, aggregate, and hydrochloric acid with the ratios of products dependent on the brine or evaporite deposit composition. In addition to the negative emissions realized through direct removal of CO2 from the atmosphere, the co-products drive out existing production methods resulting in CO2 emissions reduction. Notably, the process uses no chemicals or fossil fuels and can be powered completely by electricity. This not only increases the net CO2 removal it also leverages the decreasing cost of renewables and batteries to increase operating profit. We outline how extant equipment and technologies can be used to implement this process. The net energy usage and CO2 removal of the process are calculated, accounting for differences with current production methods for the co-products. At large enough implementation, some products will saturate their respective markets, converting the excess product into a waste stream. As such, performance indices for the process (e.g., GJ/t-CO2, USD/t-CO2) depend on the extent of implementation. We limit our investigation to prior to such market saturation effects. Assuming the global average CO2 intensity of electricity generation, the process provides 4.1 t-CO2 of emissions reduction for every tonne of negative CO¬ emissions. Per tonne of total CO2 reduction (mitigated+removed), the process operates at an energy consumption of 2.1 GJ/t-CO2, falling to 1.1 GJ/t-CO2 if the system is powered by renewable energy. Via Monte Carlo analysis using global price distributions, we find that even without including a price on CO2 the process operates, on average, at a profit of 196 USD/t-CO2 (total reduction). Applying the process to evaporite deposits of Bischofite or Carnallite provides a profit of 47 USD/t-CO2 and 103 USD/t-CO2 (total reduction), respectively.

Micron-Nanometer Evaporite Mineral Compositions in the Jiangling Depression, Jianghan Basin, China, by Means of Scanning Electron Microscopy.

Scanning electron microscopy (SEM) was used to analyze and study micron-nanometer evaporite samples collected from Paleocene and Eocene drill cores in the Jiangling Depression. Accordingly, seven beds of potassium-bearing solid rocks were accurately identified. Sylvite, carnallite, syngenite, dolomite, thenardite, anhydrite, glauberite, halite, barite, celestite, and other solid salt minerals were found, and carnallite, syngenite, and thenardite were found for the first time in the Jiangling Depression. Sylvite, syngenite, and carnallite indicate that the Paleogene salt lakes in the Jiangling Depression had evolved to the sylvite stage and that prospecting for solid sylvite would be satisfactory. Micron-nanometer celestite is contained in the evaporites, from which we can infer that strontium may have been provided by deep formation water (or oil-field water). This finding is of great significance to studying the genesis of sylvite sediment in the Jiangling Depression. From the extensive development of primary glauberite beds typical of warm salt minerals in the Shashi Formation, it can be inferred that the late Paleogene paleoclimate in the Jiangling Depression of the Jianghan Basin was dry and hot. Based on the extensive distribution of micron-nanometer pyrite, siderite, iron and Fe₂O₃/FeO ratios in evaporite sediments and color analysis of mudstones, the evaporites in the study area formed in an underwater anoxic, reducing environment during sedimentation. Therefore, the evaporite sediments in the Paleocene-Eocene interval of the Jiangling Depression are proposed to have formed in a saltwater lake sedimentary environment, and the ancient lake was characterized by a deep-water salt lake sedimentary model.

Late Cretaceous-Paleogene Formation of the Bekrit Syncline, Middle Atlas, Morocco: Sedimentology, Geochemistry, Palynology and Paleoenvironments

Globally, the Paleogene period experienced several events marking the Paleocene-Eocene transition which is especially to one of the hottest periods that the Earth has ever known (Paleocene-Eocene Thermal Maximum, PETM), followed by the biological crisis that affected benthic foraminifera. The Bekrit Syncline, subject of this study, shows three Formations of range from the Cretaceous to the Eocene ages (the El Koubbat, Irbzer and Bekrit-Timahdite Formations). Sedimentological, palynological and geochemical analyses of collected samples, in the Bekrit syncline, were studied to determine the paleogeographic and paleoenvironmental conditions of the Middle Atlas. The carbonate rocks were analyzed by microscopic study and geochemical analysis by X-ray Fluorescence (XF) and Inductively Coupled Plasma Spectrometry (ICP). The results obtained highlight the sedimentary events that took place during the Paleogene. Thus, the Maastrichtian is characterized by a closed euxinic marine environment shared by a more open and oxidizing environment. On the other hand, the Paleocene was a restricted marine environment with evaporitic sedimentation, while the Eocene sees the installation of a carbonate platform with a bioclastic Shoal.

