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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. ...

Did you know?

That grain per gallon (gpg) is a common basis for reporting water analyses in the watertreatment industry in the united states and canada. one grain per u.s. gallon equals 17.12 milligrams per liter [6].?

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Karst environment, Culver D.C.
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Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
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Your search for matrix (Keyword) returned 176 results for the whole karstbase:
Showing 1 to 15 of 176
Conduit enlargement in an eogenetic karst aquifer, , Moore Paul J. , Martin Jonathan B. , Screaton Elizabeth J. , Neuhoff Philip S.

Most concepts of conduit development have focused on telogenetic karst aquifers, where low matrix permeability focuses flow and dissolution along joints, fractures, and bedding planes. However, conduits also exist in eogenetic karst aquifers, despite high matrix permeability which accounts for a significant component of flow. This study investigates dissolution within a 6-km long conduit system in the eogenetic Upper Floridan aquifer of north-central Florida that begins with a continuous source of allogenic recharge at the Santa Fe River Sink and discharges from a first-magnitude spring at the Santa Fe River Rise. Three sources of water to the conduit include the allogenic recharge, diffuse recharge through epikarst, and mineralized water upwelling from depth. Results of sampling and inverse modeling using PHREEQC suggest that dissolution within the conduit is episodic, occurring only during 30% of 16 sampling times between March 2003 and April 2007. During low flow conditions, carbonate saturated water flows from the matrix to the conduit, restricting contact between undersaturated allogenic water with the conduit wall. When gradients reverse during high flow conditions, undersaturated allogenic recharge enters the matrix. During these limited periods, estimates of dissolution within the conduit suggest wall retreat averages about 4 × 10−6 m/day, in agreement with upper estimates of maximum wall retreat for telogenetic karst. Because dissolution is episodic, time-averaged dissolution rates in the sink-rise system results in a wall retreat rate of about 7 × 10−7 m/day, which is at the lower end of wall retreat for telogenetic karst. Because of the high permeability matrix, conduits in eogenetic karst thus enlarge not just at the walls of fractures or pre-existing conduits such as those in telogenetic karst, but also may produce a friable halo surrounding the conduits that may be removed by additional mechanical processes. These observations stress the importance of matrix permeability in eogenetic karst and suggest new concepts may be necessary to describe how conduits develop within these porous rocks.


A New Equation Solver for Modeling Turbulent Flow in Coupled Matrix‐Conduit Flow Models, ,

Karst aquifers represent dual flow systems consisting of a highly conductive conduit system embedded in a less permeable rock matrix. Hybrid models iteratively coupling both flow systems generally consume much time, especially because of the nonlinearity of turbulent conduit flow. To reduce calculation times compared to those of existing approaches, a new iterative equation solver for the conduit system is developed based on an approximated Newton–Raphson expression and a Gauß–Seidel or successive over-relaxation scheme with a single iteration step at the innermost level. It is implemented and tested in the research code CAVE but should be easily adaptable to similar models such as the Conduit Flow Process for MODFLOW-2005. It substantially reduces the computational effort as demonstrated by steady-state benchmark scenarios as well as by transient karst genesis simulations. Water balance errors are found to be acceptable in most of the test cases. However, the performance and accuracy may deteriorate under unfavorable conditions such as sudden, strong changes of the flow field at some stages of the karst genesis simulations.

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Ecology of Fonticola notadena de Beauchamp (Turbellaria, Triclade) in the La Balme cave (Isre, France); suvival in a dry period., 1964, Ginet Rene, Puglisi Rodolphe
During many months a year the acquatic Planaria (F. notadena) living in a small pool in the La Balme cave are subjected to a drought with the complete drying out of their biotope; they support in situ this lack of water and, living in a latent way inside the clayey matrix. Thanks to the great hygroscopy of the clay, enough humidity stays around the Planarians to enable them to survive. During this period the Planaria may undergo spontaneous divisions resulting in their asexual multiplication.

Amino acid geochronology: integrity of the carbonate matrix and potential of molluscan fossils, 1980, Miller G. H.

