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Phase relations of a tephritic lava erupted at La Palma, Canary Islands, the 2nd of October 2021, during the eruption of Cumbre Vieja volcano were determined experimentally in the temperature/water content space, T (°C)/H2O (wt%). The crystallisation experiments were carried out at a fixed pressure of 275 MPa for temperatures varying from 1000 to 1200 °C and with H2O added contents ranging from 0 to 5 wt%. Results from the synthetic products are compared with those obtained from thermodynamic simulations and with the natural phases to constrain the pre-eruptive conditions of the tephritic magma stored in the shallow reservoir. The major phases (clinopyroxene + olivine + oxides) occurring in the natural products were reproduced. The experimental results combined with thermodynamic modelling allow us to constrain the pre-eruptive temperature to ∼1100 °C considering H2O to 3 wt% and to restrict the crystallisation of plagioclase at low pressures (< 20 MPa). The results indicate that, under the presence of a pure H2O fluid, amphibole is stable at pressures higher than 300 MPa and temperatures ∼1000 °C. Our results on pre-eruptive conditions of the 2021 Tajogaite eruption provide important constraints on mechanisms of storage and transport in primitive alkaline magmas.

An Upper Miocene volcaniclastic interval, up to about 2.5 m thick, is exposed at several locations along the deep-water foreland basin system of central Apennines. Geochronological dating converges to indicate that these volcanic sediments were deposited at about 5.5 Ma (e.g., Odin et al., 1997), whereas mineralogical analyses indicate that the component strata comprise 80% of blocky and vesicular glassy shards and that the mineralogical phases represent the remaining 20% (Potere et al., 2022). These features, and the observed silica and alkali content, suggest that the volcaniclastic layers can be considered as the product of a calc-alkaline rhyolitic magma (Guerrera et al., 1986; Potere et al., 2022; Trua et al., 2010). In order to determine transport directions and depositional processes, in this study the volcaniclastic strata exposed on a recently made road cut near the town of Amandola (FM) have been investigated. At this new outcrop, the volcaniclastic horizon is 1.90 m thick and it comprises twenty-three beds, each recording a discrete density flow depositional event. Individual beds are characterized by sedimentological features typical of the product of turbidity currents, such as: i) flame structures along the contacts; ii) overall normal grain-size grading formed during temporal flow deceleration; and iii) the occurrence of a massive (i.e., ‘‘structureless’’) Ta division overlain by planeparallel and cross-laminated Tb and Tc divisions, with the massive division indicating deposition at rates of suspended load fallout high enough to suppress tractional transport and the laminated divisions indicating final flow stages, in which flow density and velocity are sufficiently low for bedform development to occur. The absence of laminated Tb and Tc divisions in some of the beds can be explained by the narrow grain-size distribution (i.e. the presence of well-sorted sediment) or by the post-depositional erosion of these divisions by succeeding sediment gravity f

Patients with Noonan syndrome typically have a target height <2 standard deviations compared to the general population, and half of the affected adults remain permanently below the 3rd centile for height, though their short stature might result from a multifactorial etiology, not-yet fully understood. The secretion of growth hormone (GH) following the classic GH stimulation tests is often normal, with baseline insulin-like growth factor-1 (IGF-1) levels at the lower normal limits, but patients with Noonan syndrome have also a possible moderate response to GH therapy, leading to a final increased height and substantial improvement in growth rate. Aim of this review was to evaluate both safety and efficacy of GH therapy in children and adolescents with Noonan syndrome, also evaluating as a secondary aim the possible correlations between the underlying genetic mutations and GH responses.

Peralkaline rhyolites, associated with extensional tectonic settings, are medium to low viscosity magmas that often produce eruptive styles ranging from effusive to highly explosive eruptions. The role of pre-eruptive conditions and crystallization kinetics in influencing the eruptive style of peralkaline rhyolitic magmas has been investigated and debated considering equilibrium conditions. However, experimental constraints on the effect of disequilibrium in crystallization in such magmas are currently lacking in the literature. Therefore, we performed isobaric cooling experiments to investigate alkali feldspar crystallization kinetics in peralkaline rhyolitic melts. Experiments were performed under water-saturated, water-undersaturated, and anhydrous conditions between 25 and 100 MPa, at 670–790°C and with experimental durations ranging from 0.5 to 420 h. Here we present the first data on crystallization kinetics of alkali feldspar, which is the main crystal phase in peralkaline rhyolitic melts, in order to improve our understanding of the evolutionary timescales of these melts and their ability to shift between effusive and explosive activity. Our experimental results indicate that the alkali feldspar nucleation delay can range from hours to several days as a function of undercooling and H2O content in the melt. Thus, a peralkaline rhyolitic magma can be stored at the pre-eruptive conditions for days without important variations of its crystal fraction. This suggests that crystallization may not necessarily play the main role in triggering fragmentation during explosive eruptions of peralkaline rhyolitic magmas.

We present new experimental data on major and trace element partition coefficients between alkali feldspar and trachytic melt. Experiments were conducted at 500 MPa, 870–890 °C to investigate through short disequilibrium and long near-equilibrium experiments the influence of diffusive re-equilibration on trace element partitioning during crystallization. Our data show that Ba and Sr behave compatibly, and their partition coefficients are influenced by re-equilibration time, orthoclase (Or) content, growth rate and cation order-disorder. High field strength elements (HFSE) and rare earth elements (except Eu) are strongly incompatible, but alkali feldspar efficiently fractionates light (LREE) from heavy rare earth elements (HREE). Our crystallization experiments reveal a strong influence of disequilibrium crystal growth on the partitioning of Ba and Sr. In particular, short-duration experiments show that rapid alkali feldspar crystal growth after nucleation, promotes disordered growth and less selectivity in the partitioning of compatible trace elements that easily enter the crystal lattice (e.g., Ba and Sr). This produces partition coefficients of compatible elements higher than those obtained through long-duration experiments, in which growth is slower and more selective. On approach to equilibrium, decreasing growth rate and timescales of diffusive re-equilibration facilitates the incorporation of compatible elements within the crystal lattice (through ordered growth), on the basis of the charge and size of the octahedral site, resulting in lower partition coefficients of Ba and Sr. Therefore, our results indicate that besides crystal-chemical effects, i.e. lattice strain, the substitution mechanisms during growth (with different degrees of ordering) of Ba and Sr in alkali feldspar are strongly influenced by diffusive re-equilibration and crystal growth kinetics. This implies that partition coefficients of Ba and Sr can be used to establish timescales of crystalliz

During the first week of the 2011 El Hierro submarine eruption, abundant light-coloured pumiceous, high-silica volcanic bombs coated in dark basanite were found floating on the sea. The composition of the light-coloured frothy material (‘xeno-pumice’) is akin to that of sedimentary rocks from the region, but the textures resemble felsic magmatic pumice, leaving their exact mode of formation unclear. To help decipher their origin, we investigated representative El Hierro xeno-pumice samples using X-ray computed microtomography for their internal vesicle shapes, volumes, and bulk porosity, as well as for the spatial arrangement and size distributions of vesicles in three dimensions (3D). We find a wide range of vesicle morphologies, which are especially variable around small fragments of rock contained in the xeno-pumice samples. Notably, these rock fragments are almost exclusively of sedimentary origin, and we therefore interpret them as relicts an the original sedimentary ocean crust protolith(s). The irregular vesiculation textures observed probably resulted from pulsatory release of volatiles from multiple sources during xeno-pumice formation, most likely by successive release of pore water and mineral water during incremental heating and decompression of the sedimentary protoliths.