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1.
Most efforts in the study of sea-marginal sabkhas have concentrated on the Persian Gulf, but little is known about the sediments and mineralogy of sabkhas marginal to other seas. The purpose of this paper was to present some geochemical and mineralogical observations in a recent sabkha on the coast of Sinai along the Gulf of Suez. The sabkha is composed of coarse clastic sediments with marine-derived groundwater at depth of about 1 m. The general morphology, climate and water salinity of the Gulf of Suez resemble those of the Persian Gulf, despite the fact that the content of authigenic evaporites in this sabkha is more sparse. The evaporite minerals accumulated only in the upper 30–40 cm of the sabkha, below that and down to the groundwater table, there is no accumulation of evaporites. Laterally, the salinity of the groundwater in the sabkha and the concentration of evaporites in the sediments above it increase constantly with distance from the shore. In contrast to the Persian Gulf where anhydrite is a major evaporite mineral, in Belayim gypsum is the only calcium sulphate mineral in the recent sabkha. Anhydrite is found only in an old elevated sabkha where it recrystallized from gypsum. The gypsum occurs as interstitial crystal concentrations or lithified horizons almost exclusively at the depth of 20–40 cm below the sabkha surface. Above that, in the uppermost horizons, there is in situ accumulation of interstitial halite crystals. The total concentrations of gypsum and halite are almost equal in this sabkha. The sea water recharge in El Belayim is almost exclusively by seepage through the sabkha sediments and not by flooding. The groundwater under this sabkha is only slightly more saline than the Gulf water, thus, not heavy enough for extensive downward refluxing. The major hydrodynamic process must be upward migration of the brines from the groundwater, precipitating on the way gypsum and later halite with some magnesite. Since the sediments of the sabkha are too coarse to support extensive capillary movement, the brines must, therefore, migrate upwards due to ‘evaporative pumping’.  相似文献   

2.
Nabq sabkha exists 16 km north of Sharm El Sheikh City occupying the low land topography in the alluvial fan zone along the coastal area, Gulf of Aqaba, Sinai, Egypt. The long axis of the sabkha trends NW–SE receiving water from two different sources: meteoric water drained from the surrounding mountainous area and seawater seepage. Field observations help to divide the area into raised beach, hill slopes, sabkha basin, and coastal area. The sabkha basin can be subdivided from its center outward into (1) basin center hypersaline lake flourished with microbial mat and precipitation of halite as rafts, cumulates, and chevrons, (2) saturated saline sand and/or mud flat zone with the extensive growth of gypsum and halite crystals growing displacively as well as different forms of petee structures, and (3) an elevated marginal dry zone with tepee structures. Mineralogical analysis reveals that quartz, halite, and gypsum are the dominant minerals with subordinate amount of aragonite, anhydrite, thenardite, and/or polyhalite. In addition, clay minerals in the mudflat zone are presented by illite and smectite, indicating derivation of soil from the surrounding basement rocks. Chemical analysis of the collected brine samples reveals alkali character in the saline lake (pH?=?7.6) and high concentrations of Na+ (680 meq/l), Cl? (940 meq/l), Mg2+ (208 meq/l), Ca2+ (70 meq/l), SO 4 2+ (30 meq/l), and HCO 3 ? (6 meq/l). The high salinity values are due to the aridity of the area, which favors precipitation of halite. Using comparative sedimentological, chemical, and mineralogial methods between such modern and ancient evaporitic environments and by detailed field, petrographic and mineralogical studies of modern evaporite environments help to interpret paleo-depositional environments of ancient evaporites sequences still in debate.  相似文献   