The Coxco Deposit; a Proterozoic mississippi valley-type deposit in the McArthur River District, Northern Territory, Australia, 1983, Walker R. N. , Gulson B. , Smith J. ,
Strata-bound dolomite-hosted lead-zinc deposit. Crusts of colloform sphalerite, galena, pyrite, and marcasite (stage I mineralization) were deposited on the surfaces of the karst-produced solution cavities. Reduced sulfur was produced by sulfate-reducing bacteria within the karst system. A second stage of mineralization consisting of coarsely crystalline sphalerite, galena, pyrite, and marcasite occurs in veins and as the matrix for dolomite breccias.--Modified journal abstract

Modeling of regional groundwater flow in fractured rock aquifers, PhD Thesis, 1990, Kraemer, S. R.

The regional movement of shallow groundwater in the fractured rock aquifer is examined through a conceptual-deterministic modeling approach. The computer program FRACNET represents the fracture zones as straight laminar flow conductors in connection to regional constant head boundaries within an impermeable rock matrix. Regional scale fracture zones are projected onto the horizontal plane, invoking the Dupuit-Forchheimer assumption for flow. The steady state flow solution for the two dimensional case is achieved by requiring nodal flow balances using a Gauss-Seidel iteration. Computer experiments based on statistically generated fracture networks demonstrate the emergence of preferred flow paths due to connectivity of fractures to sources or sinks of water, even in networks of uniformly distributed fractures of constant length and aperture. The implication is that discrete flow, often associated with the local scale, may maintain itself even at a regional scale. The distribution of uniform areal recharge is computed using the Analytic Element Method, and then coupled to the network flow solver to complete the regional water balance. The areal recharge weakens the development of preferential flow pathways. The possible replacement of a discrete fracture network by an equivalent porous medium is also investigated. A Mohr's circle analysis is presented to characterize the tensor relationship between the discharge vector and the piezometric gradient vector, even at scales below the representative elementary volume (REV). A consistent permeability tensor is sought in order to establish the REV scale and justify replacement of the discrete fracture network by an equivalent porous medium. Finally, hydrological factors influencing the chemical dissolution and initiation of conduits in carbonate (karst) terrain are examined. Based on hydrological considerations, and given the appropriate geochemical and hydrogeological conditions, the preferred flow paths are expected to develop with time into caves.


DOLOMITE-ROCK TEXTURES AND SECONDARY POROSITY DEVELOPMENT IN ELLENBURGER GROUP CARBONATES (LOWER ORDOVICIAN), WEST TEXAS AND SOUTHEASTERN NEW-MEXICO, 1991, Amthor Je, Friedman Gm,
Pervasive early- to late-stage dolomitization of Lower Ordovician Ellenburger Group carbonates in the deep Permian Basin of west Texas and southeastern New Mexico is recorded in core samples having present-day burial depths of 1.5-7.0 km. Seven dolomite-rock textures are recognized and classified according to crystal-size distribution and crystal-boundary shape. Unimodal and polymodal planar-s (subhedral) mosaic dolomite is the most widespread type, and it replaced allochems and matrix or occurs as void-filling cement. Planar-e (euhedral) dolomite crystals line pore spaces and/or fractures, or form mosaics of medium to coarse euhedral crystals. This kind of occurrence relates to significant intercrystalline porosity. Non-planar-a (anhedral) dolomite replaced a precursor limestone/dolostone only in zones that are characterized by original high porosity and permeability. Non-planar dolomite cement (saddle dolomite) is the latest generation and is responsible for occlusion of fractures and pore space. Dolomitization is closely associated with the development of secondary porosity; dolomitization pre-and post-dates dissolution and corrosion and no secondary porosity generation is present in the associated limestones. The most common porosity types are non-fabric selective moldic and vuggy porosity and intercrystalline porosity. Up to 12% effective porosity is recorded in the deep (6477 m) Delaware basin. These porous zones are characterized by late-diagenetic coarse-crystalline dolomite, whereas the non-porous intervals are composed of dense mosaics of early-diagenetic dolomites. The distribution of dolomite rock textures indicates that porous zones were preserved as limestone until late in the diagenetic history, and were then subjected to late-stage dolomitization in a deep burial environment, resulting in coarse-crystalline porous dolomites. In addition to karst horizons at the top of the Ellenburger Group, exploration for Ellenburger Group reservoirs should consider the presence of such porous zones within other Ellenburger Group dolomites

