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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. ...

Did you know?

That producers is green plants, the basic link in any food chain; by means of photosynthesis, green plants manufacture the food on which all other living things ultimately depend. they are available in the cave community only in the twilight zone, or as debris that falls or washes in. a few types of bacteria also manufacture food from nonliving substances and therefore serve as producers in some cave communities [23]. see also consumer.?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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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 fluid-inclusion (Keyword) returned 32 results for the whole karstbase:
Showing 16 to 30 of 32
Geology of the Beltana Willemite Deposit, Flinders Ranges, South Australia, 2003, Groves Iain M. , Carman Cris E. , Dunlap W. James,
Beltana is a high-grade hypogene willemite deposit hosted in Lower Cambrian carbonate rocks in the Arrowie basin, northern Flinders Ranges, South Australia. It is situated adjacent to a major growth fault on the basin margin. Ooid grainstone units of the Woodendinna Dolomite and units of Archaeocyathid-rich Wilkawillina Limestone are the main host lithologies. Lead minerals in subeconomic quantities are also present in karstic collapse breccias surrounding the willemite orebodies. Mineralization is structurally controlled and associated with brecciation and extensive hematite-rich hydrothermal zincian dolomitization. Ore minerals include willemite and coronadite with lesser mimetite, hedyphane, and smithsonite. Late-stage gangue minerals include manganocalcite, dolomite, and minor quartz. The texture of willemite is heterogeneous, resulting from various depositional mechanisms such as partial to massive replacement of the carbonate host rock, internal sedimentation, fracture fill, brecciation, and vein fill. On the periphery of the deposit, smithsonite formed by weathering of willemite. Beltana is centered on a karstic collapse breccia that extends at least 100 m vertically, formed in part through corrosion by acidic ore solutions. The geochemical signature of the orebody includes high levels of Zn, Pb, Cd, As, and Mn. Notably, silver is absent from the deposit and sulfur concentrations are low (<20 ppm). Fluid inclusion studies yield a low minimum temperature range of ore deposition between 50{degrees} and 170{degrees}C. K-Ar dating of coronadite associated with the willemite orebody indicates an age of formation of ~ 435 {} 5 Ma. Premining resources of willemite ore were 850,000 t at 36 percent Zn, and an associated body of subeconomic lead contained more than 800,000 t at 8.9 percent Pb, 3.9 percent Zn and 1 percent As. The deposit has some similarities with Mississippi Valley-type deposits but differs in ore and alteration mineral assemblages

Carbonate-Hosted Zn-Pb Deposits in Upper Silesia, Poland: Origin and Evolution of Mineralizing Fluids and Constraints on Genetic Models, 2003, Heijlen Wouter, Muchez Philippe, Banks David A. , Schneider Jens, Kucha Henryk, Keppens Eddy,
Microthermometric and crush-leach analyses of fluid inclusions in ore and gangue minerals of the Upper Silesian Zn-Pb deposits, Poland, along with first results of Rb-Sr geochronology on sulfides, provide important constraints on the paleohydrogeologic and metallogenetic models for the origin of these ores. The analyzed samples comprise two generations of dolomite, two generations of sphalerite, galena, and late calcite. The two dolomite generations and the late calcite were also analyzed for their oxygen and carbon isotope compositions, allowing a characterization of the mineralizing fluids. The ore-forming fluids represent highly saline (20-23 wt % CaCl2 equiv) Na-Ca-Cl brines, episodically introduced into the Triassic host carbonates. They had an oxygen isotope composition of ~0 per mil V-SMOW. Their Na-Cl-Br content (molar Na/Br and Cl/Br ratios between 99 and 337 and between 248 and 560, respectively) suggests that they originated by evaporation of seawater, which most likely occurred in the Permian-Triassic. The relative concentrations of potassium (molar K/Cl between 0.0147 and 0.0746) and lithium (molar Li/Cl between 0.0004 and 0.0031) further indicate that the fluids significantly interacted with siliciclastic rocks. The ionic and calculated oxygen isotope compositions of the fluids indicate that they were more evolved than present-day brines in the Upper Silesian coal basin, and the present-day brines show more extensive mixing with low-salinity fluids. The first results of direct Rb-Sr dating of ore-stage sulfides yield an isochron model age of 135 {} 4 Ma for the mineralizing event. This is consistent with hydrothermal activity and ore formation in Upper Silesia occurring in response to Early Cretaceous crustal extension preceding the opening of the northern Atlantic Ocean. The data presented support a model in which bittern brines migrated down into the deep subsurface and evolved into mineralizing fluids owing to extensive water-rock interaction. They were episodically expelled along deeply penetrating faults during the Early Cretaceous to form Zn-Pb deposits in the overlying Mesozoic carbonate rocks