Геохімічні особливості евапоритових формацій Євразії у контексті еволюції хімічного складу морської води протягом фанерозою

Studies of evaporites provide new data to characterize the seawater chemistry in the Early Paleozoic and Middle Mesozoic. In particular, we studied the fluid inclusions in halite from Ordovician (China) and Cretaceous (Laos) evaporites. The corresponding sections on the plot of Ca/SO4 oscillations curve in the Phanerozoic seawater are updated. The calcium content in seawater concentrated to halite precipitation stage was 45.6 mol %, 485 million years ago and 24.3 mol % 112.2–93.5 million years ago. By analyzing the previously published and new factual material, it is established that in Permian evaporites the sulfur isotopic composition is inversely correlated with the sulfate ion content in evaporite basin brines. Thus, the evolution of seawater chemistry in Permian is confirmed by the evolution of the isotopic composition of dissolved seawater sulfate. According to the generalization of 38 Phanerozoic marine evaporite formations, it was found that the peculiarities of the clay minerals associations correlate with the change of the seawater chemical type. Clay minerals associations precipitated from the SO4-rich seawater are characterized by a larger set of minerals, among which smectite and mixed-layered minerals often occur; Mg-rich clay minerals (corensite, paligorskite, sepiolite, talc) also occur. Instead, in the associations of evaporite clay minerals formed from the Ca-rich seawater are represented by the smaller amount of minerals, and Mg-rich minerals are extremely rare. The increased content of magnesium in seawater of SO4-rich type is the main factor in the formation of Mg-rich silicates in evaporites. The composition of clay minerals associations depends on the evaporate basin brine concentration; with its increase, unstable minerals are transformed, which theoretically leads to a decrease in the number of minerals in the associations. However, it was found that evaporite deposits of higher stages of brine concentration often still contain unstable clay minerals – products of incomplete transformation of a significant amount of pyroclastic material from coeval volcanic activity. The main factor determining the composition of clay minerals associations of Phanerozoic evaporites was the seawater (and basin brines) chemical type. Geochemical studies of scattered organic matter and fluid inclusions with hydrocarbon phase in evaporites of the Upper Pechora Basin (overlying oil and gas deposits) indicate the presence of allochthonous bitumoids and allow to use this method to predict oil and gas potential of other areas. Analysis of the results of oil and gas exploration in a number of areas of the Transcarpathian Trough indicates the presence of fluid-saturated reservoirs and the prospects for the discovery of new accumulations of hydrocarbons. Geochemical studies proved the effectiveness of gas-flow survey method for oil and gas exploration, assessing the prospects for fluid saturation of seismic structures.

The onset of the Messinian Salinity Crisis in the central Mediterranean recorded by pre‐salt carbonate/evaporite deposition

AbstractThe Calcare di Base is a carbonate/evaporitic unit formed before the deposition of the massive halite bodies in the main depozones of the Mediterranean region, and has been at the centre of a fiery debate between different ‘schools of thought’ about its genesis, environmental conditions and timing of deposition. It crops out extensively in Southern Italy, across Neogene basins located on the Tyrrhenian and Ionian margins of northern Calabria, where it was studied through a detailed facies and stratigraphic analysis that revealed the presence of a continental/shallow‐marine to slope system, active during the onset of the Messinian Salinity Crisis. During the Calcare di Base deposition, an arid climate regime with intermittent humid phases occurred with a precession forced cyclicity, facing an overall generally cold climatic period. During arid periods, stressed environmental conditions permitted the establishment of widespread microbial‐mediated carbonate production, frequently associated with evaporitic (gypsum‐dominated) deposition, along a sabkha‐type environment with extensive salinas and hypersaline coastal lagoons grading seaward into a carbonate/evaporite shallow‐marine shelf. This is testified to by microbial boundstones and dissolution breccias commonly associated with nodular gypsum and arenites affected by desiccation, typically forming metre‐scale shallowing‐upward peritidal cycles. Seaward, gravity flow deposits are interpreted as re‐sedimented shelf limestones, defining a slope apron. Mixed carbonate/evaporite megabreccias and disorganized floatbreccias were deposited along the upper slope, whereas soft deformation with slides, slumps and channelized turbidites further developed along the lower slope to basin. During the humid climate episodes, that affected the platform system with a precession‐forced cyclicity, the carbonate production was reduced together with the evaporitic deposition, leading to the widespread deposition of marlstones and fine to coarse siliciclastic deposits.

