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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 homogeneous fluid is a fluid that occurs in a single phase [16].?

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 deformation (Keyword) returned 96 results for the whole karstbase:
Showing 31 to 45 of 96
Baiyun cave in Naigu Shilin, Yunnan karst, China, 2001,
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Sebela S. , Slabe T. , Kogovsek J. , Liu H. , Pruner P. ,
The Baiyun cave is a 380 m long karst cave in the Naigu Shilin, situated 70 km southeast of Kunming, Yunnan Province, China. The prevailing orientations of the cave passages are N110 degrees -120 degreesE and NO degrees -IO degreesW and those of the fissures in the cave are N30 degrees -40 degreesW and N20 degrees -30 degreesW. The cave is developed in the thick-bedded Lower Permian Qixia Formation. The cave has an active water flow and is currently at the near water-table stage. There are large amounts of different infills of cave sediments. The cave shows different stages of paragenesis. The palaeomagnetic analysis of cave sediments shows that their ages are younger than 780 ka B.P. (the Brunhes Chron). The upper part of the sampled profile belongs to the reverse Blake event (112.3-117.9 ka B.P.). The formation of the Baiyun cave is directly connected with the development of the Naigu Shilin. The formation of karst underground and surface features depends on the regional tectonic deformation and the Cenozoic extension of the study area

The stratigraphical record and activity of evaporite dissolution subsidence in Spain, 2001,
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Gutierrez F. , Orti F. , Gutierrez M. , Perezgonzalez A. , Benito G. , Prieto J. G. , Valsero J. J. D. ,
The evaporite formations tin outcrop and at shallow depth) cover an extensive area of the Spanish territory. These soluble sediments are found in diverse geological domains and record a wide time span from the Triassic up to the present day. Broadly, the Mesozoic and Paleogene formations (Alpine cycle) are affected by compressional structures, whereas the Neogene (post-orogenic) sediments remain undeformed. The subsidence caused by subsurface dissolution of the evaporites (subjacent karst) takes place in three main types of stratigraphical settings: a) Subsidence affecting evaporite-bearing Mesozoic and Tertiary successions (interstratal karst); b) Subsidence in Quaternary alluvial deposits related to the exorheic evolution of the present-day fluvial systems (alluvial or mantled karst); c) Subsidence in exposed evaporites (uncovered karst). These types may be represented by paleosubsidence phenomena (synsedimentary and/or postsedimentary) recognizable in the stratigraphical record, or by equivalent currently active or modem examples with surface expression. The interstratal karstification of the Mesozoic marine evaporites and the consequent subsidence of the topstrata is revealed by stratiform collapse breccias and wedge-outs in the evaporites grading into unsoluble residues. In several Tertiary basins, the sediments overlying evaporites locally show synsedimentary and/or postsedimentary subsidence structures. The dissolution-induced subsidence coeval to sedimentation gives place to local thickenings in basin-like structures with convergent dips and cumulative wedge out systems. This sinking process controls the generation of depositional environments and lithofacies distribution. The postsedimentary subsidence produces a great variety of gravitational deformations in the Tertiary supra-evaporitic units including both ductile and brittle structures (flexures, synforms, fractures, collapse and brecciation). The Quaternary fluvial terrace deposits on evaporite sediments show anomalous thickenings (> 150 m) caused by a dissolution-induced subsidence process in the alluvial plain which is balanced by alluvial aggradation. The complex space and time evolution pattern of the paleosubsidence gives place to intricate and anarchical structures in the alluvium which may be erroneously interpreted as pure tectonic deformations. The current subsidence and generation of sinkholes due to suballuvial karstification constitutes a geohazard which affects to large densely populated areas endangering human safety and posing limitations to the development. An outstanding example corresponds to Calatayud historical city, where subsidence severely damages highly valuable monuments. The subsidence resulting from the underground karstification of evaporites has determined or influenced the generation of some important modem lacustrine basins like Gallocanta, Fuente de Piedra and Banyoles lakes. The sudden formation of sinkholes due to the collapse of cave roofs is relatively frequent in some evaporite outcrops. Very harmful and spectacular subsidence activity is currently occurring in the Cardona salt diapir where subsidence has been dramatically exacerbated by mining practices