Geology and Geochemistry of the Reocin Zinc-Lead Deposit, Basque-Cantabrian Basin, Northern Spain, 2003, Velasco Francisco, Herrero Jose Miguel, Yusta Inaki, Alonso Jose Antonio, Seebold Ignacio, Leach David,
The Reocin Zn-Pb deposit, 30 km southwest of Santander, Spain, occurs within Lower Cretaceous dolomitized Urgonian limestones on the southern flank of the Santillana syncline. The Reocin deposit is one of the largest known strata-bound, carbonate-hosted, zinc-lead deposits in Europe. The total metal endowment of the deposit, including past production and remaining reserves, is 62 Mt of ore grading 8.7 percent Zn and 1.0 percent Pb. The epigenetic mineralization consists of sphalerite and galena, with lesser marcasite and trace pyrite with dolomite as gangue. Microprobe analyses of different generations of dolomite revealed nonstoichiometric compositions with various amounts of iron (up to 14 mol % of FeCO3). Replacement of host dolomite, open-space filling of fractures, and cementation of breccias derived from dissolution collapse are the principal types of ore occurrence. Detailed cross-section mapping indicates a stratigraphic and structural control on the deposit. A stratiform morphology is present in the western part of the orebody (Capa Sur), whereas mineralization in the eastern part is highly discordant but strata bound (Barrendera). Stratigraphic studies demonstrate that synsedimentary tectonic activity, related to the rifting of the North Atlantic (Bay of Biscay), was responsible for variation in sedimentation, presence of unconformities (including paleokarsts), local platform emergence and dolomitization along the N60 fault trend. In the Reocin area, two stages of dolomitization are recognized. The first stage is a pervasive dolomitization of the limestone country rocks that was controlled by faulting and locally affected the upper part of the Aptian and the complete Albian sequence. The second dolomitization event occurred after erosion and was controlled by karstic cavities. This later dolomitization was accompanied by ore deposition and, locally, filling of dolomite sands and clastic sediments in karstic cavities. The circulation of hydrothermal fluids responsible for sulfide deposition and the infilling of karst cavities were broadly contemporaneous, indicating a post-Albian age. Vitrinite reflectance data are consistent with previously measured fluid inclusion temperatures and indicate temperatures of ore deposition that were less than 100{degrees}C. Carbon and oxygen isotopic data from samples of regional limestone, host-rock dolostone and ore-stage dolomite suggest an early hydrothermal alteration of limestone to dolostone. This initial dolomitization was followed by a second period of dolomite formation produced by the mixing of basinal metal-rich fluids with local modified seawater. Both dolomitization events occurred under similar conditions from fluids exhibiting characteristics of basinal brines. The{delta} 34S values of sulfides are between -1.8 and .5 per mil, which is consistent with thermochemical sulfate reduction involving organic matter as the main source of reduced sulfur. Galena lead isotope compositions are among the most radiogenic values reported for Zn-Pb occurrences in Europe, and they are distinct from values reported for galena from other Basque-Cantabrian deposits. This suggests that a significant part of the lead was scavenged from the local underlying Asturian sediments. The stratigraphic and structural setting, timing of epigenetic mineralization, mineralogy, and isotopic geochemistry of sulfide and gangue minerals of the Reocin deposit are consistent with the features of most of Mississippi Valley-type ore deposits

Changing moisture sources over the last 330,000 years in Northern Oman from fluid-inclusion evidence in speleothems., 2003, Fleitmann D. , Burns S. J. , Neff U. Et Al.

