Effect of iron and nanolites on Raman spectra of volcanic glasses: A reassessment of existing strategies to estimate the water content

Martian basalts are different from Earth by their iron‐rich abundance with 18 wt% FeOtot in average for Mars upper crust. The H2O dissolution mechanism in this atypical melt composition is not well understood. We have synthesized H2O‐bearing martian basaltic glass analogs (10 < FeOtot < 16 wt%) under high pressures (0.5–1.5 GPa) and temperatures (>1500°C) conditions. We used Raman and Fourier transform infrared spectroscopies to investigate the effect of H2O as well as the high FeOtot content on the molecular structure of Fe‐rich glasses. Increasing Fe content appears to inhibit the dissolution of H2O in the melt. In fact, it appears that Free OH groups are formed at relatively low H2O content in Fe‐rich melts (1 wt%), whereas they only appeared at high H2O content (~6.5 wt%) for Fe‐poor glasses. We suggest that the Free OH are bonded to Fe2+ cations in the melt forming isolating clusters of Fe (OH)2. Such configurations are suspected to induce an increase in the melt polymerization. The presence of free hydroxyls dissolved in the melt is likely to have a major impact on the genesis of aqueous fluid phase at the surface of Mars.

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Particular H₂O dissolution mechanism in iron‐rich melt: Application to martian basaltic melt genesis

Larre

Morizet

Bézos

et al. 2019

A calibrated database of Raman spectra for natural silicate glasses: implications for modelling melt physical properties

Giordano

González-García

Russell

et al. 2019

Self Cite

The physical properties of silicate melts are of critical importance for understanding magmatic and volcanic processes on Earth and other planets. Most physical properties of melts are, ultimately, a consequence of the structural organization of the melt. Robust and fully generalizable strategies for the prediction of properties of naturally occurring melts as functions of composition, temperature, and pressure remain a challenging goal. Given the structural origin of macroscopic properties, Raman spectroscopy of glasses, which provides information on melt and glass structure, may provide a useful technique to understanding and quantify variations in macroscopic melt properties. Here, with the aim of providing a generalizable model for predicting the viscosity of silicate melts, we present the results of a Raman spectroscopy campaign performed on 30 anhydrous multicomponent silicate glasses resulting from quenching of remelted and homogenized volcanic rocks and synthetic equivalents. The sample suite comprises one of the largest databases of multicomponent melts for which (a) chemical compositions and (b) physical properties (i.e., viscosity, fragility, heat capacity, and glass transition temperature) are known. Raman spectra have been collected using green light sources at wavelengths of 532 nm. Spectra were collected on the same sample suite in four independent laboratories involving instruments from different manufacturers and, thus, using different spectrometers, detectors, and analytical conditions. Our results are also compared and integrated with published data on some of the same samples derived from two others setups using green light sources with 514.5 and 532 nm wavelegths. For the same sample, the Raman spectra acquired using different setups show different intensities and intensity ratios. However, a strategy based on the ratio between the low‐ and high‐wavenumber peaks (R) was developed to standardize the data to normalized Raman ratios (Rn) and thus to remove interlaboratory differences. Using these advances, we predict melt viscosity solely with the use of Raman spectral measurements of multicomponent silicate glasses, thus demonstrating the potential of the method in describing physical properties of silicate melts.

New insights about the role of Na–K ratio on the vibrational dynamics of synthetic‐basalt glasses

Cassetta

Zanatta

Biesuz

et al. 2022

Basalts are among the most abundant igneous rocks on Earth. Originated from the rapid cooling of magma erupted by volcanoes, they are increasingly used as raw materials in glass and ceramic technology due to their unique physicochemical properties. The characteristics of basalts, like the glass transition temperature, are strongly controlled by their structure, which is a function of composition. Therefore, the investigation of the interplay between the intimate structure and the mechanical and physical properties of basalt glasses is of paramount importance in view of their industrial exploitation. Here, we present a Raman study of a set of synthetic-basalt glasses in which the occurrence of small chemical variations appreciably affects their glass transition temperature. We analyzed the Raman spectra focusing on both the spectral regions of the so-called nonbridging oxygens and of the boson peak. We show the existence of a scaling law for the boson peak of four synthetic-basalt glasses, and we infer from its breakdown the occurrence of a deep reorganization of the glass structure resulting from the Na-K replacement in the network, despite small variations of the other major elements.