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A careful petrologic analysis of mylonites’ mineral assemblages is crucial for a thorough comprehension of the rheologic behaviour of ductile shear zones active during an orogenesis. In this view, understanding the way new minerals form in rocks sheared in a ductile manner and why relict porphyroblasts are preserved in zones where mineral reactions are generally supposed to be deformation-assisted, is essential. To this goal, the role of chemical potential gradients, particularly that of H2O (µH2O), was examined here through phase equilibrium modelling of syn-kinematic mineral assemblages developed in three distinct mylonites from the Calabria polymetamorphic terrane. Results revealed that gradients in chemical potentials have effects on the mineral assemblages of the studied mylonites, and that new syn-kinematic minerals formed in higher-µH2O conditions than the surroundings. In each case study, the banded fabric of the mylonites is related to the fluid availability in the system, with the fluid that was internally generated by the breakdown of OH-bearing minerals. The gradients in µH2O favoured the origin of bands enriched in hydrated minerals alternated with bands where anhydrous minerals were preserved even during exhumation. Thermodynamic modelling highlights that during the prograde stage of metamorphism, high-µH2O was necessary to form new minerals while relict, anhydrous porphyroblasts remained stable in condition of low-µH2O even during exhumation. Hence, the approach used in this contribution is an in-depth investigation of the fluid-present/-deficient conditions that affected mylonites during their activity, and provides a more robust interpretation of their microstructures, finally helping to explain the rheologic behaviour of ductile shear zones.

The Italian Peninsula and Islands are among the most geologically diverse and tectonically dynamic regions in Europe and in the Mediterranean area [...]

In the present study, we unveil the real significance of mylonitic reworking of the polymetamorphic crystalline basement in the Serre Massif of Calabria (Southern Italy). We use a multidisciplinary approach to comprehend the structural, microstructural and petrologic changes that occurred along a, so far, not much considered shear zone affecting the Variscan lower crustal rocks. It was never before studied in detail, although some late Cretaceous ages were reported for these mylonites, suggesting that this shear zone is of prime importance. Our observations reveal now that the formation of the new structural fabric within the shear zone was accompanied by changes in mineral assemblages, in a dominant compressive tectonic regime. During this tectono-metamorphic event, high-P mylonitic mineral assemblages were stabilized, consisting of chloritoid, kyanite, staurolite, garnet and paragonite, whereas plagioclase became unstable. Average peak P–T conditions of 1.26–1.1 GPa and 572–626 °C were obtained using THERMOCALC software. These data question (i) that the Serre Massif represents an undisturbed continuous section of the Variscan crust, as generally suggested in the literature, and (ii) highlight the role of (eo-)Alpine high-P tectonics in the Serre Massif, recorded within mylonite zones, where the Variscan basement was completely rejuvenated.

The application of zircon dating to the reconstruction of orogenic systems is invaluable since time constraints of the geological evolution of orogens are crucial for the proposal of geodynamic and paleogeographic models. Zircon is one of the most promising accessory minerals in geochronology of crystalline basements because of its high-closure temperature. Moreover, U-Pb data of relict and recrystallized grains indicate the maximum sedimentation age as well as the timing of metamorphism in metasediments. In addition, the U-Pb ages of magmatic zircons constrain the timescale of magmatism. The Calabria–Peloritani terrane (CPT) represents a key area in the Southern Variscan Belt, whose reconstruction is still unresolved. Therefore, a review of literature zircon age data accompanied with new data from six samples of orthogneisses, paragneisses, amphibolites, and actinolite schists, helps to constrain the evolution of this Cadomian fragment, affected by metamorphic and magmatic Variscan events. A revisiting of the timing of the geological events from Paleo-proterozoic to Permian is revealed by comparing the internal textures of zircons and their U-Pb age clusters. The detected age peaks at 2500 Ma, 1600 Ma, and 1000 Ma in the CPT were related to a provenance from West and East Gondwana realms. A sedimentation age around 630 Ma emerges for the middle-deep crust terranes of the CPT, affected by Ediacaran (579–540 Ma) intrusions, accompanied by metamorphism dated at 556–509 Ma in the host metasediments. In the following, during Ordovician–Silurian extensional tectonics, the former Cadomian terranes were at least locally affected by fluid-assisted metamorphism (around 450 Ma) whereas the upper extensional basins that formed, were infilled by sediments along with interspersed volcanic to subvolcanic products. All these pre-Silurian terranes were involved in the subduction process of the Palaeotethys–Gondwana margin beneath Laurussia. The compressive phase began around 347 Ma, with under-thrusting of the formerly Gondwana substrate that was subjected to middle-high grade metamorphism, while the Ordovician–Silurian sediments were scraped off along the front of the Southern Variscan Belt and affected by low-grade metamorphism. Decompression of the whole Variscan orogenic system started around 320 Ma, together with uplifting of the chain and emplacement of widespread granitic intrusions which ended around 280 Ma and completed the Variscan orogenic cycle in the CPT.

