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1.
ABSTRACT A number of non‐marine evaporite units composed of primary gypsum were deposited in saline lakes that developed in the southern Teruel Basin (NE Spain) during the Miocene. In the basin depocentre, a continuum of lacustrine evaporite lithofacies influenced by the activity of organisms is displayed. The Libros Gypsum was deposited in a deep lake, in which water stratification became unstable with progressive shoaling. Rhythmites, composed of laminae of pelletal gypsum and laminae of very fine lenticular gypsum crystals mixed with siliceous microorganisms, formed in addition to gypsum turbidites, intraformational gypsum breccias and slump structures. The pelletal laminae originated from the faecal activity of animals (crustaceans?) ingesting gypsum crystallites in the lake water during episodes of maximum evaporation, whereas the laminae of very fine lenticular gypsum mixed with microorganisms accumulated during episodes of relative dilution. In the wide marginal zones of the basin, the Libros Gypsum unit consists of massive to thin‐bedded bioturbated gypsum and thin‐bedded clotted gypsum, which formed in intermediate to very shallow (palustrine) water depths. The bioturbated gypsum lithofacies were produced by the action of diverse organisms, presumably worms and coleopterans, and chironomid larvae to a lesser extent; the massive lithofacies precipitated in very shallow water; and the thin‐bedded lithofacies formed in shallow to deeper settings. The thin‐bedded clotted gypsum is a relatively deep facies that may have diverse origins (e.g. bioturbation, compaction, disruption of soft sediments and early diagenesis). There is a well‐developed metre‐scale cyclicity in the marginal lake sequences, which is not observed in the inner lake deposits. This suggests a depth control in the various lacustrine subenvironments to record cyclic evaporitic processes. The isotopic composition of the gypsum indicates early sulphate‐reducing bacterial activity in the bottom of the lake and suggests that the sulphate was derived from the chemical recycling of Triassic evaporites of the country rocks. 相似文献
2.
The Upper Miocene and Pliocene evaporite deposits of the Atacama Desert of northern Chile (Hilaricos and Soledad Formations) are among the few non‐marine evaporites in which aridity not only formed the deposits, but has also preserved them almost unaltered under near‐surface conditions. These deposits are largely composed of displacive Ca sulphate and halite together with minor amounts of glauberite, thenardite and polyhalite. However, at the base and top of these deposits, there are also beds of gypsum crystal pseudomorphs that originally formed as free‐growth forms within shallow brine bodies, rather than as displacive sediments. The halite is present as interstitial cement, displacive cubes and shallow‐water, bottom‐growth chevron crusts. Most of the calcium sulphate is presently anhydrite, pseudomorphous after gypsum, that was the primary depositional sulphate mineral. The secondary anhydrite formed under early diagenetic conditions after slight burial (some metres) resulting from the effect of strongly evolved pore brines. The anhydrite has been preserved without rehydration during late diagenetic and exhumation stages on account of the arid environment of the Atacama Desert. Both the Hilaricos and the Soledad Formations contain geochemical markers indicating that these Neogene evaporites had a largely non‐marine origin. Bromine content in the halite is very low (few p.p.m.), indicating neither a sedimentological relation with sea water nor the likelihood of direct recycling of prior marine halites. Moreover, the δ34S of sulphates (+4·5‰ to +9‰) also reflects a non‐marine origin, with a strong volcanic influence, although some recycling of Mesozoic marine sulphates cannot be ruled out. δ34S of dissolved sulphate from hot springs and streams in the area commonly displays positive values (+2‰ to +10‰). Leaching of oxidized sulphur and chlorine compounds from volcanoes and epithermal ore bodies, very common in the associated drainage areas, have been the main contribution to the accumulation of evaporites. The sedimentary and diagenetic evolution of the Hilaricos and Soledad evaporites (based on lithofacies analysis) provides information about the palaeohydrological conditions in the Central Depression of northern Chile during the Neogene. In addition, the diagenesis and exhumation history of these evaporites confirms the persistence of strongly arid conditions from Late Miocene until the present. A final phase of tectonism took place permitting the internal drainage to change and open to the sea, resulting in dissolution and removal of a significant portion of these deposits. Despite the extensive dissolution, the remaining evaporites have undergone little late exhumational hydration. 相似文献
3.
