X-Min Learn is an open-source software for mineral recognition in natural and artificial stone materials from X-ray map data, automated through machine learning (ML) and image analysis. The most innovative software section is the Developer’s Toolkit (DT), which is useful for building up ML models in a user-friendly, no-code environment. In this first version of the software, the DT has been equipped with a fully trainable SoftMax Regressor algorithm, paired with a Stochastic Gradient Descent optimizer. Two additional operational sections are included: 1) Mineral Classifier tool, for achieving supervised or unsupervised mineral classifications based on three classifier types: (a) pre-trained, for user-developed custom models; (b) ROI-based, for supervised algorithms that rely on user-drawn regions of interest (ROIs); and (c) unsupervised, for clustering algorithms; 2) Phase Refiner tool, for removing noisy pixels from classification results through (a) a basic mode, that applies a maximum frequency filter to smooth the entire image; and (b) an advanced mode, which allows class-by-class refinements using morphological image processing. Classified mineral maps, if validated, can be employed in the DT for updating existent ML models or developing new ones tailored for the characterization of samples acquired with specific instrument (e.g., SEM, EPMA) at precise operational conditions (e.g., current, dwell time, pixel size). X-Min Learn’s interactive widgets also allow processing standard image files to populate pixel-wise mineral ground truth datasets. This makes it a versatile and autonomous tool for developing custom ML models from mineral X-ray maps data.

Seismic Microzonation studies of Level 3 (SM3) require a detailed and spatially homogeneous characterization of subsurface conditions, typically obtained by integrating geognostic and geophysical datasets. However, the distribution of existing investigations (boreholes (S), Multichannel Analysis of Surface Waves (MASW), Down‑Hole test (DH), Horizontal to Vertical Spectral Ratio (HVSR)) is often irregular and clustered and, consequently, insufficient to represent the geological and geotechnical variability of the entire study area. This is particularly true in those geological contexts, such as volcanic settings, characterized by strong lateral and vertical heterogeneities. This paper presents a reproducible GIS‑based approach for designing an optimal investigation plan for SM3 through the construction of a regular network of Control Points (CPs). The methodology is entirely implemented using open‑source GIS tools and consists of: (i) generating two regular grids (size: 500 m and 1000 m), (ii) extracting and cleaning grid centroids by removing those located outside SM3 areas, (iii) integrating additional CPs where necessary, and (iv) associating each CP with pre‑existing investigations within a significance‑based distance threshold and within the same SM1 stable or instable zone (stab/instab). The method is tested in the Etnean area (Sicily, Southern Italy), where complex volcanic architectures strongly influence the local seismic response. Results indicate that the CP network allows for a rapid identification of data gaps and supports a rational design of new investigations, ensuring homogeneous spatial coverage and improving the reliability of the SM3 subsurface model. This GIS‑based framework provides a transparent and fully reproducible workflow that can be applied to any SM3 municipality studies at national scale.

Geologists produce and analyze various multiscale datasets to reconstruct the kinematics of Earth’s deformational processes. The study of tectonic-related rocks (e.g., mylonites) allows for the extraction of geo-structural parameters, which are particularly suitable in this scenario. The use of Multiscale Geo-Structural Information Systems (MGS) is effective for a comprehensive representation of complex geodynamic processes, which can only be achieved through the simultaneous comparison of data from different scales. We propose a methodology for quick packaging of MGS, especially suitable for mylonites, using ad-hoc Python scripts and open-source software. This approach improves connecting information across various scales of observation: from petrographic micro analysis to 3D UAV surveys. We have developed an MGS for studying the mylonites occurring at Palmi Shear Zone (South Italy), one of the most important sites for understanding geodynamics processes of Mediterranean area. MGS have potential applications in territorial planning, resource management, data interoperability and risk analysis.

