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1.
F. Gutiérrez J. M. Calaforra F. Cardona F. Ortí J. J. Durán P. Garay 《Environmental Geology》2008,53(5):951-965
In Spain, evaporite outcrops cover approximately 7% of the total area of the country. Most of the evaporitic formations are made up of Ca-sulfates (gypsum/anhydrite) or Ca-sulfates and halite. Certain Paleogene marine evaporites also contain K-Mg-chlorides, and some Tertiary continental formations bear substantial amounts of Na-sulfates in the subsurface (glauberite and thenardite). Mesozoic evaporitic formations commonly wedge out towards the ground surface, passing into condensed sequences and dissolution-collapse breccias. Some of these highly porous breccias constitute major regional aquifers. In several areas, interstratal karstification of the evaporites has given rise to gravitational deformations such as basin structures, monoclines, and collapse structures covering several square kilometers that record a cumulative subsidence in excess of 200 m (Teruel and Calatayud Grabens). A widespread consequence of evaporite dissolution processes in Spain is the hydrochemical degradation of surface waters. Some of the largest and most outstanding lake systems, from an environmental perspective, occur in karstic depressions developed in evaporitic formations (Fuente de Piedra, Gallocanta, Bujaraloz, and Bañolas lakes). Sinkhole activity is a major geohazard in several evaporite karst areas. The sinkhole risk has a particularly high impact in sectors where Tertiary evaporites are overlain by Quaternary alluvial aquifers (Calatayud, Zaragoza, and Madrid areas). Some of the detrimental effects of subsidence include severe damage to historical monuments (Calatayud), the demolition of a whole village (Puilatos), or the derailment of a freight train (Zaragoza area). The deepest gypsum caves are found in Triassic diapiric structures (El Sumidor Cave, 210 m deep), and the longest ones are developed in horizontally lying Neogene sequences (Sorbas caves, and Estremera maze cave). The Cardona diapir hosts salt caves up to 4,300 m long whose genesis is related to flooding of mine galleries caused by the interception of a phreatic conduit. The main anthropogenic impacts on the endokarstic systems are related to the disposal of wastewaters and the destruction of caves by quarrying. The fluvial valleys that cross Tertiary evaporitic outcrops commonly show peculiar geological characteristics related to dissolution-induced synsedimentary subsidence phenomena: (1) Thickened alluvium filling dissolution basins up to several tens of kilometers long and more than 100 m deep. The largest thickenings are found in areas where the bedrock contains halite and glauberite. (2) Superimposed alluvial units locally bounded by angular unconformities. (3) Abundant deformational structures and paleosinkholes related to the rockhead and/or interstratal karstification of the substratum. These fluvial valleys typically are flanked by a prominent gypsum escarpment. Rock-falls favored by the dissolutional enlargement of joints derived from these scarps are the type of mass movement which has caused the highest number of casualties in Spain. 相似文献
2.
Evaporative process plays a dominant role in determining the water chemistry of the springs at Teels Marsh, a closed basin in western Nevada. Analysis of the spring waters indicates that calcium, magnesium, sulfate, and silica are removed from solution during dry periods, even though groundwater is undersaturated with respect to gypsum, amorphous silica, and sepiolite. The removal mechanism is precipitation of authigenic phases such as gypsum above the water table, in the vadose zone.In episodes of rain and snowfall in which none of the waters enters the phreatic zone, ions in the rain and snow accumulate near the ground surface. This accumulation of material, together with the sparse rain and snowfall, inhibits chemical weathering of silicate minerals. Only at high elevations in the basin is there sufficient fluxing of water through the alluvium for silicate weathering to make a significant contribution to the sodium content of the springs. When a sufficiently heavy rainfall occurs, salts are partially dissolved and the ions transported to the permanent groundwater. The kinetics of dissolution of secondary phases in the vadose zone exert an important control on the composition of the springs. 相似文献
3.