3.
Sabkhas are ubiquitous geomorphic features in eastern Saudi Arabia. Seven brine samples were taken from Sabkha Jayb Uwayyid in eastern Saudi Arabia. Brine chemistry, saturation state with respect to carbonate and evaporate minerals, and evaporation-driven geochemical reaction paths were investigated to delineate the origin of brines and the evolution of both brine chemistry and sabkha mineralogy. The average total dissolved solids in the sabkha brines is 243 g/l. The order of cation dominance is Na+   >>  Mg2+ >>  Ca2+>K+, while anion dominance is Cl− >> SO4 2− >> HCO3 −. Based on the chemical divide principle and observed ion ratios, it was concluded that sabkha brines have evolved from deep groundwater rather than from direct rainfall, runoff from the surroundings, or inflow of shallow groundwater. Aqueous speciation simulations show that: (1) all seven brines are supersaturated with respect to calcite, dolomite, and magnesite and undersaturated with respect to halite; (2) three brines are undersaturated with respect to both gypsum and anhydrite, while three brines are supersaturated with respect to both minerals; (3) anhydrite is a more stable solid phase than gypsum in four brines. Evaporation factors required to bring the brines to the halite phase boundary ranged from 1.016 to 4.53. All reaction paths to the halite phase boundary follow the neutral path as CO2 is degassed and dolomite precipitates from the brines. On average, a sabkha brine containing 1 kg of H2O precipitates 7.6 g of minerals along the reaction path to the halite phase boundary, of which 52% is anhydrite, 35.3% is gypsum, and 12.7% is dolomite. Bicarbonate is the limiting factor of dolomite precipitation, and sulfate is the limiting factor of gypsum and anhydrite precipitation from sabkha brines.  相似文献   

4.
The isotopic composition of evaporites can shed light on their environment of precipitation and their subsequent recycling processes. In this study, we performed Sr, O and S isotopic analyses on evaporitic sulphates in the halokinetic Sivas Basin. The main objectives were to decipher the age and origin of the evaporites responsible for the salt tectonics, and to test whether diapir dissolution acts as the source of younger evaporitic layers in continental mini‐basins. The Sr isotopes demonstrate that the first evaporites precipitated from seawater during the Middle–Late Eocene. The similar isotopic values measured in the halokinetic domain confirm that the Eocene evaporites triggered the salt tectonics and were continuously recycled in Oligo‐Miocene mini‐basins as lacustrine to sabkha evaporites. Modern halite precipitates suggest that the dissolution and recycling of diapiric halite is ongoing. This study demonstrates the efficiency of isotopic analyses in constraining evaporite recycling processes in continental halokinetic domains.  相似文献   

5.
The discovery of sabkha environments during the 1960's, marked the beginning of Recent evaporite sedimentological studies and their perception as models for facies analysis. However, variation among Recent sabkhas, though recognized by the geologic community, has not been duly addressed, which has resulted in overuse of the Trucial Coast model in comparative sedimentological studies. Knowledge of the dominant physical processes which determine sabkha morphology, and of the sedimentary response to those processes, can lead to a fundamental understanding of a sabkha's origin and of how it differs from other sabkhas.

Physical processes thought to be most important (besides evaporation) include those operative under: (1) marine-; (2) fluvial-lacustrine-; and (3) eolian-dominated conditions. Dominance of one or more of these in the proper settings give rise to marine coastal sabkhas, continental playas, and interdune sabkhas.

Sedimentary responses to dominant physical processes lead to the development of sabkhas consisting of a combination of either: (1) terrigenous clastics; (2) carbonate-sulfate (anhydrite-gypsum) minerals; or (3) soluble salts (halite, sylvite, polyhalite, etc.). Sediment characterization can also allow discrimination of the range or compositional variety in, for example, coastal sabkhas.

Where applied to the stratigraphic record, this classification system may help unravel the sedimentary history of an ancient sabkha system, and a determination of the dominant physical processes that ruled its development.  相似文献   


6.
We studied the effects of evaporation and groundwater flow on the formation of salt minerals in the Sabkha of Oum El Khialate in South East Tunisia, which contains large amounts of sulfate sodium mineral deposits. Due to the fact that there are no important surface water bodies present in this sabkha, transport of solutes is dominated by advection rather than mixing in lakes. For our study we used both analytical conservative and numerical reactive transport models. Results showed that salinity varies with distance and may reach very high levels near a watershed where the groundwater flux is zero. As a consequence, reactive transport simulations results showed that more minerals precipitate and water activity decreases values near this watershed. Model results also showed that a sequence of precipitating minerals could be deduced after 140,000 years. From the boundary of the sabkha towards the watershed the mineral sequence was dolomite, gypsum, magnesite, bloedite, halite and mirabilite. It was found that the amounts as well as the mineral precipitation distribution strongly depend on salinity and rates of inflowing water.  相似文献   

