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Tesi etd-05042020-091613

Thesis type
Tesi di dottorato di ricerca
Settore scientifico disciplinare
Corso di studi
tutor Prof. Conticelli, Sandro
correlatore Dott. Agostini, Samuele
Parole chiave
  • petrology
  • geochronology
  • isotope geochemistry
  • Anatolia
  • Boron
Data inizio appello
Data di rilascio
Riassunto analitico
Anatolia consists of several continental fragments joined together as response of the final closure of the Neotethys Ocean during the Cenozoic Era, and it represents one of the most tectonically complex parts of the Alpine-Himalayan Orogen. The geodynamic evolution of the Anatolia was dominated by the Northward motion of the African and Arabian plates that converged towards the Eurasian Plate since the Late Cretaceous. While in the North this convergence caused the Neothetys Ocean to subduct along the southern Eurasian margin at the beginning of the late Oligocene to early Miocene, the anti-clockwise rotation of the Arabian Plate with respect to Africa led to the initial opening of the Gulf of Aden, followed by the development of the Red Sea and Suez Rift Systems, resulting into separation between African and Arabian plates. As response of these movements, the Dead Sea Fault developed as left-lateral strike-slip fault. In the middle Miocene, the final stage of Arabia-Eurasia convergence resulted in a continent-continent collision, marked by the development of the Bitlis-Zagros Suture Zone. As a result of this geodynamic scenario, a widespread volcanic activity developed troughout Anatolian region during the Cenozoic. Radiogenic (Sr-Nd-Pb) and B isotopes, coupled with major and trace elements geochemistry, K-Ar and 40Ar-39Ar age determinations has been carried out in volcanic rocks erupted in the Central to South-East Anatolia and North-West Arabian Foreland. The purpose of this work is to characterise the magmatic rocks emplaced in these regions, to constrain the age of emplacement of the volcanic products in relation to tectonic evolution of the region, and to describe the characteristics and compositions of their mantle source/s.
In the Cappadocia Volcanic Province, no temporal transition between calc-alkaline subduction-related and Na-alkaline within-plate magmatic activity was recorded. Volcanic rocks emplaced in this region are coeval (Pleistocene), with Na-alkaline magmas not resembling typical OIB-type magmas. The distribution in incompatible trace elements, as well as the similar isotopic composition between calc-alkaline and Na-alkaline magmas suggest interaction between two different magma types: i) melts originated in a pristine sub-lithospheric mantle source; and ii) melts originated in a subduction-modified mantle domain previously metasomatised by fluids released from subducting slab sediments.
In the Sivas-Malatya Volcanic Province, calc-alkaline magmatic activity developed during the early-middle Miocene in the Yamadağ and Kepez Dağ volcanic complexes. Westward, coeval Na-alkaline magmas emplaced along the Kızılırmak strike-slip fault, and continuing to the East during the middle-late Miocene, and covering the calc-alkaline sequences of the Yamadağ in the Arguvan area. Finally, during the Pliocene, K-rich volcanic rocks emplaced in the Kangal basin. Rocks erupted in the Yamadağ and Kepez Dağ are typical arc-like magmas connected to the subduction of African plate beneath Eurasian one. On the contrary, Na-alkaline rocks are characterised by different geochemical and isotopic signatures which imply a persistence of a relict subduction-related geochemical signature for the mantle source of Sivas magmas, not recorded for the rocks of Arguvan. Yougest magmas emplaced in the Kangal basin are similar in composition to typical OIB-like magmas, with their high concentrations of K explainable with digestion of crustal material during magmatic evolution.
Further South, at the Anatolia-Africa-Arabia plate junction, and within the northern portion of the Arabian plate, volcanic activity resulted in the generation of mafic magmas and abundant eruption of alkali basalts, both pre-dating (early Miocene) and post-dating (Pleistocene) the ~13 Ma Arabia-Eurasia continental collision. In more detail, the volcanic activity is found close to the strike-slip system delimited by the Karataş-Osmaniye Fault Zone (Osmanyie volcanic field), the Amanos Fault Zone, the northern termination of the Dead Sea Fault (Karasu volcanic field), and in the North-West foreland of the Arabian Plate, within the Gaziantep Basin, and in the Karacadağ Shield Volcano. The geochemical and isotopic data obtained from this study indicate that the volcanic rocks emplaced in these areas have Na-alkaline affinity with trace element distribution and isotopic features typical of a variably depleted sub-lithosperic mantle, with no evidences of subduction-related metasomatism.