Application of protective products to “Noto” calcarenite (south-eastern Sicily): a case study for the conservation of stone materials

Noto is an important Baroque urban center in south-eastern Sicily, which was completely reconstructed after the severe earthquake of 1693. Most of its monuments and historic buildings were built in Pietra di Noto stone, a pale cream calcarenite, quarried in outcrops located near the city. This stone, still currently used as building material, is undergoing many forms of alteration and degradation, which cause significant damage to monuments. In this study, three commercial protective products were tested on some Noto calcarenite samples from quarries, with the aim of assessing their protective effectiveness. In particular, petrographic analyses by optical microscopy were carried out for textural characterization of the stone materials. Capillary water absorption, porosimetric and colorimetric procedures, UV radiation and salt crystallization aging tests were performed to better evaluate interactions between protective products and substrate.     

On the time dependence of differential rotation in young late-type stars

A model for the angular momentum transfer within the convection zone of a rapidly rotating star is introduced and applied to the analysis of recent observations of temporal fluctuations of the differential rotation on the young late-type stars AB Doradus (AB Dor) and LQ Hydrae (LQ Hya). Under the hypothesis that the mean magnetic field produced by the stellar dynamo rules the angular momentum exchanges and that the angular velocity depends only on the distance s from the rotation axis and the time, the minimum azimuthal Maxwell stress  | B_sB _φ|  , averaged over the convection zone, is found to range from ∼0.04 to  ∼0.14 T²  . If the poloidal mean magnetic field   B _s   is of the order of 0.01 T, as indicated by the Zeeman–Doppler imaging maps of those stars, then the azimuthal mean field   B _φ  can reach an intensity of several teslas, which significantly exceeds equipartition with the turbulent kinetic energy. Such strong fields can account also for the orbital period modulation observed in cataclysmic variables and RS Canum Venaticorum systems with a main-sequence secondary component. Moreover, the model allows us to compute the kinetic energy dissipation rate during the maintenance of the differential rotation. Only in the case of the largest surface shear observed on LQ Hya may the dissipated power exceed the stellar luminosity, but the lack of a sufficient statistic on the occurrence of such episodes of large shear does not allow us to estimate their impact on the energy budget of the convection zone.     

Thermodynamic modeling assisted by multivariate statistical image analysis as a tool for unraveling metamorphic P-T-d evolution: an example from ilmenite-garnet-bearing metapelite of the Peloritani Mountains, Southern Italy

An ilmenite-garnet-bearing schist from the medium-grade metapelite complex of the Mandanici Unit in the Peloritani Mountains has been investigated to constrain the P-T conditions attained in this sector of the southern European Hercynian chain. Microprobe investigations assisted by statistical handling of X-ray maps via principal component analysis allowed us to better elucidate the porphyroblast-matrix relationships, the geometry of the elemental distribution in garnet porphyroblasts and the average volume percentage of the reactant garnet during retrograde metamorphic evolution. Selected microprobe data were then used to constrain, by means of P-T pseudosections, the main P-T stages of the metamorphic evolution, using the XRF bulk-rock chemistry as the equilibrium chemical composition for the prograde and peak stages and an effective bulk-rock composition for the retrograde one. Peak metamorphic P-T estimates (~530?°C; 0.9?GPa) are consistent with a Hercynian crustal thickening stage at middle-lower crustal conditions, while subsequent evolution, constrained at 420–460?°C; 0.30–0.60?GPa, depicts a retrograde clockwise P-T trajectory linked to exhumation under likely extensional shearing conditions. The results obtained in this paper lead to envisage a new scenario for the crustal evolution of the Peloritani Mountains and stimulate a revision of previous interpretations in the light of the new investigation techniques.     

