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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

Speleology in Kazakhstan

Shakalov on 11 Jul, 2012
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

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That potential is any of several different scalar quantities, each of which involves energy as a function of position or of condition; e.g., the fluid potential of ground water [22].?

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Your search for mixing corrosion (Keyword) returned 34 results for the whole karstbase:
Showing 1 to 15 of 34
Mixing corrosion in CaCO3/1bCO2/1bH2O systems and its role in the karstification of limestone areas, 1981, Dreybrodt W,
Mixtures of two saturated H2O/1bCO2/1bCaCO3 solutions of different chemical composition gain renewed capability of dissolving calcite. This is an important mechanism in the solution processes of limestone during karstification. Using recent data on the kinetics of calcite dissolution, dissolution rates in mixture corrosion are calculated. In the region of the chemical composition of natural karst waters the solution rate is approximated by:R=-[alpha]([Ca2] - [Ca2]s where [Ca2], [Ca2]s are the concentrations of the Ca2 ion in the solution and at saturation, respectively. [alpha] ranges from 10-4 to 3[middle dot]10-4 cm s-1.This result is applied to the solution of limestone in karst water mixtures flowing in cylindrical conduits. The saturation length, i.e. the length xs which the solution has to travel to drop to 37% of its renewed dissolving capability, is calculated in the region of turbulent flow. This region starts at conduit radii R of several millimeters. At the onset of turbulent flow the saturation length is 260 m, increasing with R1.665. The increase of conduit radii is calculated from the dissolution rates of calcite solution to be on the order of 10-3 cm yr.-1.The results are discussed for a comprehensive model of karstification and cave development, which for the first time gives a realistic theoretical time region for cave development, in agreement to experience

La plate-forme du Yucatn (Mexique), 1995, Heraudpia, M. A.
The Platform of the Yucatan peninsula, south of Mexico, is constituted by a tertiary carbonated series (Eocene to Pliocene). The karst landforms are a "Kuppenkarst" whose positive reliefs are more conspicuous in the centre because of greater altitude (0 to 400 m). Most caves are developed under the base level. The cenote corres-ponds to drowned pits which can be 100 m deep or more. The flooded caves, like Nohoch Nah Chich (40km long), are the longest in the world. The history of karstification began during the Tertiary, between the end of Eocene to Pliocene in relation with uplift. The crypto-dissolution occurs under an alte-ritic cover which comes from a former silicated detritic cover (south peninsula crystalline massif). Speleogenesis depends on the halocline i.e. mixing corrosion zone (salt water/fresh water) and the fluctuations of the sea level.

Quelques mcanismes chimiques du creusement des cavernes (plus _particulirement pour ltude de la zone noye), 1999, Lismonde, Baudouin
The classical influences of physical parameters and mixing corrosion are presented to study the equilibrium of the water-air-limestone chemical system. The frequent observation of cave levels in the mountain karstic systems is often associated with the greater facility of dissolution, near the water table. Some chemical mechanisms are analysed to show the greater karst corrosion on this level. Increased air pressure induces an increase in the saturation pCO2 of the water. Two confinement coefficients are used to analyse the role of a limited quantity of air in contact with water. The first (k) is the water mass/water + air mass ratio, the second (kn) is the mass of CO2 in water/ mass of CO2 in water and air ratio. These two ratios show that the latter coefficient varies with air pressure, but is proportional to the varying pCO2.

The role of mixing corrosion in calcite-aggressive ?2?-??2-????? solutions in the early evolution of karst aquifers., 2000, Gabrovsek F. , Dreybrodt W.

The role of mixing corrosion in calcite aggressive H2O-CO2-CaCO3 solutions in the early evolution of karst aquifers., 2000, Gabrovsek F. , Dreybrodt W.

