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Enviroscan Ukrainian Institute of Speleology and Karstology

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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 azimuth is the true bearing of a survey line, determined by measurement from an accurate survey or by observations of sun or stars [25].?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms

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KarstBase a bibliography database in karst and cave science.

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 fluid-flow (Keyword) returned 19 results for the whole karstbase:
Showing 1 to 15 of 19
Assessing the importance of conduit geometry and physical parameters in karst systems using the storm water management model (SWMM), ,
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Peterson Eric W. , Wicks Carol M. ,
SummaryQuestions about the importance of conduit geometry and about the values of hydraulic parameters in controlling ground-water flow and solute transport through karstic aquifers have remained largely speculative. One goal of this project was to assess the role that the conduit geometry and the hydraulic parameters have on controlling transport dynamics within karstic aquifers. The storm water management model (SWMM) was applied to the Devil's Icebox-Connor's Cave System in central Missouri, USA. Simulations with incremental changes to conduit geometry or hydraulic parameters were performed with the output compared to a calibrated baseline model. Ten percent changes in the length or width of a conduit produced statistically significant different fluid flow responses. The model exhibited minimal sensitivity to slope and infiltration rates; however, slight changes in Manning's roughness coefficient can highly alter the simulated output.Traditionally, the difference in flow dynamics between karstified aquifers and porous media aquifers has led to the idea that modeling of karst aquifers is more difficult and less precise than modeling of porous media aquifers. When evaluated against models for porous media aquifers, SWMM produced results that were as accurate (10% error compared to basecase). In addition, SWMM has the advantage of providing data about local flow. While SWMM may be an appropriate modeling technique for some karstic aquifers, SWMM should not be viewed as a universal solution to modeling karst systems

Thermal aspects of the East Midlands aquifer system, 1987,
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Wilson N. P. , Luheshi M. N. ,
A case study of a heat flow anomaly in the E Midlands of England is reported. The anomaly has been suggested to be an effect of water movement at depth within the E Midlands basin, with recharge to the Lower Carboniferous limestones in their outcrop, eastward movement and ascent of water up a steep faulted anticline at Eakring where the heat flow measurements were made. Numerical modelling of heat and fluid flow has been undertaken for a section running from the Peak District through Eakring to the coast. The results indicate that, although an anomaly is expected for reasonable values of hydrological parameters, its magnitude is less than that observed. The geological structure at Eakring is such that three-dimensional flow is likely to be important, and this could easily account for the discrepancy between the modelling results and the observations. The regional water flow regime has other effects on heat flow, notably the depression of heat flow above the Sherwood Sandstone aquifer

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Turner S. J. , Flindell P. A. , Hendri D. , Hardjana I. , Lauricella P. F. , Lindsay R. P. , Marpaung B. , White G. P. ,
The Ratatotok district in the Minahasa Regency of North Sulawesi, Indonesia is an area of significant gold mineralisation. Gold has been mined in the district since at least the 1850s, and intensively by the Dutch between 1900 and 1921 with a recorded production of 5,060 kg of gold. Newmont began exploring the district in 1986, and has delineated a major sediment-hosted replacement-style deposit at Mesel, and other smaller deposits in an 8 X 5 km area. A total drill-indicated resource of over 60 metric tonnes of gold ( 2 Moz) is reported for Mesel, and three of the smaller deposits. Approximately 80% of this resource is refractory. Silver grades are usually low (< 10 g/t). The Mesel deposit is similar to many Carlin-type deposits in carbonate hostrocks, alteration, geochemical signature and ore mineralogy, but is distinct in tectonic setting. The discovery of replacement-style mineralisation at Mesel, in an impure limestone within a Tertiary island arc environment, demonstrates that deposits with outward characteristics similar to Carlin-type mineralisation are not restricted to a continental setting. Carbonate sediments in the Ratatotok district were deposited in a Late Miocene restricted basin. Later compressional tectonics caused uplift that resulted in karst development in the limestone and erosion of the adjacent volcanic arc with deposition of a thick epiclastic unit. This was followed by intrusion of shallow level pre-mineral andesite into the sequence. Mineralisation at Mesel, and probably elsewhere in the district, is synchronous with the late-stage reactivation of strike-slip faults. Mineralising fluids at Mesel were focussed along steep structures sympathetic to these faults, and trapped below a relatively impermeable andesite cap rock. Hydrothermal fluids caused decalcification of the silty, more permeable carbonate units with the formation of secondary dolomite, deposition of fine arsenian pyrite, silica veinlets and gold. Volume loss due to decalcification and dolomite formation caused collapse brecciation which enhanced fluid flow and further mineralisation. This locally culminated in total decarbonation and deposition of massive silica. Late-stage stibnite occurs in structural zones within the ore deposit, whereas arsenic (as realgar and orpiment) and mercury (as cinnabar) are concentrated on the periphery. Elsewhere in the Ratatotok district, gold mineralisation is restricted to replacement-style mineralisation in permeable zones along limestone-andesite contacts, open-space-filling quartz-calcite veins and stockworks, and residual quartz-clay breccias. The residual breccias are developed in-situ, and are interpreted to form by dissolution of the wallrock limestone from around pre-existing mineralisation. This has resulted in widespread eluvial gold occurrences