Sedimentology and isotope geochemistry of transitional evaporitic environments within arid continental settings: From erg to saline lakes

AbstractArid continental basins typically contain a spectrum of coeval environments that coexist and interact from proximal to distal. Within the distal portion, aeolian ergs often border playa, or perennial, desert lakes, fed by fluvial incursions or elevated groundwaters. Evaporites are common features in these dryland, siliciclastic dominant settings. However, sedimentary controls upon evaporite deposition are not widely understood, especially within transitional zones between coeval clastic environments that are dominantly controlled by larger scale allocyclic processes, such as climate. The sulphur (δ34S) and oxygen (δ18O, Δ17O) isotope systematics of evaporites can reveal cryptic aspects of sedimentary cycling and sulphate sources in dryland settings. However, due to the lack of sedimentological understanding of evaporitic systems, isotopic data can be easily misinterpreted. This work presents detailed sedimentological and petrographic observations, coupled with δ34S, δ18O and Δ17O data, for the early Permian Cedar Mesa Sandstone Formation (western USA). Depositional models for mixed evaporitic/clastic sedimentation, which occurs either in erg‐marginal or lacustrine‐marginal settings, are presented to detail the sedimentary interactions present in terms of climate variations that control them. Sedimentological and petrographical analysis of the evaporites within the Cedar Mesa Sandstone Formation reveal a continental depositional environment and two end member depositional models have been developed: erg‐margin and lake‐margin. The δ34S values of gypsum deposits within the Cedar Mesa Sandstone Formation are consistent with late Carboniferous to early Permian marine settings. However, a marine interpretation is inconsistent with sedimentological and petrographic evidence. Consequently, δ34S, δ18O and Δ17O values are probably recycled and do not reflect ocean‐atmosphere values at the time of evaporite precipitation. They are most likely derived from the weathering of older marine evaporites in the hinterland. Thus, the results demonstrate the need for a combination of both sedimentological and geochemical analysis of evaporitic systems to better understand their depositional setting and conditions.

The Late Cretaceous source-to-sink system at the eastern margin of the Tibetan Plateau: Insights from the provenance of the Lanping Basin

The surface uplift of the Tibetan Plateau (TP) and its geomorphology evolution has triggered aridification of Asia's interior and drainage development at the eastern margin of the plateau. However, how the pre-Cenozoic early growth histories of the TP impact the drainage system and climate is poorly constrained. The Late Mesozoic Lacustrine evaporite-bearing basins on the eastern margin of the TP record significant information on the uplift of the source terranes, source-to-sink system development and climate change. In this study, we presented detrital zircon U–Pb ages from the Upper Cretaceous Yunlong Formation in the Lanping Basin, as well as Hf isotopic, petrographic, direct statistical, and multidimensional scaling analyses, and use them to characterize the provenance and reconstruct the drainage system. All of the samples have five major age peaks at 200–290 Ma, 400–490 Ma, 750–1000 Ma, 1750–1950 Ma, and 2400–2600 Ma with mostly negative ɛHf(t) values (81%). We infer the sediments are primarily derived from recycled sediments of the Songpan-Garze terrane, and partly from the Sichuan Basin and the Southern Qiangtang terrane, as well as the exposed magmatic rocks of the Yidun Arc and Songpan-Garze terrane. The provenance features of the contemporaneous sediments from the Sichuan, Xichang, Chuxiong, and Simao basins indicate a complex hierarchical drainage pattern on the eastern margin of the TP during the Late Cretaceous. The hierarchical drainage system exhibits a complete gradational cycle of lake-basin types from overfilled freshwater Sichuan Basin through balanced fill saline Xichang Basin and underfilled hypersaline Chuxiong, Lanping, Simao, and Khorat Plateau basins from proximal to distal. The early growth of the TP primarily controlled the drainage and lake-basin evolution by not only causing the uplift and exhumation of the source areas and providing large amounts of clastic material to the proximal sub-drainage areas but also intensifying the aridity and deposition of evaporites.