Role of mixing corrosion in calcite-aggressive H2O-CO2-CaCO3 solutions in the early evolution of karst aquifers in limestone, 2000, Gabrovsek F, Dreybrodt W,
Two cave-forming mechanisms in limestone are discussed currently. First, when two H2O-CO2-CaCO3 solutions, saturated with respect to calcite but with different chemical compositions mix, renewed aggressiveness to limestone dissolution occurs. This process called mixing corrosion [Bogli, 1964, 1980], in combination with linear dissolution kinetics, has been suggested as cave forming. Second, it has been shown that solely the action of nonlinear dissolution kinetics can generate extended karst conduits. This paper combines both mechanisms. By digital modeling of the evolution of the aperture widths of a confluence of two fractures into a third one it is shown that the first mechanism does not create large cave conduits. The combination of mixing corrosion and nonlinear kinetics, however, considerably intensifies karstification, compared to that of nonlinear kinetics solely. The times to terminate early evolution of karst are significantly reduced when the CO2 concentrations of the inflowing solutions differ by no more than 30%. We discuss the underlying mechanisms by inspection of the time dependence of the evolution of aperture widths, flow rates through them, and of the renewed undersaturation of the mixed solution at the confluence of two fractures. Finally, the evolution of a karst aquifer on a two-dimensional percolation network is modeled when mixing corrosion is present, and compared to that on an identical net with identical nonlinear dissolution kinetics, but mixing corrosion excluded. Large differences in the morphology of the net of cave conduits are found and also a reduction of the time of their evolution. From these findings we conclude that climatic changes, which influence the p(CO2) in the soil, can divert the evolving cave patterns

Dissolution tubules: A new karst structure from the English chalk, 2000, Lamontblack J. , Mortimore R. ,
The Chalk of England is not renowned for producing karst landforms. This paper introduces a previously undescribed karst phenomenon, termed here dissolution tubules, from the Chalk of Sussex. The internal structure of these features was investigated by developing a novel method of resin impregnation and acid digestion. This revealed tubules to be a truly dendritic landform. Their relationships with chalk macrotextures were investigated using the Bushinski oil technique (BROMLEY 1981) and revealed an association with trace fossil burrows. Detailed electron microscopic examination of chalk adjacent to the karst surface, employing the textural analysis methods of MORTIMORE & FIELDING (1990), revealed dissolutional textural modification of the chalk to a depth of approximately 15 mm beneath the dissolution surface and a possible spatial association of dissolution tubules with microfractures. Dissolution tubules in the field were found overlying major discontinuities such as subhorizontal sheet flints, marl seams, hardgrounds, major fractures and caves. Evidence gathered suggests mixing corrosion (BOGLI 1964) as the process responsible for their formation

Speleogenesis of the Botovskaya Cave, Eastern Siberia, Russia, 2000, Filippov A. G.
Botovskaya Cave is located in the Angaro-Lensky artesian basin in the southern Siberian craton, Russia. It developed under confined conditions in the 6-12 m thick Ordovician limestone strata. The cave is a subhorizontal, two-dimensional maze 32 km long. The limestone beds are confined above and below by massive marine sandstones which contain thick silty and argilaceous layers. Cave passages are guided by an orthogonal fissure system. Embryonic passages are tube-shaped with oval and round cross sections. The mature passages are corridor-like with wide low notches at their bases between sandstone beds. The cave system probably originated due to mixing corrosion involving meteoric artesian waters flowing from a major recharge area, and ascending waters migrating toward surface valleys from underlying artesian aquifers.

Dynamics of Cave development by Allogenic water, 2001, Palmer, Arthur N.

Streams that drain from non karstic surfaces tend to have great discharge fluctuations and low concentrations of dissolved solids. Where these streams encounter karstic rocks they can form caves with hydraulic and chemical dynamics quite different from those fed by autogenic recharge (e.g. through dolines). Caves in carbonate rocks that are fed by allogenic streams have a relatively short inception period, after which the mean annual rate of dissolutional wall retreat is typically about 0.01 cm/yr. Most of the annual growth takes place during a few major floods that occupy only a small fraction of the year. Local growth rates can be enhanced by abrasion from sediment. During floods, highly aggressive water is delivered rapidly to points deep within the karst aquifer. As flood discharge increases, cave streams become ponded by constrictions caused by detrital sediment, insoluble beds, or collapse material. Because the discharge during a flood rises by several orders of magnitude, the head loss across constrictions can increase enormously, causing water to fill parts of the cave under considerable pressure. This highly aggressive water is injected into all available openings in the surrounding bedrock, enlarging them at a rapid and nearly uniform rate. Depending on the structural nature of the bedrock, a dense array of blind fissures, pockets, anastomoses, or spongework is formed. Many such caves develop traversable mazes that serve either as bypass routes around constrictions, or as "karst annexes", which store and later release floodwaters. Many features that are sometimes attributed to slow phreatic flow or mixing corrosion are actually generated by ponded floodwaters. In caves that experience severe flooding, adjacent fissures or bypass routes with initial widths at least 0.01 cm can grow to traversable size within 10,000 years.


