Ricerc@Sapienza

Alkali and lime-rich igneous rocks are among the most puzzling magmas known in literature. Several young (Holocene) case studies crop out in central Italy (San Venanzo and Cupaello villages), and slightly older (Pleistocene) or much older (Triassic) rock types cropping out in central Iran (Nawbaran area and surrounding zones) and southern Italian Alps (Dolomites), respectively will be investigated aiming to shed light on this debated topic. Together with these localities, also other volcanic districts in N Egypt, central Europe (e.g., Eifel, Germany) and NE Spain will be used as benchmarks.
The identification of Ca-carbonatitic activity in central Italy and Iran, as well as K-rich lithologies (shoshonite) in the Italian Alps have been considered key features to unravel the geodynamic settings of such three areas. In particular, the presence of carbonatitic magmas has been previously used to deny the existence of active or fossil subduction tectonic settings along peninsular Italy, proposing the existence of a deep seated mantle plume. The finding of ultrabasic compositions in a clear subduction-related setting in central Iran certainly reduces the validity of such an assumption.
The CaO and Na2O+K2O enrichment of these rare rock types can alternatively be related to the presence of carbonates stable at mantle depths or to interaction with limestones and dolostones at very shallow - crustal - pressures. This research study aims to understand which of these two main hypotheses can be considered reliable in these case studies.
Igneous activity has also a strong influence on the deposition, contributing to release large amounts of CO2 to the atmosphere-ocean system. Repeated volcanic CO2 pulses may cause a repeated decrease in pH and weak CaCO3 saturation and decreasing the calcification potential of carbonate biota up to the drowning of marine carbonate factories. Several case studies from central Italy and other circum-Tyrrhenian areas will be investigated.