Volcanic Holocrystalline Bedrock and Hydrothermal Alteration: A Terrestrial Analogue for Mars

Clay minerals have been detected on Mars to outcrop mainly as alteration of ancient bedrock, and secondarily, as deposition from aqueous environments or interlayered with evaporitic deposits on Mars. In order to better constrain the alteration environments, we focused on the process to form clays from volcanic rocks and experimentally reproduced it at different temperature and pH. A fresh, holocrystalline alkali-basalt sample collected in the Mount Etna volcanic sequence has been used as analogue of the Martian unaltered bedrock. Previous works considered only volcanic glass or single mineral, but this may not reflect the full environmental conditions. Instead, we altered the bulk rock and analyzed the changes of primary minerals to constrain the minimum environmental parameters to form clays. We observed that under acidic aqueous solution (pH ~ 3.5–5.0) and moderate temperature (~150–175 °C), clinopyroxene and plagioclase are altered in smectite in just a few days, while higher temperature appear to favor oxides formation regardless of pH. Plagioclases can also be transformed in zeolite, commonly found in association with clays on Mars. This transformation may occur even at very shallow depth if a magmatic source is close or hydrothermalism is triggered by meteoritic impact.

Mineral Systems Based on the Number of Species-Defining Chemical Elements in Minerals: Their Diversity, Complexity, Distribution, and the Mineral Evolution of the Earth’s Crust: A Review

Abstract—The chemical diversity of minerals can be analyzed in terms of the concept of mineral systems based on the set of chemical elements that are essential for defining a mineral species. Only species-defining elements are considered to be essential. According to this approach, all minerals are classified into ten types of mineral systems with the number of essential components ranging from 1 to 10. For all known minerals, only 70 chemical elements act as essential species-defining constituents. Using this concept of mineral systems, various geological objects may be compared from the viewpoint of their mineral diversity: for example, alkali massifs (Khibiny and Lovozero in Russia; Mont Saint Hilaire in Canada), evaporite deposits (Inder in Kazakhstan and Searles Lake in the United States), fumaroles of active volcanoes (Tolbachik in Kamchatka and Vulcano in Sicily, Italy), and hydrothermal deposits (Otto Mountain in the United States and El Dragon in Bolivia). Correlations between chemical and structural complexities of the minerals were analyzed using a total of 5240 datasets on their chemical compositions and 3989 datasets on their crystal structures. The statistical analysis yields strong and positive correlations (R2 > 0.95) between chemical and structural complexities and the number of different chemical elements in a mineral. The analysis of relationships between chemical and structural complexities provides strong evidence for the overall trend of a greater structural complexity at a higher chemical complexity. Following R. Hazen, four groups of minerals representing four mineral evolution stages have been considered: (I) “Ur-minerals,” (II) minerals from chondrite meteorites, (III) Hadean minerals, and (IV) contemporary minerals. According to the obtained data, the number of species-defining elements in minerals and their average contents increase regularly and significantly from stage I to stage IV. The analyzed average chemical and structural complexities in these four groups demonstrate that both are gradually increasing in the course of mineral evolution. The increasing complexity follows an overall trend: the more complex minerals were formed in the course of geological time, without replacing the simpler ones. The observed correlations between chemical and structural complexities understood in terms of the Shannon information suggest that chemical differentiation is the major force that drives the increase of mineral complexity over the course of geological time.

Oldest preserved sodium carbonate evaporite: Late Paleozoic Fengcheng Formation, Junggar Basin, NW China

