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Enviroscan Ukrainian Institute of Speleology and Karstology


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Community news

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 stress, effective is stress (pressure) that is borne by and transmitted through the grain-to-grain contacts of a deposit, and thus affects its porosity or void ratio and other physical properties. in onedimensional compression, effective stress is the average grain-to-grain load per unit area in a plane normal to the applied stress. at any given depth, the effective stress is the weight (per unit area) of sediments and moisture above the water table, plus the submerged weight (per unit area) of sediments between the water table and the specified depth, plus or minus the seepage stress (hydrodynamic drag) produced by downward or upward components, respectively, of water movement through the saturated sediments above the specified depth. thus, effective stress may be regarded as the algebraic sum of the two body stresses, gravitational stress, and seepage stress. effective stress mal also be regarded as the difference between geostatic and neutral stress [21].?

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


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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
See all featured articles
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 ratios (Keyword) returned 116 results for the whole karstbase:
Showing 91 to 105 of 116
Observations on the Cave-Associated Beetles (Coleoptera) of Nova Scotia, Canada, 2009,
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Moseley M.
The cave-associated invertebrates of Nova Scotia constitute a fauna at a very early stage of post-glacial recolonization. The Coleoptera are characterized by low species diversity. A staphylinid Quedius spelaeus spelaeus, a predator, is the only regularly encountered beetle. Ten other terrestrial species registered from cave environments in the province are collected infrequently. They include three other rove-beetles: Brathinus nitidus, Gennadota canadensis and Atheta annexa. The latter two together with Catops gratiosus (Leiodidae) constitute a small group of cave-associated beetles found in decompositional situations. Quedius s. spelaeus and a small suite of other guanophiles live in accumulations of porcupine dung: Agolinus leopardus (Scarabaeidae), Corticaria serrata (Latrididae), and Acrotrichis castanea (Ptilidae). Two adventive weevils Otiorhynchus ligneus and Barypeithes pellucidus (Curculionidae) collected in shallow cave passages are seasonal transients; Dermestes lardarius (Dermestidae), recorded from one cave, was probably an accidental (stray). Five of the terrestrial beetles are adventive Palaearctic species. Aquatic beetles are collected infrequently. Four taxa have been recorded: Agabus larsoni (Dytiscidae) may be habitual in regional caves; another Agabus sp. (probably semivittatus), Dytiscus sp. (Dytiscidae), and Crenitis digesta (Hydrophilidae) are accidentals. The distribution and ecology of recorded species are discussed, and attention is drawn to the association of beetles found in a Nova Scotia ice cave.

MORPHOLOGY AND GENESIS OF THE MAIN ORE BODY AT NANISIVIKZINC/LEAD MINE, BAFFIN ISLAND, CANADA: AN OUTSTANDING EXAMPLEOF PARAGENETIC DISSOLUTION OF CARBONATE BEDROCKS WITHPENE-CONTEMPORANEOUS PRECIPITATION OF SULFIDES AND GANGUEMINERALS, 2009,
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Ford D.

Nanisivik (Inuit – “the place where they find things’) zinc/lead mine is located at Lat. 73o N in northwestern Baf?n Island. The host rock is a Proterozoic platform carbonate 260-800 m thick, medium to massively bedded and pervasively dolomitized. It rests on mixed shales and shaly dolomites, and is overlain by 150+ m of further shales functioning as an aquitard. These formations were buried by later Proterozoic strata, uplifted, eroded and buried again in a Cambrian sedimentary basin. The ore-grade deposits are contained within a horst block of the dolomites dipping NW at 15o across it. Graben to the north and south are roofed in the overlying shales. The principal deposit, the Main Ore, is of zinc, lead and iron sul?de precipitates plus gangue minerals, chie?y secondary dolomite. It extends for three km E-W along the horst. It is horizontal, at ~300 m above sea level and terminated at both ends by modern valley entrenchments. The Main Ore body is consistently ~100 m in width and ?ve-seven m in depth. This wide ceiling is a nearly planar, horizontal corrosion bevel. The sulfdes scarcely extend above it anywhere. Within the Main Ore two or more generations of tapered ?ns of dolomite in situ extend from both south (updip) and north (downdip) walls into the cavity. Fin surfaces truncate the bedding. Edges of ?ns are sinuous, some meandering with a wavelength of ~50 m. Very sharp, horizontal corrosion notches 20-30 cm high extend into the dolomite walls for at least 20 m (the limit of deep crosscuts in the mine). They are ?lled with layered pyrites which continue out into the ore body as regular sheets truncating earlier, dipping mineral layers until they themselves are truncated by later fillings. One exceptional notch, one meter deep, is at least 350 m in breadth. The ore displays four sedimentary modes: (i) regular layers settled or precipitated onto the cavity floor; (ii) chaotic polymict breccias suggestive of channel cut-and-?ll episodes; (iii) the horizontal pyrite sheets in corrosion notches; (iv) minor metasomatic replacements of dolomite. The ore cavity was created by paragenesis in a channel ?ow mode, with ore and gangue deposition on the floor taking place in tandem with dissolutional cavity creation upwards,. Principal deposition took place when a fluid interface could be rigorously maintained. Fluid inclusions indicate derivation of the metals from exchange reactions with metalliferous sediments (the underlying shales), indicating low water/rock ratios and moderate temperatures. The ore fluids were similar to oil field brines. Sulfur isotope fractionations indicate temperatures of 90-150 +/-40o C, suggesting that the Main Ore formed along a gas/brine interface at a depth of at least 1600 m as a consequence of ?uid expulsion in the subsiding Cambrian sedimentary basin.