Palaeo-mixing zone karst features from Palaeocene carbonates of north Spain: criteria for recognizing a potentially widespread but rarely documented diagenetic system, 2001, Bacetaa J. I. , Wrightb V. P. , Pujalte V.

Marine-meteoric mixing zone dissolution effects are a major feature of present day karst systems in carbonate platforms,yet are rarely reported in the geological record. An example is described from the upper Danian platform limestones of the Alava province,in  the western Pyrenees,north Spain. This consists of several narrow zones with sponge-like porosity analogous to the "Swiss-cheese" features found in present day mixing  zones. These zones are stained by Fe-oxides and overlie limestones which are irregularly  dolomitized  and contain disseminated pyrite. These high-porosity  zones are interpreted as having developed in marine mixing zones where mixing corrosion and microbially  mediated processes increased dissolution. If collapsed,ancient mixing zones could be misinterpreted as "terra-rossa" palaeosols. The main criteria to identify them as mixing zone products are their occurrence below a palaeo-meteoric phreatic zone,their association with stratified oxic and anoxic redox zones and petrographic evidence for highly variable calcite saturation states.


Palaeo-mixing zone karst features from Palaeocene carbonates of north Spain: criteria for recognizing a potentially widespread but rarely documented diagenetic system , 2001, Baceta J. I. , Wrightb V. P. , Pujaltec V.

Marine-meteoric mixing zone dissolution effects are a major feature of present day karst systems in carbonate platforms,yet are rarely reported in the geological record. An example is described from the upper Danian platform limestones of the Alava province,in the western Pyrenees,north Spain. This consists of several narrow zones with sponge-like porosity analogous to the "Swiss-cheese" features found in present day mixing zones. These zones are stained by Fe-oxides and overlie limestones which are irregularly dolomitized and contain disseminated pyrite. These high-porosity zones are interpreted as having developed in marine mixing zones where mixing corrosion and microbially mediated processes increased dissolution. If collapsed,ancient mixing zones could be misinterpreted as "terra-rossa" palaeosols. The main criteria to identify them as mixing zone products are their occurrence below a palaeo-meteoric phreatic zone,their association with stratified oxic and anoxic redox zones and petrographic evidence for highly variable calcite saturation states


Basic processes and mechanisms governing the evolution of karst, 2003, Dreybrodt W, Gabrovek F.

Models of karstification based on the physics of fluid flow in fractures of soluble rock, and the physical chemistry of dissolution of limestone by CO2 containing water have been presented during the last two decades. This paper gives a review of the basic principles of such models, their most important results, and future perspectives.
The basic element of evolving karst systems is a single isolated fracture, where a constant hydraulic head drives calcite aggressive water from the input to the output. Non linear dissolution kinetics with order n = 4 induce a positive feedback by which dissolutional widening at the exit enhances flow rates thus increasing widening and so on until flow rates increase dramatically in a breakthrough event. After this the hydraulic head breaks down and widening of the fracture proceeds fast but even along its entire length under conditions of constant recharge. The significance of modelling such a single fracture results from the fact that an equation for the breakthrough time specifies the parameters determining the processes of early karstification. In a next step the boundary conditions for isolated fractures are varied by including different lithologies of the rock, expressed by different dissolution kinetics. This can enhance or retard karstification. Subterranean sources of CO2 can also be simulated by changing the equilibrium concentration of the solution at the point where CO2 is injected. This leads to accelerated karstification. At the confluence of solutions from two isolated tubes into a third one, mixing corrosion can release free carbon dioxide. Its effect to solutional widening in such a system of three conduits is discussed.
Although these simple models give interesting insights into karst processes more realistic models are required. Combining single fractures into two-dimensional networks models of karst in its dimensions of length and breadth under constant head conditions are presented. In first steps the Ford-Ewers' high-dip and low-dip models are simulated. Their results agree to what one expects from field observations. Including varying lithologies produces a variety of new features. Finally we show that mixing corrosion has a strong impact on cave evolution. By this effect micro climatic conditions in the catchment area of the cave exert significant influence. A common feature in the evolution of such two-dimensional models is the competition of various possible pathways to achieve breakthrough first. Varying conditions in lithologies, carbon dioxide injection or changing hydrological boundary conditions change the chances for the competing conduits.
Karst systems developing at steep cliffs in the dimensions of length and depth are characterized by unconfined aquifers with constant recharge to the water table. Modelling of such systems shows that dissolution of limestone occurs close to the water table. The widening of the fractures there causes lowering of the water table until it becomes stable when base level is reached, and a water table cave grows headwards into the aquifer. When prominent deep fractures with large aperture widths are present deep phreatic loops originate below the water table. A river or a lake on a karst plateau imposes constant head conditions at this location in addition to the constant recharge from meteoric precipitation. In this case a breakthrough cave system evolves along the water table kept stable by the constant head input. But simultaneously deep phreatic loops arise below it.
In conclusion we find that all cave theories such as those of Swinnerton (1932), Rhoades and Sinacori (1941), and the Four-state-model of Ford are reconciled. They are not contradictory but they result from the same physics and chemistry under different boundary conditions