The adoption of semi-automated image processing methods to investigate geo-petrological processes has grown quickly in recent years. Utilizing multivariate statistical analysis of X-ray maps, these methods effectively extract quantitative textural, chemical, and modal parameters from selected thin sections or micro-domains in volcanic samples whose constituents can show peculiar textures due to the magmatic processes involved. In this study, we have processed X-ray maps of major elements from the 2021 basaltic lava rocks of Pacaya volcano (Guatemala) through the Quantitative X-ray Map Analyzer (Q-XRMA) software. The processing strategy is based on the sequential application of the Principal Components Analysis and the supervised Maximum Likelihood Classification algorithms that allow us distinguishing among rock constituents (mineral phases, vesicles and glasses), quantifying their modal abundances, and identifying textural and chemical variations in a simplified and quick process. Here, the capability of the software has been applied to plagioclase crystals, whose textural and chemical complexities are faithful recorders of the physical and chemical conditions and processes controlling the evolution of the magmatic system. Plagioclase displays a variable extent of disequilibrium at the core and rim, as well as growth textures developed at different degrees of undercooling. This variability makes it very difficult to establish how many crystal populations are present in a sample, and to objectively decide whether there are crystals that can be considered representative of a population. The procedure applied in this study has proved to be effective for rapidly gathering chemical and textural data on plagioclase, and quantitatively document the distribution of crystals according to their size, shape, and compositions. Results demonstrate that the chemical and textural variability of crystals can be fully discerned at microscopic scale, and thus it can be adopted as a template for interpretation of magmatic processes.

This study focused on collecting structural data orientations of a crustal-scale shear zone (Palmi Shear Zone, PSZ, southern Calabria, Italy) by integrating various analytical and field-based techniques. The PSZ consists of deformed metamorphic rocks (migmatitic biotitic paragneiss, marbles, and skarns) showing multiple folding phases, and Hercynian tonalites and pegmatites (306-290 Ma), crosscut by Late Hercynian leucocratic dykes (ca. 290 Ma). Multi-sized clasts composed of different lithologies are preserved on clean outcrop surfaces, and are sheared into both sigma - and delta -type objects that collectively suggest opposing senses of shear. The study incorporates structural analysis of folds, field and aerial surveys (UAV), digital mapping, and microcomputed tomography. Various kinematic indicators were observed in the PSZ, indicating a mix of factors influencing the shear strain patterns (e.g. fold interference patterns, different rock types with high viscosity contrast). The findings suggest a clear consistency between structural data inferred from 3D VOM (Virtual Outcrop Model) and those collected directly in the field, confirming the occurrence of both sinistral and dextral shear in the PSZ, providing important insights into the tectonic evolution of the Calabrian-Peloritani Terrane.

Due to the ongoing development of new technologies, many instruments are available to assist geological investigations at different scales. These techniques, including 3D outcrop modelling from aerial photogrammetry, and quantitative microstructural analysis are useful in crystalline basement studies. This contribution combines traditional and quantitative multiscale structural analysis techniques to the migmatitic rocks of the Valpelline Series (Dent-Blanche Tectonic System, Western Alps). Conventional structural analysis is integrated with the extraction of structural data from 3D models of representative smooth outcrops. Quantitative microstructural and mineral-chemical analyses are combined to link structural and metamorphic evolution. This approach allows identifying and correlating foliations that developed during three tectono-metamorphic stages. The first (D1) includes solid-state deformation associated with an early foliation (S1) preserved within metabasite boudins enclosed in migmatite gneiss. The second (D2) is related to the dominant foliation in migmatite gneiss (S2), coeval with the regional scale anatexis and growth of garnet and cordierite. The third (D3) is related to the late folding of S2 and the development of a sillimanite-rich axial plane foliation (S3) which wraps around garnet and cordierite. Finally, this work discusses pros and cons of each innovative methodology, still emphasising the importance of using manual field data as ground control.

Since Roman Age, the reactiveness of the mortars was empirically sought using different aggregates added to lime to confer hydraulic properties. With the advent of microanalytical studies, great strides have been made toward a better understanding of how the aggregates can catalyze the formation of hydraulic phases. However, due to the small scale and the different distribution speeds of the reactions, the techniques routinely used are not fully performing for answering this task. In this work, an innovative semi-automated image processing procedure based on the multivariate statistical analysis of X-ray maps is adopted to highlight and quantify, for the first time, the hydraulic behavior of mortars in terms of reactivity between binder and aggregate. The method proposed has been applied to two different volcanic-based mortars (known as "ghiara- and azolo-mortars") collected from historic buildings in Catania (Sicily, Italy). Obtained results allowed identifying, in both mortars, four distinct compositional sub-zones within the binder as well as mapping the distribution of the Hydraulicity Index (HI). This latter resulted to be quite higher for the ghiara mortar (HI from properly hydraulic lime to cement for -50% of the binder) with respect to the azolo one (HI from properly hydraulic lime to cement for -10% of the binder).

