Physical, chemical and rheological properties of glasses and melts depend upon their structural arrangement at atomic scale. The extensive investigation conducted so far, mainly for industrial and volcanological purposes, lead to a rapid increase in diversification of technological materials and linked properties of erupted lavas to network structures in volcanic silicate melts and glasses. Conversely, very little is known for melts and magmas produced in the Earth's mantle, which are characterized by important amounts of volatiles (CO2, H2O) dissolved and are subject to considerable high pressure. This project aims to fill this gap through in-situ spectroscopic measurements combined with the use of a diamond anvil cell on synthetic volatile-bearing glasses representative of magmas that were observed to form in the Earth's mantle by experimental, geochemical and geophysical studies. Synchrotron micro-FTIR measurements in the mid-infrared region will be performed at the Material Science branch of SISSI beamline of Elettra Sincrotrone Trieste and Raman spectra will be acquired through the micro-Raman available at University of Roma Tre.
Results will be combined to in-situ multi-angle energy dispersive X-ray diffraction and viscosity measurements previously conducted at high pressure and temperature on the same molten starting materials at 16 BM-B HPCAT beamline of the Advanced Photon Source (Lemont, IL, USA) the Advanced Photon Source. This project will result in the use of the most innovative techniques in the field of Earth Sciences and will allow to evaluate the effect of pressure and volatile content on both the atomic structure and rheology of mantle magmas, to model their mobility and ascent and shed light on the flux of volatile species from the Earth's interior up to shallow depths.
In-situ synchrotron measurements combined with high pressure devices represent recently developed tools that open up the possibility to observe mantle melts and glasses response at the exact moment they are subject to pressure conditions which occur at mantle depths. It follows that such innovative techniques allow to obtain direct information, overcoming traditional methods that relied on inferences made from ex-situ investigations, therefore taking deep Earth science a step ahead. Noteworthy, the diamond anvil cell (DAC) that will be used in this project is a new model developed and, to date, no data relative to this device are available in literature. This therefore represents a unique opportunity to conduct in parallel testing and calibration of this DAC along with the achievement of the stated goals.
In addition, compositions employed in this study will overcome the employment of synthetic simplified compositions investigated in previous studies, instead exploring amorphous geomaterials which have both been demonstrated to form by partial melting experiments on carbonated mantle rocks and retrieved in nature with an unequivocal mantle signature. This project will thus allow to clarify the structural role of dissolved volatile species, largely ignored so far due to experimental issues, which is a distinctive characteristic of primitive melts formed by partial melting of mantle rocks.
Results arising from this research will thus allow to determine pressure-induced structural transformations of glasses and melts representative of the most primitive magmas originated in the Earth's upper mantle by combining in-situ vibrational spectroscopy at high pressure with previously conducted in-situ high pressure-high temperature EDXD melt structure and viscosity measurements, elucidating structural properties of deep magmas and major configurational changes that occur upon compression, allowing a quantitative correlation between structural and rheological properties, depicting an additional frame on the carbon and hydrogen cycle through the Earth's interior and magma ascent from great depth.