This paper concerns the evaporite units, depositional systems, cyclicity, diagenetic products and anhydritization patterns of the Calatayud Basin (nonmarine, Miocene, central Spain). In outcrop, the sulphate minerals of these shallow lacustrine evaporites consist of primary and secondary gypsum, the latter originating from the replacement of anhydrite and glauberite. In the evaporative systems of this basin, gypsiferous marshes of low salinity can be distinguished from central, saline lakes of higher salinity. In the gypsiferous marsh facies, the dominant, massive, bioturbated gypsum was partly replaced by synsedimentary chert nodules and siliceous crusts. In the saline lake facies, either cycles of gypsiferous lutite‐laminated gypsarenite or irregular alternations of laminated gypsum, nodular and banded glauberite, thenardite and nodular anhydrite precipitated. Early replacement of part of the glauberite by anhydrite also occurred. Episodes of subaerial exposure are represented by: (1) pedogenic carbonates (with nodular magnesite) and gypsiferous crusts composed of poikilitic crystals; and (2) nodular anhydrite, which formed in a sabkha. Additionally, meganodular anhydrite occurs, which presumably precipitated from ascending, highly saline solutions. The timing of anhydritization was mainly controlled by the salinity of the pore solutions, and occurred from the onset of deposition to moderate burial. Locally, a thick (>200 m) sequence of gypsum cycles developed, which was probably controlled by climatic variation. A trend of upward‐decreasing salinity is deduced from the base to the top of the evaporite succession. 相似文献
4.
柴达木盆地位于青藏高原北部,沉积和储存了巨量的蒸发岩。其独特的地理位置、构造特征、盐类沉积和其它资源优势,成为地学领域各方向学者关注的焦点。2008年,中德合作在盆地西部取得千米深的钻孔,上部400 m表现为碳酸盐粘土层与盐层的交替,盐层的矿物种类是石盐（NaCl）,石膏（CaSO4·2H2O）,芒硝（Na2SO4·10H2O）,无水芒硝（Na2SO4）,钙芒硝（Na2Ca(SO4)2）,杂卤石（K2MgCa2(SO4)4·2H2O）,尤钠钙矾（Na4Ca(SO4)3·2H2O）和白钠镁矾（Na2Mg(SO4)2·4H2O）,以石盐和石膏为主。碳酸盐粘土层中还出现了少量重晶石（BaSO4）、碳酸钠钙石（Ca2Na2(CO3)3）、钠钙矾（Ca2Na3(SO4)3(OH)）、苏打石（NaHCO3）、斜碳钠钙石（Na2Ca(CO3)2·5H2O）、一水碳酸钠（Na2CO3·H2O）和水硼镁石（CaMg(B3O3(OH)5)2·6H2O）。碳酸盐粘土层中不同形态的石膏单晶、双晶和集合体,形成于次生浓卤水溶液,晶体形状与生长速度、溶液性质和环境条件有关。单盐矿物石盐、石膏和无水芒硝从卤水中直接结晶,复盐钙芒硝、白钠镁矾和尤钠钙矾则由单盐反应形成。尤钠钙矾为罕见的亚稳定矿物,柴达木盆地和青藏高原其它地区的研究中尚未见报道,该矿物形成温度远高于室温,可能是由石膏或无水芒硝在富Na SO4卤水溶液中反应形成。根据矿物种类、组合和阳离子含量推断,古卤水类型主要为Na Cl型,其次为Na Ca SO4、Na SO4、Na SO4 Cl、Na Ca SO4 Cl,少数层位为Ca SO4和Na Mg SO4型卤水。盐层和碳酸盐粘土层的交替说明,1 Ma以来钻孔所在区域为干湿交替气候,18个成盐阶段或气候干旱阶段出现在0.97~0.03 Ma,最早的两个蒸发阶段为0.96~0.97 Ma和0.87 Ma,其它蒸发阶段出现在0.78~0.03 Ma,厚盐层集中出现在0.5~0.03 Ma。 相似文献
5.
