Influence of Pre-Existing Nuclei on the Crystallization Kinetics of Primitive Alkaline Magmas: Insights on the Deep Feeding System of the Campi Flegrei Volcanic District

Abstract

Aiming to evaluate the influence of pre-existing nuclei on the clinopyroxene crystallization kinetics, time-series experiments were performed using both natural and vitrified starting materials. Experiments were carried out at pressure of 0.8 GPa, temperatures between 1220 and 1250 °C, and dwell times ranging from 0.16 to 12 h. Clinopyroxene growth rates of the runs performed using the natural starting material containing pre-existing nuclei (~2 × 10−7 to ~6 × 10−8 cm∙s−1) are higher than those of the runs performed using the vitrified one (~3 × 10−7 to ~2 × 10−8 cm∙s−1). In both cases the growth rates decrease with increasing time. Conversely, clinopyroxene nucleation rates are lower in the experiments performed using the natural powder (102 and 10 mm−3∙s−1) compared to those performed with the glassy starting material (105 and 103 mm−3∙s−1). The nucleation rates tend to decrease increasing dwell time in all the series up to ~3 h, after which it remains nearly constant. Finally, the combination of the obtained clinopyroxene growth rates with the crystal size analysis of natural clinopyroxenes, allowed to estimate the magma ascent rate and the recharge rate of the Campi Flegrei Volcanic District deep reservoir.

Experimental investigation of trace element partitioning between amphibole and alkali basaltic melt: Toward a more general partitioning model with implications for amphibole fractionation at deep crustal levels

“…As a whole, the estimated range of fO2 values agree with those estimated for similar furnace assemblages (Conte et al 2009;Weaver et al 2013;Perinelli et al 2019;Bonechi et al 2020a). Finally, we determined the undercooling (DT; Table 2) that is the difference between the liquidus temperature and the nominal temperature of the experiment (Bonechi et al 2020a(Bonechi et al , 2020bBonechi 2020). For calculations, the liquidus temperature (TL) of APR16 experiments was taken from Procida K-basalt experimental data (1095 °C; Perinelli et al 2019, Bonechi et al 2020a.…”

Editorial for the Special Issue “Properties of Melt and Minerals at High Pressures and High Temperature”

“…The second study regards the ascent and recharge rate of ultrapotassic melts derived from crystallization kinetics studies of clinopyroxenes at the particularly highly hazardous system of the Campi Flegrei Volcanic district [32]. Bonechi [32] performed time-series experiments using both natural and vitrified starting materials.…”

“…The second study regards the ascent and recharge rate of ultrapotassic melts derived from crystallization kinetics studies of clinopyroxenes at the particularly highly hazardous system of the Campi Flegrei Volcanic district [32]. Bonechi [32] performed time-series experiments using both natural and vitrified starting materials. Experiments were carried out at a pressure of 0.8 GPa, temperatures between 1220 and 1250 • C and dwell times ranging from 0.16 to 12 h. The influence of the starting material and the dwell time and undercooling on the nucleation and growth rates of clinopyroxenes was determined.…”