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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. ...

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 waterlogged is water saturated.?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for crystallization (Keyword) returned 35 results for the whole karstbase:
Showing 1 to 15 of 35
DISSOLUTION OF ARAGONITE-STRONTIANITE SOLID-SOLUTIONS IN NONSTOICHIOMETRIC SR(HCO3)2-CA(HCO3)2-CO2-H2O SOLUTIONS, 1992, Plummer L. N. , Busenberg E. , Glynn P. D. , Blum A. E. ,
Synthetic strontianite-aragonite solid-solution minerals were dissolved in CO2-saturated nonstoichiometric solutions of Sr(HCO3)2 and Ca(HCO3)2 at 25-degrees-C. The results show that none of the dissolution reactions reach thermodynamic equilibrium. Congruent dissolution in Ca(HCO3)2 solutions either attains or closely approaches stoichiometric saturation with respect to the dissolving solid. In Sr(HCO3)2 solutions the reactions usually become incongruent, precipitating a Sr-rich phase before reaching stoichiometric saturation. Dissolution of mechanical mixtures of solids approaches stoichiometric saturation with respect to the least stable solid in the mixture. Surface uptake from subsaturated bulk solutions was observed in the initial minutes of dissolution. This surficial phase is 0-10 atomic layers thick in Sr(HCO3)2 solutions and 0-4 layers thick in Ca(HCO3)2 solutions, and subsequently dissolves and/or recrystallizes, usually within 6 min of reaction. The initial transient surface precipitation (recrystallization) process is followed by congruent dissolution of the original solid which proceeds to stoichiometric saturation, or until the precipitation of a more stable Sr-rich solid. The compositions of secondary precipitates do not correspond to thermodynamic equilibrium or stoichiometric saturation states. X-ray photoelectron spectroscopy (XPS) measurements indicate the formation of solid solutions on surfaces of aragonite and strontianite single crystals immersed in Sr(HCO3)2 and Ca(HCO3)2 solutions, respectively. In Sr(HCO3)2 solutions, the XPS signal from the outer approximately 60 angstrom on aragonite indicates a composition of 16 mol% SrCO3 after only 2 min of contact, and 14-18 mol% SrCO3 after 3 weeks of contact. The strontianite surface averages approximately 22 mol% CaCO3 after 2 min of contact with Ca(HCO3)2 solution, and is 34-39 mol% CaCO3 after 3 weeks of contact. XPS analysis suggests the surface composition is zoned with somewhat greater enrichment in the outer approximately 25 angstrom (as much as 26 mol% SrCO3 on aragonite and 44 mol% CaCO3 on strontianite). The results indicate rapid formation of a solid-solution surface phase from subsaturated aqueous solutions. The surface phase continually adjusts in composition in response to changes in composition of the bulk fluid as net dissolution proceeds. Dissolution rates of the endmembers are greatly reduced in nonstoichiometric solutions relative to dissolution rates observed in stoichiometric solutions. All solids dissolve more slowly in solutions spiked with the least soluble component ((Sr(HCO3)2) than in solutions spiked with the more soluble component (Ca(HCO3)2), an effect that becomes increasingly significant as stoichiometric saturation is approached. It is proposed that the formation of a nonstoichiometric surface reactive zone significantly decreases dissolution rates

