Tesi di Dottorato
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Item Facies analysis and fluid inclusion studies of the Messinian evaporites, Calabria, Southern Italy(Università della Calabria, 2020-03-26) Cipriani, Mara; Critelli, Salvatore; Costanzo, Alessandra; Dominici, RoccoMessinian salinity crisis (MSC) is, from about 30 years, one of the most important and debated topic in the scientific community, both in environment and economic field. In this context, Calabrian evaporite deposits, poorly investigated in the past, offer an interesting opportunity to expand the knowledge because they confirm and increase the models created for other Mediterranean basins, and add important information on the main halite and gypsum facies. In this regard, saline evaporitic facies outcropping in the Crotone, Catanzaro and Ionic Basins were investigated using a multidisciplinary approach from classical petrography, to the study of fluid inclusions (FIs) to isotopic geochemistry. (A) The halite samples from the Crotone Basin have highlighted three primary facies; two known in the literature as banded and white while the third, never observed before, called in this work transparent. The transparent facies seems recrystallized but the analyses conducted show instead a primary origin. The three facies form in different environment and with a dissimilar deposition rate (fast or slow) due to pycnocline oscillation (daily or seasonal). Pycnocline oscillations can explain the different temperature of homogenization found within the FIs (from +20° to +33°C). The facies form in a hybrid brine (salinity av. ̴ 26.2 eq. wt% NaCl) enriched in Ca-Mg-Na-K-Cl elements, regardless of their deposition rates. During their fluid inclusions testifying plastic and ductile deformations that don’t remove primary features, demonstrating low recrystallization during burial process. Moreover, isotopic data attribute these facies at the second step of the MSC (5.6-5.5 Ma) during Halite deposition stage in the Mediterranean Basin. (B) The selenite samples from the Catanzaro Trough belong to banded and giant facies. The crystals record middle-frequency climatic oscillation between the depositional cycles and high-frequency climatic oscillation (seasonal) between cloudy and clear microfacies observed within the crystals. These microfacies testify a different brine condition associated with seasonal variation: cloudy intervals form during continental water inflow in the humid phase (Mg and Ca as dominant elements and low salinity values - av. ̴ 3 eq. wt% NaCl), while, clear intervals form in marine water during the arid phase (Na, K and Cl as dominant elements and high salinity values - av. ̴ 21.5 eq. wt% NaCl). Isotopic data attribute these facies at the third step of the MSC (5.5-5.3 Ma) placing, for the first time, the formation of the giant facies at the Upper Gypsum stage in the Mediterranean Basin. (C) The analyses conducted on the gypsum deposit from the Ionian Basin have shown that these crystals do not display primary features. This deposit is an olistostrome. The isotopic data confirm secondary origin attributing these facies at the second step of the MSC (5.5-5.3 Ma) during the Resedimented Lower Gypsum deposition stage in the Mediterranean Basin. The data obtained from the study of the Calabrian Messinian deposits indicate a surprising variety and diversity of evaporitic facies. In this work, it emerges that the formation of, crystals trap primary FIs and microalgae (blue, green and yellow). Primary FIs and organic matters, associated with secondary the different facies is strongly conditioned by climate (wet/arid) and intrinsic characteristics of the basin (depth, arrival of continental water flows etc.) which promote the development of one facies rather than of another.Item Petrographic and geochemical study of the Jarosite bearing layers of Aeolian Islands(2014-11-26) Khyabani, Fahimeh Ryazi; Pantano, Pietro Salvatore; Barca, Donatella; Crisci, Gino MirocleA thin reddish-brown Surface Coating (SC) layer has diffusely covered many outcrops of Vulcano Island (one of the Aeolian Islands), located in the Tyrrhenian Sea, south Italy. Vulcano, in the last 120ka has been subjected to volcanic activities including both eruptions (pyroclastic and lava types in shoshonitic and leucite-tephritic series) and fumarolic degassing. The SC that has been formed on almost all these lithologies appears as a reddish (sometimes pinkish) brown glass-like rind with a greasy luster which adheres to substratum and fills and completely seals its surface irregularities. The precise formation process of the SC is what we have tried to model in the present work. The SC in Vulcano, like other active volcanic