Determination of cooling rates of glasses over four orders of magnitude

Abstract

Volcanic materials can experience up to eleven orders of magnitude of cooling rate (qc) starting from 10–5 K s−1. The glassy component of volcanic material is routinely measured via differential scanning calorimeter (DSC) to obtain qc through the determination of the glass fictive temperature (Tf). Conventional DSC (C-DSC), which has been employed for decades, can only access a relatively small range of qc (from ~ 10–2 to ~ 1 K s−1). Therefore, extrapolations up to six orders of magnitude of C-DSC data are necessary to derive qc of glasses quenched both at extremely low and high qc. Here, we test the reliability of such extrapolations by combining C-DSC with the recently introduced flash calorimetry (F-DSC). F-DSC enables to extend the qc exploration up to 104 K s−1. We use three synthetic glasses as analogs of volcanic melts. We first apply a normalization procedure of heat flow data for both C-DSC and F-DSC to derive Tf as a function of experimental qc, following the “unified area-matching” approach. The obtained Tf–qc relationship shows that Arrhenius models, widely adopted in previous studies, are only valid for qc determination within the calibration range. In contrast, a non-Arrhenius model better captures qc values, especially when a significant extrapolation is required. We, therefore, present a practical “how-to” protocol for estimating qc using DSC.

A chemical threshold controls nanocrystallization and degassing behaviour in basalt magmas

“…1) in the heat flow curve, defined as the signal undershoot (exothermic = positive value) after the onset of the glass transition T onset (Supplementary Fig. 1) 32,77,94,197,198 ; we subsequently cooled the material down to room temperature at 10 K min −1 (Supplementary Fig. 2).…”

Timescale of Emplacement and Rheomorphism of the Green Tuff Ignimbrite (Pantelleria, Italy)

“…The unmatching cycles at q h = 10°C/min are shown as blue curves, whereas the matching cycles at q c,h = 10°C/min are reported in red lines. Scarani, Vona, et al, 2022). Error bars are smaller than symbols.…”

“…The heat capacity (c P ; J/(g °C)) of each sample was measured at the Experimental Volcanology and Petrology Laboratory of the Science Department of Roma Tre University (EVPLab). We followed the procedure of baseline, standard sapphire (21.21 mg; Archer, 1993), and sample measurements via DSC (e.g., Di Fiore et al, 2023;Hui et al, 2018;Nichols et al, 2009;Potuzak et al, 2008;Scarani, Vona, et al, 2022, Scarani, Zandonà, et al, 2022.…”

“…Following the strategy of Scarani, Vona, et al (2022), the experimentally calibrated rheological model has been finally used to estimate the viscosity at T f (i.e., η(T f )) for samples with unknown natural cooling history and to retrieve the values of cooling rates as:…”

“…The procedure allowed obtaining the excess c P contribution (Δc P , i.e., the difference between c P of the liquid state and c P of the glassy state; Figure S2 in Supporting Information S1). Finally, these pair of normalized measurements allowed to retrieve the T f of each unmatching cycle via the "unified area-matching" approach (Figure S2 in Supporting Information S1; Guo et al, 2011;Scarani, Vona, et al, 2022) as follows:…”