Thorium-uranium ratios of rocks and speleothems based on the high-resolution gamma-spectrometry, 2009,
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Gudzenko V. V.

Impacts of Alterations of Organic Inputs on the Bacterial Community within the sediments of Wind Cave, South Dakota, USA, 2009,
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Chelius M. K. , Beresford G. , Horton H. , Quirk M. , Selby G. , Simpson R. T. , Horrocks R. , Moore J. C.

Père Noël cave climatology (air and water temperature, PCO2), hydrology (drip rate, conductivity) and geochemistry of water and calcite deposits (δ18O, δ13C, Mg/Ca and Sr/Ca) where studied to better interpret stable isotopic and trace element variations of speleothems. Results of an automated monitoring station and of manual sampling between 1991 and 1998 have demonstrated the highly seasonal signal of drip rate, its control by water excess and rainfall, and, at a shorter scale to air pressure changes. The modern calcite deposit study suggests a relationship between cave calcite isotopic composition (δ18O and δ13C) and drip rate likely due to variations in degree of isotopic equilibrium during calcite precipitation. δ18O and δ13C of the calcite are therefore, through drip rate, linked to water recharge. Mg/Ca and Sr/Ca ratios of Père Noël cave calcite, depend closely on the residence time of the water, and therefore are also linked to drip rate and therefore to water recharge. This crossed link of δ18O and δ13C as of Mg/Ca and Sr/Ca to water recharge may explain the very similar variations of these four parameters along the longitudinal axis of a Holocene stalagmite, but it may also be the consequence of kinetic effects during calcite precipitation as suggested by similar variations of the four parameters along a single layer of the Holocene stalagmite.


Observations on the Cave-Associated Beetles (Coleoptera) of Nova Scotia, Canada, 2009,
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Moseley, M.

The cave-associated invertebrates of Nova Scotia constitute a fauna at a very early stage of post-glacial recolonization. The Coleoptera are characterized by low species diversity. A staphylinid Quedius spelaeus spelaeus, a predator, is the only regularly encountered beetle. Ten other terrestrial species registered from cave environments in the province are collected infrequently. They include three other rove-beetles: Brathinus nitidus, Gennadota canadensis and Atheta annexa. The latter two together with Catops gratiosus (Leiodidae) constitute a small group of cave-associated beetles found in decompositional situations. Quedius s. spelaeus and a small suite of other guanophiles live in accumulations of porcupine dung: Agolinus leopardus (Scarabaeidae), Corticaria serrata (Latrididae), and Acrotrichis castanea (Ptilidae). Two adventive weevils Otiorhynchus ligneus and Barypeithes pellucidus (Curculionidae) collected in shallow cave passages are seasonal transients; Dermestes lardarius (Dermestidae), recorded from one cave, was probably an accidental (stray). Five of the terrestrial beetles are adventive Palaearctic species. Aquatic beetles are collected infrequently. Four taxa have been recorded: Agabus larsoni (Dytiscidae) may be habitual in regional caves; another Agabus sp. (probably semivittatus), Dytiscus sp. (Dytiscidae), and Crenitis digesta (Hydrophilidae) are accidentals. The distribution and ecology of recorded species are discussed, and attention is drawn to the association of beetles found in a Nova Scotia “ice cave”.