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

Concepts and models of dolomitization: a critical reappraisal, 2004, Machel Hans G. ,
Despite intensive research over more than 200 years, the origin of dolomite, the mineral and the rock, remains subject to considerable controversy. This is partly because some of the chemical and/or hydrological conditions of dolomite formation are poorly understood, and because petrographic and geochemical data commonly permit more than one genetic interpretation. This paper is a summary and critical appraisal of the state of the art in dolomite research, highlighting its major advances and controversies, especially over the last 20-25 years. The thermodynamic conditions of dolomite formation have been known quite well since the 1970s, and the latest experimental studies essentially confirm earlier results. The kinetics of dolomite formation are still relatively poorly understood, however. The role of sulphate as an inhibitor to dolomite formation has been overrated. Sulphate appears to be an inhibitor only in relatively low-sulphate aqueous solutions, and probably only indirectly. In sulphate-rich solutions it may actually promote dolomite formation. Mass-balance calculations show that large water/rock ratios are required for extensive dolomitization and the formation of massive dolostones. This constraint necessitates advection, which is why all models for the genesis of massive dolostones are essentially hydrological models. The exceptions are environments where carbonate muds or limestones can be dolomitized via diffusion of magnesium from seawater rather than by advection. Replacement of shallow-water limestones, the most common form of dolomitization, results in a series of distinctive textures that form in a sequential manner with progressive degrees of dolomitization, i.e. matrix-selective replacement, overdolomitization, formation of vugs and moulds, emplacement of up to 20 vol% calcium sulphate in the case of seawater dolomitization, formation of two dolomite populations, and -- in the case of advanced burial -- formation of saddle dolomite. In addition, dolomite dissolution, including karstification, is to be expected in cases of influx of formation waters that are dilute, acidic, or both. Many dolostones, especially at greater depths, have higher porosities than limestones, and this may be the result of several processes, i.e. mole-per-mole replacement, dissolution of unreplaced calcite as part of the dolomitization process, dissolution of dolomite due to acidification of the pore waters, fluid mixing (mischungskorrosion), and thermochemical sulphate reduction. There also are several processes that destroy porosity, most commonly dolomite and calcium sulphate cementation. These processes vary in importance from place to place. For this reason, generalizations about the porosity and permeability development of dolostones are difficult, and these parameters have to be investigated on a case-by-case basis. A wide range of geochemical methods may be used to characterize dolomites and dolostones, and to decipher their origin. The most widely used methods are the analysis and interpretation of stable isotopes (O, C), Sr isotopes, trace elements, and fluid inclusions. Under favourable circumstances some of these parameters can be used to determine the direction of fluid flow during dolomitization. The extent of recrystallization in dolomites and dolostones is much disputed, yet extremely important for geochemical interpretations. Dolomites that originally form very close to the surface and from evaporitic brines tend to recrystallize with time and during burial. Those dolomites that originally form at several hundred to a few thousand metres depth commonly show little or no evidence of recrystallization. Traditionally, dolomitization models in near-surface and shallow diagenetic settings are defined and/or based on water chemistry, but on hydrology in burial diagenetic settings. In this paper, however, the various dolomite models are placed into appropriate diagenetic settings. Penecontemporaneous dolomites form almost syndepositionally as a normal consequence of the geochemical conditions prevailing in the environment of deposition. There are many such settings, and most commonly they form only a few per cent of microcrystalline dolomite(s). Many, if not most, penecontemporaneous dolomites appear to have formed through the mediation of microbes. Virtually all volumetrically large, replacive dolostone bodies are post-depositional and formed during some degree of burial. The viability of the many models for dolomitization in such settings is variable. Massive dolomitization by freshwater-seawater mixing is a myth. Mixing zones tend to form caves without or, at best, with very small amounts of dolomite. The role of coastal mixing zones with respect to dolomitization may be that of a hydrological pump for seawater dolomitization. Reflux dolomitization, most commonly by mesohaline brines that originated from seawater evaporation, is capable of pervasively dolomitizing entire carbonate platforms. However, the extent of dolomitization varies strongly with the extent and duration of evaporation and flooding, and with the subsurface permeability distribution. Complete dolomitization of carbonate platforms appears possible only under favourable circumstances. Similarly, thermal convection in open half-cells (Kohout convection), most commonly by seawater or slightly modified seawater, can form massive dolostones under favourable circumstances, whereas thermal convection in closed cells cannot. Compaction flow cannot form massive dolostones, unless it is funnelled, which may be more common than generally recognized. Neither topography driven flow nor tectonically induced ( squeegee-type') flow is likely to form massive dolostones, except under unusual circumstances. Hydrothermal dolomitization may occur in a variety of subsurface diagenetic settings, but has been significantly overrated. It commonly forms massive dolostones that are localized around faults, but regional or basin-wide dolomitization is not hydrothermal. The regionally extensive dolostones of the Bahamas (Cenozoic), western Canada and Ireland (Palaeozoic), and Israel (Mesozoic) probably formed from seawater that was pumped' through these sequences by thermal convection, reflux, funnelled compaction, or a combination thereof. For such platform settings flushed with seawater, geochemical data and numerical modelling suggest that most dolomites form(ed) at temperatures around 50-80 {degrees}C commensurate with depths of 500 to a maximum of 2000 m. The resulting dolostones can be classified both as seawater dolomites and as burial dolomites. This ambiguity is a consequence of the historical evolution of dolomite research

