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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

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That artificial recharge is recharge at a rate greater than natural, resulting from deliberate or incidental human activities [6].?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for crystal growth (Keyword) returned 12 results for the whole karstbase:
Kinetics and mechanisms of precipitation of calcite as affected by P-CO2 and organic ligands at 25 degrees C, 1998, Lebron I. , Suarez D. L. ,
This study was conducted to develop a model for the precipitation rate of calcite under varying CO2 partial pressures and concentrations of dissolved organic carbon (DOG). Precipitation rates of calcite were measured in solutions with supersaturation values (Omega) between 1 and 20 and in the presence of 2 m(2)L(-1) of calcite. Experiments were run at partial pressures of CO2 (P-CO2) in the range of 0.035-10 kPa and DOC concentrations in the range of 0.02-3.50 mM. The effects of these two variables were quantified separately for the precipitation mechanisms of crystal growth and heterogeneous nucleation. We found an increase in precipitation rate (at constant Omega) when P-CO2 increased. For constant Omega, we also found a linear relationship between calcite precipitation rate and activity of CaHCO3, indicating that CaHCO3 species have an active role in the mechanism of calcite precipitation. These findings suggest that the increase in the precipitation rate with higher P-CO2 levels is likely caused by the increase in the negative charge on the calcite surface together with an increase in the activity of CaHCO3 species in solution. The mechanism of inhibition of calcite crystal growth by organic ligands has been shown to be surface coating of the crystals by DOG. The amount of DOC adsorbed on the surface of the calcite crystals follows a Langmuir isotherm for all the P-CO2 levels studied; however, the amount of DOC necessary to inhibit calcite precipitation increased. With increasing P-CO2, the negative charge on the crystal increases, which affects crystal growth, but also these increases in P-CO2 cause a decrease in the solution pH and increase in the ionic strength for constant Omega. Solution pH and ionic strength affect the structure and degree of dissociation of the organic functional groups, which in turn affects the and DOC concentration on the inhibition of crystal growth and heterogeneous nucleation. The effect of P-CO2 and DOC concentration on the precipitation rate of calcite is expressed in a precipitation rate model which reflects the contributions of crystal growth and heterogeneous nucleation. Copyright (C) 1998 Elsevier Science Ltd

Les stalagmites : archives environnementales et climatiques haute rsolution, prsentation des protocoles dtudes et premiers rsultats sur des splothmes du Vercors, 1999, Perrette, Yves
Since the late 80's, the detailed study of speleothem has deve_loped from the crossing of two main approachs; one comes from the ques_tions of speleologists confronted with magnificent cave scenery, the other comes from citizen questions about climatic and environmental changes. The aim of this paper is to show the diversity and the relevance of the data collected by such studies on stalagmitic samples from the Vercors -France. The knowledge of the chemical processes of the H20 - CaCO3 - C02 system in the perspective of the karst infiltration leads to ques_tions about the role of the "supstrat". This word has been used to describe the "roofrock" rather than the bedrock. So, to better unders_tand the different modes of drainage in karst, a global hydrologic study of the Choranche cave vadose zone has been realised, e.g. seepage water rates have been monitoring. These recent studies allow us to model the structural and functional hydrologic network of such a well developed karst system. Actually we demonstrated the hierar_chisation of the drainage and the relation between a transmissive system and a capacitive one. They have been used to propose a graphical typology leading to a better appreciation of the various environmental interests of speleothems. Understanding the processes of speleothem environmental and climatic archiving, needs to know the processes of calcite crystal growth. They are briefly presented through some usual fabrics like columnar, palissadic or dendritic ones and through the optical relation between macroscopic colours and crys_talline porosity. It is the evolution of these crystalline features, which creates the laminae. To explain what are laminae, the diffe_rent type of emission by a solid after a laser irradiation are shown. It justifies the choice of two kinds of laminae measurement i.e. reflectance and fluorescence. Then, results of spectroscopic studies which show a covariation between Mn2+ concentration, the maximum intensity wave length of fluorescence spectra and the reflec_tance trend, allow us to consider reflectance measurement as a water excess proxy. This experimental approach is confirmed by the infra annual laminae. The hydrological interest of "visible" laminae (i.e. reflectance one) is increased by the fluorescence "invisible" lami_nae. In fact, the presence of a wide diversity of organic molecule in the calcite lead us to consider the fluorescence lamina as a temporal proxy controlled by the annual leaf fall and biopedological degradation. To measure these two proxies, an original experimental set has been developed in collaboration with the PhLAM laboratory (Lille, France). Particularly, this experimental set up permits to realise simultaneously a reflectance and a fluorescence image. The data collected are processed and are analysed in the frequency domain. All these data allow us to extract different proxies from speleothems. These proxies have been studied for some Vercors samples. We present the global environmental and climatic data archiving of the post_wurmian (isotopic stage 1) warming. At a higher resolution, the Vercors climate forcing is shown through the spectral analysis of the reflectance of a well laminated sample. The solar (T=22y) and atmospheric (NAO, T=17y) forcings are clearly distinguished. The climate analysis of this sample is limited by an anthropic mask. We show the similarity of the crystal facies evolution of two samples located around the Alps but far from more than 100 km. We would like to interpret this changes as an archiving of the post Little Ice Age warming but here too, Man interfere with climate to induce environmental changes. We show an example of the possibility for distinguishing climate from anthropic changes in environmental evolutions. The wealth of data of the speleothem allows us to appreciate the environ_ment stability of the Vercors which is confirmed in the spectral analysis of the growth rates of a Gouffre Berger sample. The diversity of the data collected in speleothems is directly linked to the diversity of the way of archiving in a karst system. It is why only a global approach seems to be relevant for answering environmental hydrological or morphological karst questions.