The presence of recently intruded granites at Earth's surface suggests that their exhumation may have occurred rapidly. The Neogene granites of the Tuscan Magmatic Province (Italy) were emplaced during a period of extensional tectonics and are ideal for determining and quantifying the exhumation process. The peraluminous monzogranite of Giglio Island in the northern Tyrrhenian Sea is characterized by the presence of roof pendants, xenoliths and miarolitic cavities. The petrologic study of metamorphic xenoliths and new zircon U-Pb ages show that the granite was emplaced at 6.4-10 km depth at 5.7 ± 0.4 Ma. Exhumation, constrained by apatite (U-Th)/He ages, was essentially complete in 0.9 Myr at a minimum rate of 6 mm/year. This requires rapid tectonic unroofing, isostatic rebound and thermal softening activity, weakening the upper crust and favouring exhumation at a previously undocumented rate.

Terra rossa is a reddish clay soil which is often present on the surface of limestone in regions with a Mediterranean-type climate. Its genesis is a controversial subject in terms of the origin of the parent material, from the residuum of underlying (carbonate/dolomite) bedrock in the absence/presence of an external silicate contribution (e.g., aeolian dust). Within this context the main goal of the present work was the understanding of the geochemical processes leading to the formation of the terra rossa starting from the carbonate bedrock. We report the results of a multi-method analysis on a terra rossa deposit occupying the bottom of a Quaternary karst depression on Mesozoic limestones exposed in the Murge area (Apulia Foreland, southern Italy). Geological, petrographic, textural, and chemical data were collected on karst products (reddish calcite incrustations and nodules, and fine-grained portion of terra rossa) by a detailed field mapping, optical microscopy, XRF and fusion ICP/MS analyses and by scanning electron microscope. New collected data show that the mineralogical composition of reddish incrustations and nodules is comparable, consisting of fibrous and impure calcite, detrital fragments of quartz, K-feldspar, zircon and authigenic minerals as (Mn, Ba, Ca) phases, (Al, Si, Mn, Fe, Mg, Ba, Ca) minerals, Fe-kaolinite and anatase. The prevailing minerals, instead, in the fine-grained portion of terra rossa are hematite, kaolinite, and goethite. Based on the chemical composition, and especially on REE patterns, a progressive interaction of silicate aqueous solutions (with Al, Si, Fe), containing pelite material, with the calcareous bedrock, as a source of carbonic acid, was the process driving the formation of terra rossa. Obtained results add new elements to the definition of the long-lasting question about the genetic processes responsible for the formation of terra rossa, corroborating their polygenetic origin, as result of limestone alteration in conjunction with the chemical interaction with allochthonous siliciclastic material.

In the present study, we unveil the real significance of mylonitic reworking of the polymetamorphic crystalline basement in the Serre Massif of Calabria (Southern Italy). We use a multidisciplinary approach to comprehend the structural, microstructural and petrologic changes that occurred along a, so far, not much considered shear zone affecting the Variscan lower crustal rocks. It was never before studied in detail, although some late Cretaceous ages were reported for these mylonites, suggesting that this shear zone is of prime importance. Our observations reveal now that the formation of the new structural fabric within the shear zone was accompanied by changes in mineral assemblages, in a dominant compressive tectonic regime. During this tectono-metamorphic event, high-P mylonitic mineral assemblages were stabilized, consisting of chloritoid, kyanite, staurolite, garnet and paragonite, whereas plagioclase became unstable. Average peak P–T conditions of 1.26–1.1 GPa and 572–626 °C were obtained using THERMOCALC software. These data question (i) that the Serre Massif represents an undisturbed continuous section of the Variscan crust, as generally suggested in the literature, and (ii) highlight the role of (eo-)Alpine high-P tectonics in the Serre Massif, recorded within mylonite zones, where the Variscan basement was completely rejuvenated.