Javier García-Veigas Laura Rosell Federico Ortí İbrahim Gündoğan Cahit Helvacı 《Chemical Geology》2011,280(3-4):352-364
The Emet basin is one of the Neogene basins in western Turkey containing significant amounts of borate minerals, mainly colemanite. The petrologic study of core samples from two exploratory wells in the Do?anlar sector, under optic and electron microscopy, reveals a complex mineral association in which probertite, glauberite, and halite constitute the major primary phases (without mineral precursors) precipitated in a saline lake placed in a volcano-sedimentary context. Other sulfates (anhydrite, gypsum, thenardite, celestite and kalistrontite), borates (colemanite, ulexite, hydroboracite, tunellite, kaliborite and aristarainite), and sulfides (arsenopyrite, realgar and orpiment) are attributed to early diagenesis. So far, the Do?anlar deposit is the most important deposit of probertite known up to now.Chemical changes in the groundwater inflow led to the precipitation of Ca-bearing borates (colemanite) in the tuff-flat environment surrounding the lake, while Na–Ca sulfates and borates (glauberite and probertite) precipitated in the center of the lake. Fluid inclusion compositions in halite indicate that the advanced brines correspond to the Na-K-Cl-SO4 type. During restricted stages of the saline lake, the residual brines seeped through the tuff-flat sediments, leading to transformations of previous precipitates that resulted in the formation of K-bearing minerals.The abundance of coccoid-like biogenic dolomite, colloidal arsenopyrite and the isotopic composition of sulfates are indicative of bacterial sulfate reduction. In contrast, arsenic sulfides are attributed to acidophilic micro-organisms in oxidizing conditions. Fluctuations of redox conditions in both free and interstitial brines control the biological influence in some diagenetic transformations. 相似文献
6.
H. Mirnejad V. Sisakht H. Mohammadzadeh A. H. Amini B. J. Rostron G. Haghparast 《Geological Journal》2011,46(1):1-9
Cation and anion concentrations and oxygen and hydrogen isotopic ratios of brines in the Asmari Formation (Oligocene–early Miocene) from the Marun oil field of southwest Iran were measured to identify the origin of these brines (e.g. salt dissolution vs. seawater evaporation) as well as the involvement of water–rock reaction processes in their evolution. Marun brines are characterized by having higher concentrations of calcium (11 000–20 000 mg/L), chlorine (120 000–160 000 mg/L) and bromide (600–1000 mg/L) compared to modern seawater. Samples are also enriched in 18O relative to seawater, fall to the right of the Global Meteoric Water Line and local rain water, and plot close to the halite brine trajectory on the δD versus δ18O diagram. Geochemical characteristics of Marun brines are inconsistent with a meteoric origin, but instead correspond to residual evaporated seawater modified by water–rock interaction, most significantly dolomitization. In addition, anhydrite precipitation or sulphate reduction appears to be important in chemical modification of the Marun brines, as indicated by lower sulphate contents relative to evaporated seawater. Extensive dolomitization, the presence of anhydrite nodules and high salinity fluid inclusions in the upper parts of the Asmari Formation fit a model whereby the Marun brines likely originated from the seepage reflux of concentrated seawater during the deposition of the overlying Gachsaran Formation evaporites in the Miocene. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
7.