The applicability of numerical models to adequately characterize ground-water flow in karstic and other triple-porosity aquifers, 1996,
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Quinlan J. F. , Davies G. J. , Jones S. W. , Huntoon P. W.

Mixed transport reaction control of gypsum dissolution kinetics in aqueous solutions and initiation of gypsum karst, 1997,
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Raines M. A. , Dewers T. A. ,
Experiments with gypsum in aqueous solutions at 25 degrees C, low ionic strengths, and a range of saturation states indicate a mixed surface reaction and diffusional transport control of gypsum dissolution kinetics. Dissolution rates were determined in a mixed flow/rotating disc reactor operating under steady-state conditions, in which polished gypsum discs were rotated at constant speed and reactant solutions were continuously fed into the reactor. Rates increase with velocity of spin under laminar conditions (low rates of spin), but increase asymptotically to a constant rate as turbulent conditions develop with increasing spin velocity, experiencing a small jump in magnitude across the laminar-turbulent transition. A Linear dependence of rates on the square root of spin velocity in the laminar regime is consistent with rates being limited by transport through a hydrodynamic boundary layer. The increase in rate with onset of turbulence accompanies a near discontinuous drop in hydrodynamic boundary layer thickness across the transition. A relative independence of rates on spinning velocity in the turbulent regime plus a nonlinear dependence of rates on saturation state are factors consistent with surface reaction control. Together these behaviors implicate a 'mixed' transport and reaction control of gypsum dissolution kinetics. A rate law which combines both kinetic mechanisms and can reproduce experimental results under laminar flow conditions is proposed as follows: R = k(t) {1 - Omega(b)() zeta [1 - (1 2(1 - Omega(b)())(1/2)]} where k(t) is the rate coefficient for transport control, and Omega(b)() is the mean ionic saturation state of the bulk fluid. The dimensionless parameter zeta(=Dm(eq)()/2 delta k() where m(eq)() = mean ionic molal equilibrium concentration, D is the diffusion coefficient through the hydrodynamic boundary layer, delta equals the boundary layer thickness and k() is the rate constant for surface reaction control) indicates which process, transport or surface reaction, dominates, and is sensitive to the hydrodynamic conditions in the reactor. For the range of conditions used in our experiments, zeta varies from about 1.4 to 4.5. Rates of gypsum dissolution were also determined in situ in a cavern system in the Permian Blaine Formation, southwestern Oklahoma. Although the flow conditions in the caverns were not determinable, there is good agreement between lab- and field-determined rates in that field rate magnitudes lie within a range of rates determined experimentally under zero to low spin velocities A numerical model coupling fluid flow and gypsum reaction in an idealized circular conduit is used to estimate the distance which undersaturated solutions will travel into small incipient conduits before saturation is achieved. Simulations of conduit wall dissolution showed-member behaviors of conduit formation and surface denudation that depend on flow boundary conditions (constant discharge or constant hydraulic gradient and initial conduit radius. Surface-control of dissolution rates. which becomes more influential with higher fluid flow velocity, has the effect that rate decrease more slowly as saturation is approached than otherwise would occur if rates were controlled by transport alone. This has the effect that reactive solutions can penetrate much farther into gypsum-bearing karst conduits than heretofore thought possible, influencing timing and mechanism of karst development as well as stability of engineered structures above karst terrain