Reactivated interstratal karst--example from the Late Silurian rocks of western Lake Erie (U.S.A.), 1992, Carlson Eh,
Interstratal karst developed in the Late Silurian rocks of western Lake Erie that, after a long interruption, was exhumed and reactivated. The dissolution front of the G evaporite of the Salina Group receded in the downdip direction during these two well-documented periods of subaerial exposure. The karst features that developed in the overlying Bass Islands Dolomite (Pridolian) consist of a large tabular body of collapse breccia and a number of smaller features including breccia pipes, partially filled pipes, blister caves and collapse dolines.The tabular breccia body and the breccia pipes, which originated penecontemporaneously during post-Silurian and pre-Middle Devonian subaerial exposure, occur along the updip edge of the present outcrop belt of the dolostone. They are monolithologic, fragment-supported rubble breccias, with the pipes exhibiting a greater fragment displacement, rotation and rounding, and a smaller fragment size. The matrix sediment of the tabular body is a quartz sand, an equivalent of the basal sandstone that filtered down from the erosion surface. The presence in the matrix sediment of nodular celestite, a later replacement of evaporites that formed when the sediment was still soft, indicates that a sabkha environment existed at the time the breccia was infilled. The partially filled pipes, which form cylindrical caves that are lined with late diagenetic celestite, are believed to be cogenetic with the collapse breccias.The blister caves and dolines occur downdip from the breccias, postdating Pleistocene glaciation and predating isostatic rebound. These caves are isolated, crescent- or oval-shaped openings with domed roofs, averaging about 60 m in width and 4 m in height. The hydration and resulting expansion of lenticular bodies of anhydrite along the receding solution front of the G unit is believed to be the cause of doming. The numerous crescentic caves, originating from the dissolution of this gypsum and the subsequent collapse of the domed roofs, are expressed at the surface as shallow dolines

REACTIVATED INTERSTRIATAL KARST EXAMPLE FROM THE LATE SILURIAN ROCKS OF WESTERN LAKE ERIE (USA), 1992, Carlson Eh,
Interstratal karst developed in the Late Silurian rocks of western Lake Erie that, after a long interruption, was exhumed and reactivated. The dissolution front of the G evaporite of the Salina Group receded in the downdip direction during these two well-documented periods of subaerial exposure. The karst features that developed in the overlying Bass Islands Dolomite (Pridolian) consist of a large tabular body of collapse breccia and a number of smaller features including breccia pipes, partially filled pipes, blister caves and collapse dolines. The tabular breccia body and the breccia pipes, which originated penecontemporaneously during post-Silurian and pre-Middle Devonian subaerial exposure, occur along the updip edge of the present outcrop belt of the dolostone. They are monolithologic, fragment-supported rubble breccias, with the pipes exhibiting a greater fragment displacement, rotation and rounding, and a smaller fragment size. The matrix sediment of the tabular body is a quartz sand, an equivalent of the basal sandstone that filtered down from the erosion surface. The presence in the matrix sediment of nodular celestite, a later replacement of evaporites that formed when the sediment was still soft, indicates that a sabkha environment existed at the time the breccia was infilled. The partially filled pipes, which form cylindrical caves that are lined with late diagenetic celestite, are believed to be cogenetic with the collapse breccias. The blister caves and dolines occur downdip from the breccias, postdating Pleistocene glaciation and predating isostatic rebound. These caves are isolated, crescent- or oval-shaped openings with domed roofs, averaging about 60 m in width and 4 m in height. The hydration and resulting expansion of lenticular bodies of anhydrite along the receding solution front of the G unit is believed to be the cause of doming. The numerous crescentic caves, originating from the dissolution of this gypsum and the subsequent collapse of the domed roofs, are expressed at the surface as shallow dolines