7.
Lithologic succession, microscopic examination as well as X-ray diffraction and chemical data revealed that the surface Middle Miocene evaporites of Wadi Quei are composed of anhydrite beds intercalated with carbonate and green shale, whilst the subsurface evaporites of Gemsa locality are composed of gypsum, anhydrite, carbonates and celestite with a rare amount of halite. The anhydrite is found to be formed diagenetically after gypsum. The carbonate is interpreted as having been of biogenic origin. The strong smell of H2S and golden crystals of pyrite at Wadi Quei beds are indications of the biogenic action of sulphate-reducing bacteria in the presence of organic matter. It is suggested that the evaporite sequence which was deposited in a supratidal sabkha environment is characterized by alkaline-reducing conditions. The presence of nodular gypsum at Gemsa locality is probably deposited in a supratidal environment with oscillation of sea level.  相似文献   

8.
In Sicily, Messinian evaporitic sedimentary deposits are developed under a wide variety of hypersaline conditions and in environments ranging from continental margin (subaerial), to basin-margin supratidal, to intertidal, to subtidal and out into the hypersaline basin proper. The actual water depth at the time of deposition is indeterminate; however, relative terms such as ‘wave base’ and ‘photic zone’ are utilized. The inter-fingering relationships of specific evaporitic facies having clear and recognizable physical characteristics are presented. These include sub-aerial deposits of nodular calcium sulphate formed displacively within clastic sediments; gypsiferous rudites, arenites and arenitic marls, all of which are reworked sediments and are mixed in varying degrees with other clastic materials (subaerial, supratidal, and intertidal to deep basinal deposits). Laminated calcium sulphate alternating with very thin carbonate interlaminae and having two different aspects; one being even and continuous and the other of a wavy, irregular appearance (subtidal, intertidal, and supratidal deposits). Nodular calcium sulphate beds, usually associated with wavy, irregular laminated beds (supratidal, sabkha deposits); very coarsely crystalline gypsum beds (selenite), associated with more even, laminated beds (subaqueous, intertidal to subtidal deposits); wavy anastomozing gypsum beds, composed of very fine, often broken crystals (subaqueous, current-swept deposits); halite having hopper and chevron structures (supratidal to intertidal); and halite, potash salts, etc. having continuous laminated structure (subaqueous, possibly basinal). Evidence for diagenetic changes is observed in the calcium sulphate deposits which apparently formed by tectonic stress and also by migrating hypersaline waters. These observations suggest that the common, massive form of alabastrine gypsum (or anhydrite, in the subsurface) may not always be ascribed to original depositional features, to syndiagenesis or to early diagenesis but may be the result of late diagenesis.  相似文献   

9.
Vast expanses of arid, saline soils that occur along the Arabian Gulf seaboard and elsewhere possess a very low density and strength that necessitate improvement before any actual construction takesplace. For large-scale constructions, several field improvement techniques have recently been implemented with various degrees of success. In surficial, small-scale applications, chemical stabilization provides a potential technique to improve the inferior properties of these soils, known locally as sabkha. A literature search indicates that chemical stabilization of soils usingasphalt, lime and cement is usually conducted at lower moisture contents than the optimum. Such moisture contents are also much lower than the natural moisture content of sabkha, and if applied to sabkha in the field, this wouldrequire lowering the moisture content before any stabilization commenced; whichwould be neither feasible nor economical.

In this investigation, an eastern Saudi sabkha soil was chemically stabilized at its natural moisture level, which varies from 16% to 22%. In addition to the characterization of the soil and standard compaction tests, cement and lime sabkha mixtures were prepared at five additions and cured for up to 90 days in plastic wrap. Results indicate that cement-stabilized sabkha gained high strength with time and proved to have a potential use in construction.  相似文献   


10.
Microbial mediation is the only demonstrated mechanism to precipitate dolomite under Earth surface conditions. A link between microbial activity and dolomite formation in the sabkha of Abu Dhabi has, until now, not been evaluated, even though this environment is cited frequently as the type analogue for many ancient evaporitic sequences. Such an evaluation is the purpose of this study, which is based on a geochemical and petrographic investigation of three sites located on the coastal sabkha of Abu Dhabi, along a transect from the intertidal to the supratidal zone. This investigation revealed a close association between microbial mats and dolomite, suggesting that microbes are involved in the mineralization process. Observations using scanning electron microscopy equipped with a cryotransfer system indicate that authigenic dolomite precipitates within the exopolymeric substances constituting the microbial mats. In current models, microbial dolomite precipitation is linked to an active microbial activity that sustains high pH and alkalinity and decreased sulphate concentrations in pore waters. Such models can be applied to the sabkha environment to explain dolomite formation within microbial mats present at the surface of the intertidal zone. By contrast, these models cannot be applied to the supratidal zone, where abundant dolomite is present within buried mats that no longer show signs of intensive microbial activity. As no abiotic mechanism is known to form dolomite at Earth surface conditions, two different hypotheses can reconcile this result. In a first scenario, all of the dolomite present in the supratidal zone formed in the past, when the mats were active at the surface. In a second scenario, dolomite formation continues within the buried and inactive mats. In order to explain dolomite formation in the absence of active microbial metabolisms, a revised microbial model is proposed in which the mineral‐template properties of exopolymeric substances play a crucial role.  相似文献   

