Petrophysical properties, composition and deterioration of the Calatorao biogenic stone: case of the sculptures masonry of the Valley of the Fallen (Madrid, Spain)

The huge sculptures placed outdoors in the Valley of the Fallen Memorial Park (El Escorial, Madrid) made with blocks of Black-Limestone from Calatorao-Zaragoza, Spain (BLCZ) and disposed on a concrete core exhibit weathering traces, flaking, saline efflorescence and falling fragments, currently represent a danger for visitors. Frost action is important in the Valley of the Fallen by the large number of freeze–thaw cycles produced during Sculptures‘live under a temperate Mediterranean climate with severe seasonality. The formation of fissures facilitates the water transport within the rock and the salt- and ice-induced deterioration. Temperate climates with frequent freezing and thawing cycles can be the most effective drivers of the visible physical weathering. In order to propose a suitable weathering model, collected black-limestones from sculptures and Calatorao quarries were analyzed by optical microscopy, environmental scanning electron microscopy with energy dispersive spectrometry (ESEM-EDS), inductively coupled mass spectrometry (ICP-MS) and X-ray diffraction. Mercury intrusion porosimetry (MIP), nitrogen absorption and helium pycnometry techniques were used for pore analyses of the BLCZ micro-blocks (10 × 10 × 10 cm) described in terms of pore size distribution, pore volume and specific surface area. The appreciable amount of organic matter was isolated by solvent extraction, acid treatment, flotation and perborate degradation followed by Gas Chromatography–Mass Spectrometry (GC–MS), Analytical Pyrolysis (Py-GC/MS), Fourier Transformed Infrared Spectroscopy and Raman techniques. Both weathered and fresh BLCZ samples contained more than 90 % calcite shells with circa 10 % of pyrite (fresh samples) or iron hydroxides (weathered samples), quartz grains, claystone and fossil organic matter consisting of a condensed matrix with polyalkyl chains and polycyclic methoxyl-lacking aromatic structures. The petrophysical analyses revealed volumes of pores, sized <0.025 μm obtained by N₂ adsorption, of 3.18 × 10^?3 cm³ g^?1 while the measured porosity by MIP in the pore range from 0.005 to 200 μm was 3.30 × 10^?3 cm³ g^?1. These data could be explained by the existence of clay minerals and organic matter in the pore system less than 50 nm of diameter. Concerning BLCZ deterioration it was found that the porous framework of BLCZ was filled with sulphates formed from artificial cement observed in the sculptures inside trough a testing hole and from its intrinsic pyrite. The results suggested that although biological processes were not major agents in rock deterioration, there was also weak compatibility between sculptures‘constituents, (limestone, concrete and oxidized iron clamps) which under, continental Mediterranean conditions, were continuously releasing weathering compounds accelerating disruption of the cut-stone sculptures.     

Ultra long period Cepheids: a primary standard candle out to the Hubble flow

The cosmological distance ladder crucially depends on classical Cepheids (with P=3–80 days), which are primary distance indicators up to 33 Mpc. Within this volume, very few SNe Ia have been calibrated through classical Cepheids, with uncertainty related to the non-linearity and the metallicity dependence of their period–luminosity (PL) relation. Although a general consensus on these effects is still not achieved, classical Cepheids remain the most used primary distance indicators. A possible extension of these standard candles to further distances would be important. In this context, a very promising new tool is represented by the ultra-long period (ULP) Cepheids (P≳80 days), recently identified in star-forming galaxies. Only a small number of ULP Cepheids have been discovered so far. Here we present and analyse the properties of an updated sample of 37 ULP Cepheids observed in galaxies within a very large metallicity range of 12+log(O/H) from ∼7.2 to 9.2 dex. We find that their location in the colour-magnitude (V−I,V) diagram as well as their Wesenheit (V−I) index-period (WP) relation suggests that they are the counterparts at high luminosity of the shorter-period (P≲80 days) classical Cepheids. However, a complete pulsation and evolutionary theoretical scenario is needed to properly interpret the true nature of these objects. We do not confirm the flattening in the studied WP relation suggested by Bird et al. (Astrophys. J. 695:874, 2009). Using the whole sample, we find that ULP Cepheids lie around a WP relation similar to that of the LMC, although with a large spread (∼ 0.4 mag).     