The impact of hydrochemical boundary conditions on the evolution of limestone karst aquifers, 2003, Romanov D. , Gabrovsek F. , Dreybrodt W. ,
The early evolution of karst aquifers depends on a manifold of initial and boundary conditions such as geological setting, hydrologic properties of the initial aquifer, and petrologic properties of the rock. When all water entering at various inputs into the aquifer has equal chemical composition with respect to the system H2O-CO2-CaCO3 early evolution under conditions of constant head exhibits breakthrough (BT) behaviour. If the chemical compositions of the input waters are different, deep in the aquifer where the saturated solutions mix renewed aggressiveness occurs, and additional dissolutional widening of fractures by mixing corrosion (MC) changes the hydrologic properties of the aquifer. To study the impact of MC on the evolution of karst we have modelled a simple karst aquifer consisting of a confined limestone bed, with two symmetrically located inputs at constant head and open flow conditions along the entire width at base level. To calculate dissolutional widening of the fractures the well-known dissolution kinetics of limestone was used, which is linear up to 90% of saturation with respect to calcite and then switches to a nonlinear fourth order rate law. First, two extremes are modelled: (a) Both inputs receive aggressive water of equal chemical composition with [Ca2] = 0.75[Ca2](eq). In this case two channels migrate downstream with that from one input more competitive and reaching base level first, causing BT. (b) Water at both inputs is saturated with respect to calcite, but in equilibrium with different partial pressures Of CO2. Therefore, dissolution widening can occur only where these waters mix. A central channel starts to grow extending down-head until base level is reached. Flow rates through the aquifer first rise and become constant after the channel has reached base level. In the following runs these two extreme modes of karstification are combined. The waters entering have different chemical compositions and therefore different equilibrium concentrations [Ca2](eq). This allows MC to be active. They are also undersaturated with the inflowing solutions at concentration [Ca2](in) = f[Ca2](eq) where f is the ratio of saturation. In comparison to the extreme limit (a) the action of MC now creates permeability where the solutions mix and diverts the evolution of conduits into this region. Finally one conduit reaches base level and causes BT. This behaviour is found for f = 0.7, 0.9, and 0.96. For solutions more close to equilibrium with respect to calcite (f = 0.99, 0.9925, and 0.995) BT behaviour is replaced by a steady increase in flow rates. In the early state as in the case of MC controlled evolution (case b) a central channel not connected to the input is created by MC and reaches base level. After this event, further increase in flow rates is caused by slow dissolutional widening by the slightly undersaturated input solutions flowing towards the central channel. Comparison of the various model aquifers at termination of the computer runs reveals significant differences in their properties caused solely by changes of the hydrochemical boundary conditions. (C) 2003 Elsevier Science B.V. All rights reserved