Speleogenetic history of the Hungarian hydrothermal karst 总被引：2，自引：0，他引：2
Y. V. Dublyansky 《Environmental Geology》1995,25(1):24-35
The hydrothermal karst of Hungary displays at least two principal stages of development in two differing environments. Caves of an early stage were formed within a deep zone of low thermal gradient. These caves (vugs) are small (tens of centimeters) and lined with scalenohedral crystals of calcite that are often in association with barite. Calcite yields fluid inclusion temperatures of 55–95°C and is depleted in18O (–11.2 to –17.6 per mil PDB). The caves were formed by ascending thermal waters charged with CO2. Solubility of CaCO3 in such a system gradually increases with the ascent of the fluid (solutional zone) but drops sharply at a depth of –250 m to –500 m below the water surface (depositional zone). Caves formed in the solutional zone may be shifted into the depositional zone due to tectonic uplift, and calcite lines their walls. Large caves (tens to thousands of cubic meters) of a late stage were formed within a shallow zone of high thermal gradient immediately below and above the thermal water table. The calcite of the phreatic crusts has a rhombohedral habit, displays lower fluid inclusion temperatures (35–55°C and less), and a depletion in18O of –9.5 to –14.6 per mil PDB. Several powerful cave-forming processes may operate there including convection, mixing/cooling corrosion, and condensation corrosion. Due to differences in the rate of tectonic uplift, rate of hydrothermal system decay, and hydrogeologic pattern, these caves were either filled with water for a long period of time (phreatic calcite crusts are formed) or partly dewatered early in their history (waterline and subaerial speleothems are formed). The zones of thermal cave formation recognized in Hungary may have a universal character. Very similar features are found in other hydrothermal karst areas of the world (Kirghizia, Algeria, South Dakota). 相似文献
4.
5.
This article highlights the relationship between speleothems growing inside gypsum caves and the particular climate that existed
during their development. Speleothems in gypsum caves normally consist of calcium carbonate (calcite) or calcium sulphate
(gypsum) and the abundance of such deposits greatly differs from zone to zone. Observations carried out over the last 20 years
in gypsum caves subjected to very different climates (Italy, Spain, New Mexico, northern Russia, Cuba, Argentina) highlight
wide variation in their cave deposits. In arid or semi-arid climates, the speleothems are mainly composed of gypsum, whilst
in temperate, humid or tropical regions, carbonate formations are largely predominant. In polar zones no speleothems develop.
These mineralogical details could be useful paleoclimatic indicators of climate change. The interpretation proposed is based
on the fact that in gypsum karst the kind of speleothems deposited is determined by competition between the two principal
mechanisms that cause precipitation of calcite and gypsum. These mechanisms are completely different: calcite speleothem evolution
is mainly controlled by CO2 diffusion, while gypsum deposits develop mostly due to evaporation. Therefore, the prevalence of one kind of speleothem over
the other, and the relationship between the solution–precipitation processes of calcite and gypsum, may provide evidence of
a specific paleoclimate. Additionally, other non-common deposits in gypsum caves like moonmilk, cave rafts and dolomite speleothems
can be used as markers for the prevalence of long, dry periods in humid areas, seasonal changes in climate, or rainfall trends
in some gypsum areas. Moreover, the dating of gypsum speleothems could contribute paleoclimatic data relating to dry periods
when calcite speleothems are not deposited. In contrast, the dating of calcite speleothems in gypsum caves could identify
former wet periods in arid zones. 相似文献
6.
A better understanding of heat fluxes and temperature distribution in continental rocks is of great importance for many engineering aspects (tunnelling, mining, geothermal research, etc.). This paper aims at providing a conceptual model of temperature distribution in karst environments which display thermal ‘anomalies’ as compared with other rocks. In temperate regions, water circulation is usually high enough to ‘drain‐out’ completely the geothermal heat flux at the bottom of karst systems (phreatic zone). A theoretical approach based on temperature measurements carried out in deep caves and boreholes demonstrates, however, that air circulation can largely dominate water infiltration in the karst vadose zone, which can be as thick as 2000 m. Consequently, temperature gradients within this zone are similar to the lapse rate of humid air (～0.5 °C 100 m?1). Yet, this value depends on the regional climatic context and might present some significant variations. 相似文献
7.
An approach combining the use of water dissolved chemical species and isotopic fingerprints has been used to understand the behavior of a phreatic aquifer and to determine the origin of its different water components. This aquifer is located in the large sedimentary basin of the Great Oriental Erg (Algeria) and overlies two deeper aquifers: the Complexe Terminal (CT) and the Continental Intercalaire (CI). Besides the deterioration of its groundwater quality, its water table has risen during the last 20 years. A water budget surplus between 950 and 2500 l s?1 was estimated. Down-gradient groundwater evolution (south-north) has shown that the mineralisation increases from 1.23 to 5.20 g l?1 due to evaporite minerals dissolution. Chemical and isotopic data demonstrated that in addition to rainfall there is a contribution from the CT and CI aquifers. The latter are tritium-free and less mineralized than the phreatic aquifer. Their radiocarbon contents are very low (<10 pmC, percent modern Carbon) (Pleistocene recharge) whereas quite the contrary is observed for the superficial aquifer which exhibits fairly high and variable C-14 activities (50–100 pmC), evidence of recent recharge. On the basis of tritium contents, two groundwater groups were identified for the phreatic aquifer. 相似文献
8.