罗布泊盐湖富钾卤水成因再探讨——碎屑层卤水蒸发实验分析 总被引：1，自引：0，他引：1
罗布泊盐湖钙芒硝岩孔隙中蕴藏有超大型规模的卤水钾矿,富钾卤水成因一直备受关注。罗北凹地从统一的罗布泊大湖区中分隔出来后,成盐过程中其湖水仍以南部大湖的补给为主,罗北凹地卤水化学演化与"大耳朵"湖水密切相关。"大耳朵"湖区含石膏碎屑层普遍储藏有卤水,应该是罗北凹地盐湖的"源卤水",钾离子(ρ(K~+)为3.12 g/L左右)已初步富集,平均矿化度为198.83 g/L。为了查明该卤水的化学演化趋势及析盐序列,笔者于2009年、2010年两次采集了大量卤水样品,分别进行室内等温蒸发和自然蒸发实验。蒸发实验结果表明:随着卤水浓缩首先析出(硬)石膏,随后析出大量石盐,最后出现少量钾石盐和光卤石,与EQL/EVP卤水蒸发模型模拟结果相似。将碎屑层卤水蒸发过程中化学组成变化与罗北凹地卤水进行对比,结果显示罗布泊古湖水蒸发至石膏沉积之后,在罗北凹地水化学组成明显发生变化,没有大量石盐沉积,而以钙芒硝沉积为主。推测应是受到深部"富钙水"的持续补给,而"大耳朵"湖起到"预备盆地"的作用,罗布泊古湖水经"大耳朵"湖蒸发浓缩后,钾离子得到初步富集,在流入罗北凹地后与深部"富钙"水混合,强烈蒸发浓缩,大量钙芒硝矿物析出,最后形成富钾卤水。 相似文献
8.
新疆巴里坤盐湖是一个常年性固、液并存的硫酸盐型盐湖。盐湖卤水中含Ｎａ＋、Ｋ＋、Ｃａ２＋、Ｃｌ－、ＳＯ２－４、ＨＣＯ－３、ＣＯ２－３等主要成分，沉积物中有芒硝、无水芒硝、石膏、水钙芒硝、半水石膏、石盐等盐类矿物及碳酸盐和泥质矿物。盐湖中有大量卤虫及卤虫卵自湖中心向湖岸呈环带状分布，在成盐过程中起着重要作用。盐湖形成于第三纪，第四纪以来，曾经历２次成岩期，约自１７ｋａＢ．Ｐ．湖水多次蒸发浓缩，成岩作用加强，形成芒硝等矿产 相似文献
9.
Leila Abdi Hossain Rahimpour-Bonab Mohsen Mirmohammad-Makki Johann Probst Saeed Rezaeian Langeroudi 《Arabian Journal of Geosciences》2018,11(19):589
Playas are shallow ephemeral lakes that form in arid and semi-arid regions. Iran has a large number of playas such as Meyghan Playa, which is located in the northeast of Arak city that borders the central Iran and Sanandaj-Sirjan zones. This study aims to investigate the mineralogical, sedimentological, and geochemical characteristics of the playa sediments. In order to determine the palaeoenvironment, we carried out X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM) studies. Meyghan Playa sediments consist of very fine-grained sediments and contain both evaporite and clastic minerals. The evaporite minerals include calcite, gypsum, halite, glauberite, and thenardite, whereas clastic minerals are quartz and clay. The calcite abundance decreases from the margin to the central portion of the playa but gypsum and halite abundances show an increasing trend from the margin to the center. This observation is consistent with the general zonation of other playas. Variations of calcite and gypsum concentration profiles present increasing and decreasing trends with depth, which could be ascribed to the changes in climatic factors. These factors include brine chemical modifications owing to changes in evaporation and precipitation rates and variations in relative abundance of anions-cations or in the rate of clastic and evaporite minerals due to variations in the freshwater influx (climatic changes) with time. A decrease in calcite and increase in sulfate minerals (especially gypsum) with depth is probably due to the higher water level and rainfall, a more humid climate, and salinity variations. 相似文献
10.