STABLE ISOTOPIC COMPOSITION OF METEORIC CALCITES - EVIDENCE FOR EARLY MISSISSIPPIAN CLIMATE-CHANGE IN THE MISSION CANYON FORMATION, MONTANA, 1993, Smith T. M. , Dorobek S. L. ,
The Lower Mississippian Mission Canyon Formation of central to southwestern Montana was deposited under dominantly semiarid to arid climatic conditions during Osagean to early Meramecian times. Following deposition, a pronounced climatic shift to more humid conditions occurred during middle Meramecian times. This climatic change is indicated by extensive, post-depositional karst fabrics and in the stable isotopic composition of early, meteoric calcite cements and diagenetically altered sediments. Early meteoric calcite cement in Mission Canyon limestones is generally nonluminescent and fills intergranular and fenestral porosity. Petrographic data indicate that this cement formed during intermittent subaerial exposure of the Mission Canyon platform during Osagean times. This initial generation of meteoric calcite cement has deltaO-18 values from -8.1 to -2.6 parts per thousand PDB. These data, and the oxygen isotopic values from nonluminescent skeletal grains and micrite in host limestone indicate that Osagean meteoric water may have had deltaO-18 values as low as -6.0 parts per thousand SMOW. A second generation of petrographically similar, but isotopically distinct, calcite cement fills biomolds and porosity within solution-collapse breccias in the Mission Canyon Formation. This cement generation postdates earlier nonluminescent Osagean calcite cement and is volumetrically most abundant near the top of the Mission Canyon Formation. DeltaO-18 values from these cements and from nonluminescent lime mudstone clasts and matrix in solution collapse breccias range from -13.8 to -8.2 parts per thousand PDB. These data indicate that Meramecian meteoric water may have had deltaO-18 values as low as - 12.0 parts per thousand. However, a higher-temperature burial overprint on the deltaO-18 values of the calcite cement cannot be ruled out. The more positive deltaO-18 values of the Osagean calcite components probably indicate warm and arid conditions during short-term [10(4)(?) yr) subaerial exposure along intraformational sequence and parasequence boundaries. The more negative deltaO-18 values from Meramecian calcite components and the extensive karst associated with the post-Mission Canyon unconformity may have developed because of cooler and more humid climatic conditions and possible rain-out effects during middle Meramecian times. A dramatic shift towards cooler and more humid climatic conditions may be coincident with the onset of major continental glaciation in the Early Carboniferous. The post-Mission Canyon unconformity has been attributed to a major fall in sea level that may have glacio-eustatic origins. Growth of continental glaciers during a time of global cooling would have caused migration of polar fronts further toward the paleoequator. These polar fronts in turn, would have pushed moist, mid-latitude weather systems toward the paleoequator, resulting in cooler, more humid conditions in low-latitude settings during ''icehouse'' times

VARIOUS APPROACHES FOR FLOW SIMULATIONS IN A KARST - APPLICATION TO ROSPO MARE FIELD (ITALY), 1994, Corre B,
Rospo Mare field is located in the Adriatic Sea, 20 km of the Abruzzes coast, at an average depth of 80 m. The reservoir is a karst which is essentially conductive; yet unlike a conventional porous medium, it cannot be simulated by the usual tools and techniques of reservoir simulation. Therefore, several approaches were used to describe the flow mechanism during the production period in greater detail. The first approach consisted of generating three-dimensional images which were constrained by both petrophysical and geological factors and then, using up-scaling techniques, obtaining the equivalent permeabilities (scalar or tensorial) of grid blocks located in different zones within the karst. This approach shows that within the infiltration zone it is possible, whatever the scale, to find an equivalent homogeneous porous medium; on the other hand, within the epikarst this equivalent medium does not exist below pluridecametric dimensions. Thus it is impossible to study the sweeping mechanism on a small scale, so we must use a deterministic model which describes the network of pipes in the compact matrix, in which a waterflood is simulated by means of a conform finite-element model. This constituted the second approach. The third and final approach consisted of inventing a system of equations to analytically solve the pressure field in a network of vertical pipes which are intersected by a production drain and submitted to a strong bottom water-drive. This model allows us to simulate the water-oil contact rise within the reservoir and study the flows depending on the constraints applied to the production well. It appears that cross flows occur in the pipes even during the production period