Mixing and transport of water in a karst catchment: a case study from precipitation via seepage to the spring, 2009,
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Schwarz K. , Barth J. A. C. , Postigorebollo C. , Grathwohl P.

One of the best-known and largest karst areas in Germany, the Blautopf Catchment, offers unique access to waters of the unsaturated zone through a large cave system. It was investigated with stable isotopes (18O/16O and D/H ratios expressed in permille = ‰) in precipitation, seepageand groundwater as tracers for water flow, mixing, and storage. The precipitation showed a distinct seasonality with _18O values between −2.9 and −24.6‰ during summer and winter, respectively. However, the isotope signals in seepage water in the caves as well as the discharge were almost completely buffered and ranged around an average _18O value of −10‰. This value was also close to the long-term average value of local precipitation, −9.3‰. The homogeneous isotopic composition of the Blautopf Spring was unexpected, as its highly variable discharge (0.3 to 32m3 s−1) is typical for a fast responsive karst system. These isotopic similarities could be explained by nearly complete mixing of the water already in the vadose zone. The data set therefore presents a case study to narrow down zones of mixing in karst catchments. It also confirms the minor role of the fast conduit system in the water balance of the Blautopf Catchment.

 


Polyphase speleogenesis in Lick Creek Cave, Little Belt Mountains, Montana, USA, 2010,
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Carriere K. L. , Machel H. G. , Hopkins J. C.

Lick Creek Cave in northern Montana (USA) is hosted in limestones of the Lower Carboniferous Madison Group near Tiger Butte, an Eocene quartz–syenite porphyry intrusive dome. The cave is located within the zone of contact metamorphism of the dome, which crops out 300 m from the cave entrance. The cave consists of two genetically distinct cave systems separated by a fracture zone: (1) a 80 50 m dome-shaped cavern in breccias of a Carboniferous paleocave, and (2) anastomosing conduits 2–10 m across, parallel to the bedding of the Madison Group and extending 100 m up dip to the present cave entrance. The conduits are further subdivided into a tectonised and a maze zone and are variably decorated in several combinations by phreatic isopachous calcite spar cements, with crystals up to several cm long, and with vadose speleothems, including stalactite–stalagmite pairs, flowstone, corallite (cave popcorn), and moonmilk. Our database is comprised of field survey, thin section, XRD, and SEM observations along with 118 ?18O/?13C analyses and 27 87Sr/86Sr measurements from samples of county rock and speleothems. The limestone matrix samples with the heaviest ?18O/?13C ratios are interpreted as the least recrystallised proxy to Tournaisian seawater. Stable isotope data from other Carboniferous limestones, including paleocave breccias, follow a regional meteoric pathway established elsewhere in the Madison for the Late Carboniferous transition from greenhouse to icehouse conditions. Isopachous calcite spar cements from the conduit zone are interpreted as the result of late-stage, Eocene hydrothermal fluid circulation. Stalactite–stalagmite pairs, flowstone, corallite, and moonmilk carry a signature similar to modern or Quaternary high-alpine meteoric water. Previous workers have determined separate hydrothermal and meteoric ?18O/?13C stable isotope fields for speleothems in caves in Carboniferous limestones from the Black Hills, South Dakota. We re-define the stable isotope ranges for meteoric and magmatic–hydrothermal calcites based on a comparison of stable isotope data from the Little Belt Mountains with those from the Black Hills. We further propose that the hydrothermal calcite end-member ?18O composition is around ?20‰ PDB, represented by the lowest oxygen isotope values from all data sets, with a corresponding ?13C of about ?7‰ PDB. Sr-isotope data from speleothems, Carboniferous limestone wall rocks, and from the igneous intrusion itself support the interpretation of an Eocene hydrothermal speleogenic event. The integration of petrographic and geochemical data shows that Lick Creek Cave is the result of polyphase speleogenesis in three major episodes: (1) Middle to Late Carboniferous, (2) Eocene, and (3) (sub-)Recent to Recent. The Carboniferous and (sub-)Recent to Recent speleogenesis appear epigenic, i.e., driven by surface-derived waters, whereas the Eocene event was hypogenic, i.e., driven by ascending hydrothermal waters. Each of the three major speleogenic events probably consisted of two or more distinct “phases”, but our database does not permit these phases to be resolved with certainty.


