Determination of cooling rates of glasses over four orders of magnitude
Alex Scarani, Alessandro Vona, Danilo Di Genova, Raschid Al-Mukadam, Cláudia Romano, Joachim Deubener
Abstract
Abstract Volcanic materials can experience up to eleven orders of magnitude of cooling rate ( q c ) starting from 10 –5 K s −1 . The glassy component of volcanic material is routinely measured via differential scanning calorimeter (DSC) to obtain q c through the determination of the glass fictive temperature ( T f ). Conventional DSC (C-DSC), which has been employed for decades, can only access a relatively small range of q c (from ~ 10 –2 to ~ 1 K s −1 ). Therefore, extrapolations up to six orders of magnitude of C-DSC data are necessary to derive q c of glasses quenched both at extremely low and high q c . 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 q c exploration up to 10 4 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 T f as a function of experimental q c , following the “unified area-matching” approach. The obtained T f – q c relationship shows that Arrhenius models, widely adopted in previous studies, are only valid for q c determination within the calibration range. In contrast, a non-Arrhenius model better captures q c values, especially when a significant extrapolation is required. We, therefore, present a practical “how-to” protocol for estimating q c using DSC.