11.
Paleo-temperature and paleo-environment can be interpreted from measuring homogenization temperatures of fluid inclusions within halite. In order to conduct such measurements, vapor bubbles within low-temperature fluid inclusion often need to be created through cooling process by using cooling stage or freezer. Proper cooling is critical for interpreting measured temperature data. We tested two common cooling methods, using heating/freezing stage and freezer, for studying fluid inclusions in halite precipitated in laboratory at conrtolled temperature of 25℃. While using the heating/freezing stage, halite samples were kept at-18℃ for 40–50 min; whereas for freezer, samples were stored at-18℃ for 1, 10, 20 and 40 days, respectively. By comparing the homogenization temperatures of the two cooling processes, we explored the detailed experimental processes and developed an optimal cooling nucleation procedure for homogenization temperature analyses of fluid inclusions within surface-temperature halite. The results show that the maximum homogenization temperatures from both methods approximate the actual brine temperature of 25℃. However, extended refrigeration time has noticeable influence on the results. The refrigeration time of the experiment can be shortened to meet requirements.  相似文献   

12.
A suite of unusual highly skeletal halite pseudomorphs is described from the lower Middle Cambrian rocks that crop out at Ardmore in the Georgina Basin, northern Australia. The pseudomorphs are preserved as both moulds and casts within a dark and light colour-banded chert. They are orientated parallel to bedding and represent halite crystal growth within a brine pool. Laterally equivalent rocks are characterized by sedimentary textures and structures indicative of periodic emergence and desiccation. Laboratory grown halite crystals are also described and compared with the pseudomorphs from Ardmore. Experimentally produced halite crystals formed from either: (1) brine solutions obtained as residues after organic matter extraction from phosphate rocks, or (2) solutions of NaCI and distilled water. Both pyramidal rafted hoppers and floor nucleated cuboids formed in solutions containing only NaCI and distilled water; whereas in the residue solutions, that contained humic acids, rafted pyramidal forms were absent and crystal nucleation was restricted to the floor of the evaporative dish. As brine depth decreased the halite precipitation rate increased and resulted in a suite of excrescent, highly skeletal crystals that formed as a result of brine evaporation to dryness. The variable crystal morphology depended upon both the brine depth and slope of the evaporative dish floor. Horizontally orientated chevron halite crystals formed where the evaporative dish was inclined and precipitation preferentially occurred on cube faces. Pagoda, reticulate ridge and dendritic forms represent an increasingly skeletal crystal suite characterized by the preferential precipitation of NaCI on cube edges and corners rather than faces. Using the experimentally grown crystals as analogues the pseudomorphs at Ardmore are interpreted as forming in very shallow brine pools that evaporated to dryness.  相似文献   

13.
This paper addresses global oxygenation and establishment of a marine sulphate reservoir in the Palaeoproterozoic. We report syn-depositional, marine, anhydrite-containing pseudomorphs after Ca-sulphates as widespread throughout the Tulomozero Formation in the SE Fennoscandian Shield, implying that surface waters were oxidized and a large SO marine reservoir was developed as early as 2100 Ma. The Ca-sulphates and associated magnesite and halite precipitated syn-depositionally from oxidized, evolved and modified seawater in coastal playa, sabkha and intertidal flat settings. 87Sr/86Sr and δ13C of associated 13C-rich stromatolitic dolostones were environmentally controlled with the highest ratios occurring in playa and sabkha carbonates. The results imply that the Palaeoproterozoic δ13Ccarb excursion was amplified by 8‰ by local environmental factors and calls into question many observations of putative δ13C global signals reported previously from similar Palaeoproterozoic, evaporitic, dolostones. The local environmental amplification can explain a large regional and intercontinental δ13C discrepancy observed in synchronous carbonates.  相似文献   