'Sour gas' hydrothermal jarosite: ancient to modem acid-sulfate mineralization in the southern Rio Grande Rift, 2005, Lueth V. W. , Rye R. O. , Peters L. ,
As many as 29 mining districts along the Rio Grande Rift in southern New Mexico contain Rio Grande Rift-type (RGR) deposits consisting of fluorite-barite sulfide-jarosite, and additional RGR deposits occur to the south in the Basin and Range province near Chihuahua, Mexico. Jarosite occurs in many of these deposits as a late-stage hydrothermal mineral coprecipitated with fluorite, or in veinlets that crosscut barite. In these deposits, many of which are limestone-hosted, jarosite is followed by natrojarosite and is nested within silicified or argillized wallrock and a sequence of fluorite-barite sulfide and late hematite-gypsum. These deposits range in age from similar to 10 to 0.4 Ma on the basis of Ar-40/Ar-39 dating of jarosite. There is a crude north-south distribution of ages, with older deposits concentrated toward the south. Recent deposits also occur in the south, but are confined to the central axis of the rift and are associated with modem geothermal systems. The duration of hydrothermal jarosite mineralization in one of the deposits was approximately 1.0 my. Most Delta(18)O(SO4)-OH values indicate that jarosite precipitated between 80 and 240 degrees C, which is consistent with the range of filling temperatures of fluid inclusions in late fluorite throughout the rift, and in jarosite (180 degrees C) from Pena Blanca, Chihuahua, Mexico. These temperatures, along with mineral occurrence, require that the jarosite have had a hydrothermal origin in a shallow steam-heated environment wherein the low pH necessary for the precipitation of jarosite was achieved by the oxidation of H2S derived from deeper hydrothermal fluids. The jarosite also has high trace-element contents (notably As and F), and the jarosite parental fluids have calculated isotopic signatures similar to those of modem geothermal waters along the southern rift; isotopic values range from those typical of meteoric water to those of deep brine that has been shown to form from the dissolution of Permian evaporite by deeply circulating meteoric water. Jarosite delta(34)S values range from -24 parts per thousand to 5 parts per thousand, overlapping the values for barite and gypsum at the high end of the range and for sulfides at the low end. Most delta(34)S values for barite are 10.6 parts per thousand to 13.1 parts per thousand and many delta(34)S values for gypsum range from 13.1 parts per thousand to 13.9 parts per thousand indicating that a component of aqueous sulfate was derived from Permian evaporites (delta(34)S = 12 2 parts per thousand). The requisite H2SO4 for jarosite formation was derived from oxidation of H2S which was likely largely sour gas derived from the thermochemical reduction of Permian sulfate. The low delta(34)S values for the precursor H2S probably resulted from exchange deeper in the basin with the more abundant Permian SO42-- at similar to 150 to 200 degrees C. Jarosite formed at shallow levels after the PH buffering capacity of the host rock (typically limestone) was neutralized by precipitation of earlier minerals. Some limestone-hosted deposits contain caves that may have been caused by the low pH of the deep basin fluids due to the addition of deep-seated HF and other magmatic gases during periods of renewed rifting. Caves in other deposits may be due to sulfuric acid speleogenesis as a result of H2S incursion into oxygenated groundwaters. The isotopic data in these 'sour gas' jarosite occurrences encode a recod of episodic tectonic or hydrologic processes that have operated in the rift over the last 10 my. (c) 2004 Elsevier B.V. All rights reserved