Quaternary tectonics: Influence on the structure of two karstic aquifers of Languedoc (France), 2001,
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Josnin J. Y. ,
Our research focuses on the effect of Quaternary tectonics on the organization of the conduit network of karst ground water flow. In the Languedoc region, the major karstic systems are developed in Malm and Lower Cretaceous platform limestones. Most of these systems are polygenetic, their genesis and evolution having been controlled by fracturing that occurred during major tectonic phases (ante-Senonian, Eocene, Oligocene, Aquitanian, Pliocene). These complex karst systems were reactivated following Messinian eustatic events, under tectonic conditions which are not well-known, particularly those that occurred during the Quaternary. Small scale deformations and a lack of seismic activity make characterization of current tectonics in Mediterranean Languedoc difficult. The presence of vertical offsets, however, demonstrates that there are active faults in the interior of or in proximity to karst systems. In two karst aquifers within the Garden basin, we have observed a correlation between the orientations of active faults and the principal karst conduits. In the Mialet basin, we demonstrate that erosion resulting from post-Miocene uplift (and so changes of boundary conditions) divides the aquifer into smaller, independent units. In the St Chaptes basin, we reconstruct the history of the karst, proposing that tectonic and eustatic events were predominant in the karstification process and that the climatic conditions were only of secondary importance. We also show how the reactivation of faults can lead to the unblocking of abandoned karst conduits, allowing their reintroduction into the active flow system, a phenomenon that can be explained by the combined influence of the present stress field and hydraulic gradients. This work, which represents a preliminary study, leads to hypotheses that we will subsequently validate through different successive modelings

Recent active faults in Belgian Ardenne revealed in Rochefort Karstic network (Namur Province, Belgium), 2001,
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Vandycke S. , Quinif Y. ,
This paper presents observations of recent faulting activity in the karstic network of the Rochefort Cave (Namur Province, Belgium, Europe). The principal recent tectonic features are bedding planes reactivated as normal faults, neo-formatted normal faults in calcite flowstone, fresh scaling, extensional features, fallen blocks and displacement of karstic tube. The seismotectonic aspect is expanded by the presence of fallen blocks where normally the cavity must be very stable and in equilibrium. Three main N 070degrees fault planes and a minor one affect, at a decimetre scale, the karst features and morphology. The faults are still active because recent fresh scaling and fallen blocks are observable. The breaking of Holocene soda straw stalactites and displacements of artificial features observed since the beginning of the tourist activity, in the last century, also suggest very recent reactivation of these faults. This recent faulting can be correlated to present-day tectonic activity, already evidenced by earthquakes in the neighbouring area. Therefore, karstic caves are favourable sites for the observation and the quantification of recent tectonic activity because they constitute a 3-D framework, protected from erosion. Fault planes with this recent faulting present slickensides. Thus a quantitative analysis in term of stress inversion, with the help of striated faults, has permitted to reconstruct the stress tensor responsible for the brittle deformation. The principal NW-SE extension (sigma(3) horizontal) is nearly perpendicular to that of the present regional stress as illustrated by the analysis of the last strong regional earthquake (Roermond, The Netherlands) in 1992. During the Meso-Cenozoic, the main stress tectonics recorded in this part of the European platform is similar to the present one with a NE-SW direction of extension. The discrepancy between the regional stress field and the local stress in the Rochefort cave can be the result of the inversion of the sigma(2) and sigma(3) axes of the stress ellipsoid due to its symmetry or of a local modification at the ground surface of the crustal stress field as it has been already observed in active zones