10Be surface exposure dating reveals unexpected high deformation rates in the central Andean wedge interior

Understanding deformation associated with active thrust wedges is essential to evaluate seismic hazards. In this study, we investigate the spatial distribution, timing, and rates of deformation across the central Andean backarc of Argentina, where deformation and shortening have been assumed to occur within a narrow wedge‐front zone. The combined results of our geomorphic mapping, topographic surveying, and ¹⁰Be exposure dating demonstrate that fault activity related to the growth of the Andean orogenic wedge is not only limited to a narrow thrust front zone but also occurs in the Andean wedge interior. There, internal structures with deformation rates of ca. 1.3 mm/year have been active during the last ~140 ka. Widely distributed deformation implies that seismic hazards may have been underestimated in the internal part of the Andean orogen.     

Microbiological and physicochemical analysis of the coastal waters of southern Brazil

The aim of this study was to assess the impact of sewage discharge on coastal waters by evaluating the influence of physicochemical parameters on the presence of enteric microorganisms in seawater samples collected from 11 beaches in Florianopolis, Santa Catarina, Brazil, over a one-year period (August 2009 to July 2010). Samples were assessed for the presence of human adenoviruses (HAdV), polyomavirus (JCPyV), hepatitis A virus (HAV), and noroviruses (HuNoV GI and GII). Escherichia coli and physicochemical parameters (salinity, temperature, pH and dissolved oxygen) were also evaluated. From the 132 samples analyzed, 55% were positive for HAdV, 51.5% for HAV, 7.5% for HuNoV GI, 4.5% for HuNoV GII, and 3% for JCPyV. E. coli levels ranged from 8 to 1325 CFU/100mL at all sites. The overall results highlight the problem of sewage discharge into coastal waters and confirm that there is no correlation between viral presence and bacterial contamination.     

Investigating the partonic entanglement entropy at low Bjorken-x within Gluon saturation approach

In this work, the entanglement entropy is examined within the context of deep inelastic scattering in $ep$ collisions. The calculation is based on a formalism where the partonic state at small- $x$ is maximally entangled, consisting of a large number of micro-states occurring with equal probabilities. Analytical expressions for the number of gluons, $N_{\text{gluon}}$, are considered, derived from gluon saturation models for dipole-target amplitudes within the framework of the Quantum Chromodynamics (QCD) color dipole picture. A comparison of the entanglement entropy with thermodynamic entropy measured in $pp$ and $ep$ collisions at high energies is done.     

Radiation-induced defects in euclase: formation of O<Superscript>−</Superscript> hole and Ti<Superscript>3+</Superscript> electron centers

Irradiation techniques are often applied to gem minerals for color enhancement purposes. Natural green, blue and colorless specimens of rare gemological quality euclase, BeAlSiO₄(OH), from Brazil were irradiated with gamma rays in the dose range from 10 to 500 kGy. Although the colors of the different specimens were not strongly influenced, two different irradiation-induced paramagnetic defect centers were found by electron paramagnetic resonance (EPR). The first one is an O⁻ hole center interacting with one Al neighbor and the second is a Ti³⁺ electron center. The EPR angular rotation patterns of both irradiation-induced defects were measured and analyzed. The results suggest that O⁻ hole centers are formed by dissociation of the hydroxyl ions, similar as in topaz crystals. In euclase the OH⁻ ions interconnect distorted Al octahedra and Be tetrahedra in O₅ positions. During irradiation, the electrons are captured by titanium ions (Ti⁴⁺ + e⁻), leading to the formation of paramagnetic Ti³⁺ ions. From the EPR rotation patterns it is clear that these ions substitute for Al ions. The spin Hamiltonian parameters of the irradiation-induced defects are analyzed and compared to similar defect centers in other mineral specimens. Thermal annealing experiments show that the O⁻ hole centers and Ti³⁺ electron centers are directly connected through the radiation process.     

High‐frequency cycles of brachiopod shell beds on subaqueous delta‐scale clinoforms (early Pliocene,south‐east Spain)