Numerical models for mixing corrosion in natural and artificial karst environments, 2003, Kaufmann G. ,
[1] The enlargement of initially small fractures in a karst aquifer by chemical dissolution is studied. Flow in the aquifer is driven by head differences between sinks and resurgences, and flow depends on the permeability of small fissures and fractures in the aquifer. Enlargement of fractures is controlled by the chemical composition of the recharge, as water undersaturated with respect to calcite is able to dissolve material from the fracture walls. As fractures are enlarged with time, permeability within the aquifer increases significantly, and flow becomes very heterogeneous. Two different processes are considered: enlargement due to normal corrosion, where water is undersaturated with respect to calcite, and enlargement due to mixing corrosion, where two solutions saturated with respect to calcite but with different carbon dioxide concentrations mix and the resulting solution becomes undersaturated again. The importance of mixing corrosion is discussed for two boundary conditions: A natural karst aquifer is modeled with fixed recharge boundary conditions representing sinking streams, and an artificial karst aquifer is simulated with fixed head boundary conditions representing a reservoir. In both cases, mixing corrosion is important, especially if recharge is characterized by an almost saturated chemistry. Mixing corrosion significantly changes the evolving passage pattern, as dissolution due to mixing of solutions is possible deep in the aquifer. Mixing corrosion also reduces breakthrough times of the aquifer and can result in dramatic leakage underneath dam sites, even if the impounded water is almost saturated with respect to calcite

Evolution of Karst Aquifers in Natural and Man Made Environments: A Modeling Approach. Ph.D. thesis, 2003, Romanov, Douchko

The evolution of karst aquifers under various hydrological and chemical boundary conditions is studied.
In the first part the influence of exchange flow from a prominent fracture into a two-dimensional network of fissures is compared to the evolution of a fracture isolated from this net. The modeling domain is 742.5 m long and 375 m wide dissected by fractures into 100 by 51 blocks. The wide prominent fracture extends along its center, thus constituting a part of the network. Under constant head conditions between the left and the right hand side of the domain it looses flow into the network. We have studied the influence of the fracture widths of the fine net to the breakthrough time (BT) of the system. Because of loss of flow from the central fracture to the net, aggressive solution from the input enhances dissolution and breakthrough times are reduced. This effect is most effective, when the aperture width of the fine net is only smaller by about 1% than the widths of the prominent fracture, such that a large amount of water can flow into the net. To obtain further information on the processes involved, an isolated one-dimensional fracture with an additional single point of outflow from it, is investigated.
As an application of the results above, the evolution of a karst aquifer below dam sites is studied. The modeling domain is a 2D, 1 m wide vertical section of soluble rock (gypsum and limestone), perpendicular to the dam. The block extends 750 m horizontally and 375 m vertically. It is divided by fractures and fissures into blocks of 7.5 m x 7.5 m x 1m. The chemical composition of the inflowing water is equal at all input points. Because of dissolution along the fractures, a large zone of increasing permeability is created below the structure, causing high unbearable water losses from the dam site and also endangering the mechanical stability of the dam. The dependence of BT on the basic parameters - the height of the impounded water, the depth of the grouting curtain, the initial aperture widths of the fractures and the fissures, and the chemical parameters of the inflowing water (equilibrium concentration with respect to calcite and input concentration) is investigated. For fracture aperture widths larger than 0.02 cm breakthrough occurs within the lifetime of the structure.
In the second part the effect of chemical boundary conditions on the evolution of a karst aquifer is studied. The model domain is 500 m x 225 m, divided into blocks of 5 m x 5 m x 1 m by fracture network. There are two input points at constant head (25 m) at the inflow side of the block. The outflow side is open at constant head – 0 m. The hydrological boundaries are equal for all simulated scenarios. The chemical composition of the inflowing water at both inputs is varied, and the reaction of the aquifer is studied. Mixing corrosion is the reason for zones of increased permeability deep inside the aquifer along the boundary, where the solutions mix. The influence of mixing corrosion for various values of the input Ca concentration is studied. The results show two types of evolution. Breakthrough (BT) governed evolution – for values of cin<0.96?ceq, and mixing corrosion (MC) - governed evolution for values of cin>0.96?ceq. The BT - type is characterized by enlarged pathways connecting an inflow point with the outflow boundary. For increasing values of the input concentrations the effect of MC becomes stronger. For high Ca concentrations, MC is dominating. There is no considerably widened connection between the inflow points and the out flow boundary. but an enlarged channel along the mixing zone is observed. The timescale for this type of evolution is considerably longer. For solutions saturated with respect to calcite, the mixing zone is the only area of widening inside the aquifer.


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