Abstract Sodium carbonate evaporites can provide important paleoclimatic constraints and economic resources but are relatively rare; most known examples are limited to the Cenozoic. The first known late Paleozoic occurrence was recently reported from the Fengcheng Formation in the northwestern Junggar Basin, NW China. However, its mineralogy, age, and geologic setting have been sparsely documented. To help establish a broader understanding of the formation of these important deposits, this paper presents a comprehensive new data set that includes drill core, well logs, petrographic analyses, X-ray diffraction data, organic geochemistry (biomarkers), and U-Pb zircon age data. Evaporite deposition is estimated to have occurred between ca. 305 Ma and 296 Ma in a series of extensional grabens that hosted a stratified, hypersaline lake (or lakes). The lake deposits are closely associated with coeval volcanic rocks, suggesting that subsurface interaction of these with CO2-enriched hydrothermal fluids may have contributed to the excess alkalinity required to precipitate Na-carbonate. Trona (NaHCO3 · Na2CO3 · 2H2O) in the Fengcheng Formation was likely formed syndepositionally and then partly replaced by wegscheiderite (Na2CO3 · 3NaHCO3). Other evaporite minerals most likely formed during diagenesis. The Fengcheng Formation also contains nahcolite (NaHCO3), which requires pCO2 >680 ppm to form, although no textural evidence was found to demonstrate a primary origin. The presence of extensive lacustrine evaporites nonetheless reflects a relatively warm and arid climate at ∼40–50°N that apparently coincided with the late Paleozoic icehouse.

Modern and Holocene microbial mats and associated microbially induced sedimentary structures (MISS) on the southeastern coast of Tunisia (Mediterranean Sea)

AbstractOn the southeastern Tunisian coastline, very diverse living microbial mats colonize the lower supratidal and intertidal zones, and locally may extend into the upper infratidal zone. The interaction between the benthic cyanobacteria and their siliciclastic substratum leads to the development of several types of microbially induced sedimentary structures (MISS). The mapping of the microbial mats has allowed the identification of the types of MISS that characterize the different segments of the coastal environment. The modern microbial mats have been compared with those recorded at the top of the Holocene deposits, which are composed of biodegraded microbial black mats alternating with white laminae made of clastic and evaporitic sediments, indicative of very high frequency cycles of flood and drought. A hypothetic profile showing their occurrences along the different areas bordering the coastline is proposed as a guide for the reconstruction of the ancient depositional environment. The roles of tidal dynamics, storms, and climate in controlling their genesis and spatial distribution, are discussed and highlighted. The modern MISS of southeastern Tunisia are compared with their equivalents that are well documented through the different geological eras.

Unraveling groundwater functioning and nitrate attenuation in evaporitic karst systems from southern Spain: An isotopic approach

High evaporation rates in semi-arid to arid regions result in an increase in salinity that can exacerbate the effect of pollutants in water bodies.This study examines how groundwater drives pollution removal in wetlands, wells and springs within the Chaotic Subbetic Complexes (southern Spain). This evaporitic system, localy with a clear karstic functioning, is characterized by groundwater with a wide range of mineralization. Hydrochemical and multi-isotopic (δ34S, δ18O, δ15N, δ13C and δ2H) techniques were used to understand the geochemical processes leading to pollutant attenuation within the complexes. There, regional groundwater evolve from recharge/transition areas, with low salinity, to the discharge zone. Mineralization of groundwater depends on the dissolution of evaporitic deposits (gypsum, halite) of Keuper age, which increases salinity of the water drained by the outlet springs. δ15N and δ18O values of dissolved nitrate (NO3−) were used to estimate the relative contribution of N sources. NO3− is mainly derived from agricultural inputs (nitrate and urea fertilizers). Long-residence groundwater plays an important role in the biogeochemical evolution. Denitrification is responsible for NO3− removal in transitional zones and discharge springs. This process is promoted by the oxidation of organic carbon, derived from recharge areas and further transported to deeper zones of the aquifer. The findings of this study provide a new understanding of how hydrogeological functioning is connected to pollutant removal in an evaporitic karst system, where the scale of groundwater flows plays a key role in biogeochemical processes.

Evaporite weathering and deposition as a long-term climate forcing mechanism

AbstractAlthough it is widely accepted that Earth’s long-term surface temperature is regulated by the mutual dependence of silicate weathering and climate on CO2, the root causes of some climatic events remain unresolved. We show here for the first time that imbalances between evaporite weathering and deposition can affect climate through the process of carbonate sedimentation. Calcium sulfate weathering supplies Ca2+ ions to the ocean unaccompanied by carbonate alkalinity, so that increased carbonate precipitation strengthens greenhouse forcing through transfer of CO2 to the atmosphere. Conversely, calcium sulfate deposition weakens greenhouse forcing, while the high depositional rates of evaporite giants may overwhelm the silicate weathering feedback, causing several degrees of planetary cooling. Non-steady-state evaporite dynamics and related feedbacks have hitherto been overlooked as drivers of long-term carbon cycle change. Here, we illustrate the importance of evaporite deposition, in particular, by showing how a series of massive depositional events contributed to global cooling during the mid–late Miocene.

