Dissolution/crystallization kinetics recorded in the 2002–2003 lavas of Stromboli (Italy)

Abstract

On 28 December 2002, new vents opened on the flanks of Stromboli, just below the summit craters, interrupting the persistent activity of the volcano with a 7-month-long effusive eruption. We here report on the plagioclase size distribution (PlgSD) in lava samples collected following the chronology of the 2002-2003 eruption. Data reveal a linear PlgSD similar to that found in samples of normal Stromboli activity, indicating that the switch from Strombolian explosive to effusive activity is not associated with changes in texture. Nevertheless, the crystal size distribution slopes and intercepts exhibit slight sinusoidal temporal variations that are here ascribed to a magma supply mechanism able to induce "resonance" in the crystal size distribution, with an amplitude that depends on the supply rate.

The rheology of crystal-bearing basaltic magmas from Stromboli and Etna

“…It is continuously refilled by deeper hot volatile-rich LP magma batches, which periodically intrude the shallow reservoir, crystallizing by decompression and volatile loss at low pressure (Metrich et al, 2001;Francalanci et al, 2005). Evidence of continuous mixing between LP and the HP magmas have been observed in textural, mineralogical, chemical and isotopic studies (Francalanci et al, 1999(Francalanci et al, , 2004(Francalanci et al, , 2005Landi et al, 2004Landi et al, , 2006Landi et al, , 2008Armienti et al, 2007;Fornaciai et al, 2009). According to this model, the steady state behavior of the plumbing system is a consequence of the balance between magma refilling and magma expulsion.…”

Crystal recycling in the steady-state system of the active Stromboli volcano: a 2.5-ka story inferred from in situ Sr-isotope and trace element data

“…The evidence at point (i) is also corroborated by the occurrence of few LP glassy shards in ashes erupted on 8-March-2003 (Schiavi et al, 2010), together with changes in fluid geochemistry (Aiuppa and Federico 2004;Carapezza, 2004) and lowering of Sr isotope ratios in scoria groundmasses during October-November 2002. As for the considerations at point (ii), it is also worthy noting that the mineral bulk compositions and zoning patterns of post-paroxysm lavas do not change, maintaining the typical crystal outer-rim compositions in equilibrium with the HP-magmas Landi et al, 2006Landi et al, , 2008; furthermore, no variations in the crystal size distribution of lavas are found immediately after the paroxysm, and the decrease in nucleation density observed in the 20--July lavas can be considered to be the only petrographic effect of the arrival of LP magmas in the shallow system (Fornaciai et al, 2009). …”

“…On the contrary, plagioclase is the dominant mineral phase of the shallow degassed HP-magmas where it crystallizes in equilibrium with clinopyroxene and olivine (e.g., Francalanci et al, 2004;Landi et al, 2004;Di Carlo et al, 2006;Bertagnini et al, 2008). scoria-pumice mingling) because only in those cases they arrive directly to the surface without mixing with the HP-magmas at shallow levels (Francalanci et al, 1999Armienti et al, 2007;Fornaciai et al, 2009). …”

“…This suggests they are recycled by the dynamic processes of the Strombolian activity, which appear to be particularly efficient in recycling crystals considering the high percentage content of these high Sr-isotope antecrysts. On the other hand, whatever the conceptual model of the volcano is proposed, it is nowadays believed that the periodic mild Strombolian explosions leave in the conduit a degassed dense HP-magma descending downwards possibly along the conduit walls (Chouet et al, 2003;Colò et al, 2010;Lautze and Houghton, 2007;Burton et al, 2007;Fornaciai et al, 2009;Metrich et al, 2010). This mechanism leads minerals (with possibly degassed silicate melt) to be also recycled from the upper part of the plumbing system into the HP-magma reservoir.…”

From magma ascent to ash generation: investigating volcanic conduit processes by integrating experiments, numerical modeling, and observations

“…Textural measurements on samples Textural data provide information on magma pressure and thermal histories in conduits and plumes. For example, vesicle number densities (VNDs; i.e., the number of vesicles per unit bulk volume) provide estimates of magma decompression rates [Toramaru 2006, Shea et al 2011, Wright et al 2012b] and eruption intensities Cashman 2011, Alfano et al 2012], while crystal size distributions (CSDs) and vesicle size distributions (VSDs) (i.e., the number of crystals or vesicles in each size class per unit bulk volume) provide information on crystallization and differentiation in magma reservoirs and conduits [Fornaciai et al 2009, Shea et al 2009, Brugger and Hammer 2010, Arzilli and Carroll 2013, and on magma vesiculation [Bai et al 2008, Gurioli et al 2008, Colò et al 2010, Shea et al 2010, Carey et al 2012, permeability [Mueller et al 2008, Bouvet de Maissoneuve et al 2009, Polacci et al 2014, Heap et al 2014, Kendrick et al 2016, Colombier et al 2017, and degassing/outgassing [Burton et al 2007, Degruyter et al 2010a, 2012. Furthermore, VSDs, CSDs, melt chemistry and volatile content feed into magma rheology estimates [Mader et al 2013, Vona et al 2013.…”