根据地层基准面原理,通过对岩心、测井、录井资料的综合分析,将研究区Es3.3-Es3.2层段的地层划分出4个中期地层旋回（层序）：MSC1,MSC2,MSC3,MSC4。其中大致发育2种类型的层序,即陆源碎屑岩层序和膏盐岩层序。陆源碎屑岩层序多形成于基准面上升期,以发育泥质岩夹浊积砂体、三角洲前缘砂质沉积为主;膏盐岩层序多形成于基准面下降期,以发育厚层的盐岩、膏盐岩、膏岩、泥膏岩、膏泥岩夹浊积席状砂为特征。识别出3种类型的沉积体系：较深水湖－浊积扇、较深水盐湖、浅湖－三角洲体系,并在层序格架内分析了各旋回的沉积体系构成和储层砂体的发育情况。综合分析生、储、盖条件后认为,在垂向上,MSC2上升半旋回为本区最有利的储集层段;在平面上,本区的油气勘探应主要寻找洼陷东、西两侧断层下降盘的浊积砂体,主要储层砂体类型为浊积水道及浊积席状砂。 相似文献
11.
腾格里沙漠122个盐湖分为石盐、石盐-芒硝、石盐-白钠镁矾及芒硝(石膏)4种类型。盐湖含盐系厚度一般4～9m,总体呈现下部为含盐碎屑沉积,上部以盐类沉积为主,构成储卤层,卤水赋存其中,由湖岸至湖心储卤层厚度增长。含卤层理渐小,卤水含KCl渐高。盐湖中矿物主要为碳酸盐矿物,以芒硝、石膏为主的硫酸盐矿物、石盐以及粘土矿物。盐湖卤水以晶间卤水为主。许多卤水含K+大于2g/L。K+含量最高的红盐池,平均含量达19.14g/L。对钾矿而言,在盐湖分布相对集中地区,有一定的综合开发利用前景。 相似文献
12.
Extensive deposition of marine evaporites occurred during the Early–Middle Eocene in the South‐eastern Pyrenean basin (north‐east Spain). This study integrates stratigraphic and geochemical analyses of subsurface data (oil wells, seismic profiles and gravity data) together with field surveys to characterize this sedimentation in the foredeep and adjacent platform. Four major evaporite units were identified. The oldest was the Serrat Evaporites unit, with a platform‐slope‐basin configuration. Thick salina and sabkha sulphates accumulated on the platform, whereas resedimented and gravity‐derived sulphates were deposited on the slope, and salt and sulphates were deposited in the deep basin. In the subsequent unit (Vallfogona evaporites), thin sulphates formed on the platform, whereas very thick siliciclastic turbidites accumulated in the foredeep. However, some clastic gypsum coming from the platform (gypsarenites and gypsum olistoliths) was intercalated in these turbidites. The following unit, the Beuda Gypsum Formation developed in a sulphate platform‐basin configuration, where the topography of the depositional surface had become smooth. The youngest unit, the Besalú Gypsum, formed in a shallow setting. This small unit provides the last evidence of marine influence in a residual basin. Sulphur and oxygen isotope compositions are consistent with a marine origin for all evaporites. However, δ34S and δ18O values also suggest that, except for the oldest unit (Serrat Evaporites), there was some sulphate recycling from the older into the younger units. The South‐eastern Pyrenean basin constitutes a fine example of a foreland basin that underwent multiepisodic evaporitic sedimentation. In the basin, depositional factors evolved with time under a structural control. Decreasing complexity is observed in the lithofacies, as well as in the depositional models, together with a diminishing thickness of the evaporite units. 相似文献
13.