Location Performance and Detection Magnitude Threshold of the Romanian National Seismic Network

Romania is an earthquake prone area with a few destructive earthquakes per century. The National Institute for Earth Physics carries out the seismic survey of Romania through the Romanian National Seismic Network (RNSN) consisting of 65 real-time seismic stations. Daily reports and monthly bulletins are delivered after routinely analyzing and processing the recorded data. In the present paper we applied the Seismic Network Evaluation through Simulation method for the RNSN configuration as it was in August 2011 to estimate the background noise level, assess the appropriateness of the velocity model adopted in routine location procedure, evaluate the hypocenter location uncertainty and determine the detection magnitude threshold. Areas of greater (southern Romania) and lower (Carpathians and Apuseni Mountains) background noise within the RNSN are identified by mapping the average power of noise in 1–12?Hz frequency range. The statistical study of the P and S phases residual times allow us to assess the appropriateness of the velocity model used in routine location. Both P- and S-wave velocity models can be optimized to improve the quality of the hypocenter location. As shown by our analysis, the RNSN is able to detect and locate earthquakes with M _L magnitude above 2.5 anywhere on the Romanian territory, except the border areas, such as the Crisana–Maramures seismic source zone. Merging data from both sides of the border significantly improves the quality of hypocenter location in these areas.     

Combined statistical and petrological analysis of provenance and diagenetic history of mudrocks: Application to Alpine Tethydes shales (Sicily,Italy)

Mineralogical (X-ray diffraction) and geochemical (X-ray fluorescence) compositional data of Alpine Tethyde mudrocks from Sicily were used to unravel the interplay of provenance and diagenesis by means of multivariate statistical methods (PCA, discriminant function analysis) designed for non-negative constant-sum data. The Sicilian Alpine Tethydes comprise Cretaceous–Eocene scaly shales (Mt. Soro and Upper Scagliose Shales Units), Eocene–Oligocene variegated shales (Troina and Nicosia Units), and Miocene Numidian shales (Nicosia Unit). The use of biplots of clr-transformed variables allows discrimination of two different groups of shales. High CIA values reveal a strongly weathered source area especially for the Numidian shales. The analyses of mixed-layered clay minerals indicate that the behaviour of K2O and geochemical affine elements is controlled by the diagenetic grade, which increases from south-west to north-east in response to tectonic loading. Ratios of selected elements (Zr, Y, La, Nb, Ti, Co, Cr, Ni), considered essentially unchanged with respect to the source rocks, are similar in the scaly and variegated shales, and resemble the Variscan Peloritani metamorphic basement. In contrast, the distinct geochemical signature of the Numidian shales reveals a source similar to the average cratonic sandstone, suggesting derivation from external sources located in the foreland. Multivariate discriminant analysis performed on selected trace elements confirms the previous suggestions.     

Diagnostics,deterioration and provenance of stone materials from the Jefferson Page tomb (Non-Catholic Cemetery of Rome,Italy)

The monumental tomb of Jefferson Page, an officer in the American Navy, was built in 1899 and is located in the Non-Catholic Cemetery of Rome (Italy). This study presents complementary diagnostic studies characterizing the stone of the tomb and the weathering and decay phenomena it has undergone. The monument is made of a single type of whitish marble, variously veined and often covered with black patinas. Petrographic, isotopic and LA-ICP-MS analyses attribute the marble to the Carrara district. SEM/EDS and microbiological analyses indicate that the black patinas are due to cyanobacterial autotrophic and fungin heterotrophic colonization. Fourier-transform infrared spectroscopy revealed the presence of organic material on some portions of the tomb, due to undocumented restoration carried out with a mixture of marble powder and a polyester resin.     

Fault‐controlled dolomite bodies as palaeotectonic indicators and geofluid reservoirs: New insights from Gargano Promontory outcrops

The Upper Jurassic to Lower Cretaceous platform‐slope to basinal carbonate strata cropping out in Gargano Promontory (southern Italy) are partly dolomitized. Fieldwork and laboratory analyses (petrographic, petrophysical and geochemical) allowed the characterization of the dolomite bodies with respect to their distribution within the carbonate succession, their dimensions, geometries, textural variability, chemical stability, age, porosity, genetic mechanisms and relation with tectonics. The dolomite bodies range from metres to kilometres in size, are fault‐related and fracture‐related, and probably formed during the Early Cretaceous at <500 m burial depths and temperatures <50°C. The proposed dolomitization model relies on mobilization of Early Cretaceous seawater that flowed, downward and then upward, along faults and fractures and was modified in its isotopic composition moving through Triassic and Jurassic strata that underlie the studied dolomitized succession. Despite the numerous cases reported in literature, this study demonstrates that hydrothermal and/or high‐temperature fluids are not necessarily required for fault‐controlled dolomitization. Distribution and geometries of dolomite bodies can be used for palaeotectonic reconstructions, as they partly record the characteristics (size, attitude and kinematics) of the palaeo‐faults, even if not preserved, that controlled dolomitization. In Gargano Promontory, dolomites record Early Cretaceous palaeo‐faults from metres to kilometres long, striking north‐west/south‐east to east/west and characterized by normal to strike‐slip kinematics. Dolomitization increases the matrix porosity by up to 7% and, therefore, can improve the geofluid storage capacity of tight, platform‐slope to basinal limestones. The results have a great significance for characterization of geofluid (for example, hydrocarbons) reservoirs hosted in similar dolomitized carbonate successions. Distribution, size and shapes of reservoir rocks (i.e. dolomite bodies) could be broadly predictable if the characteristics of the palaeo‐fault system present at the time of dolomitization are known.     