Analysis of evaporation of high-salinity phreatic water at a burial depth of 0 m in an arid area 
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下载免费PDF全文 High-salinity phreatic water refers to which with total dissolved solids(TDS)30 g/L. Previous studies have shown that high salinity phreatic water evaporation is different at different depths. High salinity phreatic water evaporation under 0 m depth is the basis of the high salinity phreatic water evaporation studies. In this study, evaporation of high-salinity phreatic water at a burial depth of 0 m in arid area was investigated. New insights were gained on evaporation mechanisms via experiments conducted on high-salinity phreatic water with TDS of 100 g/L at 0 m at the study site at Changji Groundwater Balance Experiment Site, Xinjiang Uygur Autonomous Region in China, where the lithology of the vadose(unsaturated zone) was silty clay. Comparison was made on the data of high-salinity phreatic water evaporation, water surface evaporation(E_(Φ20)) and meteorological data obtained in two complete hydrological years from April 1, 2012 to March 31, 2014. The experiments demonstrated that when the lithology of the vadose zone is silty clay, the burial depth is 0 m and the TDS is 100 g/L, intra-annual variation of phreatic water evaporation is the opposite to the variation of atmospheric evaporation E_(Φ20) and air temperature. The salt crust formed by the evaporation of high-salinity phreatic water has a strong inhibitory effect on phreatic water evaporation. Large volumes of precipitation can reduce such an inhibitory effect. During freezing periods, surface snow cover can promote the evaporation of high-salinity phreatic water at 0 m; the thicker the snow cover, the more apparent this effect is. 相似文献
9.
云南石林洞穴发育特征 总被引：2，自引：0，他引：2
石林位于滇东喀斯特高原南部,喀斯特极其发育,以发育了典型的石林地形而闻名遐迩,倍受国内外喀斯特学者的关注。洞穴是本区广泛发育分布的一种喀斯特地下形态,类型多样。依据它们的剖面形态、成因和所处的地貌部位差异,将其划分为罅状洞穴、水平洞穴和倾斜洞穴三个类型。洞穴在发育分布上受到区域碳酸盐岩地层分布的控制,表现出洞穴分布的相对集中性、洞穴发育对地层的选择性和洞穴发育的成层性等特征。洞穴发育规模绝大多数为中小型洞穴;洞穴多为现代地下洞河,埋藏浅且多天窗,并且洞穴的发育延伸方向明显受裂隙构造的控制。通过对石林地区喀斯特洞穴发育条件、洞穴发育类型、分布特征和洞穴发育的古地理环境特征分析,论述了石林地区洞穴的发育特征。 相似文献
10.
《Geodinamica Acta》1999,12(3-4):201-211
Three large (kilometric-scale) caves were studied in the Buda hills and the main directions of cave corridors, fault planes and mineralized veins were measured. Different stages of mineralizations are recognised: calcite scaleno-hedrons, baryte, silica, gypsum. New investigations of fluid inclusions in the baryte suggest a crystallization temperature of 50 °C and a freshwater fluid source. Microtectonic analysis allows the reconstruction of the successive tectonic events: (1) a NE-SW extensional phase at the Late Eocene-Early Oligocene limit (phase I), (2) a strike-slip phase with NW-SE compression and NE-SW extension during the Late Oligocene-Early Miocene (phase II), (3) a NW-SE transtensional phase (phase III) and finally (4) a NE-SW extensional phase of Quaternary age (phase IV). The major phase is the strike-slip one, characterized by an important dextral strikeslip zone: the Ferenc-hegy zone. 相似文献
11.
LYNTON S. LAND 《Sedimentology》1973,20(3):411-424
Wholesale removal of the unstable carbonate phases aragonite and Mg-calcite, and precipitation of calcite and dolomite is currently taking place where phreatic waters (the modern water table) invade 120,000-year-old Pleistocene biolithites (Falmouth Formation), North Jamaica. Pleistocene rocks presently in the vadose zone are relatively unaltered, and consist of mineralogically unstable scleractinian biolithites. At the water table, a narrow zone of solution, a ‘water table cave’ is commonly encountered. Below the water table the rocks are invariably more highly altered than those above. Mg-calcites are very rare, and considerable dissolution of aragonite has commonly occurred. Dolomite occurs as 8–25 μm, subhedral to euhedral crystals replacing micrite, or precipitated as void linings. The isotopic composition of the dolomite (δO18=-1·0 %0, δC13=-8·4 %0), and its high strontium content (3000 p.p.m.) suggest precipitation as CO2-oversaturated meteoric groundwaters invade the mineralogically unstable biolithites, dissolve Mg-calcites and Sr-rich aragonites, and de-gas. Because some dolomitized rocks are enriched in magnesium relative to unaltered biolithites, addition of magnesium to the system is necessitated, and is probably derived from sea water in the mixing zone. Phreatic meteoric diagenesis is thus demonstrated to be a rapid process, and to be capable of dolomitization. 相似文献
12.