A new geological-structural map of the southern Serre Massif (SM), in the south-central part of the Calabrian-Peloritani-Orogen (CPO), is provided. CPO is a ribbon-like microplates puzzle, originally belonging to the southern European Variscan Belt and, later involved into the Alpine geodynamics of the central Mediterranean Area. The SM represents one of the key European Variscan basement relicts, because of its exhumation mechanisms as well as for the absence of any Alpine metamorphic overprint. This map has the aim to better delineate the sequence of the Variscan blasto-deformational relationships consisting in a prograde multistage history, followed by an extensional/transpressional multistage retrograde evolution, which triggered the intrusion of the former plutonic products. The mylonitic fabric resulted finally replaced by the effects of the late- to post-kinematic plutonic intrusions coeval with a former late-Variscan exhumation stage, followed, during Mesozoic, by carbonate platform sedimentation, before to be completed exhumed during the Oligocene-Miocene Alpine stages.

Micro-Fabric Analyzer (MFA) is a new GIS-based tool for the quantitative extrapolation of rock microstructural features that takes advantage both of the characteristics of the X-ray images and the optical image features. Most of the previously developed edge mineral grain detectors are uniquely based on the physical properties of the X-ray-, electron-, or optical-derived images; not permitting the exploitation of the specific physical properties of each image type at the same time. More advanced techniques, such as 3D microtomography, permit the reconstruction of tridimensional models of mineral fabric arrays, even though adjacent mineral grain boundaries with the same atomic density are often not detectable. Only electron backscatter diffraction (EBSD) allows providing high-performing grain boundary detection that is crystallographically differentiated per mineral phase, even though it is relatively expensive and can be executed only in duly equipped microanalytical laboratories by suitably trained users. Instead, the MFA toolbox allows quantifying fabric parameters subdivided per mineral type starting from a crossed-polarizers high-resolution RGB image, which is useful for identifying the edges of the individual grains characterizing rock fabrics. Then, this image is integrated with a set of micro-X-ray maps, which are useful for the quantitative extrapolation of elemental distribution maps. In addition, all this is achieved by means of low-cost and easy-to-use equipment. We applied the tool on amphibolite, mylonitic-paragneiss, and -tonalite samples to extrapolate the particle fabric on different metamorphic rock types, as well as on the same sandstone sample used for another edge detector, which is useful for comparing the obtained results.

Three samples of meta-acidic rocks with pre-Alpine metamorphic relicts from the Sesia-Lanzo Zone eclogitic continental crust were investigated using stepwise controlled elemental maps by means of the Quantitative X-ray Maps Analyzer (Q-XRMA). Samples were chosen with the aim of analysing the reacting zones along the boundaries between the pre-Alpine and Alpine mineral phases, which developed in low chemically reactive systems. The quantitative data treatment of the X-ray images was based on a former multivariate statistical analytical stage followed by a sequential phase and sub-phase classification and permitted to isolate and to quantitatively investigate the local paragenetic equilibria. The parageneses thus observed were interpreted as related to the pre-Alpine metamorphic or magmatic stages as well as to local Alpine re-equilibrations. On the basis of electron microprobe analysis, specific compositional ranges were defined in micro-domains of the relict and new paragenetic equilibria. In this way calibrated compositional maps were obtained and used to contour different types of reacting boundaries between adjacent solid solution phases. The pre-Alpine and Alpine mineral parageneses thus obtained allowed to perform geothermobarometry on a statistically meaningful and reliable dataset. In general, metamorphic temperatures cluster at 600–700 °C and 450–550 °C, with lower temperatures referred to a retrograde metamorphic re-equilibration. In all the cases described, pre-Alpine parageneses were overprinted by an Alpine metamorphic mineral assemblage. Pressure-temperature estimates of the Alpine stage averagely range between 420 to 550 °C and 12 to 16.5 kbar. The PT constraints permitted to better define the pre-Alpine metamorphic scenario of the western Austroalpine sectors, as well as to better understand the influence of the pre-Alpine metamorphic inheritance on the forthcoming Alpine tectonic evolution.