DISLOCATION OF THE EVAPORITIC FORMATIONS UNDER TECTONIC AND DISSOLUTION CONTROLS - THE MODEL OF THE DINANTIAN EVAPORITES FROM VARISCAN AREA (NORTHERN FRANCE AND BELGIUM), 1993, Rouchy J. M. , Groessens E. , Laumondais A. ,
Within the Franco-Belgian segment of the Hercynian orogen, two thick Dinantian anhydritic formations are known, respectively in the Saint-Ghislain (765 m) and Epinoy 1 (904 m) wells. Nevertheless, occurrences of widespread extended breccias and of numerous pseudomorphs of gypsum/anhydrite in stratigraphically equivalent carbonate deposits (boreholes and outcrops), suggest a larger extent of the evaporitic conditions (fig. 1, 2). The present distribution of evaporites is controlled by palaeogeographical differentiation and post-depositional parameters such as tectonics and dissolution. These latter have dissected the deposits formerly present in all the structural units. By using depositional, diagenetic and deformational characters of these formations, the article provides a model for the reconstruction of a dislocated evaporitic basin. This segment of the Hercynian chain is schematically composed of two main units (fig. 1, 3) : (1) the autochthonous or parautochthonous deposits of the Namur synclinorium, (2) the Dinant nappe thrusted northward over the synclinorium of Namur. The major thrust surface is underlined by a complex fault bundle (faille du Midi) seismically recognized over more than 100 km. A complex system of thrust slices occurs at the Hercynian front. Except for local Cretaceous deposits, most of the studied area has been submitted to a long period of denudation since the Permian. Sedimentary, faunistic and geochemical data argue for a marine origin of the brines which have generated the evaporites interbedded with marine limestones. Sedimentary structures. - The thick evaporitic formations are composed of calcium-sulfates without any clear evidence of the former presence of more soluble salts (with the exception of a possible carbonate-sulfate breccia in the upper part of the Saint-Ghislain formation). As in all the deeply buried evaporitic formations, the anhydrite is the main sulfate component which displays all the usual facies : pseudomorphs after gypsum (fig. 4A, B), nodular and mosaic (fig. 4C), laminated. The gypsum was probably an important component during the depositional phase despite the predominant nodular pattern of the anhydrite. Early diagenetic nodular anhydrite may have grown during temporary emersion of the carbonates (sabkha environments), but this mechanism cannot explain the formation of the whole anhydrite. So, most of the anhydrite structures result from burial-controlled gypsum --> anhydrite conversion and from mechanical deformations. Moreover, a complex set of diagenetic processes leads to various authigenic minerals (celestite, fluorite, albite, native sulfur, quartz and fibrous silica) and to multistaged carbonate <> sulfate replacements (calcite and dolomite after sulfate, replacive anhydrite as idiomorphic poeciloblasts, veinlets, domino-like or stairstep monocrystals...). These mineral transformations observed ill boreholes and in outcrops have diversely been controlled during the complex evolution of the series as : depositional and diagenetic pore-fluid composition, pressure and temperature changes with burial, bacterial and thermochemical sulfate reduction, deep circulations favored by mechanical brecciation, mechanical stresses, role of groundwater during exhumation of the series. Deformational structures. - A great variety of deformational structures as rotational elongation, stretching, lamination, isoclinal microfolding, augen-like and mylonitic structures are generated by compressive tectonic stresses (fig. 4D to J). The similarities between tectonic-generated structures and sedimentary (lamination) or diagenetic (pseudo-nodules) features could lead lo misinterpretations. The calcareous interbeds have undergone brittle deformation the style and the importance of which depend of their relative thickness. Stretching, boudins, microfolds and augen structures F, H. I) affect the thin layers while thicker beds may be broken as large fractured blocks dragged within flown anhydrite leading to a mylonitic-like structure (fig, 4G). In such an inhomogeneous formation made of interlayered ductile (anhydrite) and brittle (carbonate) beds, the style and the intensity of the deformation vary with respect to the relative thickness of each of these components. Such deformational features of anhydrite may have an ubiquitous significance and can result either from compressive constraints or geostatic movements (halokinesis). Nevertheless, some data evidence a relation with regional tangential stresses: (1) increase of the deformation toward the bottom of the Saint-Ghislain Formation which is marked by a deep karst suggesting the presence of a mechanical discontinuity used as a drain for dissolving solutions (fig. 3, 4); (2) structural setting (reversed series, internal slidings) of the Epinoy 1 formation under the Midi thrust. However, tectonic stresses also induce flowing deformations which have contributed to cause their present discontinuity. It can be assumed that the evaporites played an active role for the buckling of the regional structure as detachment or gliding layers and more specifically for the genesis of duplex structures. Breccia genesis. - Great breccia horizons are widely distributed in outcrops as well as in the subsurface throughout the greater part of the Dinant and Namur units (fig. 2). The wide distribution of pseudomorphosed sulfates in outcrops and the stratigraphical correlation between breccia and Saint-Ghislain evaporitic masses (fig. 2) suggest that some breccia (although not all) have been originated from collapse after evaporites solution. Although some breccia may result from synsedimentary dissolution, studied occurrences show that most of dissolution processes started after the Hercynian deformation and, in some cases, were active until recently : elements made of lithified and fractured limestones (Llandelies quarries) (fig. 5A), preservation of pseudomorphs of late replacive anhydrite (Yves-Gomezee) (fig. 5B, C), deep karst associated with breccia (Douvrain, Saint Ghislain, Ghlin boreholes) (fig. 3, 4, 5D)). Locally, the final brecciation may have been favored by a mechanical fragmentation which controlled water circulations (fig. 5E). As postulated by De Magnee et al. [19861, the dissolution started mostly after the Permian denudation and continued until now in relation with deep circulations and surface weathering (fig. 6). So, the above-mentioned occurrences of the breccia are logically explained by collapse after dissolution of calcium-sulfates interbeds of significant thickness (the presence of salt is not yet demonstrated), but other Visean breccia may have a different origin (fig. 5F). So, these data prove the extension of thick evaporitic beds in all the structural units including the Dinant nappe, before dissolution and deformation. Implications. - Distribution of Visean evaporites in northern France and Belgium is inherited from a complicated paleogeographic, tectonic and post-tectonic history which has strongly modified their former facies, thicknesses and limits (fig. IA, 6). Diversified environments of deposition controlled by both a palaeogeographical differentiation and water level fluctuations led to the deposition of subaqueous (gypsum) or interstitial (gypsum, anhydrite) crystallization. Nevertheless, most of the anhydrite structures can be interpreted as resulting from burial conversion of gypsum to anhydrite rather than a generalized early diagenesis in sabkha-like conditions. Deformation of anhydrite caused by Hercynian tangential stresses and subsequent flow mechanisms, have completed the destruction of depositional and diagenetic features. The tectonic deformations allow us to consider the role of the evaporites in the Hercynian deformations. The evaporites supplied detachment and gliding planes as suggested for the base of the Saint-Ghislain Formation and demonstrated by the structural setting of Epinoy 1 evaporites in reverse position and in a multi-system of thrust-slices below the Midi overthrust (fig. 7). So, although the area in which evaporation and precipitation took place cannot be exactly delineated in geographic extent, all the data evidence that the isolated thick anhydritic deposits represent relics of more widespread evaporites extending more or less throughout the different structural units of this Hercynian segment (fig. 1B). Their present discontinuity results from the combination of a depositional differentiation, mechanical deformations and/or dissolution