Age of the Sherman-Type Zn-Pb-Ag Deposits, Mosquito Range, Colorado, 2000,
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Symons D. T. A. , Lewchuk M. T. , Taylor C. D. , Harris M. J. ,
The Sherman-type Zn-Pb-Ag dolomite deposits in central Colorado are hosted in dolostones of the Early Mississippian Leadville Formation. Paleomagnetic analysis, using progressive alternating field and thermal demagnetization and isothermal remanent magnetization acquisition methods, was performed on specimens from samples at 37 sites in the Sherman-type Continental Chief, Peerless, Ruby, Sacramento, and Sherman deposits, in their host rocks, in the 72 Ma Pando Porphyry sill(s) and in the ~40 Ma Leadville-type Black Cloud massive sulfide deposit. Paleomagnetic fold, contact, and breccia tests were performed to test for the antiquity of the magnetizations. The results are interpreted to indicate that the Leadville carbonates were regionally dolomitized at ~308 {} 6 (1{sigma}) Ma in the Early Pennsylvanian and that the Sherman-type deposits were emplaced at ~272 {} 18 (1{sigma}) Ma during the Early Permian after northeast-trending block faulting, karstification, and ~4 {} 1 km of sedimentary burial, possibly as the result of subsurface gravity-driven fluid flow related to the Ouachita-Marathon orogen. Following late Ouachita-Marathon or earliest Laramide (Late Cretaceous) folding, the remanence in the Sherman-type deposits and the Leadville dolostone rocks within the contact alteration zone of the 72 Ma Pando Porphyry sill(s) was reset to acquire a Late Cretaceous normal characteristic remanent magnetization. Thereafter the Black Cloud Leadville-type massive sulfide deposit was magnetized in the Eocene to acquire a reversed polarity characteristic remanent magnetization that was not found in the Sherman-type deposits

Growth of hematite and boehmite in concretions from ancient karst bauxite: clue for past climate, 2002,
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Mongelli G. ,
In the Peri-Adriatic Apulia Carbonate Platform (southern Italy), late Cretaceous karst bauxites mark an emergence period during a wet tropical climate. Bauxite formed through clay accumulation in the karst, 'in situ' bauxitization and late formation of iron-rich concretions in a water-unsaturated pedogenic environment. The concretions, which are geochemical recorders of the environment of formation, have a large core of Al-hematite surrounded by a cortex of alternating M-hematite and boehmite. Boehmite forms instead of Al-hematite at lower water activity values. Using a model of molecular diffusion and assuming the fluid flow negligible, the time necessary for growth of the concretions has been calculated. The average-sized core grew in similar to180 ka. The Al-hematite accretionary band grew in similar to180 ka whereas the boehmite accretionary band grew in similar to4.5 ka. The average bulk concretions possibly formed in 300-400 ka. The growth of the concretions is assumed to be a two-stage process. In the first stage, the core grew in a relatively long period of wet tropical climate. In the second stage, drier conditions favouring boehmite stability alternated to a wetter climate favouring Al-hematite stability. The growth of the bulk concretions is consistent with the Earth's long eccentricity cycle. (C) 2002 Elsevier Science B.V. All rights reserved