Water-upwelling pipes and soft-sediment-deformation structures in lower Pleistocene calcarenites (Salento, southern Italy), 2001,
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Massari F. , Ghibaudo G. , D'alessandro A. , Davaud E. ,
A thin sedimentary blanket, consisting mostly of subtidal, unconformity-bounded calcarenite units, was deposited in the small Novoli graben (Apulian foreland, southern Italy) in Pliocene-Pleistocene time. In a limited part of the study area the lower Pleistocene 'Calcarenite di Gravina,' forming the thicker part of this blanket, is crossed by continuous to discontinuous cylindrical pipes as much as 12 m high, most commonly consisting of stacked concave- upward laminae, locally grading upward into soft-sediment-deformation features and large dishes. The evidence favors an origin linked to upwelling of overpressured groundwater from a large karstic reservoir hosted in the Mesozoic carbonate rocks; the reservoir periodically developed a relatively high hydrostatic head due to Tertiary to Pleistocene cover acting as an aquitard or aquiclude. As a result, submarine springs were generated, the activity of which was primarily controlled by relative sea-level fluctuations. It is suggested that the pipes were located in those points where the hydrostatic pressure was sufficient to fluidize the overlying sediment and could be released without notably affecting the surrounding sediments. Some pipes cross calcarenitic infills of karstic sinkholes developed in the underlying units, whereas others follow the course of vertical to high-angle extensional synsedimentary tectonic fractures generated when the calcarenites were still in an unconsolidated to semiconsolidated state. The former relationships suggest that vertical routes of water upwelling during highstand of base level commonly coincided with axes of vadose solution during base-level lowstand; the latter suggest that opening of fractures enhanced the connection of the deep aquifer with the surface, hence intensifying water upwelling. We think that fluidization along the fractures was not hindered by the partially coherent state, and that pipes with a cylindrical geometry could form in spite of the planarity of the fractures. The formation of the pipes and their internal structure of stacked concave-upward laminae is thought to be consistent with a process of fluidization due to through-flowing waters. We believe that essential in this process is the role of upward-migrating transient water-filled cavities, akin to the voidage waves (Hassett's [1961a, 1961b] parvoids) experimentally reproduced by several authors in liquid fluidized beds, and regarded as true instability phenomena of a fluidized suspension occurring above minimum fluidization velocity. It is suggested that the process is akin to the production of the dish structure. It consists of the filling of transient, upward-migrating, water-filled cavities through steady fallout of particles from the cavity roof, their redeposition in a more consolidated state, and subsidence of the roof due to water seepage upward from the cavity. The process was accompanied by segregation of grains according to their size and density, as well by elutriation of finest particles, and led to a new pattern of sediment texture, packing, and fabric with respect to the surrounding calcarenites

Late Archaean foreland basin deposits, Belingwe greenstone belt, Zimbabwe, 2001,
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Hofmann A. , Dirks P. H. G. M. , Jelsma H. A. ,
The c. 2.65 Ga old sedimentary Cheshire Formation of the Belingwe greenstone belt (BDB), central Zimbabwe, has been studied in detail for the first time to shed some light on the much debated evolution of this classical belt. The Cheshire Formation rests sharply on a mafic volcanic unit (Zeederbergs Formation) and comprises a basal, eastward-sloping carbonate ramp sequence built of shallowing-upward, metre-scale sedimentary cycles. The cycles strongly resemble Proterozoic and Phanerozoic carbonate cycles and might have formed by small-scale eustatic sea level changes. The top of the carbonate ramp is represented by a karst surface. The carbonates are overlain by and grade laterally to the east into deeper water (sub-wave base) siliciclastic facies. Conglomerate, shale and minor sandstone were deposited by high- to low-density turbidity currents and were derived from the erosion of Zeederbergs-like volcanic rocks from the east. Shortly after deposition, the Cheshire Formation and underlying volcanics were affected by a northwest-directed thrusting event. Thrusting gave rise to the deformation of semi-consolidated sediments and resulted in the juxtaposition of a thrust slice of Zeederbergs basalts onto Cheshire sediments. The stratigraphy, asymmetric facies and sediment thickness distribution, palaeogeographic constraints and evidence for an early horizontal tectonic event suggest that the Cheshire Formation formed in a foreland-type sedimentary basin. (C) 2001 Elsevier Science B.V. All rights reserved

