Antonino Pezzino

Alpine Metamorphism in the Aspromonte Massif: Implications for a New Framework for the Southern Sector of the Calabria-Peloritani Orogen, Italy

Structural, petrologic, and thermobarometric data presented in this paper contribute to our understanding of the tectono-metamorphic evolution of the lowest tectonic slices of the Aspromonte Massif (southern Calabria, Italy), which crop out in three main tectonic windows. Despite previously being considered different units, they exhibit the following similar features: the same tectonic evolution, analogous blasto-deformation relationships, and absence of Hercynian mineralogical assemblage relics. Similar P-T paths indicate early HP-LT Meso-Alpine metamorphism (400-600° C at 0.95-1.35 GPa), evolving in the Oligocene-Miocene toward a subsequent retrograde shearing event ranging from 480° to 610°C and 0.50 to 0.95 GPa. The latest retrograde evolution is characterized by 350-480°C and 0.32-0.62 GPa. In this new tectonic framework, it is proposed to group the metapelite sequences defining the Madonna di Polsi Unit. Data presented herein suggest that the pre-Alpine geodynamic setting of southern Calabria was a thinned continental margin made up of Hercynian basement and Mesozoic terrigenous-carbonate sedimentary cover. This continental margin evolved during the early Meso-Alpine stage into a subduction zone beneath the European plate, followed by Neo-Alpine syn-convergent exhumation along a deep-seated mylonitic shear zone. These processes are responsible for the Alpine metamorphic overprint on the Hercynian terranes, as well as for Alpine metamorphism of their Mesozoic cover.

Application of spectrometric analysis to the identification of pollution sources causing cultural heritage damage

Black crusts are recognized to have been, up to now, one of the major deterioration forms affecting the built heritage in urban areas. Their formation is demonstrated to occur mainly on carbonate building materials, whose interaction with an SO2-loaded atmosphere leads to the transformation of calcium carbonate (calcite) into calcium sulfate dihydrate (gypsum) which, together with embedded carbonaceous particles, consequently forms the black crusts on the stone surface. An analytical study was carried out on black crust samples collected from limestone monumental buildings and churches belonging to the European built Heritage, i.e., the Corner Palace in Venice (Italy), the Cathedral of St. Rombouts in Mechelen (Belgium), and the Church of St. Eustache in Paris (France). For a complete characterization of the black crusts, an approach integrating different and complementary techniques was used, including laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), Fourier transform infrared spectroscopy, optical and scanning electron microscopy. In particular, the application of LA-ICP-MS permitted to obtain a complete geochemical characterization in terms of trace elements of the black crusts from the inner parts to the external layers contributing to the identification of the major combustion sources responsible for the deterioration over time of the monuments under study. In addition, the obtained results revealed a relation between the height of sampling and the concentration of heavy metals and proved that the crust composition can be a marker to evaluate the variation of the fuels used over time.

An analysis of the black crusts from the Seville Cathedral: A challenge to deepen the understanding of the relationships among microstructure, microchemical features and pollution sources

The Cathedral of Seville is one of the most important buildings in the whole of southern Spain. It suffers, like most of the historical buildings located in urban environments, from several degradation phenomena related to the high pollution level. Undoubtedly, the formation of black crusts plays a crucial role in the decay of the stone materials belonging to the church. Their formation occurs mainly on carbonate building materials, whose interaction with a sulfur oxide-enriched atmosphere leads to the transformation of calcium carbonate (calcite) into calcium sulfate dihydrate (gypsum) which, together with embedded carbonaceous particles, forms the black crusts on the stone surface. To better understand the composition and the formation dynamics of this degradation product and to identify the pollutant sources and evaluate their impact on the stone material, an analytical study was carried out on the black crust samples collected from different areas of the building. For a complete characterization of the black crusts, several techniques were used, including laser ablation inductively coupled plasma mass spectrometry, Fourier transform infrared spectroscopy, micro infrared spectroscopy, optical and scanning electron microscopy. This battery of tests provided information about the nature and distribution of the mineralogical phases and the elements within the crusts and the crust-substrate interface, contributing to the identification of the major pollution sources responsible for the deterioration of the monument over time. In addition, the results revealed a relation among the height of sampling, the surface exposure and the concentration of heavy metals. Finally, information has been provided about the origin of the concentration gradients of some metals.