Permo-Mesozoic multiple fluid flow and ore deposits in Sardinia: a comparison with post-Variscan mineralization of Western Europe, 2002,
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Boni M, Muchez P, Schneider J,
The post-Variscan hydrothermal activity and mineralization in Sardinia (Italy) is reviewed in the framework of the geological and metallogenic evolution of Western Europe. The deposits can be grouped into (a) skarn, (b) high- to low-temperature veins and (c) low-temperature palaeokarst. The structural, stratigraphical and geochemical data are discussed. The results suggest three hydrologically, spatially, and possibly temporally, distinct fluid systems. System 1 (precipitating skarn and high-temperature veins) is characterized by magmatic and/or (?) magmatically heated, meteoric fluids of low-salinity. The source of metals was in the Variscan magmatites, or in the Palaeozoic/Precambrian basement. System 2 (low-temperature veins and palaeokarst) is represented by highly saline, Ca-rich (formation or modified meteoric) fluids. Sources of the metals were the pre-Variscan ores and carbonate rocks. System 3 is characterized by low-temperature, low-salinity fluids of meteoric origin. The hydrothermal deposits related to Systems 1 and 2 can be framed in a crustal-scale hydrothermal palaeofield', characterizing most of the post-orogenic mineralization in Variscan regions of Western and Southern Europe, allowing for local age differences of each single ore district and background effects. The suggested timing for the hydrothermal events in Sardinia is: (1) Mid-Permian (270 Ma), (2) Triassic-Jurassic. It is suggested that the Mesozoic events were related to the onset of Tethys spreading

Alligator Ridge District, East-Central Nevada: Carlin-Type Gold Mineralization at Shallow Depths, 2003,
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Nutt Constance J. , Hofstra Albert H. ,
Carlin-type deposits in the Alligator Ridge mining district are present sporadically for 40 km along the north-striking Mooney Basin fault system but are restricted to a 250-m interval of Devonian to Mississippian strata. Their age is bracketed between silicified ca. 45 Ma sedimentary rocks and unaltered 36.5 to 34 Ma volcanic rocks. The silicification is linked to the deposits by its continuity with ore-grade silicification in Devonian-Mississippian strata and by its similar{delta} 18O values (~17{per thousand}) and trace element signature (As, Sb, Tl, Hg). Eocene reconstruction indicates that the deposits formed at depths of <300 to 800 m. In comparison to most Carlin-type gold deposits, they have lower Au/Ag, Au grades, and contained Au, more abundant jasperoid, and textural evidence for deposition of an amorphous silica precursor in jasperoid. These differences most likely result from their shallow depth of formation. The peak fluid temperature (~230{degrees}C) and large{delta} 18OH2O value shift from the meteroric water line (~20{per thousand}) suggest that ore fluids were derived from depths of 8 km or more. A magnetotelluric survey indicates that the Mooney Basin fault system penetrates to mid-crustal depths. Deep circulation of meteoric water along the Mooney Basin fault system may have been in response to initial uplift of the East Humboldt-Ruby Mountains metamorphic core complex; convection also may have been promoted by increased heat flow associated with large magnitude extension in the core complex and regional magmatism. Ore fluids ascended along the fault system until they encountered impermeable Devonian and Mississippian shales, at which point they moved laterally through permeable strata in the Devonian Guilmette Formation, Devonian-Mississippian Pilot Shale, Mississippian Joana Limestone, and Mississippian Chainman Shale toward erosional windows where they ascended into Eocene fluvial conglomerates and lake sediments. Most gold precipitated by sulfidation of host-rock Fe and mixing with local ground water in zones of lateral fluid flow in reactive strata, such as the Lower Devonian-Mississippian Pilot Shale