Les archives sdimentaires quaternaires de la grotte sous les Sangles (Bas-Bugey, Jura mridional, France). Indices palo-climatiques et sismo-tectoniques, 2002,
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Lignier Vincent, Desmet Marc
Quaternary sedimentary archives of the Sous les Sangles Cave (Lower Bugey, Southern Jura, France); paleo-climatic and sismo-tectonic evidences - The Sous les Sangles Cave is located in southern part of Jura mountain at the front part of the northwestern alpine tectonically active massifs. This region was covered by alpine and jurassian glaciers during the Last Glacial Maximum. An old gallery contains stratified fluvial and moraine injection, covered by a 3.5 meters thick deposit of finely laminated silty carbonate and clays. Sedimentological investigation reveals several periods of different water flow depending on glacial and inters glacial periods. The upper finely laminated sediments correspond to the end of the last glacial maximum according to the exokarstic equivalent of the Cerin lake and the U/Th ages obtained with speleothems. Spectral analysis (using Fourier methods and pass-band mapping techniques) on grey-level raw data have been used on the Sous les Sangles sediment. The main result shows evidence of a cyclic deposition according to the three main periodicities recognised through the 1.5-m top sequence. The laminated material is affected by plastic and brittle deformations. The entire deposit is characterised by (1) a vertical faulting without apparent dominant relative movement which can be interpreted as tension faults; (2) an associated soft and brittle deformation similar to thin skin tectonic at centimetre scale affecting the base of the deposit and testified to gravity reworking which could correspond to discrete sismotectonic activity; (3) brittle deformations associated with fluid escape patterns occurring at two specific levels along the vertical faults, emphasising the earth tremor existence according to several broken speleothems. These observations are highly supported by the geodynamic and tectonic frame of this part of Jura massif which reveal an actual uplift of several millimetre/year, especially in this part of the Cluse des Hpitaux cross valley. Numerous historical earthquakes have been documented in this area. The microtectonic study of the cave shows dominant inverse and strike-slip structures correlated to the general tectonic frame.

Mechanisms of karst breakdown formation in the gypsum karst of the fore-Ural region, Russia (from observations in the Kungurskaja cave), 2002,
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Andrejchuk Vjacheslav, Klimchouk Alexander
The fore-Ural is a classical region of intrastratal gypsum karst. The intensive development of karst in the Permian gypsums and anhydrites causes numerous practical problems, the subsidence hazard being the most severe. Mechanisms of karst breakdown formation were studied in detail in the Kunguskaya Cave area. The cave and its setting are characteristic to the region and, being a site of detalied stationary studies for many years, the cave represents a convenient location for various karst and speleological investigations. Breakdown structures related to cavities of the Kungurskaya Cave type develop by two mechanisms: gravitational (sagging and fall-in of the ceilings of cavities) and filtrational/gravitational (crumbling and fall-in of the ceilings of vertical solution pipes, facilitated by percolation). The former implies upward stoping of the breakout roof and cessation of the process at some height above the floor of the cave due to complete infilling by fallen clasts. This mechanism cannot generate surface deformation where the overburden thickness exceeds a certain value. The latter mechanism implies that breakdown will almost inevitably express itself at the surface, most commonly as a sudden collapse, even where the thickness of the overburden is large. These mechanisms resuit in different appearance, distribution and further evolution of the respective surface forms, so that subsidence hazard assessment should be performed differently for these types of breakdown. The conclusions reached by this study are representative for the region, although some of them bear more general validity for intrastratal karst conditions. This study underlines the ultimate importance of speleological investigations to the understanding of karst breakdown mechanisms.