Fault-related rocks: deciphering the structural–metamorphic evolution of an accretionary wedge in a collisional belt, NE Sicily

The Alpine chain exposed in the Western Mediterranean area represents a front several kilometres in width, dismembered by more recent tectonics and by opening of the Tyrrhenian Basin. In most exposures of this mountain belt, relics of older metamorphic rocks occur. The deformational sequence of events may be revealed by the recognition of metamorphic records associated with different structures. Within a tract of the Alpine front cropping out in the Peloritani Mountains (NE Sicily), we distinguished two metamorphic complexes characterized by different tectonometamorphic histories. Their present tectonic juxtaposition is a cataclastic thrust linked to the recent Africa-verging Sicilian–Maghrebian fold-and-thrust belt. The Lower Complex is characterized by Hercynian metamorphism (P > 0.2 GPa and T ≈ 350°C) exclusively. It essentially consists of very low-grade metapelites and metavolcanic rocks overlain by an unmetamorphosed sedimentary cover. The Upper Complex, comprising different tectonic slices, consists of medium- to high-grade Hercynian metamorphic rocks (P = 0.3–0.8 GPa and T up to 650°C) with Alpine metamorphic overprint (T > 250°C) affecting also the Mesozoic–Cenozoic cover. Lithotypes, structures, and inferred P–T conditions of investigated rocks suggest the existence of an Alpine accretionary wedge during the Cretaceous deformational collision. Within the Upper Complex, a polyphase Palaeogene mylonitic horizon involving rocks belonging to different tectonic slices fully preserves the tectonometamorphic evolution. For this reason, we focused our attention on these sheared rocks in order to reconstruct the entire tectonic history of this geologically complex area. Our new basic model allows the complex structure of the nappe-pile edifice of the Peloritani Mountains to be simplified, casting new light on the tectonic evolution of this key sector of the southern Calabrian-Peloritani Orogen.

A new methodological approach for the chemical characterization of black crusts on building stones: a case study from the Catania city centre (Sicily, Italy)

Mineralogical, petrographic and chemical analyses were carried out on black crusts covering the stone surface of monuments and buildings of the historical city centre of Catania, one of the most beautiful Baroque places in eastern Sicily. Black crusts were studied through the careful and synergic employment of traditional techniques, including polarizing optical microscopy (POM), scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDS), and infrared spectroscopic techniques (FT-IR), in combination with an innovative technique, i.e.laser ablation inductively coupled mass spectrometry (LA-ICP-MS). The validity of such an integrated approach to study black crusts has been recently demonstrated by the authors. The main goal of this study was to develop and test the reliability of the LA-ICP-MS method on black crusts in order to evaluate the degree of chemical contamination of examined stones and to determine the role of the different sources of pollution in Catania, both anthropogenic (domestic heating, industrial combustion, vehicular traffic) and natural (emissions by Mt Etna) in the formation of crusts. Results obtained demonstrated that this innovative approach has a double potential in the study of black crusts, since it allows the analysis of alteration and degradation processes induced by migration of specific chemical elements from the crust to substrate, and, at the same time, it represents a reliable indicator of the environmental pollution.