Age constraints on Late Paleozoic evolution of continental crust from electron microprobe dating of monazite in the Peloritani Mountains (southern Italy): another example of resetting of monazite ages in high-grade rocks

In situ monazite microprobe dating has been performed, for the first time, on trondhjemite and amphibolite facies metasediments from the Peloritani Mountains in order to obtain information about the age of metamorphism and intrusive magmatism within this still poorly known sector of the Hercynian Belt. All samples show single-stage monazite growth of Hercynian age. One migmatite and one biotitic paragneiss yielded monazite ages of 311 ± 4 and 298 ± 6 Ma, respectively. These ages fit with previous age determinations in similar rocks from southern Calabria, indicating a thermal metamorphic peak at about 300 Ma, at the same time as widespread granitoid magmatism. The older of the two ages might represent a slightly earlier event, possibly associated with the emplacement of an adjacent trondhjemite pluton, previously dated by SHRIMP at 314 Ma. No evidence for pre-Hercynian events and only a little indication for some monazite crystallization starting from ca. 360 Ma were obtained from monazite dating of the metasediments, suggesting either a single-stage metamorphic evolution or a significant resetting of the monazite isotope system during the main Hercynian event (ca. 300 Ma). Rare monazite from a trondhjemite sample yields evidence for a late-Hercynian age of about 275 Ma. This age is interpreted as representing a post-magmatic stage of metasomatic monazite crystallization, which significantly postdates the emplacement of the original magmatic body.     

Pair production in a strong time-depending magnetic field: The effect of a strong gravitational field

We present the calculation of the probability production of an electron–positron pair in the presence of a strong magnetic field with time-varying strength. The calculation takes into account the presence of a strong, constant and uniform gravitational field in the same direction of the magnetic field. The results show that the presence of the gravitational field in general enhances very much the production of pairs. In particular, high-energy pairs are more likely produced in the presence of the gravitational field than in Minkowski spacetime.     

The augen gneisses of the Peloritani Mountains (NE Sicily): Granitoid magma production during rapid evolution of the northern Gondwana margin at the end of the Precambrian

The medium- to high-grade polymetamorphic basement rocks of the Peloritani Mountains, northern Sicily, include large volumes of augen gneiss of controversial age and origin. By means of a geochemical and SHRIMP zircon study of representative samples, the emplacement age of the original granitoid protoliths of the augen gneisses and the most likely processes and sources involved in that granitoid magmatism have been determined. U–Pb dating of three samples from widely spaced localities in the Peloritani Mountains yielded igneous protolith ages of 565 ± 5, 545 ± 4 and 545 ± 4 Ma, respectively. These late Ediacaran/early Cambrian ages are much older than was previously assumed on geological grounds, and are typical of the peri-Gondwanan terranes involved in the geodynamic evolution of the northern Gondwana margin at the end of the Avalonian–Cadomian orogeny. Major and trace element compositions and Sr–Nd isotopic data, in combination with zircon inheritance age patterns, suggest that the granitoid protoliths of the Sicilian and coeval Calabrian augen gneisses were generated by different degrees of mixing between sediment- and mantle-derived magmas. The magmas forming the ca. 545 Ma inheritance-rich granitoids appear to have had a significant contribution from partial melting of paragneiss that is the dominant rock type in the medium- to high-grade Peloritanian basement. The closeness of the inferred deposition age of the greywacke protoliths of the paragneisses with the intrusion age of the granitoids indicates rapid latest Precambrian crustal recycling involving erosion, burial, metamorphism to partial melting conditions, and extensive granitoid magmatism in less than ca. 10 Ma.