Mn-Fe deposits in shallow cryptic marine environment: examples in northwestern Mediterranean submarine caves, 2001, Allouc J, Harmelin Jg,
Black coating of hard substrates by Mn and Fe oxides has long been reported from shallow, dark, submarine caves. However, these littoral metallic deposits have never been studied in detail, despite expected analogies with deep-sea polymetallic crusts. Submarine caves are characterized by darkness and low rates of exchanges with the open sea. Lack of primary production and confinement of inner water bodies result in marked oligotrophy and extremely reduced biomass, i.e. conditions close to those prevailing in deep-sea habitats. Field evidences suggested that the formation of Mn-Fe coatings was closely tied to these particular environmental conditions. The goal of this study was to examine the detailed features of Mn-Fe coatings from dark caves with different local conditions, and to try to identify the processes responsible for their deposition. Study sites and methods Three sublittoral, single-entrance, caves were sampled by scuba diving along the coasts of Provence (France, Mediterranean Sea) (fig. 1). The first site is a large karstic cave (Tremies Cave, 16 m depth at entrance floor, 60 m long; Marseille-Cassis area) with an ascending profile which results in a buffered thermal regime and markedly oligotrophic conditions due to warm water trapping in its upper part (fig. 1 and 2). Wall fragments were sampled at 30 m (medium confinement : zone B) and 60 in (strong confinement : zone C) from the cave entrance. The second site is a large tubular cavity open in conglomerate formations (3PP Cave, 15 m depth at entrance floor, 120 m long; La Ciotat) with a descending profile which results in relative permanence of winter temperatures within the inner parts, complex water circulation and presumed greater input of sedimented particles than in the preceding cave (fig.1 and 2). Wall samples were taken at 25 m, 70 in and 100 m from entrance. The third site is a small, horizontal, cave open in quartzite formations (Bagaud Cave, 7 in depth at entrance floor, about 10 m long; WNW of Port-Cros Island, bay of Hyeres). Sampling was performed on walls of a narrow corridor between an anterior room and a smaller inner room. A sporadic outflow of continental waters is located in the inner room. The samples were preserved in 50% ethylic alcohol or studied soon after their sampling. Before carbon coating and SEM examination, or microanalyses with SEM-associated spectrometers, they were treated in a 33% Chlorox solution and thereafter washed in demineralized water and dried. Micromorphology At low-medium magnification (<20,000), the aspect of coatings varies between caves and, especially, between inner-cave locations. All the described structures are made up of Mn and Fe oxides. In Tremies Cave, coatings of walls from zone B are composed of irregular erected constructions (height : 10s to 100s μm) formed by the aggregation of roughly ovoid primary concretions of about 10 μm (fig. 3). The surface of those primary concretions displays numerous lacunose to reticulate films (pores, about 0.5 μm in diameter, are often subrounded). Remnants of these films and organomorphic corpuscles occur also within the primary concretions (fig. 4). On younger substrates (broken wall exposed since 1970), primary concretions are poorly developed and no prominent construction is visible (fig. 5). In more confined conditions (zone C), the erected constructions of ancient coatings are smaller and less numerous than in zone B but are well individualized (fig. 6). In this zone: C, besides some remnants of lacunose to reticulate films (fig. 7), there is an appearance of filaments and ovoid corpuscles (height/width : 10-30/5-15 μm), which seem to be linked to filaments by a short stalk (fig. 8). In 3 PP Cave, at 25-70 m from entrance, wall coatings present porous heaps of primary concretions (fig. 9). The surface and the inside of the latter comprise remnants of lacunose to reticulate films that evoke those observed in Tremies Cave (fig. 10 and 11). On younger substrates (hard parts of sessile invertebrates), coatings