Ricerc@Sapienza

The oxidation state of the Earth's interior is the main variable controlling the speciation and cycle of volatile elements like carbon in the reduced form of diamond, or oxidized carbonate minerals and CO2-rich melts. The release of carbon into the atmosphere as CO2 is likely to have occurred as consequence of sudden changes of the mantle redox state promoted by increase of oxygenation (Kasting et al. 1993, Stagno and Fei 2020). Such increase is known to cause changes in the ferrous/ferric iron ratio of the surrounded minerals that, at depths below 400 km are represented by majoritic garnet, ferropericlase and bridgmanite (Frost and McCammon 2008; Stagno 2019).
The main goal of this project is twofold: 1) to determine the ferric/ferrous iron ratio of synthetic majoritic garnet, ferropericlase and bridgmanite as function of pressure (P), temperature (T) and oxygen fugacity (fo2) through a series of experiments performed using the multi anvil press to simulate the interior of Earth; 2) to measure the ferric/ferrous iron ratio of natural majoritic garnet, ferropericlase and bridgmanite found as mineral inclusions in diamonds from Sao Luiz (Brazil). The aims of this ambitious research project will be achieved by performing experiments at pressures of 14-28 GPa and temperatures between 800-1700 °C using several multi anvil presses installed in Rome and abroad taking benefits of ongoing collaborative projects and agreements. Natural diamonds will be provided by international and national collaborators. Measurements of ferric/ferrous iron will be performed at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France). All expected results are novel and of high impact to the international community of geoscience with the chance to be published on high-IF journals. The collected data will have important implications for the redox state of the deep Earth's interior, the transport of volatiles through time and the origin of diamonds.