14.
The Alpine Haselgebirge Formation represents an Upper Permian to Lower Triassic evaporitic rift succession of the Northern Calcareous Alps (Eastern Alps). Although the rocksalt body deposits are highly tectonised, consisting mainly of protocataclasites and mylonites of halite and mudrock, the early diagenetic history can be established from non-tectonised mudrock bodies: Cm-sized euhedral halite hopper crystals formed as displacive cubes within mud just during shallow burial. The crystals were deformed by subsequent compaction. Later, migrating fluids led to the replacement of halite by anhydrite retaining the shapes of deformed halite cubes. Polyhalite formed from subsequent enhanced fluid migration. Mudrock provided water by dewatering, while potassium and magnesium were dissolved from primary salt minerals. When these fluids interacted with sulphates, polyhalite precipitated. 40Ar/39Ar analyses date the polyhalite from within the retaining shapes of deformed halite hopper-shaped cubes from two localities to ca. 235–232 Ma (Middle Triassic). At this time, ca. 20–25 Ma after sedimentation, polyhalite crystallised at shallow levels.  相似文献   

15.
Late Neoproterozoic to Early Cambrian carbonates of the Ara Group form important intra‐salt ‘stringer’ reservoirs in the South Oman Salt Basin. Differential loading of thick continental clastics above the six carbonate to evaporite cycles of the Ara Group led to the formation of salt diapirs, encasing a predominantly self‐charging hydrocarbon system within partly highly overpressured carbonate bodies (‘stringers’). These carbonates underwent a complex diagenetic evolution, with one stage of halite cementation in a shallow (early) and another in a deep (late) burial environment. Early and late halite cements are defined by their microstructural relationship with solid bitumen. The early phase of halite cementation is post‐dated by solid reservoir bitumen. This phase is most pervasive towards the top of carbonate stringers, where it plugs nearly all available porosity in facies with initially favourable poroperm characteristics. Bromine geochemistry revealed significantly higher bromine contents (up to 280 p.p.m.) in the early halite compared with the late halite (173 p.p.m.). The distribution patterns and the (high) bromine contents of early halite are consistent with precipitation caused by seepage reflux of highly saturated brines during deposition of the overlying rock salt interval. Later in burial history, relatively small quantities of early halite were dissolved locally and re‐precipitated as indicated by inclusions of streaky solid bitumen within the late halite cements. Late halite cement also seals fractures which show evidence for repeated reopening. Initially, these fractures formed during a period of hydrothermal activity and were later reopened by a crack‐seal mechanism caused by high fluid overpressures. Porosity plugging by early halite cements affects the poroperm characteristics of the Ara carbonates much more than the volumetrically less important late halite cement. The formation mechanisms and distribution patterns of halite cementation processes in the South Oman Salt Basin can be generalized to other petroliferous evaporite basins.  相似文献   

16.
In the Tarim Basin, dolomite, which formed during the middle Cambrian associated with evaporites, has been attributed to the sabkha-style dolomite formed during the syndepositional period. The sedimentary microfacies suggests dolomite formation in the middle Cambrian is an ancient analogue of the sabkha of Abu Dhabi. Poorly crystallised dolomite spheroids or ovoids within or on the surface of dolomite crystals are a common phenomenon that can be widely observed in different stromatolites in the upper part of the intertidal zone and strongly resemble the morphology in modern sabkha dolomite-producing microbial mats and in microbial culture experiments. These lines of evidence suggest organic substrates for dolomite nucleation. Dolomite formation in the middle Cambrian in the Tarim Basin has been considered a classic analogue for carbonate and evaporate assemblages. The extent of microbial dolomite in ancient sabkha environments is proposed as an alternative model for dolomite formation, in which the mineral properties of organic substrates play a crucial role.  相似文献   