During the Cenozoic numerous shallow epicontinental evaporite basins formed due to tectonic movements in the Northern Province of the Central Iran Tectonic Zone (the Great Kavir Basin). During the Miocene, due to sea‐level fluctuations, thick sequences of evaporites and carbonates accumulated in these basins that subsequently were overlain by continental red beds. Development of halite evaporites with substantial thickness in this area implies inflow of seawater along the narrow continental rift axis. The early ocean basin development was initiated in Early Eocene time and continued up to the Middle Miocene in the isolated failed rift arms. Competition between marine and non‐marine environments, at the edge of the encroaching sea, produced several sequences of both abrupt and gradual transition from continental wadi sediments to marginal marine evaporites in the studied area. These evaporites show well‐preserved textures indicative of relatively shallow‐brine pools. The high Br content of these evaporites indicates marine‐derived parent brines that were under the sporadic influence of freshening by meteoric water or replenishing seawater. However, the association of hopper and cornet textures denotes stratified brine that filled a relatively large pool and prevented rapid variations in the Br profile. Unstable basin conditions that triggered modification of parent brine chemistry prevailed in this basin and caused variable distribution patterns for different elements in the chloride units. The presence of sylvite and the absence of Mg‐sulphate/chlorides in the paragenetic sequence indicate SO4−depleted parent brine in the studied sequence. Petrographic examinations along with geochemical analyses on these potash‐bearing halites reveal parental brines which were a mixture of seawater and CaCl2‐rich brines. The source of CaCl2‐rich brines is ascribed to the presence of local rift systems in the Great Kavir Basin up to the end of the Early Miocene. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
14.
WILLIAM M. LAST 《Sedimentology》1989,36(1):109-123
Ceylon Lake, a small salt playa located in southern Saskatchewan, is typical of many shallow ephemeral lacustrine basins found in the northern Great Plains of western Canada. The present-day brine, dominated by magnesium, sodium, and sulphate ions, shows wide variation in composition and concentration on both a temporal and a spatial basis. The modern sediments overall exhibit relatively simple facies relationships. An outer ring of coarse grained shoreline and colluvial clastics surrounds mixed fine grained clastics and salts and, in the centre of the basin, salt pan evaporites composed mainly of mirabilite, thenardite, and bloedite. Coring of the late Pleistocene and Holocene sedimentary fill shows that the lake has evolved from a relatively dilute, deep water, clastic dominated basin through a shallower, brackish water, carbonate-clastic phase, and finally into the present salt dominated playa. The thick sequence of evaporites preserved in the basin suggests evolution of the brine from a Na-rich solution to a mixed Mg-Na system. The most important post-depositional processes affecting Ceylon Lake sediments are mud diapirism and salt karsting. 相似文献
15.
Heterozoan carbonate deposition on a steep basement escarpment (Late Miocene,Almería,south‐east Spain) 
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下载免费PDF全文 Heterozoan temperate‐water carbonates mixed with varying amounts of terrigenous grains and muddy matrix (Azagador limestone) accumulated on and at the toe of an inherited escarpment during the late Tortonian–early Messinian (late Miocene) at the western margin of the Almería–Níjar Basin in south‐east Spain. The escarpment was the eastern end of an uplifting antiform created by compressive folding of Triassic rocks of the Betic basement. Channelized coralline‐algal/bryozoan rudstone to coarse‐grained packstone, together with matrix‐supported conglomerate, are the dominant lithofacies in the higher outcrops, comprising the deposits on the slope. These sediments mainly fill small canyon‐shaped, half‐graben depressions formed by normal faults active before, during and after carbonate sedimentation. Roughly bedded and roughly laminated coralline‐algal/bryozoan rudstone to coarse‐grained packstone are the main lithofacies forming an apron of four small (kilometre‐scale) lobes at the toe of the south‐eastern side of the escarpment (Almería area). Channelized and roughly bedded coralline‐algal/bryozoan rudstone to coarse‐grained packstone, conglomerates, packstone and sandy silt accumulated in a small channel‐lobe system at the toe of the north‐eastern side of the escarpment (Las Balsas area). Carbonate particles and terrigenous grains were sourced from shallow‐water settings and displaced downslope by sediment density flows that preferentially followed the canyon‐shaped depressions. Roughly laminated rudstone to packstone formed by grain flows on the initially very steep slope, whereas the rest of the carbonate lithofacies were deposited by high‐density turbidite currents. The steep escarpment and related break‐in‐slope at the toe favoured hydraulic jumps and the subsequent deposition of coarse‐grained, low‐transport efficiency skeletal‐dominated sediment in the apron lobes. Accelerated uplift of the basement caused a relative sea‐level fall resulting in the formation of outer‐ramp carbonates on the apron lobes, which were in turn overlain by lower Messinian coral reefs. The Almería example is the first known ‘base of slope’ apron within temperate‐water carbonate systems. 相似文献
16.