Solution-collapse breccias of the Minkinqellet and Wordiekammen Formations, Central Spitsbergen, Svalbard: a large gypsum palaeokarst system, 2005, Eliassen A, Talbot Mr,
Large volumes of carbonate breccia occur in the late syn-rift and early post-rift deposits of the Billefjorden Trough, Central Spitsbergen. Breccias are developed throughout the Moscovian Minkinfjellet Formation and in basal parts of the Kazimovian Wordiekammen Formation. Breccias can be divided into two categories: (i) thick, cross-cutting breccia-bodies up to 200 m. thick that are associated with breccia pipes and large V-structures, and (ii) horizontal stratabound breccia beds interbedded with undeformed carbonate and siliciclastic rocks. The thick breccias occur in the central part of the basin, whereas the stratabound breccia beds have a much wider areal extent towards the basin margins. The breccias were formed by gravitational collapse into cavities formed by dissolution of gypsum and anhydrite beds in the Minkinfjellet Formation. Several dissolution fronts have been discovered, demonstrating the genetic relationship between dissolution of gypsum and brecciation. Textures and structures typical of collapse breccias such as inverse grading, a sharp flat base, breccia pipes (collapse dolines) and V-structures (cave roof collapse) are also observed. The breccias are cemented by calcite cements of pre-compaction, shallow burial origin. Primary fluid inclusions in the calcite are dominantly single phase containing fresh water (final melting points are ca 0 degrees C), suggesting that breccia diagenesis occurred in meteoric waters. Cathodoluminescence (CL) zoning of the cements shows a consistent pattern of three cement stages, but the abundance of each stage varies stratigraphically and laterally. delta(18)O values of breccia cements are more negative relative to marine limestones and meteoric cements developed in unbrecciated Minkinfjellet limestones. There is a clear relationship between delta(18)O values and the abundance of the different cement generations detected by CL. Paragenetically, later cements have lower delta(18)O values recording increased temperatures during their precipitation. Carbon isotope values of the cements are primarily rock-buffered although a weak trend towards more negative values with increasing burial depth is observed. The timing of gypsum dissolution and brecciation was most likely related to major intervals of exposure of the carbonate platform during Gzhelian and/or Asselian/Sakmarian times. These intervals of exposure occurred shortly after deposition of the brecciated units and before deep burial of the sediments

Fluid inclusion study of a sedimentary basin: an example of Culberson sulfur and barite deposit, Texas, 2006, Lu H. Z. ,
The Culberson sulfur-barite deposit is located in Culberson county, West Texas. Geologically, it is occurred ill Delaware sedimentary, petroleum and natural gas basin. There are several sulfur-barite deposits occurring in the basin, Culberson is the largest one. Culberson deposit is hosted by Upper Permian Castile and Salado formation. The Castile and Salodo formation consist of limestone with thin layers of evaporate and organic materials. Natural sulfur and barite is formed post diagenesis, filled into the palco karst and replaced the internal layers of anhydrite. Two generation fluid inclusions are found: I. Fluid inclusion formed during the diagenesis, and II. Fluid inclusion trapped during the authigenic calcite, barite overgrowth. According to the phases and composition at room temperature, the fluid inclusions could be divided into: one phase liquid inclusion; two phases vapor and liquid inclusion, and oil inclusion. In a same growth zone of calcite, several types of fluid inclusions, such as one phase liquid, different vapor/liquid ratio inclusions and oil inclusions occurred. These inclusions are hardly to he used to gel the temperature of homogenization, since they are formed in heterogeneous trapping or an immiscibility environment. The eutectic temperatures of fluid inclusions range from -18 to -24 degrees C, indicating life fluid belongs to a NaCl-H2O system, with the salinity ranges from 2% to 10%, and co-existing with the oil inclusions, these show that the ore forming fluid is an oil filed brine and with temperature less than 100 degrees C