The dissolution and conversion of Gypsum and Anhydrite., 1996, Klimchouk Alexander
The development of karst is a complex system driven by the dissolution of a host rock and the subsequent removal of dissolved matter by moving water. It is the process that, at various stages, initiates or triggers associated processes including erosion, collapse and subsidence. The dissolution of sulphate rocks proceeds by different mechanisms and at different rates to those associated with the dissolution of carbonate rocks. For each rock type different factors influence the process. This chapter is an attempt to summarise the present knowledge of the dissolution chemistry and kinetics of gypsum and anhydrite. These are important for the genetic interpretation of karst features in these rocks. The gypsum-anhydrite-gypsum transitions and recrystallization processes are also addressed, because of their importance to karst development.

Gypsum Speleothems of Freezing Origin, 1998, Korshunov, V. V. , Shavrina, E. V.
Seasonal freezing affects the development of gypsum speleothems in caves of the Pinega area of the Russian European North including two types of deposits not previously described. One type, called gypsum yozh (hedgehog), grows in dense clay sediment within a high supersaturation environment. Originally growing in a direction away from the freezing front, they later enlarge almost symmetrically. Their shapes and characteristics are dependent on various factors and provide interesting comparisons with gypsum roses from arid regions. A second, very rare, type of gypsum speleothem appears to be produced from concretions of gypsum powder accumulated in cavities within an underground ice body. Recrystallization of the gypsum is controlled by fluctuating local temperature and seasonal freezing in an environment of low supersaturation