THE ORIGIN OF RAUHWACKES (CORNIEULES) BY THE KARSTIFICATION OF GYPSUM, 1995, Schaad W. ,
Rauhwackes (cornieules or cargneules) are breccias with a caicareous matrix and mainly dolomitic components that weather to form cavernous rocks. They are very often associated with tectonic contacts, e.g. detachment horizons. The origin of rauhwackes is still controversial, but has been attributed to the weathering and alteration of dolomite-bearing evaporites, the tectonisation of dolomites or other processes. New data based on field investigations show that the karstification of evaporites leads to the formation of rauhwackes. Two end member evaporitic protoliths can be distinguished: dolomite-bearing gypsum and gypsum-bearing dolomite. The karstification of the different protoliths leads to the formation of structurally distinct rauhwackes. Dolomite-bearing gypsum is associated with unstructured, often polymictic rauhwackes which reflect the shape of the karst cavities and which are interpreted as karst sediments. Gypsum-bearing dolomite occurs with stratiformal rauhwackes with fitting dolomite fragments that are arranged in layers. These rauhwackes can be regarded as collapse breccias. All investigated rauhwackes seem to have been formed after the alpine deformations and are probably of Quaternary age. In certain cases, the karstification of the evaporites and the formation of rauhwackes may have been favoured by fluvial or fluvioglacial processes at the surface. Therefore, these rauhwackes have nothing to do with alpine tectonics. Rather, it was the evaporitic protoliths of the rauhwackes that acted as detachment horizons and incompetent layers during folding

THE EFFECT OF ZONES OF HIGH-POROSITY AND PERMEABILITY ON THE CONFIGURATION OF THE SALINE FRESH-WATER MIXING ZONE, 1995, Wicks C. M. , Herman J. S. ,
Coastal karst aquifers have highly variable distributions of porosity and permeability. The ability to assess the volume of aquifer occupied by freshwater in coastal karst aquifers is limited by both the lack of understanding of the effect that regions of cavernous porosity and permeability have on the configuration of the saline-freshwater mixing zone and by the limited knowledge of the location of the cavernous regions. A dual-density ground-water flow and solute transport model was used to explore the effect that the depth, lateral extent, and proximity to the coast of zones of high porosity and permeability has on the configuration of the saline-freshwater mixing zone. These aquifer heterogeneities tend to shift the mixing zone upward relative to the position it would have in aquifers with homogeneous porosity and permeability, Zones of high porosity and permeability located at positions shallow in the aquifer or nearer to the coast had the greatest effect. In fact, for the conditions modeled, position was more important in modifying the configuration of the mixing zone than was changing the ratio of the intrinsic permeability of the cavernous zone to the aquifer matrix from 100 to 1000. Modeling results show that ground-water flow is concentrated into the zones of high porosity and permeability and that flow configuration results in steep salinity gradients with depth, Field observations of the location of the halocline and of step changes in ground-water composition coincident with regions of cavernous porosity in coastal karst aquifers corroborate the model results, In a coastal setting with saline water intruding into an aquifer, the effect of cavernous porosity and associated high permeability is to decrease the volume of aquifer in which freshwater occurs by a greater degree than would occur in an aquifer with homogeneous porosity and permeability