are restricted to micrometric organomorphic corpuscles with some remnants of lacunose or fibrous films (fig. 12). At 100 in from the entrance, coatings are shaped by numerous erected constructions, more or less coalescing (fig. 13). Besides remnants of lacunose films, the primary concretions contain interlacing filaments (diameter : 0.2-0.3 μm) forming cords or veils (fig. 14). In Bagaud Cave, the primary concretions are aggregated in irregular heaps (fig. 15). Lacunose films are particularly frequent and tend to form three-dimensional mamillated structures that were not observed in the other caves (fig. 16). In particular, there is an appearance of tubular structures (fig. 17) and of numerous hemispheroidal structures (diameter : 4-5 μm) with an upper orifice (fig. 18 and 19). At higher magnification (20,000), whatever the cave and inner-cave location, the aspect of oxide deposits is rather smooth or, especially, microgranular (fig. 20). Mineral composition The composition of coatings is different between caves and according to their inner-cave location. In both large caves (Tremies and 3 PP), the Mn/Fe ratio increases with the distance from the cave entrance, i.e. when exchanges with the open sea diminish (fig. 21a). This trend is particularly clear in Tremies Cave, where the confinement gradient is strongly marked. Besides, the Mn/Fe ratio also seems to increase when films are present in the analysed volume (some cubic micrometers) (fig. 21b). In Bagaud Cave, the Mn/Fe ratio reaches high values despite the small size of this cave and its low confinement level. Discussion and conclusions SEM observations suggest that in each studied cave, the Mn-Fe coatings are biosedimentary deposits. Genesis of these deposits is assumed to result mainly from the replacement of biofilms (composed of cells and slime, i.e, of extracellular polymeric substance produced by microorganisms) generated by microbial populations colonizing the cave walls. Considering the darkness of the cave-locations, microbes consist mainly in bacteria, but fungi are probably responsible for the filaments and ovoids corpuscules (evoking sporocysts) occurring in innermost parts. Observations at different scales of the morphological features of oxide deposits reveal a structured organisation which varies along the strong environmental gradients (particularly the confinement level) that occur from the entrance to the innermost parts : erected constructions made up of primary concretions become more and more defined and acquire a pseudo-columnar shape. The aspect of biofilms appears to be controlled by the same environmental parameters. In open or relatively open environments, they frequently show a three-dimensional development (with frequent skullcape-like shapes), while in more confined conditions they exhibit a planar layout. These changes reflect either the adaptation of the slime-producing bacteria to the local trophic resources (correlated to the rate of exchange with the open sea) and water movements, or spatial replacement of taxa. It is assumed that slime (mainly composed of water and exopolysaccharides) induces a local increase of the concentration in dissolved Mn and acts as an ion exchange resin that allows the retention of Mn on the functional groups of EPS. These conditions promote the nucleation of Mn oxide crystallites in the slime. Then. the anionic character of Mn oxides in seawater, and their capacity to catalyse the oxydation of Mn2 to Mn4, allow the process to go on without any other biological intervention; thus, the process of crystal growth becomes possible. In caves where Mn is only supplied by seawater (Tremies and 3 PP), the average value of the Mn/Fe ratio of coatings is negatively correlated to the local availability of nutrients. This trend is probably linked to changes in the selectivity of slimes towards the processes of retention of cations, because this ratio is clearly influenced by the occurrence of biofilms. However, independently from trophic resources, the Mn/Fe ratio can be notably increased when additional Mn is provided by the seeping or flowing of continental waters (Bagaud Cave)