Ancient helictites and the formation of vadose crystal silt in upper Jurassic carbonates (Southern Germany), 1998, Reinhold C. ,
Speleothems and vadose crystal silt are effective indications for karstification processes in the fossil record. Upper Jurassic limestones in Southern Germany that have undergone vadose diagenesis contain on crystal margins and tips of coarse bladed calcites numerous fibrous calcite crystals, formed by abnormal growth conditions, and internal sediment within fractures and vugs, Fibrous calcite crystals grew as crusts, in fence and mesh-like arrangements. Fibrous crystals, which have a length:width ratio of greater than 1:10, are made up of stacked subcrystals composed of an alternation of hexagonal prisms and rhombohedra, They exhibit a central to somewhat eccentric capillary. Electron probe microanalysis shows low-Mg calcite mineralogy with negligible amounts of Fe, Mn, and Sr as well as dis seminated clay and metal hydroxide impurities. Stable-isotope data show relatively C-13-enriched and O-18-depleted values (delta(13)C similar to parts per thousand PDB, delta(18)O similar to -6 parts per thousand PDB), suggesting a meteoric environment and CO2 degassing as the main process of formation, Fibrous calcite crystals form from capillary fluids that are highly supersaturated with respect to calcium carbonate, contaminated with alien mineral impurities. The abnormal growth pattern is suggested to be substrate-controlled and attributed to mineral impurities that produce numerous crystallization nuclei. Fibrous calcite crystals are comparable to helictites of the filiform type that are reported only from Quaternary caves. Nevertheless, the diagenetic sequence and oxygen isotope data suggest a Late Cretaceous to early Tertiary age for their formation. The internal sediment consists exclusively of silt-size fragments of fibrous crystals and therefore is comparable to vadose crystal silt. Crystal silt is generated by the erosion of fibrous crystals both by va dose seepage and air currents. This study is the first observation of ancient helictites and related vadose crystal silt, documenting the close relationship between pore ceiling vadose cements and the generation of crystal silt

Brittle tectonics and major dextral strike-slip zone in the Buda karst (Budapest, Hungary), 1999, Benkovics L, Obert D, Bergerat F, Mansy Jl, Dubois M,
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 degrees 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 strike-slip zone: the Ferenc-hegy zone. (C) Elsevier, Paris

Alteration of magnetic properties of Palaeozoic platform carbonate rocks during burial diagenesis (Lower Ordovician sequence, Texas, USA), 1999, Haubold Herbert,
Palaeomagnetic and sedimentological investigations of samples from two sections of correlative Iapetan platform carbonate rocks from Texas, USA, were made to test whether their magnetic properties reflect diagenetic alteration associated with regional and local tectonism. The Honeycut Formation (Llano Uplift area, central Texas), in close proximity to the late Palaeozoic Ouachita orogenic belt, exhibits a distinct correlation between magnetization intensity, magnetization age (direction) and lithofacies. Mudstones preserve their weak primary Early Ordovician magnetization, whereas dolo-grainstones carry a strong Pennsylvanian magnetization residing in authigenic magnetite. Fluid migration associated with the Ouachita Orogeny has been focused in lithofacies with high permeability and caused dolomite recrystallization and pervasive remagnetization. Magnetization intensity trends covary with fluid/rock ratios. However, aquitards were either not affected or less affected by these fluids. Unlike the Honeycut Formation, permeable rocks of the El Paso Group (Franklin Mountains, west Texas) carry only a non-pervasive Pennsylvanian magnetization. Therefore, a larger percentage of El Paso Group samples retain a primary Early Ordovician signature. This area is further removed from the Ouachita front, and, thus, the influence by Pennsylvanian orogenic fluids was less pronounced

Dolomitization of Holocene Shallow-Marine Deposits Mediated by Sulfate Reduction and Methanogenesis in Normal-Salinity Seawater, Northern Belize, 2000, Teal Chellie S. , Mazzullo S. J. , Bischoff William D. ,
Dolomite constitutes an average of 12% of the Holocene organic-rich sediments over a 15 km2 area of the Cangrejo Shoals mudbank in northern Belize. Although it defines a laterally persistent stratiform body that averages 3 m thick, it is present throughout the 7.6-m-thick sediment section. These transgressive sediments are less than [~]6400 years old and were deposited in shallow-marine environments of normal salinity. The dolomite is dominantly cement, and average crystal size is 7 m. There are no significant correlations among amount of dolomite vs. sediment texture, mineralogy, porosity, or mole % MgCO3 in associated particulate high-Mg calcite, depth, or location on the shoals. The dolomites are poorly ordered and calcic (39.5-44.5 mole % MgCO3), with low mean Mn (210 ppm) and relatively high mean Sr (1034 ppm) concentrations. There is no evidence of recrystallization or geochemical alteration of the dolomite. {delta}18O values of the dolomites range from 0.5 to 2.8{per thousand}PDB, and the mean value (2.1{per thousand}) suggests that the dolomite precipitated from normal-salinity pore water. Dolomite {delta}13C values range from -5.2{per thousand} to .6{per thousand}PDB (mean seawater {delta}13C = 0.5{per thousand}), which suggests dolomitization promoted by both bacterial sulfate reduction and methanogenesis in environments with anoxic pore water. Dolomitization attending these organodiagenetic reactions apparently was reversible over time, and episodic rather than continual precipitation is indicated. Requisite Mg and Ca were provided by seawater and by some dissolution of host sediments. The most rapid period of dolomitization may have been during early transgression, when relatively high sedimentation rates sustained high levels of organodiagenesis and pore-water alkalinities