Community Structure of Subsurface Biofilms in the Thermal Sulfidic Caves of Acquasanta Terme, Italy, 2010,
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Jones D. S. , Tobler D. J. , Schaperdoth I. , Mainiero M. , Macalady J. L.

We performed a microbial community analysis of biofilms inhabiting thermal (35 to 50°C) waters more than 60m below the ground surface near Acquasanta Terme, Italy. The groundwater hosting the biofilms has 400 to 830 mkM sulfide, <10 mkM O2, pH of 6.3 to 6.7, and specific conductivity of 8,500 to 10,500 mkS/cm. Based on the results of 16S rRNA gene cloning and fluorescent in situ hybridization (FISH), the biofilms have low species richness, and lithoautotrophic (or possibly mixotrophic) Gamma- and Epsilonproteobacteria are the principle biofilm architects. Deltaproteobacteria sequences retrieved from the biofilms have <90% 16S rRNA similarity to their closest relatives in public databases and may represent novel sulfate-reducing bacteria. The Acquasanta biofilms share few species in common with Frasassi cave biofilms (13°C, 80 km distant) but have a similar community structure, with representatives in the same major clades. The ecological success of Sulfurovumales-group Epsilonproteobacteria in the Acquasanta biofilms is consistent with previous observations of their dominance in sulfidic cave waters with turbulent water flow and high dissolved sulfide/oxygen ratios.


Recent developments on morphometric analysis of karst caves, 2011,
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Piccini, Leonardo

Nowadays, the use of computers and the digital techniques for survey processing easily allows to carry out morphometric analysis of caves and karst systems. Morphometric indices have been proposed by many authors in order to describe the genetic features of some particular types of caves, such as coastal ones, maze caves or isolated voids. Large cave systems can be analyzed through the reconstruction of a 3D model. The digital model can be used to evaluate the role of the structural setting or the evolution stages through the recognizing of particular levels where epi-phreatic passages are more developed. These levels are particularly significant when a lithological or structural control can be excluded. Some morphometric indices, obtained by the ratios of simple dimension parameters of caves, allow the statistical analysis of large databases, collected in the regional speleological inventories, in the attempt to recognize different geomorphic populations of caves. Further studies and a greater number of analysis could allow to use these morphometric indices to distinguish genetic categories of caves and to get a useful instrument for the study of the evolution of karst areas.


Recent developments on morphometric analysis of karst caves, 2011,
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Piccini L.

Nowadays, the use of computers and the digital techniques for survey processing easily allows to carry out morphometric analysis of caves and karst systems. Morphometric indices have been proposed by many authors in order to describe the genetic features of some particular types of caves, such as coastal ones, maze caves or isolated voids. Large cave systems can be analyzed through the reconstruction of a 3D model. The digital model can be used to evaluate the role of the structural setting or the evolution stages through the recognizing of particular levels where epi-phreatic passages are more developed. These levels are particularly significant when a lithological or structural control can be excluded. Some morphometric indices, obtained by the ratios of simple dimension parameters of caves, allow the statistical analysis of large databases, collected in the regional speleological inventories, in the attempt to recognize different geomorphic populations of caves. Further studies and a greater number of analysis could allow to use these morphometric indices to distinguish genetic categories of caves and to get a useful instrument for the study of the evolution of karst areas.


The first cave occurrence of orpiment (As₂S₃) from the sulfuric acid caves of Aghia Paraskevi (Kassandra Peninsula, N. Greece), 2011,
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Lazaridis Georgios, Melfos Vasilios, Papadopoulou Lambrini

Orpiment, tamarugite and pickeringite occur in close association above the surface of thermal water cave pools in the active sulfuric acid caves of Aghia Paraskevi on the Kassandra peninsula, northern Greece. Gypsum also occurs as small interstitial crystals or encrustations. Orpiment is of high significance since it has not previously been reported as a cave mineral. In addition, tamarugite and pickeringite rarely occur in karst caves. Water from a borehole and a spring is of Na-Cl type and contains traces of CO2 and H2S. The B/Cl ratios indicate seawater participation with a possible mixing with geothermal water of meteoric origin. Oxidation of fumarolic H2S and incorporation of seawater is a possible cause for the deposition of tamarugite. Orpiment accumulated from vapors under sub-aerial conditions at low temperatures in acidic conditions through an evaporation-condensation process. Fluid cooling and/or acidification of the solution resulting from H2S oxidation were responsible for orpiment precipitation. Oxidation of H2S to sulfuric acid dissolved the limestone bedrock and deposited gypsum.


