Gypsum Speleothems

Cueva de Castañar constituye una cavidad única tanto por la variedad de minerales y formas de sus espeleotemas, como por el tono rojizo de sus paredes. Estas dos características responden a las características de los materiales sobre los que se desarrolla la cueva. Son materiales correspondientes al Ediácarico (635-541 M.a.), que incluyen una amplia variedad de rocas (dolomías, magnesitas, pizarras y areniscas). Estos materiales, muy ricos en magnesio y sílice, son los que se disuelven y alteran para dar lugar a la formación de la cavidad y de sus espeleotemas. La alteración de las pizarras y areniscas, la disolución de las dolomías y magnesitas y la infiltración de arcillas desde el suelo dan lugar a la formación de un fino tapiz de color rojo intenso que se deposita sobre las paredes de la cueva, sobre el que muchas veces nuclean los espeleotemas. La disolución de las dolomías y magnesitas aporta mucho magnesio a las aguas que circulan por la cueva, lo cual favorece la formación no sólo de calcita (que es lo habitual), sino también de aragonito. Pero además la composición de las aguas no se ha mantenido constante, lo que ha favorecido que se produjeran muchas transformaciones entre los minerales ya formados. En definitiva, el amplio espectro mineralógico y las variadas transformaciones mineralógicas que se observan en la cueva, hacen de esta un laboratorio natural y por tanto una cavidad única, que se debe conocer, para así poderla conservar en las mejores condiciones posibles. Estas condiciones son las que hacen que el número de visitantes sea muy limitado, por ello el Centro de Interpretación inaugurado en 2010, cumple sobradamente la labor de dar a conocer los valores únicos de la Cueva de Castañar.

First results of a study on hypogenic caves in Sicily are presented. Inactive water-table sulphuric acid caves and 3D maze caves linked to rising of thermal waters rich in H 2 S were recognized. Cave patterns are guided by structural planes, medium and small scale morphological features are due mainly to condensation-corrosion processes. Calcite and gypsum represent the most common cave minerals. Different types of phosphates linked to the presence of large bat guano deposits were analyzed.

Stalagmites and stalactites, as observed within natural caves, may develop inside geological repositories during constructional and post-operational periods. It is therefore important to understand actinide sorption within such materials. Towards this, experimental studies were carried out with233U,238Np (VI),238Np (IV),239Pu and241Am radiotracers using natural speleothem samples collected from the Dharamjali cave of the Kumaon Lesser Himalayas, India. Petrological/mineralogical studies showed that natural speleothems have three general domains: (1) columnar calcite; (2) microcrystalline calcite; and (3) botryoidal aragonite – each with ferruginous materials. Results showed that all domains of speleothems can take up >99% actinides, irrespective of valence state and pH (1–6 range) of the solution. However, distribution coefficients were found to be at a maximum in aragonite for most of the actinides. Such data are very important for long-term performance and safety assessments of...

The caves of the Naica Mine have been the subject of study by scientists from up to seven counties over the past decade. Up to fifty research works have published to date, most relating to the origin of the giant selenite crystals of the Cueva de los Cristales. Nevertheless, a great deal of knowledge has been generated about other relevant aspects of the Naica system. This paper puts together the vast information available about the Naica caves, from the discovery of the Cueva de los Cristales in 2000 to the more recent investigations addressing mineralogy, microclimatology and the use of gypsum speleothems as a palaeo-environmental proxy. Special attention has been paid to novel research lines that have started to use the speleothems of Naica as a study case, particularly in fields such as Astrobiology and Planetary geology. Moreover, the conservation challenges which these caves will face in the near future as consequence of the end of mining activities have also been addressed in this article.

Early human footprints are rare in the fossil record. A survey of the literature reveals very few well documented and dated cases. Here, we report the first clear Homo neanderthalensis footprint. It was found in Vaˆrtop Cave, Romania. The individual stepped into calcareous mud that later hardened. The 22 cm long print suggests a body height of 1.46 m; a gap of 1.6 cm marks the separation of big and second toes. The date of the footprint is constrained by three coeval dates of 62 kyr on sub-samples from the basal layer of a nearby stalagmite that grew on top of the layer of calc-tufa covering the footprint. The lower constraint is a poorly constrained uranium (U)-thorium (Th) isochron date of 97 kyr on the calc-tufa layer in which the footprint is embedded. Thus, the Vaˆrtop Cave individual lived in Romania sometime before 62 kyr, long before the appearance of Homo sapiens in Central and Eastern Europe, the earliest records of which date from only 35 kyr. To our knowledge, this is the first recognised and dated Homo neanderthalensis footprint.