Terra rossa is a reddish clay soil which is often present on the surface of limestone in regions with a Mediterranean-type climate. Its genesis is a controversial subject in terms of the origin of the parent material, from the residuum of underlying (carbonate/dolomite) bedrock in the absence/presence of an external silicate contribution (e.g., aeolian dust). Within this context the main goal of the present work was the understanding of the geochemical processes leading to the formation of the terra rossa starting from the carbonate bedrock. We report the results of a multi-method analysis on a terra rossa deposit occupying the bottom of a Quaternary karst depression on Mesozoic limestones exposed in the Murge area (Apulia Foreland, southern Italy). Geological, petrographic, textural, and chemical data were collected on karst products (reddish calcite incrustations and nodules, and fine-grained portion of terra rossa) by a detailed field mapping, optical microscopy, XRF and fusion ICP/MS analyses and by scanning electron microscope. New collected data show that the mineralogical composition of reddish incrustations and nodules is comparable, consisting of fibrous and impure calcite, detrital fragments of quartz, K-feldspar, zircon and authigenic minerals as (Mn, Ba, Ca) phases, (Al, Si, Mn, Fe, Mg, Ba, Ca) minerals, Fe-kaolinite and anatase. The prevailing minerals, instead, in the fine-grained portion of terra rossa are hematite, kaolinite, and goethite. Based on the chemical composition, and especially on REE patterns, a progressive interaction of silicate aqueous solutions (with Al, Si, Fe), containing pelite material, with the calcareous bedrock, as a source of carbonic acid, was the process driving the formation of terra rossa. Obtained results add new elements to the definition of the long-lasting question about the genetic processes responsible for the formation of terra rossa, corroborating their polygenetic origin, as result of limestone alteration in conjunction with the chemical interaction with allochthonous siliciclastic material.

We provide an updated overview of the known mineral deposits from the Sila and Serre Massifs in Calabria, contributing to setting their genesis within a complex geologic history, starting from the late-Carboniferous. We summarize the mineralization reported in the literature, with a critical review of the host tectonic units, by taking into account the upgrades in the knowledge of these areas. We also set them in updated geological maps and in stratigraphic columns, highlighting the crustal levels to which they pertain. Despite the geologic and minerogenetic similarities potentially existing with late- to post-Variscan mineral deposits from other regions (e.g., Sardinia and French Central Massif), the scientific literature on the Calabria mineralization is out-of-date and not exhaustive. Moreover, these ore deposits were likely considered not economically attractive enough to stimulate new scientific studies. However, in our opinion, such studies are needed to resolve the main open questions, which rely on deciphering the origin and age of mineralization. Finally, research for critical elements hosted by the Sila and Serre mineralization (e.g., In, Ge and Ga in sphalerites) is a possible interesting new perspective.

Cartilaginous fish are particularly vulnerable to anthropogenic stressors and environmental change because of their K-selected reproductive strategy. Accurate data from scientific surveys and landings are essential to assess conservation status and to develop robust protection and management plans. Currently available data are often incomplete or incorrect as a result of inaccurate species identifications, due to a high level of morphological stasis, especially among closely related taxa. Moreover, several diagnostic characters clearly visible in adult specimens are less evident in juveniles. Here we present results generated by the ELASMOMED Consortium, a regional network aiming to sample and DNA-barcode the Mediterranean Chondrichthyans with the ultimate goal to provide a comprehensive DNA barcode reference library. This library will support and improve the molecular taxonomy of this group and the effectiveness of management and conservation measures. We successfully barcoded 882 individuals belonging to 42 species (17 sharks, 24 batoids and one chimaera), including four endemic and several threatened ones. Morphological misidentifications were found across most orders, further confirming the need for a comprehensive DNA barcoding library as a valuable tool for the reliable identification of specimens in support of taxonomist who are reviewing current identification keys. Despite low intraspecific variation among their barcode sequences and reduced samples size, five species showed preliminary evidence of phylogeographic structure. Overall, the ELASMOMED initiative further emphasizes the key role accurate DNA barcoding libraries play in establishing reliable diagnostic species specific features in otherwise taxonomically problematic groups for biodiversity management and conservation actions.