WANG Mili LIU Chenglin JIAO Pengcheng YANG Zhichen Institute of Mineral Resources Chinese Academy of Geological Sciences Baiwanzhuang Ro Beijing Department of Environment Physical Geography School of Environment Peking University Beijing 《《地质学报》英文版》2005,79(1):53-65
Located in the eastern part of the Tarim basin, Xinjiang, the Lop Nur was an ultimate water catchment area of the Tarim basin during the Quaternary. Through nearly ten years of investigation and research, the authors have found a superlarge brine potash deposit in the Luobei subbasitv—a secondary basin of the Lop Nur depression. The deposit has been mined now. On that basis, the authors propose new theories on the genesis of the potash rock deposit. In the tectonic and geomorphologic contexts, the Tarim basin lies in a “high mountain-deep basin” environment. At the beginning of the Quaternary, influenced by the neotectonic movement, the Lop Nur evolved into a “deep basin” in the Tarim basin. At the end of the middle Pleistocene, neotectonic migration began to take place in the interior of the Lop Nur and a new secondary deep basin—the Luobei subbasin—formed gradually. Despite its small area, it is actually the deepest subbasin in the Lop Nur depression, where brines of the Lop Nur Salt Lake gather and evaporate, thus providing materials for the formation of a superlarge brine potash rock deposit. With respect to the phenomenon of brine concentration and change with deepening of the lake, the authors propose a model of “high mountain-deep basin” tectonic migration for potash concentration. In the sedimentological context, the honeycomb-shaped voids developed in glauberite rock in the subbasin are good space for potash-rich brine accumulation. Study indicates that the deposition of glauberite requires recharge of calcium-rich water.In the Tarim area the calcium-rich water might come from deep formation water or oilfield water, and the river water recharging the Lop Nur Salt Lake was rich in sulfate radicals and other components; in addition, the climate in the area was very dry and the brine evaporated steadily, thus resulting in deposition of substantial amount of glauberite, potash accumulation in intercrystal brine and final formation of the potash deposit. Generally, potash formation in a salt lake undergoes a three-stage process of “carbonates→sulfates (gypsum and glauberite)→chlorides (halite etc.)”, but in the study area there only occurred a two-stage process of “carbonates→sulfates (gypsum and glauberite)”. The authors call this new geological phenomenon the “two-stage potash formation” model. In conclusion, the superlarge Lop Nur potash deposit is the result of combined “high mountain-deep basin” tectonism and “two-stage potash formation”. 相似文献
17.
Geochemical Evolution of Great Salt Lake, Utah, USA 总被引：1，自引：0，他引：1
Blair F. Jones David L. Naftz Ronald J. Spencer Charles G. Oviatt 《Aquatic Geochemistry》2009,15(1-2):95-121
The Great Salt Lake (GSL) of Utah, USA, is the largest saline lake in North America, and its brines are some of the most concentrated anywhere in the world. The lake occupies a closed basin system whose chemistry reflects solute inputs from the weathering of a diverse suite of rocks in its drainage basin. GSL is the remnant of a much larger lacustrine body, Lake Bonneville, and it has a long history of carbonate deposition. Inflow to the lake is from three major rivers that drain mountain ranges to the east and empty into the southern arm of the lake, from precipitation directly on the lake, and from minor groundwater inflow. Outflow is by evaporation. The greatest solute inputs are from calcium bicarbonate river waters mixed with sodium chloride-type springs and groundwaters. Prior to 1930 the lake concentration inversely tracked lake volume, which reflected climatic variation in the drainage, but since then salt precipitation and re-solution, primarily halite and mirabilite, have periodically modified lake-brine chemistry through density stratification and compositional differentiation. In addition, construction of a railway causeway has restricted circulation, nearly isolating the northern from the southern part of the lake, leading to halite precipitation in the north. These and other conditions have created brine differentiation, mixing, and fractional precipitation of salts as major factors in solute evolution. Pore fluids and diagenetic reactions have been identified as important sources and especially sinks for CaCO3, Mg, and K in the lake, depending on the concentration gradient and clays. 相似文献
18.