Partitioning of Sr2 and Mg2 into calcite under karst-analogue experimental conditions, 2001, Huang Yiming, Fairchild Ian J. ,
There is a paucity of experimental data on calcite precipitation from waters at low ionic strength and low ratios of Mg/Ca and Sr/Ca, using controlled and constant precipitation rates. Such data are particularly needed for studies of speleothem geochemistry in relation to palaeoclimates.We carried out a series of experiments using a karst-analogue set-up in a chamber of constant temperature and 100% humidity. A steady flow of NaHCO3 and CaCl2 solutions at PCO2 around 10-3.2 were mixed just before passage through a tube (analogous to a soda-straw stalactite) and allowed to drip onto a surface, analogous to a stalagmite. Growth rates were comparable with linear extension rates of natural speleothems.Analytical spots gave reproducible analyses in later analytical cycles after ablation of surface calcite with Na and Mg contamination. Different crystals from the same experiment tended to show positive covariation of Na and Mg with negative covariation with Sr. This may be due to the presence of growth hillocks with vicinal faces with differential partitioning behaviour.The result for the partition coefficient for Mg (DMg) at 25[deg]C is 0.031 0.004, which is quantitatively in good agreement with the trends of previous workers. At 15[deg]C, the result is 0.019 0.003. The temperature dependency is higher than experimental data on seawater-analogue solutions, but lower than a previous estimate based on a comparison of speleothem chemistry with single water analyses.Data for DSr are mainly in the range of 0.057 to 0.078, with a possible weak dependency on growth rate, consistent with previous experimental work. Absolute values are higher than studies in Mg-free saline solutions, which is attributed mainly to salinity effects. Values of DSr are nevertheless somewhat lower than in natural caves, which may relate to crystal growth factors.Mg partition coefficient values should allow robust determination of solution Mg/Ca compositions in enclosed caves, which are at constant temperature on the decadal timescale. The inferred sensitivity of DSr to growth rate factors implies that Sr values should be interpreted more cautiously. Muted changes could relate entirely to growth rate variations, whereas changes of large magnitude imply a control by solution composition. The absence of local (tens of micron scale) antipathetic variations in Sr and Mg in studied natural speleothems, implies that intracrystalline zoning phenomena, if present, are on a finer scale in those natural materials compared with experimental products