Variscan veins: record of fluid circulation and Variscan tectonothermal events in Upper Palaeozoic limestones of the Moravian Karst, Czech Republic, 2006, Slobodnik M. , Muchez P. H. , Kral J. , Keppens E. ,
Numerous Variscan syntectonic calcite veins cross-cut Palaeozoic rocks in the Moravian Karst. A structural, petrographic and stable isotopic analysis of the calcite veins and a microthermometric study of fluid inclusions in these vein cements have been carried out to determine the origin of the Variscan fluids and their migration during burial and deformation. The isotopic parameters of white (older, more deformed) and rose (younger) calcites are: 87Sr/86Sr is between 0.7078 and 0.7082 (white) and 0.7086 (rose), {delta}18O is between .7 and .1 (white) and between .8 and .7 {per thousand} SMOW (rose), {delta}13C ranges from .1 to .5 (white) and from -0.3 to .6 {per thousand} V-PDB (rose). The isotopic signatures point to precipitation in an older fluid system buffered by the host rock (white calcites) and to an open, younger fluid-dominated system (rose calcites). Parent fluids (H2O-NaCl system) had salinities between 0.35 and 17.25 eq. wt % NaCl. The pressure-corrected and confined homogenization temperatures suggest formation of the calcite veins from a fluid with a temperature between 120 and 170 {degrees}C, a pressure of 300-880 bar at a depth between 2.1 and 3.2 km. The fluids were most likely confined to a particular sedimentary bed as a bed-scale fluid migration (white older calcite veins) or, later, to a pile of Palaeozoic sediments as a stratigraphically restricted fluid flow (rose younger calcite veins). The low temperatures and pressures during precipitation of calcites, which took place close to a peak of burial/deformation, confirm the distal position of the Moravian Karst region within the Variscan orogen

Pleistocene speleothems of Mallorca: implications for palaeoclimate and carbonate diagenesis in mixing zones, 2006, Csoma Ae, Goldstein Rh, Pomar L,
The Pleistocene speleothems of Sa Bassa Blanca cave, Mallorca, are excellent indicators of palaeoclimate variations, and are samples that allow evaluation of the products and processes of mixing-zone diagenesis in an open-water cave system. Integrated stratigraphic, petrographic and geochemical data from a horizontal core of speleothem identified two main origins for speleothem precipitates: meteoric-marine mixing zone and meteoric-vadose zone. Mixing-zone precipitates formed at and just below the water-air interface of cave pools during interglacial times, when the cave was flooded as a result of highstand sea-level. Mixing-zone precipitates include bladed and dendritic high-Mg calcite, microporous-bladed calcite with variable Mg content, and acicular aragonite; their presence suggests that calcium-carbonate cementation is significant in the studied mixing-zone system. Fluid inclusion salinities, delta(13)C and delta(18)O compositions of the mixing-zone precipitates suggest that mixing ratio was not the primary control on whether precipitation or dissolution occurred, rather, the proximity to the water table and degassing of CO2 at the interface, were the major controls on precipitation. Thus, simple two-end-member mixing models may apply only in mixing zones well below the water table. Meteoric-vadose speleothems include calcite and high-Mg calcite with columnar and bladed morphologies. Vadose speleothems precipitated during glacial stages when sea level was lower than present. Progressive increase in delta(13)C and delta(18)O of the vadose speleothems resulted from cooling temperatures and more positive seawater delta(18)O associated with glacial buildup. Such covariation could be considered as a valid alternative to models predicting invariant delta(18)O and highly variable delta(13)C in meteoric calcite. Glacio-eustatic oscillations of sea-level are recorded as alternating vadose and mixing-zone speleothems. Short-term climatic variations are recorded as alternating aragonite and calcite speleothems precipitated in the mixing zone. Fluid-inclusion and stable-isotope data suggest that aragonite, as opposed to calcite, precipitated during times of reduced meteoric recharge