Paleosubsidence and active subsidence due to evaporite dissolution in Spain, 2002,
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Gutierrez F. , Orti F. , Gutierrez M. , Perezgonzalez A. , Benito G. , Gracia F. J. , Duran J. J. ,
Evaporite formations crop out or are at shallow depth present in an extensive area of Spain. These soluble sediments occur in diverse geological domains and were deposited over a long time span, from the Triassic up to the present day. Broadly, the Mesozoic and Paleogene formations (Alpine cycle) are affected by compressional structures, whereas the Neogene (post-orogenic) sediments remain undeformed. Subsidence caused by subsurface dissolution of evaporites (subjacent karst) takes place in three main types of stratigraphic settings: a) subsidence affecting evaporite-bearing Mesozoic and Tertiary successions (interstratal karst); b) subsidence in Quaternary alluvial deposits related to the exorheic evolution of present-day fluvial systems (alluvial or mantled karst); and c) subsidence in exposed evaporites (uncovered karst). These types may be represented by paleosubsidence phenomena (synsedimentary and/or postsedimentary) recognizable in the stratigraphic record, or by equivalent, currently active or modem examples which have a surface expression. Interstratal karstification of Mesozoic marine evaporites, and the consequent subsidence of overlying strata, is revealed by stratiform collapse breccias and wedge outs of the evaporites grading into unsoluble residues. In several Tertiary basins, the sediments overlying evaporites locally show synsedimentary and/or postsedimentary subsidence structures. Dissolution-induced subsidence coeval with sedimentation is accompanied by local thickening of strata in basin-like structures with convergent dips and cumulative wedge-out systems. This sinking process controls the generation of depositional environments and lithofacies distribution. Postsedimentary subsidence produces a great variety of gravitational deformations in Tertiary supra-evaporitic units, including both ductile and brittle structures (flexures, synforms, fractures, collapse, and brecciation). Quaternary fluvial terrace deposits overlying evaporites show anomalous thickenings (>150 m) caused by a dissolution-induced subsidence process in the alluvial plain, which is balanced by alluvial aggradation. The complex evolution (in time and space) of paleosubsidence leads to intricate and chaotic structures in the alluvium, which may be erroneously interpreted as pure tectonic deformations. The current subsidence and generation of sinkholes due to suballuvial karstification constitutes a geohazard which affects large, densely populated areas, and thus endangers human safety and poses limitations on development. An outstanding example can be seen in Calatayud, an important historical city where subsidence has severely damaged highly valuable monuments. Subsidence resulting from the underground karstification of evaporites has caused or influenced the generation of some important modem lacustrine basins, such as Gallocanta, Fuente de Piedra, and Banyoles Lakes. The sudden formation of sinkholes due to collapse of cave roofs is fairly frequent in some evaporite outcrops. Very harmful and spectacular subsidence activity is currently occurring in the Cardona salt diapir, where subsidence has been dramatically exacerbated by mining practices

Comments on the planation surface once more, 2002,
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Cui Zj, Li Dw, Feng Jl, Liu Gn,
The authors reviewed the research of planation surface in recent years and commented on the development of method and theory about the planation surface. Some aspects of research, such as the restrictive planation surface, the karst planation surface, the fossil planation surface, the dating of weathering crust, the research of weathering crust and environmental evolution, extremely enriched the method and theory of the planation surface. Besides, the authors pointed out that we must take further steps to study the following issues: the deformation of planation surface, the original height of planation surface, the recognition and contrast of the planation surface. The weathering crust and planation surface should be regarded as a whole, and it will still be a principal aspect in the future

Deep karst conduits, flooding, and sinkholes: lessons for the aggregates industry, 2002,
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Lolcama J. L. , Cohen H. A. , Tonkin M. J. ,
Limestone aggregate quarries in deeply penetrating karst terrain are often at considerable risk of artesian inflow from groundwater or surface water channeled through the karstic aquifer. The inflow occurs through what are likely to be complex conduits that penetrate hundreds of feet into bedrock. Rates of inflow can exceed the operation's pumping capabilities proving to be uneconomic to manage over the long term. Over time, inflow rates can increase dramatically as turbulent flow through the conduit erodes its soft residual clay-rich fill. One recent investigation observed an inflow rate of more than 40,000 gpm from a surface water source. Floodwater persistently laden with sediment is an indicator of conduit washout and implies increasing inflow rates over time. Conduits carrying floodwater can exist in a variety of forms: along deeply penetrating geologic faults, joints, or following the path of preferentially eroded bedding. Preferential structural deformation along faults or bedding can enhance dissolution during subsequent interaction with groundwater. The resulting conduit may be a complex combination of many geological features, making the exploration and remediation of the pathway difficult. Sinkholes at the site can occur within several contexts. Pre-existing subsidence structures can reactivate and subside further, forming new collapse sinkholes within soil directly overlying the conduit. Cover-collapse sinkhole development can be a direct result of increasing downward groundwater velocities and subsurface erosion associated with the enlargement of a conduit. Normal operation events such as a quarry blast can also provide a significant new linkage between the groundwater and the quarry, allowing rapid drainage of the groundwater reservoir. With such drainage and erosion of karst-fill, sinkholes will develop over localized water table depressions, most significantly over enhanced permeability zones associated with fractures. Paradoxically, although the rise in quarry water level will lead to regional reduction in the hydraulic gradients, on local scales, drainage of the groundwater reservoir increases gradients and leads to the development of cover-collapse sinkholes. Recommended methods for preliminary site investigation can include a detailed review of geological literature and drilling logs to compile a conceptual model of the site. A fracture trace analysis with EM geophysics can confirm the locations of major faults and fractures. Fingerprinting of the various water sources to the quarry and the water in the quarry is an inexpensive and effective means of identifying the source and likely direction of the groundwater and surface water flow. Automated geophysical equipment on the market for performing rapid resistivity and microgravity surveys speeds up the site screening process during reconnaissance exploration for deep structure. It is recommended that mine planning fully incorporate this information so that quarry operators can take proactive measures to avoid catastrophic and costly flooding events. (C) 2002 Elsevier Science B.V. All rights reserved