ArcStereoNet is a new ArcGIS® based toolbox for stereographic projections that we implement here using Python 2.7 programming language. The reason to develop another stereographic projection package arises from the recent use of Python as an exclusive programming language within the ArcGIS® environment. This permits a more flexible approach for the development of tools with very intuitive GUIs, and also allows the user to take full advantage of all potential GIS mapping processes. The core of this new projections toolbox is based on the capability to easily apply and compare most of the commonly used statistical methods for cluster and girdle analysis of structural data. In addition to the well-known Fisher, K-means, and Bingham data elaborations, a completely new algorithm for cluster analysis and mean vector extraction (Mean Extractor from Azimuthal Data), was developed, thereby allowing a more reliable interpretation of any possible structural data distribution. Furthermore, as in any other GIS platform, users can always precisely correlate each single projected data point with the corresponding geographical/locality position, thereby merging or subdividing groups of structural stations with a simple selection procedure. ArcStereoNet also creates rose diagrams, which may be applied not only to fault/joint planes orientation data, but also for the analysis of 2D microstructural fabric parameters. These include geometrical datasets derived from the minimum bounding approach as applied to vectorized grains in thin sections. Finally, several customization settings ensure high-quality graphic outputs of plots, that also allow easy vector graphics post-processing.

The Rocca Canavese Thrust Sheets Unit (RCTU) is a subduction-related mélange that represents the eastern-most complex of the Sesia–Lanzo Zone (SLZ), bounded by the Periadriatic (Canavese) Lineament that separates the Alpine subduction complex from the Southalpine domain. The RCTU is limited to the south by the Lanzo Massif (LM) and to the east by the Eclogitic Micaschists Complex (EMC). Particularly the tectonic contact area of the RCTU, adjacent to the neighbouring SLZ and the LM is characterised by a 100–200-m-thick mylonitic to ultra-mylonitic zone (MZ) that was active under blueschist-to greenschist-facies conditions. Despite the dominant mylonitic structure, some rocks (garnet-bearing gneiss, garnet-free gneiss and orthogneiss) still preserve pre-mylonitic parageneses in meter-sized domains. The scarcity of superposed structures and the small size of relicts impose a detailed microstructural analysis supported by chemical investigation to reconstruct the tectono-metamorphic history of the MZ. Therefore, we integrated the classical meso- and microstructural analysis approach with a novel quantitative technique based on the Quantitative X-Ray Map Analyzer (Q-XRMA), used to classify rock-forming minerals starting from an array of X-ray elemental maps, both at whole thin section and micro-domain scale, as well as to calibrate the maps for pixel-based chemical analysis and end-member component maps, relevant for a more robust conventional geothermobarometer application as well for calculating reliable PT pseudosections. Pre-Alpine relicts are garnet and white mica porphyroclasts in the garnet-bearing gneiss and biotite and K-feldspar porphyroclasts in garnet-free gneiss and orthogneiss, respectively, providing no PT constraints. The Alpine evolution of the MZ rocks, has been subdivided in three deformation and metamorphic stages. The first Alpine structural and metamorphic equilibration stage (D1 event) occurred at a pressure of ca. 1.25–1.4 GPa and at a temperature of ca. 420–510 °C, i.e. under blueschist-facies conditions. The D2 event, characterised by a mylonitic foliation that is pervasive in the MZ, occurred at ca. 0.95–1.1 GPa and ca. 380–500 °C, i.e. under epidote-blueschist-facies conditions. The D2 PT conditions in the MZ rocks are similar to those predicted for the blocks that constitute the RCTU mélange, and they overlap with the exhumation paths of the EMC and LM units. Therefore, the RCTU, EMC and LM rocks became coupled together during the D2 event. This coupling occurred during the exhumation of the different tectono-metamorphic units belonging to both continental and oceanic lithosphere and under a relatively cold thermal regime, typical for an active oceanic subduction zone, pre-dating Alpine continental collision.