Isverna Cave is situated on the eastern slope of the Mehedinți Mountains, at an altitude of 450 m. It is over 4 km long, and it functions as the water collector for a karst area of over 20 km 2. It is traversed by a river with very clear water except during flood conditions. A series of sumps, of which the longest is the Black Sump (*700 m), are spread along the underground river. This makes the cave an excellent destination for cave diving activities. The first few hundred meters of galleries host hibernation and maternity bat colonies.

In Chihuahua State, a little town called Naica has the largest gypsum single crystals in the world. The growth of these structures has been described as a long and stable process developed over thousands of years. Due to the change in the environmental conditions, these crystals could suffer alterations on their surface. In this project we study the cause of possible deterioration of the giant crystals and intend to suggest measures for their preservation. For this sake, our first experiment consists on several gypsum crystals that have been subjected in a climate chamber to a fog at high CO 2 concentration and 51 °C for a period of time of six months, extracting two crystals every 15 days. Then the crystals have been characterized through Grazing Incidence X-Ray Diffraction using a diffractometer PanAlytical X'PertPro with two different detectors; Xe-filled proportional detector and a Pixel 3D detector. The results were compared to determine which technique is the most suitable to study the degradation of gypsum single crystals. In the two cases, we have identified only the gypsum phase, but with different crystal plane orientations.

3 Research performed in the framework of the "Naica Project" lead by Speleoresearch and Films in cooperation with La Venta Exploring Team fact many are their features worth to be studied, from biology to microclimate, from physiology to palynology etc. The study of Naica caves and crystals is a part of a general research project which the owner of the mine, the Peñoles Company, committed to La Venta Exploring Team and Speleoresearch & Films in 2006 (Bernabei et al. 2009). A workshop was organized at the end of the first year of the project, which was attended by researchers from 16 Universities of 6 Countries (Mexico, USA, Spain, Italy, Switzerland and Norway). The presented talks covered all the research fields of the project: from palynology to laser scanner techniques, from physiology to mineralogy, from climatology to speleogenesis, from geochemistry to documentation. When all the researches will be over (probably in 2011) a symposium will be organized in Mexico to share the results of the Naica project with the whole scientific community. In the present paper, after a short geological outline of the area, the Naica project and its first achieved results within the field of earth sciences are presented. Geological Setting Naica mine is located in a semi-desertic region some 100 km southeast of Chihuahua, the capital town of the homonymous Mexican State bordering the USA (Fig. 1). The mine opens at 1385 m a.s.l. in the northern flank of the Sierra de Naica, a 12 km long, 7 km wide, anticline structure of carbonate formations oriented northwestsoutheast. This antiform outcrops from a very extensive alluvial plain. At the regional scale the Naica carbonate sequence consists of limestone, dolomitic limestone and calcitic dolostone with lutitic interbeds overlying an Aptian evaporitic sequence. The carbonate sequence started its deposition during Albian age (Cretaceous) and its sedimentation went on for several tens of millions of years. In the mine location the whole ore body is within the carbonate sequence and up to now no trace of the Aptian evaporites has been found within cores drilled up to over 1 km in depth. Tertiary intrusive magmatic activity, which characterized this part of the North American subcontinent, caused the development of acid dykes, some 26.2-25.9 Myr BP within the carbonate sequence (Megaw et al., 1988). Recent magnetometric studies have unveiled an igneous source at a depth of between 2.5 and 5 km, some 4 km south of Naica, while in 2007 a drilling close to the mine shaft met an igneous body about 1140 m below the surface. The polysulphide (Pb, Zn, Ag) ore bodies are related to hydrothermal flows (Erwood et al., 1979) induced by the Tertiary dykes. The caves of Naica (Chihuahua, Mexico) are perhaps the most famous mine caves of the world due to the presence of gigantic gypsum crystals. Nevertheless, very little research has been carried out on these crystals until now. An international multidisciplinary investigation started in 2006 with the aim not only to define the genesis and the age of the Naica gypsum crystals, but also to focus other important scientific aspects of these caves and to ensure a complete documentation and knowledge of these natural wonders which will not be accessible anymore in a few couple of years. The preliminary results of this, still in progress, research allow to date the giant crystals and to define the boundary conditions and the mechanisms which induced their development. For the first time pollens have been extracted from gypsum crystals and their analyses evidenced that some 35 Ky BP the Naica climate was cooler and more humid than today.