Microstructure and elastic anisotropy of naturally deformed leucogneiss from a shear zone in Montalto (southern Calabria, Italy)

Abstract A strain gradient was mesoscopically recognized in sheared leucogneisses cropping out near Mount Montalto (Calabria, southern Italy) in the Aspromonte–Peloritani Unit on the basis of field observations. In order to investigate the relationship between textural and physical anisotropy, a microstructural and petrophysical study was carried out on selected mylonites exhibiting different stages of deformation. The main mineral assemblage is Qtz+Pl+Kfs+Wm, displaying S–C and shear-band textures; mica-fish and ribbon-like quartz are widespread. As strain increases K-feldspar, biotite and premylonitic low phengite white mica transformed to synmylonitic high phengite white mica and quartz, accompanied by an increasing albitization. Different quartz c-axis patterns are ascribable to non-coaxial progressive deformation; we suggest that deformation proceeded under greenschist- up to amphibolite-facies conditions owing to a local increase in shearing temperature. Laboratory seismic measurements were carried out on sample cubes (43 mm edged) cut according to the structural frame (foliation, lineation) of the rock. At 400 MPa and room temperature the averages of compressional (Vp) and shear-wave velocities (Vs) are very similar: 5.70–5.91 and 3.36–3.55 km s−1, respectively. Seismic anisotropy and shear-wave splitting are related to the modal amounts of constituent minerals (in particular mica) and their crystallographic preferred orientation. Importantly, anisotropy is lowest in the most strained rock.

The Use of FTIR and Micro-FTIR Spectroscopy: An Example of Application to Cultural Heritage

Micro-FTIR and FTIR spectroscopy is useful for the study of degradation forms of cultural heritage. In particular it permits to identify the degradation phases and to establish the structural relationship between them and the substratum. In this paper, we report the results obtained on marble from a Roman sarcophagus, located in the medieval cloister of St. Cosimato Convent (Rome), and on oolitic limestone from the facade of St. Giuseppe Church in Syracuse (Sicily). The main components found in the samples of both monuments are: gypsum, calcium oxalate, and organic matter due to probably conservation treatments. In particular, the qualitative distribution maps of degradation products, obtained by means of micro-FTIR operating in ATR mode, revealed that the degradation process is present deep inside the stones also if it is not visible macroscopically. This process represents the main cause of crumbling of the substrate. The results of this research highlight the benefits of the 𝜇-FTIR analysis providing useful insights on the polishing and consolidation processes of stone materials.

Application of laser ablation ICP-MS and traditional techniques to the study of black crusts on building stones: a new methodological approach

IntroductionIn this work, we propose an innovative application of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as a methodological approach for the chemical characterisation of black crusts on stone monuments, associated with traditional micro-morphological (optical and scanning electron microscopy) and infrared spectroscopic techniques (FTIR).MethodsThis new approach was tested on black crusts developing on two marble substrates, one, the columns of the San Cosimato cloister in Rome, and the other, a sculpture representing an angel, located in Pessano con Bornago, a small industrial town near Milan.DiscussionThe main aim of this study was to develop and test the reliability of the LA-ICP-MS analytical method on black crusts and to explore the idea that trace element concentrations in black crusts can be applied to investigate their origin and the relations between concentrations of polluting elements in black crusts and environmental conditions.ConclusionThe results obtained by applying traditional techniques find considerable support in the innovative method used here, which could determine the concentrations of a large number of trace elements (including heavy metals) in the black crusts examined, and thus could also be used as a reliable indicator of environmental pollution.

Sub-greenschist facies assemblages of metabasites from south-eastern Peloritani range (NE-Sicily)