Origin and reservoir characteristics of Upper Ordovician TrentonBlack River hydrothermal dolomite reservoirs in New York , 2006, Smith, Jr. , L. B.

In the past decade, more than 20 new natural gas fields have been discovered in laterally discontinuous dolomites of the Upper Ordovician Black River Group in south-central New York. The dolomites form around basement-rooted wrench faults that are detectable on seismic data. Most fields occur in and around elongate faultbounded structural lows interpreted to be negative flower structures. Away from these faults, the formation is composed of impermeable limestone and forms the lateral seal for the reservoirs. In most cases, the faults die out within the overlying Trenton Limestone and Utica Shale. Most porosity occurs in saddle dolomitecoated vugs, breccias, and fractured zones. Matrix porosity is uncommon in the Black River cores described for this study. The patchy distribution around basement-rooted faults and geochemical and fluid-inclusion analyses supports a fault-related hydrothermal origin for the saddle and matrix dolomites. This play went for many years without detection because of its unconventional structural setting (i.e., structural lows versus highs). Using the appropriate integrated structural-stratigraphic-diagenetic model, more hydrothermal dolomite natural gas reservoirs are likely to be discovered in the Black River of New York and in carbonates around the world. 

Evidence against the Dorag (mixing-zone) model for dolomitization along the Wisconsin arch - A case for hydrothermal diagenesis , 2006, Luczaj, J. A.

Ordovician carbonates near the Wisconsin arch represent the type locality in ancient rocks for the Dorag, or mixing-zone, model for dolomitization. Field, petrographic, and geochemical evidence suggests a genetic link between the pervasive dolomite, trace Mississippi Valley–type (MVT) minerals, and potassium (K)-silicate minerals in these rocks, which preserve a regional hydrothermal signature. Constraints were placed on the conditions of water-rock interaction using fluid-inclusion methods, cathodoluminescence and plane-light petrography, stable isotopic analyses, and organic maturity data. Homogenization temperatures of two-phase aqueous fluid inclusions in dolomite, sphalerite, and quartz range between 65 and 120°C. Freezing data suggest a Na-Ca-Mg-Cl-H2O fluid with salinities between 13 and 28 wt.% NaCl equivalent. The pervasive dolomitization of Paleozoic rocks on and adjacent to the Wisconsin arch was the result of water-rock interaction with dense brines at elevated temperatures, and it was coeval with regional trace MVT mineralization and K-silicate diagenesis. A reevaluation of the Dorag (mixing-zone) model for dolomitization, in conjunction with convincing new petrographic and geochemical evidence, has ruled out the Dorag model as the process responsible for pervasive dolomitization along the Wisconsin arch and adds to the abundant body of literature that casts serious doubt about the viability of the Dorag model in general.

John Luczaj is an assistant professor of earth science in the Department of Natural and Applied Sciences at the University of Wisconsin–Green Bay. He earned his B. S. degree in geology from the University of Wisconsin–Oshkosh. This was followed by an M.S. degree in geology from the University of Kansas. He holds a Ph.D. in geology from Johns Hopkins University in Baltimore, Maryland. His recent interests include the investigation of water-rock interaction in Paleozoic sedimentary rocks in the Michigan Basin and eastern Wisconsin. Previous research activities involve mapping subsurface uranium distributions, reflux dolomitization, and U-Pb dating of Permian Chase Group carbonates in southwestern Kansas.

Pervasive dolomitization with subsequent hydrothermal alteration in the Clarke Lake gas field, Middle Devonian Slave Point Formation, British Columbia, Canada , 2006, Lonnee J. , Machel H. G.