INFILTRATION MECHANISMS RELATED TO AGRICULTURAL WASTE TRANSPORT THROUGH THE SOIL MANTLE TO KARST AQUIFERS OF SOUTHERN INDIANA, USA, 1995, Iqbal M. Z. , Krothe N. C. ,
A hydrogeological study was conducted, during the 1991-1992 water year, in the clay-soil mantled portion of a limestone terrain in southern Indiana. The purpose of the study was to investigate the modes of soil-water infiltration contributing to rapid transport of nitrate to the saturated zone. The I-year-cycle profiles of nitrate concentration vs. time show a consistent increase of nitrate at various depths in the unsaturated zone during the period of investigation. The increase of nitrate in soil water is attributed to the rapid flushing of the inorganic fertilizers from the fields after the area received sufficient rainfall in late fall. The investigation also showed a major movement of nitrate in quick pulses through the unsaturated zone, rather than a slow uniform recharge, immediately after a major storm event. The asymmetric profiles of nitrate concentration vs. depth point to the existence of preferential flow through macropores in the clay-soil mantle above the bedrock. Soil-water transport between storm events is by matrix type flow. Nitrogen isotopes were analyzed for representative groundwater samples collected before and immediately after fertilization of fields in the summer, 1991. The delta(15)N values of the samples did not show any major shift in nitrate sources between the sampling periods. The summer of 1991 was extremely dry prohibiting vertical transport of nitrate from the fields to the groundwater system. Any change in nitrate concentration in groundwater during this time is attributed to the mixing through lateral flow within the aquifer

Evaporites, brines and base metals: What is an evaporite? Defining the rock matrix, 1996, Warren J. K. ,
This paper, the first of three reviews on the evaporite-base-metal association, defines the characteristic features of evaporites in surface and subsurface settings. An evaporite is a rock that was originally precipitated from a saturated surface or near-surface brine in hydrological systems driven by solar evaporation. Evaporite minerals, especially the sulfates such as anhydrite and gypsum, are commonly found near base-metal deposits. Primary evaporites are defined as those salts formed directly via solar evaporation of hypersaline waters at the earth's surface. They include beds of evaporitic carbonates (laminites, pisolites, tepees, stromatolites and other organic rich sediment), bottom nucleated salts (e.g. chevron halite and swallow-tail gypsum crusts), and mechanically reworked salts (such as rafts, cumulates, cross-bedded gypsarenites, turbidites, gypsolites and halolites). Secondary evaporites encompass the diagenetically altered evaporite salts, such as sabkha anhydrites, syndepositional halite and gypsum karst, anhydritic gypsum ghosts, and more enigmatic burial associations such as mosaic halite and limpid dolomite, and nodular anhydrite formed during deep burial. The latter group, the burial salts, were precipitated under the higher temperatures of burial and form subsurface cements and replacements often in a non-evaporite matrix. Typically they formed from subsurface brines derived by dissolution of an adjacent evaporitic bed. Because of their proximity to 'true' evaporite beds, most authors consider them a form of 'true' evaporite. Under the classification of this paper they are a burial form of secondary evaporites. Tertiary evaporites form in the subsurface from saturated brines created by partial bed dissolution during re-entry into the zone of active phreatic circulation. The process is often driven by basin uplift and erosion. They include fibrous halite and gypsum often in shale hosts, as well as alabastrine gypsum and porphyroblastic gypsum crystals in an anhydritic host. In addition to these 'true' evaporites, there is another group of salts composed of CaSO4 or halite. These are the hydrothermal salts. Hydrothermal salts, especially hydrothermal anhydrite, form by the subsurface cooling or mixing of CaSO4- saturated hydrothermal waters or by the ejection of hot hydrothermal water into a standing body of seawater or brine. Hydrothermal salts are poorly studied but often intimately intermixed with sulfides in areas of base-metal accumulations such as the Kuroko ores in Japan or the exhalative brine deeps in the Red Sea. In ancient sediments and metasediments, especially in hydrothermally influenced active rifts and compressional belts, the distinction of this group of salts from 'true' evaporites is difficult and at times impossible. After a discussion of hydrologies and 'the evaporite that was' in the second review, modes and associations of the hydrothermal salts will be discussed more fully in the third review

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