Basin fluid flow, base-metal sulphide mineralization and the development of dolomite petroleum reservoirs, 2004,
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Gregg Jay M. ,
Saline basinal fluids, at temperatures from 60 to 250 {degrees}C, have affected almost every sedimentary basin in the world including rocks from Palaeoproterozoic to Cenozoic age. These fluids commonly precipitate base-metal sulphides (pyrite, sphalerite, galena, etc.) and associated minerals (barite, fluorite, calcite, dolomite, etc.) ranging in volume from trace amounts to large economic ore deposits. Such deposits are commonly referred to as Mississippi Valley-type (MVT) after the large Palaeozoic deposits of this kind found in the Mississippi Valley of North America. They are primarily hosted by platform carbonates, typically dolomite, and are usually associated with hydrocarbons. Dolomites not affected by mineralizing fluids commonly display micron- to decimicron-size planar textures, and have well-developed micro- and mesoporosity networks dominated by intercrystal and vug porosity. However, these and other carbonate rocks affected by basinal fluids may undergo massive geochemical and textural alteration. This occurs even when the affected rocks are distal from the main loci of sulphide mineralization. Alteration includes: dolomitization of limestone; neomorphic recrystallization of existing dolomite; and precipitation at intervals of large volumes of open-space-filling dolomite, calcite and quartz cements alternating with dissolution. Dolomitization of limestone and/or neomorphic recrystallization of dolomite, at elevated temperatures, commonly results in centimicron and larger size crystals, and development of nonplanar textures that increase pore-throat tortuosity. Open-space-filling dolomite, calcite and quartz cementation causes a dramatic reduction of porosity and blockage of pore throats. Periods of carbonate dissolution, proximal to intense sulphide mineralization, result in the development of large-scale macroporosity such as breccias that are commonly superimposed on karst and tectonic fractures. Exposure to mineralizing basinal fluids substantially alters porosity and permeability distribution, and thus the potential reservoir properties of the dolomite. The resulting reservoir may have little resemblance to its precursor. Understanding the epigenetic history of a dolomite is critical, therefore, as this will ultimately affect its development strategy and production history

Concepts and models of dolomitization: a critical reappraisal, 2004,
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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

Dissolution of limestone fractures by cooling waters: Early development of hypogene karst systems, 2005,
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Andre Bj, Rajaram H,

[1] Fracture dissolution in the early stages of karstification under hypogene conditions is investigated using a coupled numerical model of fluid flow, heat transfer, and reactive transport. Dissolution of calcite in the H2O-CO2-CaCO3 system along a cooling flow path is investigated using both equilibrium and kinetic models. During the very early stages of fracture growth, there is a positive feedback between flow, heat transfer, and dissolution. In this stage the dissolution rate is largely controlled by the retrograde solubility of calcite, and aperture growth is relatively uniform along the fracture length. There is a period of slow continuous increase in the mass flow rate through the fracture, which is followed by an abrupt rapid increase. We refer to the time when this rapid increase occurs as the maturation time. As the flow rate continues to increase after maturation, forced convective effects lead to higher fluid temperatures in the fracture, resulting in a negative feedback that slows the rate of fracture growth. The behavior of aperture growth before the maturation time can be described by a simple ordinary differential equation. The solution of this differential equation provides an estimate of the maturation time, in terms of the initial aperture, hydraulic and thermal gradients, and the change in solubility with temperature. The behavior before maturation in two-dimensional variable aperture fractures is investigated using a simplified model. The maturation time is shown to decrease with the degree of aperture variability due to highly selective growth along preferential flow paths

Methane discharge into the Black Sea and the global ocean via fluid flow through submarine mud volcanoes, 2006,
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Wallmann Klaus, Drews Manuela, Aloisi Giovanni, Bohrmann Gerhard,
During the MARGASCH cruise M52/1 in 2001 with RV Meteor we sampled surface sediments from three stations in the crater of the Dvurechenskii mud volcano (DMV, located in the Sorokin Trough of the Black Sea) and one reference station situated 15[no-break space]km to the northeast of the DMV. We analysed the pore water for sulphide, methane, alkalinity, sulphate, and chloride concentrations and determined the concentrations of particulate organic carbon, carbonate and sulphur in surface sediments. Rates of anaerobic oxidation of methane (AOM) were determined using a radiotracer (14CH4) incubation method. Numerical transport-reaction models were applied to derive the velocity of upward fluid flow through the quiescently dewatering DMV, to calculate rates of AOM in surface sediments, and to determine methane fluxes into the overlying water column. According to the model, AOM consumes 79% of the average methane flux from depth (8.9 [middle dot] 10 6[no-break space]mol a- 1), such that the resulting dissolved methane emission from the volcano into the overlying bottom water can be determined as 1.9 [middle dot] 10 6[no-break space]mol a- 1. If it is assumed that all submarine mud volcanoes (SMVs) in the Black Sea are at an activity level like the DMV, the resulting seepage represents less than 0.1% of the total methane flux into this anoxic marginal sea. The new data from the DMV and previously published studies indicate that an average SMV emits about 2.0 [middle dot] 10 6[no-break space]mol a- 1 into the ocean via quiescent dewatering. The global flux of dissolved methane from SMVs into the ocean is estimated to fall into the order of 10 10[no-break space]mol a- 1. Additional methane fluxes arise during periods of active mud expulsion and gas bubbling occurring episodically at the DMV and other SMVs