precincts, includes amorphous silica associated with a sulfate phase as jarosite mineral. Jarosite as a basic hydrous sulfate of potassium and iron is the head member of jarosite subgroup. Under the microscope, SC is consisted of a micro laminated layer (less than 1μm to 7μm in thickness) which is composed of alternative dark and light laminae. The light laminae are composed of jarosite, while the darker ones are made of almost pure silica. In many cases of the SC, the laminae encompass lenticular areas containing coarser mineral crystals and noticeable number of glass shards, very fresh to altered in different grades, within an inexplicit background. The relations between all these components (laminated portion and the trapped area between different subsets of laminae) creates some particular textures such as lentic/eye texture; convoluted texture (flow of laminae); branching, rejoining, and tee-shaped perpendicular junctions of the laminae. These particular textures are quite comparable to the patterns of Liesegang Bands in the microscopic scale. Permeability of the rock; the presence of reactants such as oxygen, iron, and sulfur; and a potential fluid to be supersaturated are required factors for developing the Liesegang bands. The porous surface of the pyroclastic deposits of Vulcano can be exposed to the acidic fluids (produced by the interaction between water and fumarolic gases) and the availability of the iron and sulfur can provide the suitable condition to form the Liesegang patterns.Item Genesi ed evoluzione del magmatismo basico nelle successioni carbonatiche triassiche nel Complesso Alpujárride (Cordigliera Betica) e nelle Unità Appenniniche della Calabria settentrionale(2012-11-28) Matrangolo, Gilda; Piluso, Eugenio; Liberi, Francesca; Rojas, Iván MartinPermo-Mesozoic extension represents one of the most noticeable geological processes in the western Mediterranean. Triassic sedimentary sequences observed along the Dinaride-Hellenide orogenic belts and in Betic Cordillera are locally related with a basic magmatism in an extensional tectonic setting. Carbonates sequences which include basic rocks can be observed in the Alpujarride Complex (central-eastern Betic Cordillera, Spain) and in the Lungro-Verbicaro Unit (northern Calabria). Betic Cordillera represents an important orogenic belt sited in the southern and southeastern side of the Iberian Peninsula and it is commonly divided into three main geological units: the Betic External Zone, Campo de Gibraltar Complex and the Betic Internal Zone, which include various tectonostratigraphic units arising from previous paleogeographical domains developed during the Mesozoic, as a consequence of the break-up of the Pangaea supercontinent. According to Iannace et al. (2007), the Meso-Cenozoic carbonates sequences outcropping in northern Calabria can be grouped into three tectonic units: the Lungro-Verbicaro Unit, the Cetraro Unit and the Pollino-Ciagola Unit. The Lungro-Verbicaro Unit is represented by a thick sedimentary succession affected by HP-LT metamorphism and consisting of phyllites and metarenites with carbonate intercalations in its lowermost part of Middle Triassic. Basic rocks can be found as a small intrusive complex within the Anisian phyllites and the Ladinian-Carnian carbonates of the Lungro-Verbicaro Unit. As Mesozoic geodynamic processes, since the opening of the Tethys, are recorded in the above rocks, the attention was focused on these two areas. The aim of this research was to study these basic magmatic rocks in order to obtain a better interpretation of the extensional tectonic process and to recognize a possible hydrothermal metamorphic overprint. In fact, the latter process is suggested by significant mineralizations observed in the outcrops of the Alpujarride Complex, due to the activity of a hydrothermal metamorphism in the Betic area. Basic rocks were characterized from a petrological and geochemical standpoint with the purpose of determining the characteristics of their source. A multidisciplinary approach was followed in both areas. Firstly, a field geology work (with the addition of photo-geological analyses for the Betic area) was performed to constrain relationships between basic rocks and wall rocks. Secondly, laboratory analyses were carried out in order to determine petrographic, petrological and geochemical characteristics of study samples. Petrographic analyses were performed using both the optical and scanning electron microscopy techniques, whereas petrological data were obtained by the electron microprobe. Lastly, geochemical composition of study rocks was characterized by X-ray fluorescence spectroscopy (XRF), and the obtained data were processed using suitable diagrams.