17.
This study represents a preliminary investigation of the late Messinian subsurface Marsa Zouaghah Formation in the Western Libyan Offshore, Central Mediterranean Sea. The formation was deposited in three major environmental settings: (a) Marginal Sabkha; (b) Open Lagoon; and (c) Hypersaline Lagoon. The marginal sabkha and open lagoonal settings are locally interrupted by intertidal oolitic shoal deposits. The marginal sabkha facies is replaced in central parts of the Libyan offshore by a narrow zone of aeolian-fluvial facies, the distribution and thickness of which is entirely controlled by a local uplift, the Tripoli Nose'. The marginal sabkha facies broadly defines the late Messinian palaeoshoreline lying parallel to, and north of, the E-W Jifarah fault system which dominated the southern part of the Libyan offshore. This fades is, thus, interpreted as being structurally controlled by fault systems. The hypersaline lagoonal facies is developed in areas of relatively higher rates of subsidence than that of adjacent facies belts. It is therefore, related to restriction formed by continuous subsidence and evaporation. The Marsa Zouaghah Formation constitutes saltern evaporates deposited over a wide platform in sabkha and lagoonal settings, forming part of the 'basin-wide-evaporites' of the Mediterranean Basin deposited during the Messinian salinity crisis. The evaporites formed during a major relative sea-level fall within a subsiding basin situated on the northern continental margin of the African plate. Local, vertical and lateral variations in lithofacies and thickness within the Messinian deposits of the north-west Libyan offshore were controlled by contemporaneous strike-slip movements in addition to sea-level change.  相似文献   

18.
中更新世气候转型事件(MPT)是全球性冷气候事件,在柴达木盆地也有记录,但关于该事件形成时的古温度数据较少。石盐原生流体包裹体形成于浅水环境,其均一温度可直接反映晶体形成时的卤水温度,是恢复古温度常用的指标之一。本文选择柴达木盆地西部钻孔SG-1中1.22~0.88 Ma期间的石盐晶体进行流体包裹体均一温度测试,共获得390个石盐流体包裹体数据。其均一温度最高为50 ℃,最低为6.8 ℃,90%以上温差值在10 ℃以内,且石盐流体包裹体大小与温度没有明显线性相关关系,这说明SG-1钻孔石盐流体包裹体被捕获后没有受到后期热液的改造。均一温度数据反映了石盐沉积时的古水温特征。石盐晶体主要在暖季析出,原生流体包裹体恢复的古水温可能是暖季节的温度。均一温度的最高值可能受到热液和气候的共同作用。MPT时期,石盐流体包裹体均一温度(中位值Th,med)接近于现代盆地7月份大气温度的平均值,高于盆地的全年温度及MPT时期的全球气温,与MPT时期地中海的海水表面温度相当,均一温度的平均值(Th,avg)高于以上温度。SG-1钻孔记录的柴达木盆地MPT事件最冷期出现在约1.165~1.0 Ma。  相似文献   

19.
Cement-Stabilization of Sabkha Soils from Al-Auzayba,Sultanate of Oman   总被引：2，自引：1，他引：1  
Sabkha soils are salt-bearing formations that are formed in arid regions. In their in situ states the sabkha soils have high compressibility and low shear strength. These soils are also heterogeneous and their properties depend on the type and amount of salt present. Thus, these soils are not suitable for support of infrastructures without the risk of high settlement and/or bearing capacity failure. This paper investigates the possibility of using cement to improve the shear strength of sabkha soils for possible use as a foundation-bearing soil. The sabkha soil used in this study is a sandy sabkha obtained from the coastal plains at Al-Auzayba, Sultanate of Oman. Cement was added in percentages of 2.5, 5, 7.5 and 10%, by dry weight of soil. The soil-stabilizer mixers were allowed to cure for 7, 14 and 28 days. Laboratory tests such as compaction, unconfined compression, consolidated undrained triaxial and durability tests were performed to measure the engineering characteristics of the stabilized material. The results showed substantial improvements in the shear strength of the sabkha–cement mixtures and the mixtures are also durable with small weight loss after 12 wetting/drying cycles. Thus, cement can be used to improve the shear strength of sabkha soils. Furthermore, the effective stress path and the tress-strain relation of the sabkha–cement mixtures follow trends similar to those of cemented calcareous soils.  相似文献   

20.
X-ray diffractometer analysis and SEM investigation confirmed the occurrence of jarosite and alunogen minerals in the Quaternary siliciclastic sabkha sediments of northern Kuwait within the Bahrah oilfield area, Arabian Gulf. Jarosite is relatively abundant in a near-surface whitish sticky tidal muddy sand layer about 60 cm thick that overlies the ferruginous sandstone of the Oligo-Miocene Ghar Formation. Jarosite occurs as clusters of euhedral pseudo-cubes of about 1 μm in size and as agglomerated nanoglobules of 250 nm in size. A hypogenetic origin related to the reaction of sulfuric acid produced by the oxidation of H2S associated with hydrocarbon gas seepages with K and Fe leachates is suggested. The restricted occurrence of jarosite within near-surface sabkha sediments may be attributed to limited tidal inundation and prevalence of arid climatic conditions.  相似文献   

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