都匀凯口溶洞群的发育特征及旅游开发 总被引：3，自引：0，他引：3
都匀市南的凯口溶洞群包括凯口、凯酉、凯阳及石龙四个片区,溶洞发育受区域构造及地下水文网的控制,洞穴的侵蚀和堆积均十分旺盛,次生碳酸盐沉积形态丰富多彩,具有极高的科研价值和旅游开发潜力。 相似文献
13.
Speleothems occurring in some caves of the carbonate Dinarides line all channel surfaces, and have been deposited from meteoric waters under phreatic conditions. Such phreatic speleothemic deposition modifies common experience (l) that meteoric phreatic conditions cause dissolutional widening of cave voids, and (2) that speleothems imply vadose conditions. The phreatic speleothems described here postdate an early polygenetic evolution of the cave voids, and predate the last, vadose stage. They were likely produced during the late/postglacial warming period, when dissolved carbonate was amply supplied, and when there was much water available for saturation of underground voids. Phreatic speleothems may be used as a tool for time correlation of internal deposits, both within one cave and within a karst region. They indicate an important stage in the history of the ground-water regime of an area. In general, phreatic speleothems help in better understanding of the development of subterranean voids and related karst/palaeokarst. 相似文献
14.
Kenneth S. Johnson 《Environmental Geology》2008,53(5):945-950
Gypsum is a highly soluble rock and is dissolved readily to form caves, sinkholes, disappearing streams, and other karst features
that typically are also present in limestones and dolomites. Gypsum karst is widespread in the USA and has caused problems
at several sites where dams were built, or where dam construction was considered. Gypsum karst is present (at least locally)
in most areas where gypsum crops out, or is less than 30–60 m below the land surface. These karst features can compromise
on the ability of a dam to hold water in a reservoir, and can even cause collapse of a dam. Gypsum karst in the abutments
or foundation of a dam can allow water to pass through, around, or under a dam, and solution channels can enlarge quickly,
once water starts flowing through such a karst system. The common procedure for controlling gypsum karst beneath the dam is
a deep cut-off trench, backfilled with impermeable material, or a close-spaced grout curtain that hopefully will fill all
cavities. In Oklahoma, the proposed Upper Mangum Dam was abandoned before construction, because of extensive gypsum karst
in the abutments and impoundment area. Catastrophic failure of the Quail Creek Dike in southwest Utah in 1989 was due to flow
of water through an undetected karstified gypsum unit beneath the earth-fill embankment. The dike was rebuilt, at a cost of
US $12 million, with construction of a cut-off trench 600 m long and 25 m deep. Other dams in the USA with severe gypsum-karst
leakage problems in recent years are Horsetooth and Carter Lake Dams, in Colorado, and Anchor Dam, in Wyoming. 相似文献
15.
M. A. Díaz-Puga A. Vallejos F. Sola L. Daniele L. Molina A. Pulido-Bosch 《International Journal of Environmental Science and Technology》2016,13(11):2579-2596
In order to identify the origin of the main processes that affect the composition of groundwater in a karstic aquifer, a hydrogeochemical and isotopic study was carried out of water from numerous observation wells located in Sierra de Gador, a semiarid region in SE Spain. Several natural and anthropogenic tracers were used to calculate groundwater residence time within this complex aquifer system. Analysis of major ions enabled the principal geochemical processes occurring in the aquifer to be established, and the samples were classified into four distinctive solute groups according to this criterion. Dissolution of carbonate rocks determines the chemical composition of less mineralized water. In another group, the concurrent dissolution of dolomite and precipitation of calcite in gypsum-bearing carbonate aquifer, where the dissolution of relatively soluble gypsum controls the reaction, are the dominant processes. Marine intrusion results in highly mineralized waters and leads to base exchange reactions. The groundwater enrichment of minor and trace elements allowed classification of the samples into two classes that are linked to different flow patterns. One of these classes is influenced by a slow and/or deep regional flow, where the temperature is generally elevated. The influence of sulphate reduces by up to 40 % the barium concentration due to the barite precipitation. Isotope data (T, 14C) confirm the existence of recent local flows, and regional flow system, and ages of ground water may reach 8000 years. The importance of gypsum dissolution in this aquifer is proved by the δ34S content. 相似文献
16.