SummaryPre-Hercynian magmatic rocks are widespread in the Palaeozoic basement of the Peloritani range. The metabasites of the Mongiuffi-Melia and Gallodoro areas represent the largest and the most important lower-Ordovician magmatic products of this range. These rocks were metamorphosed during the Hercynian event and preserve relict igneous minerals and textures. A detailed study of the metamorphic assemblages has allowed the identification of two stages of metamorphic crystallisation; they are mainly distinguished by the differentXCO2 of the fluid phase. The first metamorphic event produced three calcite-free sub-greenschist facies assemblages that contain ubiquitous quartz+albite+titanite+chlorite+epidote along with pumpellyite or prehnite or actinolite. The second metamorphic episode produced a “Calcite+Chlorite” assemblage, non-diagnostic to evaluate P-T conditions of metamorphism. The first stage assemblages are only preserved in small domains of the rock. As even very low amounts of CO2 in the fluid phase drastically inhibit the formation of diagnostic sub-greenschist facies calc-silicate assemblages, it appears that a more CO2-rich fluid must have been introduced during the second event. We suggest that this introduction of more CO2-rich fluid occurred during the development of S2 crenulation cleavage.ZusammenfassungPrähercynische magmatische Gesteine sind weitverbreitet im paläozoischen Basement der Peloritani Range. Die Metabasite aus dem Mongiuffi-Melia und dem Gallodoro Gebiet sind die größten und wichtigsten magmatischen Produkte des unteren Ordoviziums in diesem Gebiet. Sie wurden während der hercynischen Orogenese metamorphisiert und sie bewahren reliktische magmatische Minerale und Strukturen. Eine Detailstudie der metamorphen Mineralvergesellschaftungen erlaubt die Identifikation von zwei metamorphen Kristallisationsstadien, die sich hauptsächlich im XCO2 der fluiden Phase unterscheiden. Das erste Ereignis resultierte in der Bildung von drei Calcit-freien sub-grünschieferfaziellen Mineralvergesellschaftungen, die verbreitet Quarz+Albit+Titanit+Chlorit+Epidot mit Pumpellyit oder Prehnit oder Aktinolith führen. Die zweite metamorphe Episode führte zur Bildung der Vergesellschaftung “Calcit+Chlorit”; diese ist für die Abschätzung der P-T Bedingungen der Metamorphose ungeeignet. Die erste Vergesellschaftung ist nur in kleinen Domänen in den Gesteinen erhalten geblieben. Da bereits sehr geringe Mengen an CO2 in der fluiden Phase die Bildung der diagnostischen sub-grünschieferfaziellen kalk-silikatischen Mineralassoziation verhindern, scheint es, daß das CO2-reiche Fluid während des zweiten Stadiums zugeführt wurde. Wir meinen, daß die Zufuhr dieser CO2-reichen Fluide während der Entwicklung der S2 Krenulationsschieferung erfolgt sein muß.

Microstructural, compositional and petrophysical properties of mylonitic granodiorites from an extensional shear zone (Rhodope Core complex, Greece)

At the southern boundary of the Rhodope Massif, NE Greece, the Kavala Shear Zone (KSZ) represents an example of the Eastern Mediterranean deep-seated extensional tectonic setting. During Miocene time, extensional deformation favoured syntectonic emplacement and subsequent exhumation of plutonic bodies. This paper deals with the strain-related changes in macroscopic, geochemical and microstructural properties of the lithotypes collected along the KSZ, comprising granitoids from the pluton, aplitic dykes and host rock gneisses. Moreover, we investigated the evolution of seismic anisotropy on a suite of granitoid mylonites as a result of progressive strain. Isotropic compressional and shear wave velocities ( V p , V s ) and densities calculated from modal proportions and single-crystal elastic properties at given pressure–temperature ( P – T ) conditions are compared to respective experimental data including the directional dependence (anisotropy) of wave velocities. Compared to the calculated isotropic velocities, which are similar for all of the investigated mylonites (average values: V p ~ 5.87 km s −1 , V s ~ 3.4 km s −1 , V p / V s = 1.73 and density = 2.65 g cm −3 ), the seismic measurements give evidence for marked P-wave velocity anisotropy up to 6.92% (at 400 MPa) in the most deformed rock due to marked microstructural changes with progressive strain, as highlighted by the alignment of mica, chlorite minerals and quartz ribbons. The highest P- and S-wave velocities are parallel to the foliation plane and lowest normal to the foliation plane. Importantly, V p remains constant within the foliation with progressive strain, but decreases normal to foliation. The potential of the observed seismic anisotropy of the KSZ mylonites with respect to detectable seismic reflections is briefly discussed.