The Aspromonte Geopark project rises from the peculiar geological history of this sector of the southern Italian peninsula, apparently in continuity with the rest of the thin-skinned thrust-sheet system of the Apennine-Magrebian orogenic system, although characterized by deep-seated crystalline basement rocks, interpreted as fragmented relics of a sector of the original southern European Variscan chain (Cirrincione et al., 2015). These rocks are the result of an ancient geological history rooted since the Paleozoic to arrive up to the already active seismogenic tectonic activity, passing through the Oligocene-Miocene syn-orogenic clastic deposition of the Stilo Capo d’Orlando Formation and the evaporitic deposits, which testifies the Messinian salinity crisis. This peculiar geological heritage allows the preservation of an articulated geodiversity that contribute to the unraveling of two orogenesis (i.e. Variscan and Alpine), testified by the presence of intensively deformed metamorphic rocks, involved in two orogenic cycles (Ortolano et al., 2005; 2014; 2020), as well as in the occurrence of syn-orogenic sedimentary deposits covered in turn by the back thrusting of the Varicolori Clays and the final deposition of the Gessoso-solfifera succession. At the moment, the growing Aspromonte Geopark counts 89 geosites, eight of which are of international importance and five inserted within territorial and cultural landscape units. Many of these geosites are able to experiment new ways to communicate, with the aid of new technologies (i.e. GIS, 3D Virtual outcrop reconstruction and VR), the slow movement of the Earth crust, testified and preserved in different geosites, where is possible to observe clearly the presence of mylonitic rocks (i.e. rocks involved in high strain-rate regime undergoing plastic deformation) as well as the occurrence of several types of folding system activation, such as flow perturbation fold system evolving to sheath folds (Fazio et al., 2017; 2018; Ortolano et al., 2020). This geological peculiarity can communicate as a metamorphic outcrop can be read as an Earth-moving view where are enclosed pieces of the memory of the rock incessant slow movement of Earth interior. References Cirrincione, R., Fazio, E., Fiannacca, P., Ortolano, G., Pezzino, A., Punturo, R. (2015) - Periodico di Mineralogia, 84 (3B) Fazio, E., Ortolano, G., Visalli, R., Alsop, I., Cirrincione, R., Pezzino, A. (2018) Italian Journal of Geosciences, 137 (2), pp. 208-218. Fazio, E., Ortolano, G., Cirrincione, R. (2017) International Journal of Earth Sciences, 106 (6), pp. 2039-2040. Ortolano, G., Cirrincione, R., Pezzino, A. 2005 Schweizerische Mineralogische und Petrographische Mitteilungen, 85 (1), pp. 31-56.

A combined structural and petrological study focuses on the Sila Piccola Massif to obtain new constraints on the exhumation history of a relic fragment of the intermediate to deep portion of the Variscan basement, which now belongs to the northern Calabria Peloritani Orogen. The timescale of the early (i.e. late-Variscan) shear-assisted exhumation stage is determined by diffusion-modelling and the strain rate of the latest (i.e. Alpine) shear event is determined by microstructurally derived paleopiezometry. The intermediate to deep portion of the Sila basement is characterised by a pervasive mylonitic horizon involving orthogneiss and, to a lesser extent, garnet paragneiss. Such a pervasive mylonitic foliation widely obliterated an older metamorphic fabric, which is preserved as relics in low-strain domains. The pre-mylonitic relics consist of plagioclase, biotite, white mica, sillimanite, quartz and the first generation of chemically homogeneous garnet. Our results show that the later mylonitization can be ascribed to two metamorphic stages. The first stage is associated with a late-Variscan extensional shearing, which shows a syn-kinematic growth of a second-generation garnet with plagioclase, biotite and quartz developed in the pressure shadows of garnet porphyroclasts likely during an early retrograde metamorphic stage. The second stage, characterised by a syn-shearing growth of chlorite, white mica, plagioclase and quartz, observed along the C-planes, is interpreted as a late Alpine mylonitic overprint in compressional regime.