Groundwater calcretes are a non‐pedogenic form of calcrete occurring in broad fossil drainage systems. In Australia, they only occur north of about latitude 30°S and their formation requires arid conditions with very high potential evaporation as well as the periodic recharge of groundwater systems. They are linear, tabular limestone bodies, averaging about 10 m thick, occurring at or close to the surface and forming gentle mounds. The most extensive are located in the centre of the zone of distribution, where the climatic conditions are optimal, and are of the order of 100 km by 10 km. Some groundwater calcretes are fossil and strongly dissected, others are modern and still in process of formation. A model of carbonate precepitation below the water table, i.e. in the phreatic zone, resulting in continuous calcrete growth, accounts for their morphology, their textures and the apparently inverted stratigraphy suggested by carbon‐14 dating. In areas of maximum growth, small anticlines develop which have structures engendered by both shear and concentric folding due to upward growth pressure. 相似文献
17.
轮南地区是塔里木盆地重点产油气地区之一,对其下奥陶统碳酸盐岩储层性能及分布的研究具有重要的实际意义。通过对研究区岩溶、裂缝发育、沉积和洞穴充填物分析研究,认为具渗透可溶性碳酸盐岩及温暖潮湿、多大气降水是岩溶储层形成的必要条件,构造裂缝的发育为岩溶储层发育创造了有利条件。根据裂缝性质及充填程度,本区裂缝可分为方解石完全充填张裂缝、方解石半充填张裂缝、泥质充填扭压性裂缝、未充填微细裂缝和缝合线5种,其中方解石半充填裂缝和缝合线对储层岩溶发育起重要作用。本区岩溶具明显的垂直分带性,可分为垂直渗流岩溶带、水平潜流岩溶带和过渡带,其中垂直渗流带底部及水平潜流岩溶带上部储集物性最佳。轮南地区发育的两期岩溶与石炭纪两次较大的海侵时间相一致。作者还研究了充填物的沉积特征,探讨了储层的演化模式。 相似文献
18.
The core from two boreholes (13.1 and 19.2 m depth) drilled 500 m apart in the fractured, welded tuff near the summit of the Snowshoe Mountain, Colorado (47°30′N, 106°55′W) had unique petrographic and hydrodynamic properties. Borehole SM-4 had highly variable annual water levels, in contrast to SM-1a, whose water level remained near the land surface. Core samples from both boreholes (n=10 and 11) were examined petrographically in thin sections impregnated with epoxy containing rhodamine to mark the pore system features, and were analyzed for matrix porosity and permeability. Core from the borehole sampling the vadose zone was characterized by open fractures with enhanced porosity around phenocrysts due to chemical weathering. Fractures within the borehole sampling the phreatic zone were mineralized with calcite and had porosity characteristics similar to unweathered and unfractured rock. At the top of the phreatic zone petrography indicates that calcite is dissolving, thereby changing the hydrogeochemical character of the rock (i.e. permeability, porosity, reactive surface area, and mineralogy). Radiocarbon ages and C and O stable isotopes indicate that calcite mineralization occurred about 30 to 40 ka ago and that there was more than one mineralization event. Results of this study also provide some relationships between primary porosity development from 3 types of fracture in a welded tuff. 相似文献
19.
T. Clemens D. Hückinghaus R. Liedl M. Sauter 《International Journal of Earth Sciences》1999,88(1):157-162
The evolution of a karst aquifer is modelled taking into account the karst groundwater flow as well as the dissolution kinetics
of calcite. In particular, infiltration of water from the epikarst is simulated which controls the temporal and spatial distribution
of recharge to the phreatic zone. The results show that the evolution of karst conduits is initiated in the spring. The existence
of preferential flow paths leads to the evolution of highly conductive so-called dendritic cave systems, i.e., single passages
which concentrate the flow and drain the catchment. With time, the amount of undersaturated water flowing directly into the
conduit system is increased leading to an acceleration of the conduits enlargement. Three phases are identified for the evolution
of karst aquifers: (a) an initiation stage; (b) an enlargement stage; and (c) a stagnation phase.
Received: 4 August 1997 / Accepted: 19 January 1998 相似文献
20.