Morphoanalysis of bacterially precipitated subaqueous calcium carbonate from Weebubbie Cave, Australia, 2001, Contos Ak, James Jm, Heywood B, Pitt K, Rogers P,
In this article, we present a previously unreported morphology of bacterially precipitated calcite (determined using XRD, FTIR, and SAED) occurring subaqueously in Weebubbie Cave. Observations using FESEM and TEM revealed spindle-shaped crystals with curved [hk.0] faces lying parallel to the c-axis. Calcite precipitated under conditions designed to mimic the inorganic solution chemistry of the cave revealed a different morphology. These differences between the crystals suggest that the formation of the cave crystals is a consequence of biologically activity

Petrographic and Geochemical Screening of Speleothems for U-series Dating: An Example from Recrystallized Speleothems from Wadi Sannur Cavern, Egypt, 2002, Railsback, L. B. , Dabous, A. A. , Osmond, J. K. , Fleisher, C. J.
Petrographic and geochemical analyses of four speleothems from Wadi Sannur Cavern in eastern Egypt show that petrography and geochemistry can provide a useful way to screen speleothems prior to dating via U-series analysis. The speleothems vary from inclusion-rich zoned calcite to clear featureless calcite. U concentrations (ranging from 0.01-2.65 ppm) and Sr concentrations (ranging from 0.00-0.11 wt%) are greater in inclusion-rich zoned calcite. U concentrations are also greater in speleothems with small (<1.2 mm wide) columnar calcite crystals than in speleothems with larger crystals. Mg concentrations in the speleothems range from 0.2 to 2.3 mol% MgCO3 and show no significant relationship to petrography at the microscopic scale. Geochemical considerations suggest that the Wadi Sannur speleothems were originally mostly aragonite, and that all four have undergone recrystallization. More generally, they suggest that coarse clear columnar calcite and large (>1.0 ppm) ranges of U concentration are warning signs of recrystallization and U loss. However, even finer grained, inclusion-rich columnar calcite may be the result of recrystallization while retaining U contents less depleted than those of associated clear calcite.

Geochemistry of capillary seepage in Mammoth Cave., 2003, Palmer A. N. , Palme M. V.

Low-velocity capillary seepage in the vadose zone is responsible for a variety of geochemical processes in Mammoth Cave . Water that infiltrates through the cap-rock of detrital sandstone and shale is isolated from the high-CO 2 of the soil before it encounters the underlying carbonate rocks, so that carbonate dissolution in narrow fissures around the cave takes place under nearly closed conditions with respect to CO 2 . As a result, the equilibrium P CO2 of the capillary water decreases to nearly zero and the pH can rise to more than 9.0. When the water emerges into the cave it rapidly absorbs CO 2 from the cave air and becomes highly aggressive toward carbonate rocks. Where discrete trickles exit from fissures, deep irregular rills are formed. Where the flow is more diffuse, the cave walls are weathered to a chalky white by partial dissolution and recrystallization of the carbonate rock. If the water has acquired sulfate from oxidation of pyrite or dissolution of residual gypsum within the bedrock, the SO 4 = /CO 3 = ratio of the water rises sharply at the cave walls, promoting the replacement of carbonate bedrock by gypsum. The pH decrease caused by the uptake of CO 2 enables silica to precipitate in small amounts in the weathering rind. Direct measurement of capillary water chemistry is difficult because of the small quantity and inaccessibility of the water involved, but it can be reliably inferred from the geochemical setting and the effects upon the cave.