During the early Pliocene, subaqueous delta‐scale clinoforms developed in the Águilas Basin, in a mixed temperate carbonate–siliciclastic system. The facies distribution is consistent with the infralittoral prograding wedge model. Stacking patterns and bounding surfaces indicate that the clinoforms formed during the highstand and falling sea‐level stages of a high rank cycle. Twenty‐two prograding clinothems were recognized over a distance of ≥1 km. Biostratigraphic data indicate a time span shorter than 700 kyr for the whole unit (MPl3 biozone of the Mediterranean Pliocene). Cyclic skeletal concentrations and occasional biostromes of suspension feeders (terebratulid brachiopods, modiolid bivalves and adeoniform bryozoan colonies), slightly evolved glauconite and occasional Glossifungites ichnofacies formed on the clinoforms during high‐frequency pulses of relative sea‐level rise. During such stages, increased accommodation space in the topsets of the clinoforms caused a strong reduction of terrigenous input into the foresets and bottomsets. This provided favourable conditions for the development of these suspension feeder palaeocommunities. During stillstand stages, however, reduced accommodation space in the topsets eventually resumed progradation in the foresets. There, the abundance of Ditrupa tubes indicates frequent siltation events that extirpated the terebratulid populations and other epifaunal suspension feeders in the foreset and bottomset subenvironments. The occurrence of shell beds on the clinoforms suggests that this case study represents lower progradation rates than standard examples where shell beds bound the clinobedded units at their base and top only. Importantly, the distributions of biofacies and ichnoassemblage associations contribute significantly to the understanding of the effects of relative sea‐level fluctuations on the evolution of subaqueous delta‐scale clinoform systems.     

Mineral equilibrium constraints on the feasibility of diffusive H2O-fluxed melting in the continental crust

Generation of granitic melt is believed to occur predominantly by melting through the breakdown of hydrous minerals. However, melting due to the influx of H₂O has been recognized in anatectic amphibolite facies tonalitic grey gneisses, metagreywackes and low-P metapelites, and has consequently been proposed as an alternative mechanism for the generation of granitic melt. Melting induced by H₂O addition is recognized from voluminous melt production at relatively low temperature, where hydrous minerals are stable and anhydrous minerals are preferentially consumed during melting. Mineral equilibrium modelling to determine the P–T conditions, melt volumes, melting reactions and viable H₂O sources reveals that the process is not restricted to specific compositions or P–T conditions, although lower pressure and lithologies with a low hydrous mineral content are more favourable. Melting reactions in all lithologies primarily consume quartz and feldspars to yield 5–6 mol.% melt for each mol.% of H₂O added. remains constant at ~0.70 to 0.77 during progressive melting as long as alkali feldspar is present. Once alkali feldspar is exhausted, plagioclase becomes the main reactant, producing more tonalitic melt compositions with gradually higher . Our results demonstrate that, at the site of melting, melting is driven by diffusion of H₂O into the target rock along chemical potential gradients, rather than the advective flow of a mechanically distinct water-rich fluid phase. Melting will initiate and proceed as long as a gradient exists between the H₂O source and target lithology. Our calculations show that an ordinary magma, such as an I-type magma with typical H₂O content, has a high enough to be a viable H₂O source, allowing diffusive H₂O-fluxed melting to produce melt proportions and fertility comparable to that of dehydration melting. However, high degrees of partial melting require a considerable amount of H₂O, which necessitates a continuously advecting H₂O source such as a magma conduit or melt-bearing shear zone. A magmatic H₂O source at emplacement level will undergo a similar amount of crystallization as the melt fraction produced in the target rock such that there will be no net melt production. Considering that shear-zone hosted magma conduits are localized features, diffusive H₂O-fluxed melting is likely to only be viable in a small fraction of the anatectic orogenic crust. Although it may play an important role in locally raising melt volumes and modifying magma chemistry through mingling and hybridization, it does not appear to, of itself, be able to generate significant volumes of granitic melt.     

Rare Earth Element Geochemistry of the Zigzag - Klondyke Sedimentary Rock Formations: Clues to the Evolution of the Baguio Mineral District (Luzon), Philippines

Abstract. Petrographic analysis of the Oligocene-Miocene Zigzag Formation and Miocene Klondyke Formation of the Baguio Mineral District reveals a transitional arc source for the former and an undissected arc source for the latter. Whole rock geochemistry of these sedimentary rock formations show affiliation of the Zigzag Formation to active continental margin whereas the Klondyke Formation appears to have been derived from an oceanic island arc source. A different aspect of the geology of the district is further gleaned from the whole rock rare earth element geochemistry of these rocks. Samples from the Zigzag Formation are characterized by higher REE concentrations compared to the Klondyke Formation samples. The REE data indicate that the sedimentary rocks of the Klondyke Formation had geochemically-less fractionated igneous lithologies as their progenitor whereas the older Zigzag Formation was derived from a more differentiated source. This new set of information contributes to the understanding of the evolution of this district from a marginal basin to an island arc setting.