Australian Zn-Pb-Ag Ore-Forming Systems: A Review and Analysis, 2006,
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Huston David L. , Stevens Barney, Southgate Peter N. , Muhling Peter, Wyborn Lesley,
Zn-Pb-Ag mineral deposits are the products of hydrothermal ore-forming systems, which are restricted in time and space. In Australia, these deposits formed during three main periods at ~2.95, 1.69 to 1.58, and 0.50 to 0.35 Ga. The 1.69 to 1.58 Ga event, which accounts for over 65 percent of Australia's Zn, was triggered by accretion and rifting along the southern margin of Rodinia. Over 93 percent of Australia's Zn-Pb-Ag resources were produced by four ore-forming system types: Mount Isa (56% of Zn), Broken Hill (19%), volcanic-hosted massive sulfide (VHMS; 12%), and Mississippi Valley (8%). Moreover, just 4 percent of Australia's land mass produced over 80 percent of its Zn. The four main types of ore-forming systems can be divided into two 'clans,' based on fluid composition, temperature, and redox state. The Broken Hill- and VHMS-type deposits formed from high-temperature (>200{degrees}C) reduced fluids, whereas the Mount Isa- and Mississippi Valley-type deposits formed from low-temperature (<200{degrees}C), H2S-poor, and/or oxidized fluids. The tectonic setting and composition of the basins that host the ore-forming systems determine these fluid compositions and, therefore, the mineralization style. Basins that produce higher temperature fluids form in active tectonic environments, generally rifts, where high heat flow produced by magmatism drives convective fluid circulation. These basins are dominated by immature siliciclastic and volcanic rocks with a high overall abundance of Fe2. The high temperature of the convective fluids combined with the abundance of Fe2 in the basin allow inorganic sulfate reduction and leaching of sulfide from the country rock, producing reduced, H2S-rich fluids. Basins that produce low-temperature fluids are tectonically less active, generally intracratonic, extensional basins dominated by carbonate and variably mature siliciclastic facies with a relatively low Fe2 abundance. In these basins, sediment maturity depends on the paleogeography and stratigraphic position in an accommodation cycle. Volcanic units, if present, occur in the basal parts of the basins. Because these basins have relatively low heat flow, convective fluid flow is less important, and fluid migration is dominated by expulsion of basinal brines in response to local and/or regional tectonic events. Low temperatures and the lack of Fe2 prevent in-organic sulfate reduction during regional fluid flow, producing H2S-poor fluids that are commonly oxidized (i.e., {sum}SO4 > {sum}H2S). Fluid flow in the two basin types produces contrasting regional alteration systems. High-temperature fluid-rock reactions in siliciclastic-volcanic-dominated basins produce semiconformable albite-hematite-epidote assemblages, but low-temperature reactions in carbonate-siliciclastic-dominated basins produce regional K-feldspar-hematite assemblages. The difference in feldspar mineralogy is mostly a function of temperature. In both basin types, regional alteration zones have lost, and probably were the source of, Zn and Pb. The contrasting fluid types require different depositional mechanisms and traps to accumulate metals. The higher temperature, reduced VHMS- and Broken Hill-type fluids deposit metals as a consequence of mixing with cold seawater. Mineralization occurs at or near the sea floor, with trapping efficiencies enhanced by sub-surface replacement or deposition in a brine pool. In contrast, the low-temperature, oxidized Mount Isa- and Mississippi Valley-type fluids precipitate metals through thermochemical sulfate reduction facilitated by hydrocarbons or organic matter. This process can occur at depth in the rock pile, for instance in failed petroleum traps, or just below the sea floor in pyritic, organic-rich muds

Variscan veins: record of fluid circulation and Variscan tectonothermal events in Upper Palaeozoic limestones of the Moravian Karst, Czech Republic, 2006,
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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

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