Formation of Willemite in Hydrothermal Environments, 2003, Brugger J, Mcphail Dc, Wallace M, Waters J,
Willemite (zinc silicate) is the main zinc mineral in some carbonate-hosted ore deposits (e.g., Franklin, New Jersey; Vazante, Brazil; Beltana, South Australia; Kabwe, Zambia). Recent interest in these unconventional zinc deposits has increased because of high zinc grades that exceed 40 wt percent, relatively low environmental impact of ore processing owing to the lack of acid-generating sulfides in the waste, and advances in ore processing technologies. In the past, most metallogenic studies proposed formation of willemite deposits by supergene or hypogene alteration of preexisting sulfide deposits. However, recent data on the Vazante, Beltana, and Kabwe deposits indicate willemite crystallization at temperatures in excess of 150{degrees}C, raising the possibility of primary precipitation from hydrothermal fluids. We use numerical geochemical modeling to examine the formation of willemite under hydrothermal conditions. Activity-activity diagrams reveal that, in the presence of dissolved sulfur and quartz, willemite instead of sphalerite will precipitate under oxidizing (e.g., hematite-stable, sulfate-predominant) and alkaline (pH higher than K feldspar-muscovite-quartz) conditions. Willemite also becomes more stable, relative to sphalerite, at high temperature, and willemite can coexist with magnetite at 300{degrees}C. The stabilities and solubilities of sphalerite, willemite, smithsonite, hydrozincite, and zincite were calculated for wide ranges of temperature (25{degrees}-300{degrees}C), chloride concentration, dissolved sulfur and carbon concentrations, pH, quartz saturation, and oxidation potential. Plots of the solubility of the different minerals as a function of two variables (e.g., temperature and redox state; pH and redox state) allow us to predict the effects of changing chemical conditions, which in turn permits an estimate of the efficiency of particular precipitation processes. Cooling is an effective process for precipitating sphalerite but not willemite, whereas pH increase (e.g., by acidic fluids reacting with carbonates) is effective for precipitating willemite but not sphalerite. Dynamic geochemical models that simulate physicochemical processes are used to understand the formation of the Beltana willemite deposit in the Adelaide geosyncline of South Australia. This small, high grade deposit (850,000 t at 36% Zn) is hosted in dolomite of the Cambrian Ajax Limestone, next to a tectonic contact with the diapiric, halite-bearing clastic sediments of the Callanna Group. The orebody is associated with hematite alteration and is characterized by the total absence of sulfides; willemite is the only zinc ore mineral, and the arsenate hedyphane (Ca2Pb3[AsO4]3Cl) is the main lead mineral. The model results show that willemite will precipitate in response to water-rock interaction and fluid mixing processes at temperatures above 120{degrees}C. The presence of arsenate in the hydrothermal fluid is likely to have been important at Beltana; in arsenate-absent models sulfate is reduced to sulfide by the precipitation of ferrous iron as hematite, resulting in the precipitation of sphalerite and galena. In contrast, in models including arsenate the reduction of sulfate to sulfide is inhibited and willemite is predicted to precipitate

Temporal evolution of tertiary dolostones on Grand Cayman as determined by Sr-87/Sr-86, 2003, Jones B. , Luth R. W. ,
On the Cayman Islands, the Tertiary Bluff Group (Brac Formation, Cayman Formation, Pedro Castle Formation) is onlapped and overlain by the Pleistocene Ironshore Formation. On Grand Cayman, the Brac Formation and Cayman Formation are formed of finely crystalline dolostones; whereas the Pedro Castle Formation is formed of finely crystalline dolostones, dolomitized limestones, and limestones. No dolomite has been found in the Ironshore Formation. Dolostones in the Bluff Group, which retained their original depositional textures and lack evidence of any recrystallization, are formed of small (typically 5-15 mum long) interlocking, euhedral dolomite crystals. Dolomite cement is present in the Brac Formation and Cayman Formation but is very rare in the Pedro Castle Formation. Most of the dolomite crystals are characterized by oscillatory zoning with alternating zones of low-Ca calcian dolomite and high-Ca calcian dolomite. Grand Cayman is ideal for assessing the temporal evolution of Tertiary dolostones because the dolostones are young, have not been recrystallized, and are geographically isolated by the deep oceanic waters around the island. Interpretation of 158 new Sr-87/Sr-86 ratios from the dolostones in the Bluff Group indicate that the succession underwent three time-transgressive phases of dolomitization during the Late Miocene, the Late Pliocene, and Pleistocene. Petrographically similar dolomite was produced during each phase of dolomitization that was mediated by the same type of fluid and the same general conditions. Dolomitization was part of a dynamic cycle of processes that followed major lowstands. Karst development during the lowstands preconditioned the limestones for dolomitization by increasing their porosity and permeability. Thus, vast quantities of the dolomitizing fluids could freely circulate through the strata during the subsequent transgression. Dolomitization ceased once a stable highstand had been attained