The Clarke Lake gas field in British Columbia, Canada, is hosted in pervasively dolomitized Middle Devonian carbonates of the Slave Point Formation. The Clarke Lake field consists mostly of pervasive matrix dolomite and some saddle dolomite, the latter varying in volume from about zero in limestones to normally 20–40% (locally up to 80%) in dolostones over any given 10-m (33-ft) core interval. Some of the saddle dolomite is replacive, some is cement, and both varieties are associated with dissolution porosity and recrystallized matrix dolomite. The major objective of this study is to identify the causes and timing of matrix and saddle dolomite formation, specifically, whether these dolomites are hydrothermal. A comprehensive petrographic and geochemical examination indicates that pervasive matrix dolomitization was accomplished by long-distance migration of halite-saturated brines during the Late Devonian toMississippian. Fluid-inclusion homogenization temperatures suggest about 150 (uncorrected) to 190jC (corrected) at the time of matrix dolomitization. These temperatures differ markedly from most published work on the dolomitized Devonian reefs in the Alberta Basin south of the Peace River arch, where pervasive matrix dolomitization was accomplished by advection of slightly modified seawater at temperatures of about 60–80jC, and where no hydrothermal influence was ever present. The saddle dolomites at Clarke Lake are not cogenetic with matrix dolomite and are not the product of hydrothermal dolomitization (sensu stricto). Instead, they formed through the hydrothermal alteration of matrix dolomite by way of invasion of a gypsum-saturated brine during periods of extremely high heat flow and regional plate-margin tectonics in the Late Devonian to Mississippian. Fluidinclusion homogenization temperatures suggest that hydrothermal alteration occurred between 230 (uncorrected) and 267jC (corrected), which is significantly higher than the maximumtemperature of about 190jC attained by the Slave Point Formation during burial. The sources of the halite- and gypsum-saturated brines are Middle Devonian evaporite depositional environments roughly 200 km (124 mi) south and/or east of Clarke Lake, near the Peace River arch

Textural, Elemental, and Isotopic Characteristics of Pleistocene Phreatic Cave Deposits (Jabal Madar, Oman), 2007, Immenhauser Adrian, Dublyansky Yuri V. , Verwer Klaas, Fleitman Dominik, Pashenko Serguei E. ,
Two main types of karst formation are commonly known: the surficial meteoric one and the subsurface (hypogenic) karst, which can be related to both carbonic (H2CO3) and sulfuric (H2S) acids. This paper documents evidence for a third, CO2-regime related, type of karst that is less commonly described. Petrographic and geochemical properties of exhumed Pleistocene phreatic cave deposits from the diapiric Jabal Madar dome in northern Oman are documented and discussed in a process-oriented context. These calcites form at the interface between two fundamentally different diagenetic and hydrogeological domains: the deep-seated, hydrothermal and the near-surficial, meteoric-vadose one. Four calcite phases are recognized: (i) acicular, (ii) blocky to stubby elongated, (iii) proto-palisade, and (iv) macro-columnar calcites. The macro-columnar calcites, forming the last stage of precipitation, are conspicuous due to their cyclical red zonation, and they form the main (geochemical) focus of this study. Fluid inclusion data point to fluid temperatures of between 30 to 50{degrees}C (monophase liquid inclusions) and elevated salinities (1.6 to 7.3 wt.% NaCl equivalent). Low carbon-isotope data (-8 to -9{per thousand}) are in agreement with the influx of soil-zone CO2 whereas decreasing {delta}18O (-15{per thousand}) values might point to mixing of saline hydrothermal and 18O depleted, meteoric freshwater, i.e., two fluid sources. Trace-element and stable-isotope data shift between the different cement phases and vary cyclically across the red zoning in macro-columnar calcites. With respect to the intra-crystal variability, these patterns are perhaps best explained in the context of redox potential. Two interpretations are presented; the one favored here suggests that the cyclical red zoning in macro-columnar calcites is controlled by Pleistocene monsoonal climate patterns

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