Mineralogy and geochemistry of trace elements in bauxites: the Devonian Schugorsk deposit, Russia, 2001, Mordberg L. E. , Stanley C. J. , Germann K. ,
Processes of mineral alteration involving the mobilization and deposition of more than 30 chemical elements during bauxite formation and epigenesis have been studied on specimens from the Devonian Schugorsk bauxite deposit, Timan, Russia. Chemical analyses of the minerals were obtained by electron microprobe and element distribution in the minerals was studied by element mapping. Interpretation of these data also utilized high-resolution BSE and SE images. The main rock-forming minerals of the Vendian parent rock are calcite, dolomite, feldspar, aegirine, riebeckite, mica, chlorite and quartz; accessory minerals are pyrite, galena, apatite, ilmenite, monazite, xenotime, zircon, columbite, pyrochlore, chromite, bastnaesite and some others. Typically, the grain-size of the accessory minerals in both parent rock and bauxite is from 1 to 40 {micro}m. However, even within these rather small grains, the processes of crystal growth and alteration during weathering can be determined from the zonal distribution of the elements. The most widespread processes observed are: (1) Decomposition of Ti-bearing minerals such as ilmenite, aegirine and riebeckite with the formation of leucoxene', which is the main concentrator of Nb, Cr, V and W. Crystal growth can be traced from the zonal distribution of Nb (up to 16 wt.%). Vein-like leucoxene' is also observed in association with organics. (2) Weathering of columbite and pyrochlore: the source of Nb in leucoxene' is now strongly weathered columbite, while the alteration of pyrochlore is expressed in the growth of plumbopyrochlore rims around Ca-rich cores. (3) Dissolution of sulphide minerals and apatite and the formation of crandallite group minerals: crandallite' crystals of up to 40 {micro}m size show a very clear zonation. From the core to the rim of a crystal, the following sequence of elements is observed: Ca [->] Ba [->] Ce [->] Pb [->] Sr [->] Nd. Sulphur also shows a zoned but more complicated distribution, while the distribution of Fe is rather variable. A possible source of REE is bastnaesite from the parent rock. More than twelve crandallite type cells can be identified in a single crandallite' grain. (4) Alteration of stoichiometric zircon and xenotime with the formation of metamict solid solution of zircon and xenotime: altered zircon rims also bear large amounts of Sc (up to 3.5 wt.%), Fe, Ca and Al in the form of as yet unidentified inclusions of 1-2 {micro}m. Monazite seems to be the least altered mineral of the profile. In the parent rock, an unknown mineral of the composition (wt.%): ThO2 - 54.8; FeO - 14.6; Y2O5 -2.3; CaO - 2.0; REE - 1.8; SiO2 - 12.2; P2O5 - 2.8; total - 94.2 (average from ten analyses) was determined. In bauxite, another mineral was found, which has the composition (wt.%): ThO2 - 24.9; FeO - 20.5; Y2O5 - 6.7; CaO - 2.0; ZrO - 17.6; SiO2 - 8.8; P2O5 - 5.4; total - 89.3 (F was not analysed; average from nine analyses). Presumably, the second mineral is the result of weathering of the first one. Although the Th content is very high, the mineral is almost free of Pb. However, intergrowths of galena and pyrite are observed around the partially decomposed crystals of the mineral. Another generation of galena is enriched in chalcophile elements such as Cu, Cd, Bi etc., and is related to epigenetic alteration of the profile, as are secondary apatite and muscovite