Controls on Associations of Clay Minerals in Phanerozoic Evaporite Formations: An Overview

Information on the associations of clay minerals in Upper Proterozoic and Phanerozoic marine evaporite formations suggests that cyclic changes in the (SO4-rich and Ca-rich) chemical type of seawater during the Phanerozoic could affect the composition of associations of authigenic clay minerals in marine evaporite deposits. The vast majority of evaporite clay minerals are authigenic. The most common are illite, chlorite, smectite and disordered mixed-layer illite-smectite and chlorite-smectite; all the clay minerals are included regardless of their quantity. Corrensite, sepiolite, palygorskite and talc are very unevenly distributed in the Phanerozoic. Other clay minerals (perhaps with the exception of kaolinite) are very rare. Evaporites precipitated during periods of SO4-rich seawater type are characterized by both a greater number and a greater variety of clay minerals—smectite and mixed-layer minerals, as well as Mg-corrensite, palygorskite, sepiolite, and talc, are more common in associations. The composition of clay mineral association in marine evaporites clearly depends on the chemical type of seawater and upon the brine concentration in the evaporite basin. Along with increasing salinity, aggradational transformations of clay minerals lead to the ordering of their structure and, ideally, to a decrease in the number of minerals. In fact, evaporite deposits of higher stages of brine concentration often still contain unstable clay minerals. This is due to the intense simultaneous volcanic activity that brought a significant amount of pyroclastic material into the evaporite basin; intermediate products of its transformation (in the form of swelling minerals) often remained in the deposits of the potassium salt precipitation stage.

The Messinian Salinity Crisis deposits in the Balearic Promontory: An undeformed analog of the MSC Sicilian basins??

The Messinian Salinity Crisis (MSC) is a controversial geological event that influenced the Mediterranean Basin in the late Miocene leaving behind a widespread Salt Giant. Today, more than 90% of the Messinian evaporitic deposits are located offshore, buried below the Plio-Quaternary sediments and have thus been studied mainly by marine seismic reflection imaging.Onshore-offshore records’ comparisons and correlations should be considered a key approach to progress in our understanding of the MSC. This approach has however not been widely explored so far. Indeed, because of the erosion on the Messinian continental shelves and slopes during the MSC, only few places in the Mediterranean domain offers the opportunity to compare onshore and offshore records that have been preserved from erosion. In this paper, we compare for the first time the MSC records from two basins that were lying at intermediate water depths during the MSC and in which salt layers emplaced in topographic lows: the Central Mallorca Depression (CMD) in the Balearic Promontory, and the Caltanissetta Basin (CB) in Sicily. The reduced tectonic movements in the CMD since the late Miocene (Messinian) till recent days, favored the conservation of most of the MSC records in a configuration relatively close to their original configuration, thus allowing a comparison with the reference records outcropping in Sicily. We perform seismic interpretation of a wide seismic reflection dataset in the study area with the aim of refining the mapping of the Messinian units covering the Balearic Promontory (BP) and restituting their depositional history based on a detailed comparison with the Messinian evaporitic units of the Sicilian Caltanissetta Basin. We discuss how this history matches with the existing 3-stages chrono-stratigraphic model. We show that the Messinian units of Central Mallorca Depression could be an undeformed analog of those outcropping on-land in the Sicilian Caltanissetta Basin, thus questioning the contemporaneous onset of the salt deposition on the Mediterranean scale. We show a change in seismic facies at a certain range of depth between stage 1 MSC units, and wonder if this could reflect the threshold/maximum depth of deposition of bottom growth PLG selenites passing more distally to pelagic snowfall cumulate gypsum. Moreover, we confirm that PLG could be deposited in water depths exceeding 200 m.