Early human footprints are rare in the fossil record. A survey of the literature reveals very few well documented and dated cases. Here, we report the first clear Homo neanderthalensis footprint. It was found in Vaˆrtop Cave, Romania. The individual stepped into calcareous mud that later hardened. The 22 cm long print suggests a body height of 1.46 m; a gap of 1.6 cm marks the separation of big and second toes. The date of the footprint is constrained by three coeval dates of 62 kyr on sub-samples from the basal layer of a nearby stalagmite that grew on top of the layer of calc-tufa covering the footprint. The lower constraint is a poorly constrained uranium (U)-thorium (Th) isochron date of 97 kyr on the calc-tufa layer in which the footprint is embedded. Thus, the Vaˆrtop Cave individual lived in Romania sometime before 62 kyr, long before the appearance of Homo sapiens in Central and Eastern Europe, the earliest records of which date from only 35 kyr. To our knowledge, this is the first recognised and dated Homo neanderthalensis footprint.

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Speleothems are secondary mineral structures typically found in karstic caves and usually composed of calcite or aragonite. Despite being naturally white, some might exhibit unusual colors, such as blue, black, red, yellow or green. The causes of these exceptional colorations are poorly understood, especially for green speleothems, which are barely reported. Here we describe the occurrence of the green Ni-bearing serpentine nepouite in green aragonite and calcite speleothems, in the Aven du Marcou (Hérault, France). Nepouite is mainly found as flat lamellar crystals in the outer rim of green speleothems and crystallized alongside radially grown aragonite crystals. This supports nepouite beginning to crystallize recently, due to a change in the chemical composition of the water. Nepouite also exhibits extensive substitution between Ni, Mg and Zn. The various elements responsible for nepouite precipitation are thought to come from the weathering of pyrite crystals in the overlying roc...

La provincia del Neuquén es una de las regiones cársticas más importantes del país ya que posee el cavernamiento en roca caliza más grande, el sistema Cuchillo Curá. Su extenso desarrollo y sus características espeleogenéticas motivaron los estudios exploratorios que al momento arrojaron 111 cavidades topografiadas. Estas incluyen cavernas generadas por procesos cársticos en calizas y yesos y, por procesos pseudocársticos como las cuevas volcánicas. El origen de las cavidades cársticas tuvo lugar durante el Pleistoceno-Holoceno bajo condiciones de clima húmedo, alternantemente frío y templado. Hoy en día se encuentran inactivas hidráulicamente pero sometidas a procesos cársticos mínimos debido al clima semiárido que caracteriza la región.

Lehman Caves is set in mylonitic marble in the Southern Snake Range of Eastern Nevada, USA, and is part of Great Basin National Park. Recent morphological evidence described by Hose et al. 1 indicate abundant features within the Gypsum Annex consistent with a hypogenic and sulfuric acid origin, in contrast with earlier and limited descriptions of the cave. Hose et al. propose a two-stage speleogenetic model with sulfuric acid speleogenesis (SAS) as the initial dissolution event followed by later stage epigenic overprinting in most of the cave. We sought to determine if sediments in the Gypsum Annex could be part of the proposed sulfuric acid origin versus a later-phase feature, and to compare these sediments to speleogenetic gypsum from other known SAS caves such as Carlsbad Cavern in New Mexico and the Frasassi Caves in Italy. We first characterized the mineralogy of the sediments throughout Lehman using powdered X-ray diffraction (pXRD) and, for select samples, scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS). To determine if the white sediments (gypsum and calcite) found in the Gypsum Annex were related to an SAS phase or if they precipitated during a later phase of speleogenesis, we examined the δ 34 S values of gypsum and carbonate associated sulfate. We then sought to determine if these sediments host microbial life and how they compare to microbial communities, which are observed in active SAS systems. Microbial biomass in most of the sediments is very low, although 16S rRNA gene libraries suggest segregation of microbial species within different passages of the cave, and that inorganic N compounds are important energy resources for extant cave communities. Petrographic analysis of thin sections, in progress, will be used to evaluate diagenetic processes in the white deposits and look for potential traces of past life References:

Ebro) durante el Mioceno temprano-medio, a partir del estudio de las asociaciones de ostrácodos y la interpretación sedimentológica. La parte inferior de esta sección está formada por lutitas rojas, amarillas y grises, siendo Paralimnocythere sp. el taxón más abundante. De acuerdo a la litología y el contenido faunístico, este tramo se interpreta como un ambiente de áreas con agua estancada, someras, cálidas y de dulces a oligohalinas, en áreas distales de llanura de inundación aluvial. La presencia de algunos niveles de arenisca, en los cuales la especie más abundante es Cyclocypris laevis (Müller), señala eventos puntuales de mayor energía dentro de este sistema aluvial y la llegada de aguas más salinas. La parte superior de la sección está formada por calizas grises con finas capas de lutitas grises intercaladas. En este intervalo, Pseudocandona parallela Müller es la especie más abundante, lo que indicaría el desarrollo de un medio lacustre estable con corrientes de agua, de temperaturas templadas a frías y salinidad de oligohalina a mesohalina. En la sección estudiada de Loma Negra, la transición entre el sistema aluvial y el sistema lacustre muestra una evolución gradual. Palabras clave. Mioceno. Bardenas Reales de Navarra. Ostrácodos. Evolución paleoambiental. Paleolimnología.

Folia are an unusual speleothem type resembling inverted cups or bracket fungi. The mechanism of folia formation is not fully understood and is the subject of an ongoing debate. This study focuses on an occurrence of folia present in Santa Catalina Cave, a non-thermal epigenic cave located close to Matanzas (Cuba). The sedimentology, morphology, petrology, permeability and geochemistry of these folia have been studied to gain new insight on the processes leading to their development. It is concluded that folia in Santa Catalina Cave formed at the top of a fluctuating water body, through CO 2-degassing or evaporation, which may have been enhanced by the proximity to cave entrances. Two observations strongly support our conclusions. (1) When compared to other subaqueous speleothems (e.g. cave clouds) present in the same rooms, folia occur exclusively within a limited vertical interval that likely represents an ancient water level. Folia occur together with calcite rafts and tower cones that developed, respectively, on top of and below the water level. This suggests that a fluctuating interface is required for folia formation. (2) The measured permeability of the folia is too high to trap gas bubbles. Thus, in contrast to what has been proposed in other studies, trapped bubbles of CO 2 cannot be invoked as the key factor determining the genesis and morphology of folia in this subaqueous environment.

Isverna Cave is situated on the eastern slope of the Mehedinți Mountains, at an altitude of 450 m. It is over 4 km long, and it functions as the water collector for a karst area of over 20 km 2. It is traversed by a river with very clear water except during flood conditions. A series of sumps, of which the longest is the Black Sump (*700 m), are spread along the underground river. This makes the cave an excellent destination for cave diving activities. The first few hundred meters of galleries host hibernation and maternity bat colonies.

Sulphuric acid speleogenesis (SAS) related to the upwelling of acid water enriched in H2S and CO2 represents an unusual way of cave development. Since meteoric infiltration waters are not necessarily involved in speleogenesis, caves can form without the typical associated karst expressions (i.e. dolines) at the surface. The main mechanism of sulphuric acid dissolution is the oxidation of H2S (Jones et al., 2015) which can be amplified by bacterial mediation (Engel et al., 2004). In these conditions, carbonate dissolution associated with gypsum replacement, is generally believed to be faster than the normal epigenic one (De Waele et al., 2016). In Italy several SAS caves have been identified, but only few systems have been studied in detail: Frasassi and Acquasanta Terme (Marche)(Galdenzi et al., 2010), Monte Cucco (Umbria) (Galdenzi & Menichetti, 1995), and Montecchio (Tuscany) (Piccini et al., 2015). Other preliminary studies have been carried out in Calabria (Galdenzi, 2007) and S...

First results of a study on hypogenic caves in Sicily are presented. Inactive water-table sulphuric acid caves and 3D maze caves linked to rising of thermal waters rich in H 2 S were recognized. Cave patterns are guided by structural planes, medium and small scale morphological features are due mainly to condensation-corrosion processes. Calcite and gypsum represent the most common cave minerals. Different types of phosphates linked to the presence of large bat guano deposits were analyzed.

We combine newly determined isotope fractionation factors of gypsum precipitated in the laboratory with the isotopic compositions of natural anhydrite and gypsum to unravel the sulfate sources of the giant selenite crystals in the Naica mine (Chihuahua, Mexico). Gypsum was precipitated in the laboratory from CaSO 4-NaCl-H 2 O solutions across a broad temperature range to establish the isotopic fractionation behavior of the sulfate molecule between the solid and dissolved phase. Oxygen isotopes show a significant fractionation dependence on temperature, with the solid phase more depleted in light isotopes with decreasing temperature. Sulfur isotopes display only a weak but similar dependence on temperature. At high salinity (4.5 M NaCl) no temperature dependence was found for the isotope composition. Based on this fractionation behavior, we attempt to elucidate the origin of the sulfate source(s) responsible for the formation of the (giant) gypsum crystals in the Naica mine. Detailed analysis of the isotopic composition of anhydrite, gypsum, and water samples strongly suggests that different types of anhydrite (of hypogenic and sedimentary origin) were dissolved to form these unique gypsum formations. The homogeneous isotopic composition of most gypsum crystals analyzed reveals an effective hydrodynamic mixing and a slow kinetics of precipitation fed by solutions of calcium sulfate from different anhydrite sources.

Unlike the spectacular speleothems that can often be found in numerous caves, vermiculations are rather unassuming formations, whose origin and evolution still subject of several heated debates. In order to provide a quantitative basis for the understanding of the nature and evolution of vermiculations in karst environments, the geochemical properties of one of the most important karst systems of southern Italy, the Pertosa-Auletta Cave, were studied through a comprehensive approach which included elemental, mineralogical and microscopy analyses. The chemical element abundances, mineral composition and microstructure of the vermiculations covering the entire range of morphologies and colours observed in the case-study cave were investigated, thus providing the first quantitative record of these traits. The vermiculations presented exceptional diversity in their morphology, colour, chemical and mineral composition, with it being due to exogenous determinants such as the deposition of stream sediments or organic matter as well as the development of photoautotrophic communities. They were invariably composed of calcite, associated to quartz as well as clays and other secondary minerals, the formation of which may be biologically mediated. This occurrence, and the evidences of microbial activity observed through dissolution traces, support the possible involvement of biogenic processes in vermiculation development.

Folia are an unusual speleothem type resembling inverted cups or bracket fungi. The mechanism of folia formation is not fully understood and is the subject of an ongoing debate. This study focuses on an occurrence of folia present in Santa Catalina Cave, a non-thermal epigenic cave located close to Matanzas (Cuba). The sedimentology, morphology, petrology, permeability and geochemistry of these folia have been studied to gain new insight on the processes leading to their development. It is concluded that folia in Santa Catalina Cave formed at the top of a fluctuating water body, through CO 2-degassing or evaporation, which may have been enhanced by the proximity to cave entrances. Two observations strongly support our conclusions. (1) When compared to other subaqueous speleothem (e.g. cave clouds) present in the same rooms, folia occur exclusively within a limited vertical interval that likely represents an ancient water level. Folia occur together with calcite rafts and tower cones that developed, respectively, on top of and below the water level. This suggests that a fluctuating interface is required for folia formation. (2) The measured permeability of the folia is too high to trap gas bubbles. Thus, in contrast to what has been proposed in other studies, trapped bubbles of CO 2 cannot be invoked as the key factor determining the genesis and morphology of folia in this subaqueous environment.

New insight into the timing and structure of the Last Interglacial Period (Eemian) was obtained through U-Th dating of four speleothems from Northern Spain and an analysis of their stable isotope records. The four stalagmites examined were collected from different levels of Cueva del Cobre, a cold high-mountain cave in the Cantabrian Ranges (N Spain), in which speleothem growth took place essentially during the warmer interestadials. Through 18 TIMS and ICPMS datings and 263 stable isotope analyses, the onset of the Eemian interglacial period was precisely dated at 150±2 ka, an age consistent with a few other palaeoclimatic records but notably younger than the age ascribed by the Milankovitch theory. We also date the Eemian–Weichselian transition (~115 ka)for the fi rst time in the Iberian Peninsula. U-Th ages revealed a consistent anomaly at ~105-100 ka BP, which could be related to a drastic environmental change during the MIS-5c interestadial. This event would have caused the res...

Hypogenic caves, developed by sulphuric acid speleogenesis, are known all over the world among which the Santa Cesarea Terme caves have been included. They are four submerged caves, located along a coastal carbonate sector in Southern Italy and hosting the outflow of coastal springs of thermal mixed waters (from 21 to 33 °C). These waters derive from the mixing of three water end members: the fresh pure groundwater of a wide karstic aquifer, the deep sulphur thermal water and the seawater. This cave system represents an almost unique case of hypogenic sea caves in carbonate environment. The thermal mixed waters have a different effect on the surrounding rocks of the caves, influencing the sulphuric acid speleogenetic process within the whole cave system. To understand the complex and overlapping natural processes acting on the development of these coastal caves, a multidisciplinary study has been carried out. This study has integrated all the data resulting from different methods and technologies, merging morphology, structural geology, hydrogeology, hydrogeochemistry and mineralogy. This multidisciplinary study has allowed to define the main geochemical processes acting within these caves, including the cave development and the formation of the mineral concretions. After the introduction of H 2 S in the thermal waters, formed by the reduction of sulphates in the sedimentary deposits crossed at depth in the offshore, the oxidation occurs within the caves, producing sulphuric acid. Favoured by upwelling deep-seated thermal flows, this acid dissolves the limestone, with condensation corrosion process that involve replacement of limestone rock with gypsum. This process has resulted to be more active and remarkable within the Gattulla Cave, one of the Santa Cesarea Terme sea caves.

The U.S. southwest has a limited water supply and is predicted to become drier in the 21st century. An improved understanding of factors controlling moisture sources and availability is aided by reconstruction of past responses to global climate change. New stable isotope and growth-rate records for a central Texas speleothem indicate a strong influence of Gulf of Mexico (GoM) moisture and increased precipitation from 15.5 to 13.5 ka, which includes the majority of the Bølling-Allerød warming (BA: 14.7-12.9 ka). Coeval speleothem records from 900 and 1200 km to the west allow reconstruction of regional moisture sources and atmospheric circulation. The combined isotope and growth-rate time series indicates 1) increased GoM moisture input during the majority of the BA, producing greater precipitation in Texas and New Mexico; and 2) a retreat of GoM moisture during Younger Dryas cooling (12.9-11.5 ka), reducing precipitation. These results portray how late-Pleistocene atmospheric circulation and moisture distribution in this region responded to global changes, providing information to improve models of future climate.

La provincia del Neuquén es una de las regiones cársticas más importantes del país ya que posee el cavernamiento en roca caliza más grande, el sistema Cuchillo Curá. Su extenso desarrollo y sus características espeleogenéticas motivaron los estudios exploratorios que al momento arrojaron 111 cavidades topografiadas. Estas incluyen cavernas generadas por procesos cársticos en calizas y yesos y, por procesos pseudocársticos como las cuevas volcánicas. El origen de las cavidades cársticas tuvo lugar durante el Pleistoceno-Holoceno bajo condiciones de clima húmedo, alternantemente frío y templado. Hoy en día se encuentran inactivas hidráulicamente pero sometidas a procesos cársticos mínimos debido al clima semiárido que caracteriza la región.

The article discusses the ecological significance of the phototrophic communities developing in entrance zone of grotto type caves as ecotones and refugiums. Species intrazonality and the dependence of cave species composition on geographic location were considered. The aim of present study was to identify similar caves of different regions based on the species composition of phototrophic communities using own data and data from literature. The empiric basis for investigation was present by phototropic species lists of own studies conducted by standard methods for phototropic species identification, as well as species lists from literature. The most frequently encountered phototrophs were species Chroococcus minutus and Chlorella vulgaris. Their occurrence in all the studied caves was revealed based on the taxonomic analysis. Thus, the intrazonal nature of the flora developed in grotto type caves is partially confirmed. Cluster analysis applying Euclidean distance was used to estima...

Calcium sulfate (CaSO4) is one of the most common evaporites found in the earth’s crust. It can be found as four main variations: gypsum (CaSO4∙2H2O), bassanite (CaSO4∙0.5H2O), soluble anhydrite, and insoluble anhydrite (CaSO4), being the key difference the hydration state of the sulfate mineral. Naica giant crystals’ growth starts from a supersaturated solution in a delicate thermodynamic balance close to equilibrium, where gypsum can form nanocrystals able to grow up to 11–12 m long. The growth rates are reported to be as slow as (1.4 ± 0.2) × 10−5 nm/s, taking thousands of years to form crystals with a unique smoothness and diaphaneity, which may or may not include solid or liquid inclusions. Conservation efforts can be traced back to other gypsum structures found prior to Naica’s. Furthermore, in the last two decades, several authors have explored the unique requirements in which these crystals grow, the characterization of their environment and microclimatic conditions, and the...

The giant gypsum crystals of Naica cave have fascinated scientists since their discovery in 2000. Human activity has changed the microclimate inside the cave, making scientists wonder about the potential environmental impact on the crystals. Over the last 9 years, we have studied approximately 70 samples. This paper reports on the detailed chemical–structural characterization of the impurities present at the surface of these crystals and the experimental simulations of their potential deterioration patterns. Selected samples were studied by petrography, optical and electronic microscopy, and laboratory X-ray diffraction. 2D grazing incidence X-ray diffraction, X-ray μ-fluorescence, and X-ray μ-absorption near-edge structure were used to identify the impurities and their associated phases. These impurities were deposited during the latest stage of the gypsum crystal formation and have afterward evolved with the natural high humidity. The simulations of the behavior of the crystals in...

New insight into the timing and structure of the Last Interglacial Period (Eemian) was obtained through U-Th dating of four speleothems from Northern Spain and an analysis of their stable isotope records. The four stalagmites examined were collected from different levels of Cueva del Cobre, a cold high-mountain cave in the Cantabrian Ranges (N Spain), in which speleothem growth took place essentially during the warmer interestadials. Through 18 TIMS and ICPMS datings and 263 stable isotope analyses, the onset of the Eemian interglacial period was precisely dated at 150±2 ka, an age consistent with a few other palaeoclimatic records but notably younger than the age ascribed by the Milankovitch theory. We also date the Eemian-Weichselian transition (~115 ka) for the fi rst time in the Iberian Peninsula. U-Th ages revealed a consistent anomaly at ~105-100 ka BP, which could be related to a drastic environmental change during the MIS-5c interestadial. This event would have caused the resetting of the U-Th system at the base of the stalagmites during a short time interval. In addition, we propose a new simple geochemical test to ensure the lack of disturbance of this type of samples for dating purposes.

We do not feel sufficiently qualified to discuss whether the Curie principle is so universal a tool for identifying a speleothem's origin. In real cases there may be many factors complicating this rule. It seems that Maltsev is wrong in saying that surface geometry does not affect the process of aerosol deposition. Based on the works of Hungarian researchers (Cser & Maucha, 1968; Cser & Gadoros, 1988; Gadoros, 1989) we emphasized that the behavior of charged aerosols must be determined to a certain extent by forces of electric ...

Tampa, FL (USA) September 2013 temperature, which leads to a progressive increase in CaCO 3 solubility, and also a drastic drop of solubility near the water table due to the loss of CO 2. As a result a geochemical zone of carbonate dissolution and zone of carbonate precipitation appear (Dublyansky, 2000a). Where H 2 S rich waters mix with shallower oxygen rich waters, sulfuric acid forms at or near water table, which rapidly dissolves the carbonate rocks (Egemeier, 1981). This process is known as sulfuric

Определены и охарактеризованы литогенетические типы венд-кембрийских отложений усть-кутского горизонта скважины В, кратко описаны условия их осадконакопления, проведена оценка нефтенасыщения пород по результатам люминесцентно-микроскопического анализа. При помощи специализированного программного обеспечения "Керн С7" по петрографическим шлифам выделено 3 интервала повышенной пористости. Рассмотрена связь нефтенасыщения с литогенетическими типами карбонатных пород, фильтрационно-емкостными свойствами и вторичными процессами преобразования отложений

Caves formed by rising sulfuric waters have been described from all over the world in a wide variety of climate settings, from arid regions to mid-latitude and alpine areas. H 2 S is generally formed at depth by reduction of sulfates in the presence of hydrocarbons and is transported in solution through the deep aquifers. In tectonically disturbed areas major fractures eventually allow these H 2 S-bearing fluids to rise to the surface where oxidation processes can become active producing sulfuric acid. This extremely strong acid reacts with the carbonate bedrock creating caves, some of which are among the largest and most spectacular in the world. Production of sulfuric acid mostly occurs at or close to the water table but also in subaerial conditions in moisture films and droplets in the cave environment. These caves are generated at or immediately above the water table, where condensation-corrosion processes are dominant, creating a set of characteristic meso-and micromorphologies. Due to their close connection to the base level, these caves can also precisely record past hydrological and geomorphological settings. Certain authigenic cave minerals, produced during the sulfuric acid speleogenesis (SAS) phase, allow determination of the exact timing of speleogenesis. This paper deals with the morphological, geochemical and mineralogical description of four very typical sulfuric acid water table caves in Europe: the Grotte du Chat in the southern French Alps, the Acqua Fitusa Cave in Sicily (Italy), and the Bad Deutsch Altenburg and Kraushöhle caves in Austria.

A totally new corrosion form has been recently observed inside the Natuturingam cave (better known as Puerto Princesa Underground River) in Palawan (Philippines): the guano holes. They consist of perfectly rounded holes, 4–5 cm wide and up to 10–15 cm deep, developing over a flat limestone surfaces covered by a thin layer of fresh guano. In the same cave larger guano-related corrosion forms have also been encountered, but are not presented in detail here (guano pots). A 3D photogrammetric survey has been carried out on a series of guano-holes to make some morphometric measurements. Their development is controlled by the peculiar Palawan climate, which is characterized by short but heavy rainfalls followed by rather long dry periods. During rainfalls each water drip drills a perfectly rounded hole into the fresh guano reaching the limestone surface which is then corroded by the acids produced by guano digestion. The corrosion process on the exposed limestone surface continues during ...

Hydrobasaluminite, like alunite and natroalunite, has formed as a by-product of the H2S-H2SO4 speleogenesis of Cottonwood Cave located in the Guadalupe Mountains of New Mexico. This mineral is found as the major component of white pockets in the dolostone bedrock where clay-rich seams containing kaolinite, dickite, and illite have altered during speleogenesis to hydrobasaluminite, amorphous silica, alunite, and hydrated halloysite (endellite). Gibbsite and amorphous silica are associated with the hydrobasaluminite in a small room of Cottonwood Cave. Opalline sediment on the floor of this room accumulated as the cave passage evolved. Jarosite, in trace amounts, occurs in association with the opalline sediment and most likely has the same origin as hydrobasaluminite and alunite. The hydrobasaluminite was found to be unstable at 25ºC and 50% RH, converting to basaluminite in a few hours. Basaluminite was not detected in the cave samples. Aluminite has precipitated as a secondary mineral in the same small room where hydrobasaluminite occurs. It comprises a white to bluish-white, pasty to powdery moonmilk coating on the cave walls. The bedrock pockets containing hydrobasaluminite provide the ingredients from which aluminite moonmilk has formed. It appears that recent cave waters have removed alumina and sulfate from the bedrock pocket minerals and have deposited aluminite and gypsum along the cave wall. Gypsum, amorphous silica and sulfate-containing alumina gels are associated with the aluminite moonmilk.

The article presents the results of investigations of sulfate (gypsum) mineral formation in the southern halls of the Novoafon cave in the conditions of a loose loamy aggregate. These sediments, which are sediments of cave lakes, refer to pseudomiosilites and myosilites – essentially quartz rocks, poor hydrolysates. The southern halls of the cave are characterized by air temperatures from 12.2 to 13.4 °C. The maxima and minima lag behind the surface for 2-3 months. Observations of the relative humidity of air are fragmentary, but there are data on its significant fluctuations, increased as a result of anthropogenic transformation of the air circulation system (the appearance of artificial tunnels). The studied aggregates of gypsum are characterized by a size range from less than 1 mm and up to 3-4 cm and a wide variety of morphological types. Gypsum is represented by skeletal crystals on which parts of facets of simple forms occur: {010}, {121} , {110} and rarely {011}. Rounded, lat...