Morphometric analysis of three-dimensional networks of karst conduits, 2011,
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Pardoiguzquiza Eulogio, Duranvalsero Juan J. , Rodriguezgaliano Victor

The main idiosyncrasy of a typical karst system is the presence of a three-dimensional network of conduits behaving as drains in the system and being responsible of both the quick response of karst springs to rainfall events and the complex distribution of solutes in the system. A morphometric analysis of the three-dimensional geometry of conduits provides quantitative measures that can be used in a range of applications. These morphometric parameters can be used as descriptors of the underground geomorphology, they provide information on speleogenesis processes, they can be correlated with karst denudation ratios, they can be used to control the simulation of realistic stochastic karst networks of conduits, and they can be correlated with hydrogeologic behaviour of the karst system. The main purpose of this paper is to define, describe and illustrate a range of morphometric indexes and morphometric functions that can be calculated nowadays because the availability of three-dimensional topographies provided by speleological work and the availability of the computational and graphical power provided by modern computers. Some of the morphometric parameters describe the existence of preferential directions of karstification, others describe the kartification along the vertical and the possible presence of inception horizons. Other indexes describe the shape complexity of the karstic network, whilst other indexes describe spatial variability of the conduit geometry, and other parameters give account of the connectivity of the three-dimensional network. The morphometric analysis is illustrated with a three-dimensional karstic network in Southern France.
Research highlights


Modelling of slope processes on karst , 2011,
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Stepinik Uro, Kosec Gregor

The present paper is concerned with the modelling of the karst slope processes. A simple straightforward one dimensional physical model is introduced in order to assess basic behaviour of the slope development. The model takes in account mass continuity of weathered material, the mechanical and chemical weathering of the bedrock. The paper focuses on the slope formation
with respect to the ratios between different magnitudes of governing processes (mechanical and chemical weathering and mass movement). The introduced approach representsa first step in understanding slope processes and does not pose a realistic quantitative comparison with field measurements. However, the results gathered with the model show good qualitative
agreement with the field observations. Three different representative cases are studied: dominant mechanical weathering
case, balanced mechanical and chemical weathering case and dominant chemical weathering case.


Geochemical/isotopic evolution of Pb-Zn deposits in the Central and Eastern Taurides, Turkey, 2011,
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Hanilci N. , Ozturk H.

The Central and Eastern Taurides contain numerous carbonate-hosted Pb-Zn deposits, mainly in Devonian and Permian dolomitized reefal-stramatolitic limestones, and in massive Jurassic limestones. We present and compare new fluid inclusion and isotopic data from these ore deposits, and propose for the first time a Mississippi Valley-type (MVT) mode of origin for them. Fluid inclusion studies reveal that the ore fluids were highly saline (13-26% NaCl equiv.), chloride-rich (CaCl2) brines, and have average homogenization temperatures of 112°C, 174.5°C, and 211°C for the Celal Dag, Delikkaya, and Ayrakl deposits, respectively. Furthermore, the ?34S values of carbonate-hosted Pb-Zn deposits in the Central and Eastern Taurides vary between -5.4‰ and +13.70‰. This indicates a possible source of sulphur from both organic compounds and crustal materials. In contrast, stable sulphur isotope data (average ?34S -0.15‰) for the Cadrkaya deposit, which is related to a late Eocene-Oligocene (?) granodioritic intrusion, indicates a magmatic source. The lead isotope ratios of galena for all investigated deposits are heterogeneous. In particular, with the exception of the Sucat district, all deposits in the Eastern (Delikkaya, Ayrakl, Denizovas, Cadrkaya) and Central (Katranbasi, Kucuksu) Taurides have high radiogenic lead isotope values (206Pb/204Pb between 19.058 and 18.622; 207Pb/204Pb between 16.058 and 15.568; and 208Pb/204Pb between 39.869 and 38.748), typical of the upper continental crust and orogenic belts. Fluid inclusion, stable sulphur, and radiogenic lead isotope studies indicate that carbonate-hosted metal deposits in the Eastern (except for the Cadrkaya deposit) and the Central Taurides are similar to MVT Pb-Zn deposits described elsewhere. The primary MVT deposits are associated with the Late Cretaceous-Palaeocene closure of the Tethyan Ocean, and formed during the transition from an extensional to a compressional regime. Palaeogene nappes that typically limit the exposure of ore bodies indicate a pre-Palaeocene age of ore formation. Host rock lithology, ore mineralogy, fluid inclusion, and sulphur + lead isotope data indicate that the metals were most probably leached from a crustal source such as clastic rocks or a crystalline massif, and transported by chloride-rich hydrothermal solutions to the site of deposition. Localization of the ore deposits on autochthonous basement highs indicates long-term basinal fluid migration, characteristic of MVT depositional processes. The primary MVT ores were oxidized in the Miocene, resulting in deposition of Zn-carbonate and Pb-sulphate-carbonate during karstification. The ores underwent multiple cycles of oxidation and, in places, were re-deposited to form clastic deposits. Modified deposits resemble the 'wall-rock replacement' and the 'residual and karst fill' of non-sulphide zinc deposits and are predominantly composed of smithsonite