Modeling the hydraulical behavior of a fissured-karstic aquifer in exploitation conditions, 2002,
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Debieche Th, Guglielmi Y, Mudry J,
A 5-year daily measurement of the dynamic level in a borehole was plotted versus cumulative yield since the beginning of exploitation. Eighty percent of the experimental curve is explained by a linear function (h = aQ(c) h(0)) by intervals. Only floods, which follow heavy storms and non-pumping cannot be taken into account. The slopes of the straight lines are spread around two constant values of the slope: a(r) = .35 x 10(-3) m m(-3), which characterizes the part which is controlled by recharge, and a(p) = -0.14 x 10(-3) m m(-3), which characterizes the draining part of the aquifer fractures. This linear fitting demonstrates that the borehole -aquifer system can be considered as an equivalent continuous medium, where the linear relationship between dynamic head and pumped yield are defined by the values of ar and a, Thus the hydraulic behavior of the aquifer differs according to the pumping rate: equivalent continuous medium for a low rate, dual permeability for a high one. This work demonstrates that the long-term behavior of an exploited fissured aquifer can be described by a simple model, if the duration of the aquifer test is long enough (1-3 months). It also shows that the production phase must include repetitive head measurements in order to refine the exploitation yield and the management conditions. (C) 2002 Elsevier Science B.V. All rights reserved

Melting of the glacier base during a small-volume subglacial rhyolite eruption: evidence from Blahnukur, Iceland, 2002,
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Tuffen H. , Pinkerton H. , Mcgarvie D. W. , Gilbert J. S. ,
Although observations of recent volcanic eruptions beneath Vatnajokull, Iceland have improved the understanding of ice deformation and meltwater drainage, little is known about the processes that Occur at the glacier base. We present observations of the products of a small-volume, effusive subglacial rhyolite eruption at Blahnukur. Torfajokull, Iceland. Lava bodies, typically 7 m long, have unusual conical morphologies and columnar joint orientations that suggest emplacement within cavities melted into the base of a glacier. Cavities appear to have been steep-walled and randomly distributed. These features can be explained by a simple model of conductive heat loss during the ascent of a lava body to the glacier base. The released heat melts a cavity in the overlying ice. The development of vapour-escape pipes in the waterlogged, permeable breccias surrounding the lava allows rapid heat transfer between lava and ice. The formed meltwater percolates into the breccias, recharging the cooling system and leaving a steam-filled cavity. The slow ascent rates of intrusive rhyolitic magma bodies provide ample time for a cavity to be melted in the ice above, even during the final 10 m of ascent to the glacier base. An equilibrium Cavity Size is Calculated at which melting, is balanced by creep closure, This is dependent upon the heat input and the difference between glaciostatic and cavity pressure. The cavity sizes inferred from Blahnukur are consistent with a pressure differential of 2-4 MPa, suggesting that the ice was at least 200 m thick. This is consistent with the volcanic stratigraphy, which indicates that the ice exceeded 350 in in thickness, Although this is the first time that a subglacial cavity system of this type has been reconstructed from an ancient volcanic sequence. it shares many characteristics with the modem fim cave system formed by fumarolic melting within the summit crater of Mount Rainier. Washington, At both localities, it appears that localised heating at the glacier base has resulted in heterogeneous melting patterns. Despite the different theological properties of ice and fim, similar patterns of cavity roof deformation are inferred. The development of low-pressure subglacial cavities in regions of high heat nux may influence the trajectory of rising magma, with manifold implications for eruptive mechanisms and resultant subglacial volcanic landforms. (C) 2002 Elsevier Science B.V. All rights reserved

