Direct observations of degassing-induced crystallization in basalts

Clinopyroxene and titanomagnetite cation redistributions at Mt. Etna volcano (Sicily, Italy): Footprints of the final solidification history of lava fountains and lava flows

“…(2), Applegarth et al (2013) found that the degassing-induced undercooling of Etnean magmas can be estimated as a function of water loss. Considering that the pressure of starting water degassing is~400 MPa and magmas undergo a water loss of~4 wt.% while travelling upward under pure adiabatic conditions (Armienti et al, 2013;Mollo et al, 2015), Eq.…”

An improved clinopyroxene-based hygrometer for Etnean magmas and implications for eruption triggering mechanisms

“…The predicted H 2 O contents add important context in that the immediate eruption triggering mechanisms likely began at depths equivalent to 400 MPa pressures, and were accelerated as magmas migrated to very shallow depths at P < 100 MPa (cf. Rutherford 2008;Gonnermann and Manga 2012;Rutherford and Hill 1993;Toramaru et al 2008;Applegarth et al 2013; see also Supplementary 1 Data Magma Dynamics).…”

The roles of decompression rate and volatiles (H2O + Cl ± CO2± S) on crystallization in (trachy-) basaltic magma

“…The transfer of H 2 O from the melt to the fluid phase results in an increase of the liquidus temperature of the melt, which leads to crystallization and melt differentiation (e.g., Blundy and Cashman, 2001;2005;Médard and Grove, 2008;Brugger and Hammer, 2010;Applegarth et al, 2013). This decompression induced crystallization (DIC) can affect magma viscosity to a significant extent and, hence, can influence eruption style and hazardous potential of a volcanic eruption.…”

“…The influence of r (i.e., magma ascent rate) on crystallization was determined in three volatile-bearing (trachy-) basaltic assemblages: H 2 O + Cl + CO 2 + S (EBD1), H 2 O + Cl + CO 2 (EBD2) and H 2 O + Cl (EBD3). To our knowledge, DIC experiments using a basaltic (-andesite) composition (Métrich and Rutherford, 1998;Shea and Hammer, 2013), as well as more SiO 2 -rich compositions (Hammer, 2008;Applegarth et al, 2013), have been performed only as a function of the H 2 O content of the melt, whereas the roles of CO 2 and especially of S remain undetermined. Notably, Cichy et al (2011) investigated DIC in H 2 O-and H 2 O + CO 2 -bearing rhyodacitic systems; however, they focused on microlite and bubble number densities and key information for the interpretation of DIC is not provided (e.g., the fraction of all mineral phases, and crystal fraction of CO 2 -bearing runs).…”