We apply Quantitative Microstructural Analysis (QMA) to a selection of mylonitic rocks that originate from different protoliths, ranging from tonalite to skarn and passing through migmatitic paragneiss. These rocks, that at the end of Paleozoic originally belonged to the lower crustal portion of the southern European Variscan chain, were successively involved in deep-seated strike-slip kinematics of the western Mediterranean realm, created by the relative movement in the Paleocene of the African-European colliding plates. This geodynamics leads to the roto-translation of the Sardinia-Corsica block and the drifting of the kabilo-clabride microplate system (Cirrincione et al., 2015). Remnants of these high strain-rate strike-slip zones are characterized by rheological behaviours controlled by the selective activation of their specific interconnecting weakening phase, as well as by the rheology and abundance of porphyroclasts. QMA is generated by means of new semi-automated GIS-based tools that allow us to extrapolate statistically meaningful kinematic and rheological properties of this meso-Alpine strike-slip mylonitic shear zone (i.e. Palmi Shear Zone). This, in turn, constrains the Alpine evolutionary stages of southern Calabrian geodynamics (Ortolano et al., 2020). Semi-automated image analysis of mXRF maps, combined with high-resolution thin-section scans involving new GIS-based tools developed for structural analysis (e.g. Ortolano et al., 2018; Visalli, 2018), was performed on a selection of three different mylonitic rock-types. These tools permit the user to quantitatively extrapolate rock-fabric parameters such as grain size, aspect ratio and orientation, which allows the nature and relative percentage of the weakening vs. hardening layers, as well as their kinematics, to be derived. Our results allow us to distinguish the porphyroclastic domain levels constituted alternatively by feldspar, amphibole, pyroxene or scapolite, from the weakening phase ones dominated by quartz, biotite plus quartz, or by calcite when the weakening layer is controlled by skarns. Image analysis of porphyroclastic domains has been used to infer the dominant shear-type through Rigid Grain Analysis, revealing a pure shear component of 66 to 68 % for the mylonitic tonalites; 62 to 66 % for the mylonitic paragneisses; and 58 to 62 % for the mylonitic skarn. Image analysis conducted on quartz-rich domains allows an estimate of the shear strain rate, which ranges on average from 1.14*10-12 (1/s) for mylonitic paragneiss to 5.91*10-12 (1/s) for mylonitic tonalite, and is in accord with high strain zones in natural settings. Our results provide new insights into the kinematics and rheology of this exhumed relic of the deep-rooted early-Alpine strike-slip tectonics of the western Mediterranean. References Cirrincione R., Fazio E., Fiannacca P., Ortolano G. & Pezzino A., Punturo R. 2015. Period. Mineral., 84(3B), 701-749. Ortolano G., Visalli R., Godard G. & Cirrincione R. 2018. Comput. Geosci., 115, 56-65. Ortolano, G., Fazio, E., Visalli, R., Alsop, G.I., Pagano, M., Cirrincione, R. 2020. Journal of Structural Geology, 131, art. no. 103956. Visalli R. 2018. Plinius, vol 44, DOI:10.19276/plinius.2018.01014.

The Quartz Alkali-feldspar Plagioclase Feldspathoid diagram, better known as the Streckeisen diagram, is the reference tool used for the classification of plutonic rocks cropping out on Earth's surface. To facilitate the methodical calculations and analysis procedures for a correct plutonic lithotype nomenclature, a new computer tool (Auto-QAPF Plutonic) is here provided. This tool follows the official guidelines provided by the IUGS and reaches the specific rock name using mineral modal amounts together with chemical data if available, adding some other information such as the colour index prefixes (leuco- and mela-) or the special rock nomenclatures (e.g., trondhjemite), when useful. Finally, we focussed our attention to enriching the rock-type nomenclature with the specific textural features of the sample, using a stepwise controlled procedure consisting in the application of ArcGIS-based toolboxes able to extrapolate automatically the grain boundary of the rock constituents. This is in order to get more advanced information together with the rock nomenclature, such as the mineral grain size distribution as well as the occurrence of a potential fabric anisotropy (e.g., S-L fabrics). informatic implementation of plutonic rock classification, accompanied by the automatic extrapolation of fabric parameters opens up the possibilities to the Earth science teachers of the high schoolto face a complex aspect of the geosciences, as the rock nomenclature in a speedy and easy way facilitating the process of acquiring learners.

