Novembre 2021

PubAIV 2021
(aggiornamento Novembre 2021)

1) Magmi e sistemi di alimentazione (4 articoli)
2) Dinamiche eruttive e di messa in posto (1 articolo)
3) Geologia e struttura dei vulcani (1 articolo)
4) Monitoraggio, pericolosità e rischio vulcanico (0 articoli)

Tematica 1: Magmi e sistemi di alimentazione
Costa S., Fulignati P., