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Fernandez-Cortes A.,CSIC - National Museum of Natural Sciences | Cuezva S.,CSIC - National Museum of Natural Sciences | Cuezva S.,Laboratorio Of Petrologia Aplicada | Garcia-Anton E.,CSIC - National Museum of Natural Sciences | And 2 more authors.
Spectroscopy Letters | Year: 2011

Spectra cathodoluminescence (CL) emissions of a stalactite from Castañar cave (west-central Spain) exhibit spatially resolved spectra patterns of Mn2+ and rare earth elements (REE3+). Although the REE3+ signal is smoothed in the speleothem background sample, the REE-enrichment in some growth layer derives from the presence of cerite, xenotime, monazite, and cerianite in the shale matrix. The spectra CL of both host rock and some calcite-aragonite layers show a wide range of spectral luminescence emissions attributed to REE3+, mainly Sm3+, Dy3+, and Ce3+. The high Mn2+-REE3+ anomalies in the inner calcite-aragonite layer could indicate its growth during a phase with stronger weathering of host rock and a more active dynamic hydrology. Copyright © Taylor & Francis Group, LLC. Source


Fusi N.,University of Milan Bicocca | Martinez-Martinez J.,Laboratorio Of Petrologia Aplicada
Engineering Geology | Year: 2013

The combined use of Hg-impregnation and microCT scanning is a powerful tool for detecting structural and textural features in low porosity massive carbonate rocks. Hg-impregnation of carbonate rocks can improve extremely the quality and resolution of microCT images, because of the high density contrast between Hg and the surrounding rock. The success of the combined used of these two techniques depends mainly on two different rock characters:1) Shape of the pores and characteristics of the porous system. Ink-bottle shape pores and tortuous complex porous systems prevent Hg from flowing out of the sample at the end of Hg-porosimetry test, producing reliable microCT images of the porous system itself. On the other side low tortuous cylindrical pores allow Hg flowing out, resulting in not completely true microCT images.2) Effective rock porosity. Hg-impregnation of carbonate rocks with very low porosity (<. 1%) and tortuous or ink-bottle pores improves significantly the analysis and quantification of their porous system. On the contrary, for carbonate rock with higher porosity (>. 4%), although with ink-bottle pores, microCT images are undetectable, as the relatively high quantity of Hg entrapped in the sample creates artefacts (metal effect) that completely obliterate the rock structure. Intermediate porosity (about 2%) can behave either as low porosity (<. 1%) or as higher porosity (>. 4%) depending on pore shape. A prevalence of tortuous ink-bottle pores results in undetectable microCT images, due to widespread metal effect. A small amount of cylindrical pores, reducing the quantity of entrapped Hg, results in a good quality of microCT images.The resolution of the technique depends on the rock porous system. For low porosity (<. 1%) rock, due to high density contrast between Hg and rock, pores with radius one order of magnitude smaller than the voxel size are clearly imaged by microCT and pores with radius two order of magnitude smaller than the voxel size are still detectable. Hg-impregnated pores smaller than the voxel increase the voxel density, as a function of the relative volume of Hg and rock. As a consequence, pores smaller than the voxel size appear as large as the voxel itself and bigger pores appear larger than they really are (partial volume effect). Although Hg-impregnation improves 3D qualitative analysis of porous system and its relationships with rock texture, quantification of the porous system through segmentation of microCT images is strongly affected by intrinsic error in pore dimensions, caused by partial volume effect. Quantification error is a function of the shape of the porous system, being lower for rounded pores and higher for complex tortuous pore system. © 2013 Elsevier B.V. Source


Martinez-Martinez J.,Laboratorio Of Petrologia Aplicada | Martinez-Martinez J.,University of Alicante | Benavente D.,Laboratorio Of Petrologia Aplicada | Benavente D.,University of Alicante | And 2 more authors.
Engineering Geology | Year: 2011

The evaluation of stone quality by means of non-destructive tests is of vital importance, especially when rock is used as a building material. Usually, however, only vp (P-wave velocity) is considered when rock properties such as strength, durability or decay level are assessed. In this paper, we propose a novel ultrasonic estimator based on wave energy: spatial attenuation (s). The benefits of this estimator were evaluated by comparison with five other ultrasonic parameters: compressional (vP) and shear (vS) wave velocities, velocity ratio (vP/vS), waveform energy and temporal attenuation.The sensitivity of each ultrasonic parameter was compared by measuring 300 samples from ten different types of rock. Each type was selected according to its mineralogy (calcite and/or dolomite rock) and structural complexity (homogeneous, fractured, brecciated, foliated or laminated). Samples were subjected to weathering tests (thermal shock and salt crystallisation tests) in order to study the sensitivity of both ultrasonic parameters during fracture initiation, fracture growth and rock fabric disintegration.Results show that although vp is the most widely used parameter, the information it yields is extremely imprecise. However, the new parameter s is highly sensitive to the petrographic characteristics of rocks as well as to the presence of individual defects (fractures, vugs or disintegrated areas). Moreover, the most significant aspect of s is that its values fall between two fixed limits: 0dB/cm and 20dB/cm. A rock with a s value close to 0dB/cm is an unweathered, homogeneous and good-quality rock whilst a s value higher than 12dB/cm indicates extreme decay, i.e. open fractures, developed vugs and/or disintegrated areas. © 2011 Elsevier B.V. Source


Martinez-Martinez J.,University of Alicante | Martinez-Martinez J.,Laboratorio Of Petrologia Aplicada | Benavente D.,University of Alicante | Benavente D.,Laboratorio Of Petrologia Aplicada | And 2 more authors.
Bulletin of Engineering Geology and the Environment | Year: 2012

Young's modulus is one of the most important mechanical parameters in building materials used to assess both the appropriateness of a material as well as its mechanical stability. The paper reports a study to predict the elastic modulus for ten carbonate rocks using the ultrasonic technique. The rocks varied from homogeneous limestones to rocks with abundant stylolite, veins and fissures and were subjected to both salt crystallization and thermal weathering tests in order to modify the number and features of their discontinuities. The dynamic and static elastic moduli were measured in both weathered and unweathered samples. The results confirmed the poor relationship between the static and dynamic moduli for the studied rocks. A new equation is proposed which uses both dynamic elastic modulus and spatial attenuation of compressive waves to provide an accurate prediction of static Young's modulus. As spatial attenuation is highly sensitive to the presence of rock defects, the correlation is very useful for rocks with fractures, voids and/or which have suffered weathering. © 2011 Springer-Verlag. Source


Fernandez-Cortes A.,CSIC - National Museum of Natural Sciences | Sanchez-Moral S.,CSIC - National Museum of Natural Sciences | Canaveras J.C.,University of Alicante | Canaveras J.C.,Laboratorio Of Petrologia Aplicada | And 4 more authors.
Geodinamica Acta | Year: 2010

During an annual cycle the affect of microclimatic changes (of natural and anthropogenic origin) on the geochemical characteristics of seepage water and mineral precipitation rates was analyzed for two karstic caves which contrast in environmental stability and energy exchange with exterior. On the one hand, Castañar cave (Caceres, Spain) is an extremely controlled show cave with limited visitation showing a minimum exchange rate of energy with the external atmosphere and, secondly, Canelobre cave (Alicante, Spain), is a widely visited cave where the anthropogenic impact generates rapid and high-energy environmental changes. Mineral saturation state of seepage water of both caves is controlled by microclimatic variations, such as: 1) natural underground air renewal through the porous system of the upper soil and the network of host-rock fissures, or elso through the cave entrance, 2) cumulative disruptions in the pCO2 levels of cave air due to the presence of visitors, and 3) forced ventilation of the subterranean atmosphere due to the uncontrolled opening of cave entrances. The obtained results reinforce the significance of the microclimatic fluctuations on short time scales in the dynamics of the subterranean karst systems, in terms of rates of mineral precipitation and growth of speleothems, as well as their key role for cave conservation. © 2010 Lavoisier SAS. All rights reserved. Source

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