Quantitative microstructural investigations involving new GIS-based tools are applied to three different types of mylonitic rocks. These techniques enable mineral shape distribution maps to be produced, thereby allowing the nature and relative percentage of the weakening vs. hardening layers, as well as their kinematics, to be obtained within a statistically meaningful dataset. Selected rock-types are derived from shearing associated with the meso-Alpine strike-slip tectonics of the western Mediterranean realm, which since the Paleocene has involved, skarn, migmatitic paragneiss and tonalites. These rocks belong to a deep-seated portion of the original southern European Variscan chain known as the Calabrian Pelortani Orogen. Microstructural maps reveal porphyroclastic domains, represented alternatively by feldspar, amphibole, pyroxene or scapolite, that can be distinguished from weakening phase areas, characterised by quartz, biotite plus quartz, or alternatively by calcite when the weakening layer is controlled predominantly by skarns. Image elaboration of porphyroclastic domains was employed to estimate the dominant shear-type, with Rigid Grain Analysis, indicating a pure shear component of 66–68% for the mylonitic tonalites; 62–66% for the mylonitic paragneisses; and 58–62% for the mylonitic skarn. Grain boundary mapping of the quartz-rich domains also permits an estimate of shear strain rate, which ranges from 1.14*10−12 (1/s) for mylonitic paragneiss to 5.91*10−12 (1/s), for mylonitic tonalite, and is in accord with high strain zones in natural settings. Finally, our results opened up new perspectives in the interpretation of the kinematics and rheology of this exhumed sector of the southern European Variscan chain reflecting the deep-seated meso-Alpine strike-slip tectonics of the western Mediterranean realm.

The present contribution aims to highlight the geological aspects of a path in the southern flank of Mount Etna, in terms of effectiveness for teaching geosciences. Recently, on the Etnean territory, several trails have been marked by local and national associations; nevertheless, it is worth noting that, up to now, no didactical geological paths have been proposed. The geo-trail here proposed is named after the geologist-naturalist Carlo Gemmellaro (1787-1866) and develops for similar to 3 km in length at an altitude of about 1300 m a.s.l. Along this itinerary, it is possible to admire several lava flows relative to eruptions occurring on the second half of the XIX century up to the beginning of the present century. These eruptions shaped the landscape of this sector of Mount Etna. The geo-trail is peculiar since, in a quite short distance, it permits geotourists to observe volcanic structures such as hornitos, pyroclastic cones, lava flows and lava channels as well as several volcanic rock types and to become familiar with the volcanic landscape. For the above reasons, the geo-trail constitutes a valid tool to educate students during their educational path through laboratory activities in the field, permitting direct learning of the volcanic processes and, at the same time, multidisciplinary approach to natural events. Finally, the XIX century eruptions are well documented by detailed historical and cultural reports, which explain also the close link between natural phenomena and emotional effects on the population.

In the southern sector of the Calabrian Peloritani Orogen (CPO; southern Italy), a crustal-scale shear zone (Montalto Shear Zone - MSZ) has developed under greenschist facies conditions (0.3-0.6 GPa for 350-550 degrees C) during Alpine orogenesis linked to the collision between the Adria and European plates. Deformation produced a mylonitic horizon up to 800 meters thick and a dominant top-to-NE sense of shear has been recognized. This high-strain zone is localized at the contact between two tectono-metamorphic units, the Aspromonte Peloritani Unit (APU), and the Madonna di Polsi Unit (MPU) that are characterized by a strong lithological contrast, with leucocratic ortho- and para-gneiss of the APU being thrust onto garnet-bearing phyllites (MPU). Mesoscopic structures typical of ductile shear zones are observed and include mylonitic foliation, stretching lineation, and sheath folds showing the typical eye-type cross sections, which occur at a range of outcrop to thin section scales. Several deformational phases have previously been interpreted from mesoscopic structures in this area. After careful field investigation, we propose an alternative model that interprets structural features in terms of progressive deformation developed during the same tectonic event. In particular, a folding phase, with sub-vertical axes and ca. 2 meters wavelength folds, which in past reconstructions were interpreted to be generated during a post-shear compressive episode, have now been considered the result of incremental strain coeval with the main shear zone activity (i.e. syn-shear). This new interpretation simplifies the tectonic history of the MSZ, and allows the removal of a previously identified tectonic phase.