This research project is based on two complementary approaches (igneous petrology and sedimentology) aiming to understand the shallow and the deep processes operating during the shaping of the Mediterranean Sea.
A first aim is to identify the mantle sources activated during igneous activity in the entire circum-Mediterranean area by analysing the petrography, mineral chemistry, whole-rock chemistry and Sr-Nd-Pb isotope geochemistry of selected volcanic districts in several countries (Spain, France, Italy, Egypt, Turkey). Many of these districts have been already sampled in the past years, but the collected rocks have not yet been fully processed. For this reason only limited fieldwork is scheduled for this activity.
The second aim is to reconstruct the oceanographic evolution of the Central Mediterranean area within the Eocene-Miocene interval, identifying the main controlling factors on water chemistry and discriminating between global and regional causes that affected the Central Mediterranean main water body by analysing the isotopic signature of C, Sr and Nd of different carbonate succession. In this case more abundant fieldwork is scheduled, mostly confined to Italian areas.
An innovative Sr-Nd-Pb-C-O isotopic study on both the silicatic and the carbonate rocks will be investigated, in collaboration with CNR laboratories of IGAG (Rome) and IGG (Pisa).
The role of the volatiles in the genesis and evolution of magma chambers will be investigated, with particular emphasis given on the interaction of magma with limestone country rocks in central Apennines and the effect of volcanic activity on the development of carbonate platforms during the Neogene. Also the role of H2O during the formation and evolution of subduction-related magmas in central-eastern Anatolia will be studied by means of all the most modern analytical techniques (Ar-Ar dating, LAM-ICP-MS, EMP, TIMS and so on).
The igneous districts chosen for investigation are the least studied within the circum-Mediterranean area (Lustrino and Wilson, 2007; Lustrino et al., 2011). Based on the new data a complete petrogenetic model will be proposed, aiming to constrain the role of volatile phases in the genesis and evolution of magma batches and the role of tectonic forces in triggering specific styles of igneous activity.
For example, a model invoking digestion of sedimentary carbonates (the Triassic Dolomia Principale Fm and Lower Jurassic Calcare Massiccio Fm) by ultrabasic melts will be tested for the Polino igneous rocks. This model is completely at odds with the existing model which requires digestion of silicatic rocks (peridotite) by a Ca-carbonatitic melt. For the Provençal and Anatolian case studies, a role of H2O will be investigated constraining the volatile budget of the mantle sources on the basis of the mineral chemistry and the liquid line of descent. A somewhat similar approach has been adopted successfully to re-interpret the ¿carbonatitic¿ evidences in the Calatrava volcanic district as the effect of limestone digestion by an ultrabasic silicatic melt (Lustrino et al., 2016).
A strict collaboration with Turkish colleagues, also with expertise in the field of structural geology and volcanology will lead to a full comprehension of the main mechanisms at the base of the very complex igneous activity in central-eastern Anatolia.
A close comparison of the Provençal rocks with the coeval lithologies cropping out in Sardinia (which has been deeply investigated by the principal investigator of this research project) will shed light on the causes associated to opening of the Western Mediterranean area.
Last, the comparison between the sodic alkaline volcanic rocks of SE Spain (Picasent, Cofrentes, Columbretes) and the same rock types of the Bahariya Oasis in NE Egypt will clarify the causes of igneous activity as related to shallow processes (e.g., adiabatic upper mantle upwelling) or deep mantle involvement (e.g., active upwelling of a thermal anomaly in the form of mantle plumes).
As concerns the investigation of the sedimentary rocks, it is worth noting that Sr isotopes have been extensively studied to date and correlate carbonate successions (De Paolo and Ingram 1985; McArthur 1994; Mcarthur et al. 2012; Brandano and Policicchio 2012). This project follows a different approach, measuring Sr isotopes on well age-constrained successions to see whether they follow or deviate from the reference line, and to identify the causes of the mismatches (volcanism, restricted water exchanges, fresh water input). The role of volcanism in controlling Sr isotope ratios has been demonstrated on a global scale during the onset of the Large Igneous Provinces (Larson and Erba, 1999), while little is known about the effect of regional volcanism on small basins (e.g., Brandano et al., 2010, 2015). As far as the Mediterranean is concerned, a deviation of the Sr isotope signal has been identified in the Messinian, during the isolation of the basin (Schildgen et al., 2014), but little is known about the previous time interval, notwithstanding the complex water exchanges between the Mediterranean, the surrounding oceans and the Paratethys during Miocene. Likewise, Nd isotopes have been widely studied for ocean circulation pattern reconstructions over the last decades, but literature on the Mediterranean is still very scarce (Kocsis et al., 2008; 2009).
Integrating the Sr and Nd isotopes results with the C isotope signatures of the Central Mediterranean carbonate successions will allow to identify thecontrolling factors on Mediterranean water chemistry and the consequences of volcanism, run off and circulation changes on carbonate systems, thus on the carbon cycle. Last but not least, the interdisciplinary approach of this project is itself an important innovation. Two specialized teams will, in fact, work independently on different aspects of the Mediterranean Cenozoic evolution, and then will converge on an integrated study to provide new insights on the complex oceanographic and tectonic evolution of this area.
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