唐山大气降尘的矿物组成与微观形貌特征分析 总被引：1，自引：0，他引：1
应用X射线衍射线技术(XRD)和扫描电镜技术(SEM/EDX)对唐山大气降尘中颗粒的矿物组成及微观形貌进行了研究。结果表明,唐山大气降尘的主要矿物组分是方解石、石英和粘土,次为赤铁矿、石膏、白云石及长石类矿物,其它的矿物还有菱铁矿、菱镁矿、石盐、沸石、角闪石、钙芒硝和无水芒硝等;其形貌特征主要有球状、层状、片状、柱状和块状等规则形态及矿物单体和矿物集合体等不规则形态;对XRD的检测结果进行分析后,表明大气降尘颗粒物的主要来源为地面扬尘、建筑扬尘、工业尘及在大气环境中新生成的矿物。 相似文献
19.
内蒙伊克昭盟是我国现代碱湖分布最集中的地区,各碱湖矿层的主要盐类矿物是泡碱,其次是芒硝,天然碱和石盐及少量单斜钠钙石,氯碳钠镁石,钙水碱和水碱。泡碱普遍存在于各个碱湖的矿层中,芒硝主要存在于西部碱湖的矿层中,天然碱集中分嘏于碱湖区西南部的几个碱湖中,且只分布于矿层的某些部位,碱湖矿层剖面上,天然碱与芒硝呈互为消长关系,天然碱和石盐则呈正相关。 相似文献
20.
The mid‐Permian Nippewalla Group of Kansas consists of bedded evaporites, red‐bed siliciclastics and grey siliciclastics deposited in a non‐marine environment. Lithologies and sedimentary features indicate lacustrine and aeolian deposition, subaerial exposure and palaeosol formation. Grey siliciclastic mudstones characterized by planar and convolute laminations, ostracods, peloids and plant material represent a freshwater‐brackish perennial lake facies. Bedded anhydrites containing gypsum‐crystal pseudomorphs, clastic anhydrite grains and grey mud drapes and partings suggest deposition in saline lakes. Bedded halites consist of chevron and cumulate crystals, dissolution surfaces and pipes and mudcracked microcrystalline salt crusts, which were deposited in saline pans dominated by flooding, evaporative concentration and desiccation. Chaotic halite, composed of red‐bed mudstone and siltstone with displacive halite crystals, formed in saline mudflats. Red‐bed mudstone and siltstone with little or no displacive halite, but with abundant cracking, root and plant features, suggest deposition in a dry mudflat. Red‐bed sandstone, composed of well‐sorted, well‐rounded quartz grains cemented with halite, indicate aeolian and rare shallow‐water deposition. Most deposition took place in halite‐dominated ephemeral saline lakes surrounded by saline and dry mudflats, sandflats and sand dunes. Evaporation, desiccation, flooding and wind played significant roles in this environment. The Nippewalla Group siliciclastics and evaporites represent an evolution from a perennial lacustrine system to a non‐marine, acidic saline pan system in the mid‐continent of North America. The problem of distinguishing between ancient marine and non‐marine evaporites, as well as recognizing those evaporites deposited in acid settings, with detailed field, core and petrographical study of both evaporite deposits and associated sedimentary rocks has successfully been addressed. In addition, interpretations of mid‐Permian palaeoclimate data in the form of short‐term air temperature proxies within longer‐term wet–dry trends have been made. These data provide a new palaeogeographic and palaeoclimatic model for the mid‐Permian of western Pangaea. 相似文献