EGU22-5786, updated on 05 Jan 2024
https://doi.org/10.5194/egusphere-egu22-5786
EGU General Assembly 2022
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Kinetic crystallization of a high-K basalt melt undercooled in laboratory: Implications for modeling open conduit dynamics at Stromboli volcano

Simone Costa1, Fabio Colle1, Matteo Masotta1, Silvio Mollo2, Patrizia Landi3, Alessio Pontesilli4, Stefano Peres5, Thomas Griffiths5, and Lucia Mancini6
Simone Costa et al.
  • 1Dipartimento di Scienze della Terra, Università di Pisa, via S. Maria 53, 56126 Pisa (PI), Italy (simone.costa@dst.unipi.it)
  • 2Dipartimento di Scienze della Terra, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma (RM), Italy
  • 3Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, via Cesare Battisti 53, 56125 Pisa (PI), Italy
  • 4Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma, Via di Vigna Murata 605, 00143 Roma (RM), Italy
  • 5Department of Lithospheric Research, University of Vienna, Althanstrasse 14,1090 Vienna, (Austria)
  • 6Elettra-Sincrotrone Trieste SCpA, S.S. 14 - km 163,5 in Area Science Park, 34149 Basovizza, Trieste (TS), Italy

Magma crystallization is a fundamental process driving the evolution of magmas in the crust and influencing the style of volcanic eruptions. Crystallization occurs through either (near) equilibrium or kinetically-controlled mechanisms driving the solidification of magmas and the final textural and chemical characteristics of igneous rocks. Among other factors, the degree of undercooling (∆T), expressed as the difference between the liquidus temperature and the actual temperature of solidifying magma, plays a key role. Experimental investigations on the effect of ∆T are extremely important to reconstruct the crystallization of basaltic melts under kinetic conditions which are frequently encountered in open conduit volcanoes.

Stromboli (Sicily, Italy) is a reference example for these types of volcanic systems, due to its persistent activity and periodic changes of eruptive style, from normal, mild strombolian activity to effusive events or sudden, short-lived, more violent explosions (paroxysms). In this study, we examined the effect of ∆T on the crystallization path of basaltic magmas erupted at Stromboli. The starting material is a high-K basaltic glass obtained from a low-porphyritic (LP) pumice erupted during the paroxysm of April 5, 2003. Undercooling crystallization experiments were performed in a non-end loaded piston cylinder apparatus at 350-500 MPa, 1050-1150 °C, anhydrous and hydrous (2 wt.% H2O added to the experimental charge) conditions, and NNO +1.5 buffer. The degree of ∆T imposed to the system ranges from 10 to 162 °C. Textural features and chemical composition of the experimental charges were investigated by combining synchrotron radiation X-ray microtomography (SR-µCT) for the 3D reconstruction of crystal morphologies, scanning electron microscopy (FE-SEM) and electron probe microanalysis (EPMA).

Clinopyroxene represents the main mineral phase crystallized in all the experimental charges, and shows a remarkable textural and chemical dependence on the degree of ∆T. In particular, as the degree of ∆T increases, clinopyroxene morphology evolves from prevalently skeletal to dendritic, and the crystal composition becomes enriched in incompatible elements (Ti and Al), with a simultaneous depletion in compatible elements (Si and Mg). According to this cation exchange, the degree of ∆T can be parameterized to derive a new predicting model for high-K basaltic melts and based on clinopyroxene composition only. Modeling results using natural clinopyroxene crystals open new perspectives for the interpretation of open conduit dynamics at Stromboli.

How to cite: Costa, S., Colle, F., Masotta, M., Mollo, S., Landi, P., Pontesilli, A., Peres, S., Griffiths, T., and Mancini, L.: Kinetic crystallization of a high-K basalt melt undercooled in laboratory: Implications for modeling open conduit dynamics at Stromboli volcano, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5786, https://doi.org/10.5194/egusphere-egu22-5786, 2022.