Aqueous Geochemical Evidence of Volcanogenic Karstification: Sistema Zacaton, Mexico, 2011,
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Gary M. O. , Doctor D. H. , Sharp J. M.

The Sistema Zacatón karst area in northeastern Mexico (Tamaulipas state) is limited to a relatively focused area (20 km2) in a carbonate setting not prone to extensive karstification. The unique features found here are characteristic of hydrothermal karstification processes, represent some of the largest phreatic voids in the world, and are hypothesized to have formed from interaction of a local Pleistocene magmatic event with the regional groundwater system. Aqueous geochemical data collected from five cenotes of Sistema Zacatón between 2000 and 2009 include temperature (spatial, temporal, and depth profiles), geochemical depth profiles, major and trace ion geochemistry, stable and radiogenic isotopes, and dissolved gases. Interpretation of these data indicates four major discoveries: 1) rock-water interaction occurs between groundwater, the limestone matrix, and local volcanic rocks; 2) varying degrees of hydrogeological connection exist among cenotes in the system as observed from geochemical signatures; 3) microbially-mediated geochemical reactions control sulfur and carbon cycling and influence redox geochemistry; and 4) dissolved gases are indicative of a deep volcanic source. Dissolved 87Sr/86Sr isotope ratios (mean 0.70719) are lower than those of the surrounding Cretaceous limestone (0.70730-0.70745), providing evidence of groundwater interaction with volcanic rock, which has a 87Sr/86Sr isotope ratio of 0.7050. Discrete hydraulic barriers between cenotes formed in response to sinkhole formation, hydrothermal travertine precipitation, and shifts in the local water table, creating relatively isolated water bodies. The isolation of the cenotes is reflected in distinct water chemistries among them. This is observed most clearly in the cenote Verde where a water level 4-5 meters lower than the adjacent cenotes is maintained, seasonal water temperature variations occur, thermoclines and chemoclines exist, and the water is oxic at all depths. The surrounding cenotes of El Zacatón, Caracol, and La Pilita show constant water temperatures both in depth profile and in time, have similar water levels, and are almost entirely anoxic. A sulfur (H2S) isotope value of δ34S = -1.8 ‰ (CDT) in deep water of cenote Caracol, contrasted with two lower sulfur isotopic values of sulfide in the water near the surface of the cenote (δ34S = -7 ‰ and -8 ‰ CDT). These δ34S values are characteristic of complex biological sulfur cycling where sulfur oxidation in the photic zone results in oxidation of H2S to colloidal sulfur near the surface in diurnal cycles. This is hypothesized to result from changes in microbial community structure with depth as phototropic, sulfur-oxidizing bacteria become less abundant below 20 m. Unique microbial communities exist in the anoxic, hydrothermal cenotes that strongly mediate sulfur cycling and likely influence mineralization along the walls of these cenotes. Dissolved CO2 gas concentrations ranged from 61-173 mg/L and total dissolved inorganic carbon (DIC) δ13C values measured at cenote surfaces ranged from -10.9 ‰ to -11.8 ‰ (PDB), reflecting mixed sources of carbon from carbonate rock dissolution, biogenic CO2 and possibly dissolved CO2 from volcanic sources. Surface measurements of dissolved helium gas concentrations range from 50 nmol/kg to 213 nmol/kg. These elevated helium concentrations likely indicate existence of a subsurface volcanic source; however, helium isotope data are needed to test this hypothesis. The results of these data reflect a speleogenetic history that is inherently linked to volcanic activity, and support the hypothesis that the extreme karst development of Sistema Zacatón would likely not have progressed without groundwater interaction with the local igneous rocks 


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