From doline distribution to tectonics movements example of the Velebit mountain range, Croatia, 2002,
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Faivre Sanja, Reiffsteck Philippe

The influence of tectonic forces on karst relief development has been studied using dolines as geomorphological markers. The strain and stress orientations have been calculated from the doline distribution, applying the centre to centre method (Ramsay, 1967; Fry, 1979). 623 local results have been obtained which were later injected into a 2D finite element model created in Castem 2 000 software. As the observed deformations are the consequence of the tectonic displacements, the numerical model tends to simulate the tectonic conditions, which are closely related to the observed deformations. The results were correlated with the GPS measurements as well as with the geological field mapping results and great coincidence was observed.


The Padaeng Supergene Nonsulfide Zinc Deposit, Mae Sod, Thailand, 2003,
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Reynolds Neal A. , Chisnall Tony W. , Kaewsang Kriangsak, Keesaneyabutr Chanan, Taksavasu Taksorn,
The Padaeng deposit near Mae Sod in western Thailand was the first supergene nonsulfide zinc deposit in the world to be developed as a large modern mining operation. The mine and associated zinc smelter, operated by Padaeng Industry Public Company Ltd. since 1984, went into production with reserves of 4.59 Mt at a grade of 28.9 percent zinc with a 10 percent zinc cutoff. Current resources are 5.14 Mt at a grade of 12.0 percent zinc with a 3 percent zinc cutoff. The Padaeng deposit is hosted by a mixed carbonate-clastic sequence of Middle Jurassic age. The deposit occurs in the hanging wall of the Padaeng fault, a major northwest-trending structure that was active through Cretaceous and Tertiary tectonism and uplift. Nonsulfide zinc ore comprises dominant hemimorphite with minor smithsonite and hydrozincite. Strata-bound ore zones occur within a northwest-dipping, deeply weathered, dolomitic sandstone; steeply dipping and irregular karstic zones in underlying massive, silty dolomite are controlled by north-trending fracture zones. Sulfide zinc-lead mineralization of Mississippi Valley type occured extensively in the vicinity of the Padaeng mine, most notably the small resources at Pha De and Hua Lon. Mineral deposits are typically sphalerite rich with minor galena and pyrite, forming small-scale open-space fillings, veins, and replacements within hydrothermal dolomite. Mineralization is dominantly strata bound within a horizon of intense hydrothermal dolomitization that forms the stratigraphic hanging wall to the nonsulfide ore zones at Padaeng. The only significant sulfide at the Padaeng mine is within this unit. Only trace sulfide occurs peripheral to, or down dip of, strata-bound or steeply dipping, nonsulfide orebodies. Sulfide mineralization is believed to have accompanied Cretaceous uplift and deformation, related to the onset of oblique subduction beneath the western margin of the Shan-Thai terrane. The nonsulfide deposit is believed to have formed when a substantial body of sulfide ore was uplifted on the margin of the Mae Sod Tertiary intermontane basin, commencing in the middle to late Miocene. Zinc-bearing acidic supergene fluids, generated by oxidation of the precursor sulfide body, reacted with carbonate in the underlying stratigraphic section to precipitate hemimorphite and smithsonite. Fluids were channeled by permeable dolomitic sandstones and by steep fracture and fault zones. Acidic fluids promoted deep weathering and karst formation, allowing mineralization to extend down dip in sandstone units for at least 150 m and vertically for a similar distance in steep structural zones. Transport of zinc out of the precursor sulfide body was facilitated by a falling water table, owing to uplift of the Padaeng fault block and a change from wet tropical to monsoonal or semiarid climatic conditions. There is no evidence for significant in situ replacement of sulfide deposits, and the leached remnants of the precursor sulfide body have been removed by erosion. The supergene process of dissolution and reprecipitation of zinc in the host rocks increased zinc grades and separation of zinc from lead, producing an economically attractive deposit. Successful exploration for this type of deposit requires a good understanding of the controls on primary sulfide mineralization and a good knowledge of local neotectonism, uplift history, hydrogeology, climatic evolution, and weathering history

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