Differences in evaporite geochemistry of the greater Ordos Ordovician salt basin, China: evidence from the M56 submember of the Majiagou Formation

Ordovician evaporites are very rare in the global geological record. Thick salt deposits in the Ordovician Majiagou Formation are present in the eastern greater Ordos Basin, China. Potash mineralization layers and a thin industrial grade potash layer occur in the sixth submember of the fifth member of the formation, thus indicating a good potash prospect. The eastern and western salt depressions are separated by an uplift and have been divided into five secondary salt sags (East-1, East-2, West-1, West-2, and West-3). The ratio of the salt layer thickness to that of the whole succession was very low in the West-2 sag and the salt depositional center was the East-2 sag, which implied that seawater entered the basin from the western sags and led to desalination and the formation of deep-water sediments. Analyses indicated that the potash formation conditions were obviously different in the salt sags. Although a thin potash layer was present in the East-1 sag, findings indicated that this area was not favorable for potash accumulation. The geochemical and sedimentary environment of the East-2 sag was similar to that of typical potash basins globally. Rounded sylvine grains occurred between salt crystals. The preservation characteristics indicated that evaporite deposits had reached the KCl bitterns stage. An eastward input of terrestrial materials carried a large amount of clay, and the clay layer protected previously deposited sylvine particles, thereby avoiding further potassium dissolution. Sedimentary, geochemical, and petrological evidences indicate good prospects for potash exploration in the East-2 salt sag.

Reconstructing the level of the central Red Sea evaporites at the end of the Miocene

AbstractReconstructing the original depositional level of the Mesozoic and older c‘salt giants’ can reveal if their basins became filled to global sea level, but is complicated by dissolution, diapirism and because the time elapsed is so great. This is less of a problem in the Red Sea, a young rift basin that is transitioning to an ocean basin and where the evaporites away from coastal fringes are less affected by diapirism. In this study, we explore vertical movements of the evaporite surface of the central Red Sea imaged with deep seismic profiling, for the period of time after most evaporite deposition ended at 5.3 Ma (the Miocene‐Pliocene boundary). This boundary is readily mapped across the basin as a prominent reflection in seismic data correlated with stratigraphy at three DSDP sites. We quantify changes in the average elevation of the evaporite surface due to (a) thermal lithospheric subsidence, (b) isostatic loading by Plio‐Pleistocene sediments and water, (c) deflation needed to balance the volume of evaporites overflowing oceanic crust of 5.3 Ma age, (d) loss of halite by dissolution and (e) dynamic topography. Our best estimate of the evaporite level (−132 m air‐loaded or −192 m water‐loaded) lies below the range of estimated global sea level towards the end of the Miocene, suggesting that the basin remained under‐filled. If geological interpretations of shallow water conditions existing at the end of the Miocene (Zeit Formation) are correct, this implies that the water level of the Red Sea declined and was unstable. These calculations illustrate how spreading of evaporites can enhance thermal subsidence to cause rapid development of accommodation space above major evaporite bodies, which in the Red Sea case has remained largely unfilled.

Contribution of Hydrogeochemical and Isotopic Tools to the Management of Upper and Middle Cheliff Aquifers

In the alluvial aquifers of Upper and Middle Cheliff (North-West Algeria), the groundwater quality is deteriorating. The objective of this study was to characterize the physical and chemical properties of these aquifers; and to evaluate the groundwater quality and its appropriateness for drinking and agricultural use. An investigation was carried out by estimating of the physiochemical parameters (Ca2+, Mg2+, Na+, K+, Cl−, SO 4 2− , HCO 3 − , NO 3 − , Br− and TDS) to identify the chemical characteristics of groundwater. Morever, the isotopic composition was examined to identify the sources of recharge of these aquifers. The groundwater geochemistry for the high water level (May, 2012 and June, 2017) and low water level (November, 2012 and October, 2017) was studied. Accordingly, water samples from 39 water sampling points were collected (October, 2017 and June, 2018), for the purpose of analyzing stable isotopes (18O, 2H). The results show that the groundwater is mainly characterized by Ca-Cl and Na-Cl type. The chemical quality of the water is from fair to poor with the presence of nitrates used in agricultural and urban discharge. Also, the Br/Cl ratio gives indications on the origin of the salinity. This salinity is due to the leaching of chlorinated fertilizers, the dissolution of evaporite deposits and the rise of deep salty water by the fault of Chellif. While, the diagram of δ2h=f(δ18O) indicates that the origin of the recharge of these aquifers is the Atlantic and Mediterranean oceanic meteoric rainwater.