Mineral replacement reactions: from macroscopic observations to microscopic mechanisms, 2002, Putnis, A.

Mineral replacement reactions take place primarily by dissolution-reprecipitation processes. Processes such as cation exchange, chemical weathering, deuteric alteration, leaching, pseudomorphism, metasomatism, diagenesis and metamorphism are all linked by common features in which one mineral or mineral assemblage is replaced by a more stable assemblage. The aim of this paper is to review some of these aspects of mineral replacement and to demonstrate the textural features they have in common, in order to emphasize the similarities in the underlying microscopic mechanisms. The role of volume change and evolution of porosity is explored both from natural microtextures and new experiments on model replacement reactions in simple salts. It is shown that the development of porosity is often a consequence of mineral replacement processes, irrespective of the relative molar volumes of parent and product solid phases. The key issue is the relative solubility of the phases in the fluid phase. Concepts such as coupled dissolution-precipitation, and autocatalysis are important in understanding these processes. Some consequences of porosity generation for metamorphic fluid flow as well as subsequent crystal growth are also discussed.


Modification and preservation of environmental signals in speleothems, 2006, Fairchild Ij, Smith Cl, Baker A, Fuller L, Spotl C, Mattey D, Mcdermott F, Eimp,
Speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system. However, the climatological meaning of many speleothem records cannot be interpreted unequivocally, this is particularly so for more subtle shifts and shorter time periods, but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward. An explicit description of speleothem records as time series draws attention to the nature and importance of the signal filtering processes by which the weather, the seasons, and longer-term climatic and other environmental fluctuations become encoded in speleothems. We distinguish five sources of variation that influence speleothem geochemistry, i.e. atmospheric, vegetation/soil, karstic aquifer, primary speleothem crystal growth and secondary alteration, and give specific examples of their influence. The direct role of climate diminishes progressively through these five factors. We identify and review a number of processes identified in recent and current work that bear significantly on the conventional interpretation of speleothem records, for example: (1) speleothem geochemistry can vary seasonally and hence a research need is to establish the proportion of growth attributable to different seasons and whether this varies over time; (2) whereas there has traditionally been a focus on monthly mean delta O-18 data of atmospheric moisture, current work emphasizes the importance of understanding the synoptic processes that lead to characteristic isotope signals, since changing relative abundance of different weather types might control their variation on the longer-term; (3) the ecosystem and soil zone overlying the cave fundamentally imprint the carbon and trace element signals and can show characteristic variations with time; (4) new modelling on aquifer plumbing allows quantification of the effects of aquifer mixing; (5) recent work has emphasized the importance and seasonal variability Of CO2-degassing leading to calcite precipitation upflow of a depositional site on carbon isotope and trace element composition of speleothems; (6) although much is known about the chemical partitioning between water and stalagmites, variability in relation to crystal growth mechanisms and kinetics is a research frontier; (7) aragonite is susceptible to conversion to calcite with major loss of chemical information, but the controls on the rate of this process are obscure. Analytical factors are critical in generating high-resolution speleothem records. A variety of methods of trace element analysis is available, but standardization is a common problem with the most rapid methods. New stable isotope data on Irish stalagmite CC3 compares rapid laser-ablation techniques with the conventional analysis of micromilled powders and ion microprobe methods. A high degree of comparability between techniques for delta O-18 is found on the millimeter to centimeter scale, but a previously described high-amplitude oxygen isotope excursion around 8.3 ka is identified as an analytical artefact related to fractionation of the laser-analysis associated with sample cracking. High-frequency variability of not less than 0.5 parts per thousand may be an inherent feature of speleothem delta O-18 records. (c) 2005 Elsevier B.V. All rights reserved

Kryogene Karbonate im Hhleneis der Eisriesenwelt, 2008, Sptl, C.
Progressive freezing of calcium- and bicarbonate- bearing cave waters can give rise to high supersaturation and the subsequent precipitation of microscopic calcite crystals and aggregates thereof. These particles are disseminated in the ice of ice caves and may later be concentrated by sublimation or melting of ice to form thin carbonate beds in layered ice (cryogenic carbonates). Such white to light brown, silty to fine sandy layers occur in the rear of the ice-bearing part of the Eisriesenwelt cave (Werfen, Salzburg) and were previously regarded as finely disintegrated limestone powder derived from the cave ceiling. Studies using scanning electron microscopy show that this material consists of 30-200 ?m aggregates of euhedral crystals, which, according to powder Xray diffraction analyses, are near-stoichiometric low-Mg calcite. The crystal aggregates commonly show a conspicuous flat top and resemble larger floating calcite rafts known from calcite-precipitating pools in ice-free caves. There are gradual transitions between these aggregates and skeletal crystal aggregates and (hemi)spherulitic forms, respectively. The small particle size and the skeletal crystal habit strongly argue in favour of rapid crystal growth during freezing of shallow puddles of icy water. This interpretation is corroborated by the highly positive C isotope values, which, in conjunction with the O isotope data, prove the cryogenic origin of these carbonates. The proportion of detrital contamination is very low. This study is the first report of fine-grained cryogenic speleothems in an eastalpine cave. It is supposed that such sediments are more wide spread and thicker layers may represent important paleoenvironmental marker horizons.

Preliminary U/Th dating and the evolution of gypsum crystals in Naica caves (Mexico), 2011, Sanna Laura, Forti Paolo, Lauritzen Steinerik

The origin and the evolution of giant selenite crystals in Naica caves, together with the understanding of their growth mechanisms, is one of the aims of the international multidisciplinary research, called the “Naica Project”. In this context, the exact timing of when the gypsum nucleation started and whether its growth has been constant over time, have been investigated. The preliminary data obtained with the U–Th disequilibrium method show significant differences in ages for gypsum (between 191 ± 13 kyr for one of the Ojo de la Reina cave crystals and 57 ± 1.7 kyr for the base of Espadas cave’s spar) and have produced a coarse chronological interval of growth. The crystal depositional rates vary from 0.56 to 1.22 mm/kyr, in excellent agreement with the laboratory tests for gypsum deposition under present conditions performed in the deepest part of the mine. These results are also consistent with a multistage precipitation started at different times in the Naica caves (first in caves at the upper level, where gypsum was subsequently dissolved, and only later in the deeper part of the aquifer under stable conditions) and allow us to improve the knowledge on the speleogenetic evolution of these caves.


Speleothems: General Overview, 2012, White, William B.