Temporal Evolution of Tertiary Dolostones on Grand Cayman as Determined by 87Sr/86Sr, 2003, Jones Brian, Luth Robert W. ,
On the Cayman Islands, the Tertiary Bluff Group (Brac Formation, Cayman Formation, Pedro Castle Formation) is onlapped and overlain by the Pleistocene Ironshore Formation. On Grand Cayman, the Brac Formation and Cayman Formation are formed of finely crystalline dolostones whereas the Pedro Castle Formation is formed of finely crystalline dolostones, dolomitized limestones, and limestones. No dolomite has been found in the Ironshore Formation. Dolostones in the Bluff Group, which retained their original depositional textures and lack evidence of any recrystallization, are formed of small (typically 5-15 {micro}m long) interlocking, euhedral dolomite crystals. Dolomite cement is present in the Brac Formation and Cayman Formation but is very rare in the Pedro Castle Formation. Most of the dolomite crystals are characterized by oscillatory zoning with alternating zones of low-Ca calcian dolomite and high-Ca calcian dolomite. Grand Cayman is ideal for assessing the temporal evolution of Tertiary dolostones because the dolostones are young, have not been recrystallized, and are geographically isolated by the deep oceanic waters around the island. Interpretation of 158 new 87Sr/86Sr ratios from the dolostones in the Bluff Group indicate that the succession underwent three time-transgressive phases of dolomitization during the Late Miocene, the Late Pliocene, and Pleistocene. Petrographically similar dolomite was produced during each phase of dolomitization that was mediated by the same type of fluid and the same general conditions. Dolomitization was part of a dynamic cycle of processes that followed major lowstands. Karst development during the lowstands preconditioned the limestones for dolomitization by increasing their porosity and permeability. Thus, vast quantities of the dolomitizing fluids could freely circulate through the strata during the subsequent transgression. Dolomitization ceased once a stable highstand had been attained

Fluid inclusion and stable isotopic evidence for early hydrothermal karstification in vadose caves of the Nizke Tatry Mountains (Western Carpathians), 2004, Orvosova M. , Hurai V. , Simon K. , Wiegerova V. ,
Hydrothermal paleokarst cavities with calcite crystals up to 20 cm in diameter were found in two caves of the Nizke Tarry Mountains developed in Triassic limestone and dolomite of the Guttenstein type. In both caves, older zones of tectonic and hydrothermal activity have been overprinted by vadose speleogenesis. According to fluid inclusion microthermometry data, prismatic-scalenoliedral calcite from the Silvo ova Diera Cave has precipitated at temperatures between similar to60 and 101degreesC from low salinity aqueous solutions (less than or equal to0.7 wt. % NaCl eq.). Carbon and oxygen isotope profiling revealed significant delta(13)C decrease accompanied by slight delta(18)O increase during growth of calcite crystals. The negatively correlated carbon and oxygen isotope data cannot be interpreted in terms of any geologically reasonable models based on equilibrium isotopic fractionation. Fluid inclusion water exhibits minor decrease of deltaD values from crystal core (-31 %o SMOW) to rim (-41 %(0) SMOW). Scalenohedral calcite from the NovA Stanisovska Cave has precipitated at slightly higher temperatures 63-107degreesC from aqueous solutions with salinity : less than or equal to2.7 % NaCl eq. The positively correlated trend of delta(13)C and delta(18)O values is similar to common hydrothermal carbonates. The fluid inclusion water deltaD values differ significantly between the crystal core (-50 %(0) SMOW) and rim (- 11 %o SMOW). The calcite crystals are interpreted as representing a product of an extinct hydrothermal system, which was gradually replaced by shallow circulation of meteoric water. Fossil hydrothermal fluids discharged along Alpine uplift-related NNW-SSE-trending faults in Paleogene-pre-Pliocene times. Increased deuterium concentration in the inclusion water compared to recent meteoric precipitation indicates a warmer climate during the calcite crystallization

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