Speleothems are secondary mineral deposits formed in caves by flowing, dripping, or seeping water. The most commonly occurring minerals are calcite, aragonite, and gypsum although many other minerals have been found in speleothems. The shapes of speleothems are determined by a competition between the dynamics of the water and the crystal growth habits of the constituent minerals. Stalactites, stalagmites, flowstone, and other speleothems deposited from dripping for flowing water take shapes dictated by the details of the flow behavior. Helictites, anthodites, and gypsum flowers formed from seeping water and various pool deposits take shapes dictated by the habit of crystal growth. Tan, orange, and brown colors common to calcite speleothems and also their luminescence under ultraviolet light is due to inclusion of humic and fulvic acid from overlying soils. Speleothems are also found in lava tubes.


MACROSCOPIC DIAGENETIC CHANGES IN LATE MIOCENE SPELEOTHEMS, WESTERN DESERT, EGYPT, 2012, Pickford, Martin

Understanding the diagenesis of speleothems is important on account of the fact that such deposits are often used for determining palaeoclimate parameters and for estimating the ages of speleothem growth. Impressive speleothem deposition of Vallesian age occurred in an immense palaeokarst network in the Western Desert, Egypt, the age of formation being determined on the basis of mammalian biochronology (fossils found in spelean clastic deposits intercalated between speleothems). Many of the Egyptian speleothems have been pervasively recrystallised internally, but their outer surfaces are usually well preserved except in the formations which were buried in clastic deposits, in which case the entire speleothem can be recrystallised. The recrystallisation results in large crystals (up to 20 cm diameter) growing radially outwards from the centre of stalagmites and stalactites, or at right angles to the outer surface of flowstone deposits. It is clear that crystal growth occurred without change of volume. Although the recrystallisation of speleothems in the Western Desert of Egypt resulted in the development of unusually large calcite crystals, it does indicate that diagenesis may be an important process that needs to be taken into account before speleothems in other karst systems can be used as raw material for unravelling palaeoclimatic and geochronological parameters. The gross morphology of the Egyptian speleothems is described in order to put on record the effects of diagenesis on them. The geochemistry of the speleothems remains to be studied.


Speleothem microstructure/speleothem ontogeny: a review of Western contributions, 2012, White William B.

Mineral ontogeny is the study of the growth and development of mineral deposits in general and, in the present context, speleothems in particular. Previous researchers, mainly in Russia, have developed a nomenclatural hierarchy based on the forms and habits of individual crystals and the assembly of individual crystals into both monomineralic and polymineralic aggegates (i.e. speleothems). Although investigations of the growth processes of speleothems are sparse, there is a large literature on growth processes of speleothem minerals and related crystals in the geochemical and materials science literature. The purpose of the present paper is to sort through the various concepts of crystal growth and attempt to relate these to observations on speleothems and to the Russian conceptual framework of mineral ontogeny. For calcite, the most common mineral in speleothems, the activation energy for two dimensional nucleation (required for the growth of large single crystals) is almost the same as the activation energy for three- dimensional nucleation (which would result in the growth of many small crystals). Calcite growth is highly sensitive to minor impurities that may poison growth in certain crystallographic directions or may poison growth altogether. Extensive recent research using the atomic force microscope (AFM) provides many details of calcite growth including the transition from growth on screw dislocations to growth by two-dimensional nucleation. The deposition of aragonite speleothems requires metastable supersaturation curve and is usually ascribed to the impurities Mg2+ and Sr2+. AFM studies reveal that Mg2+ poisons calcite growth by blocking deposition sites on dislocations, thus allowing supersaturation to build up past the aragonite solubility curve. Sr2+ precipitates as a Sr-rich nucleus with the aragonite structure which acts as a template for aragonite growth. The different morphology of gypsum speleothems can be explained by the different growth habit of gypsum. Examples of twinned growth, dendrite growth, and spherulitic growth are common in the crystal growth literature and can be used to interpret the corresponding cave forms. Interpretation of monomineralic aggregate growth follows from individual crystal mechanisms. Interpretation of polymineralic aggregate growth requires knowing the evolving chemistry which in turn requires new methods for the sampling and analysis of microliter or nanoliter quantities of fluid.


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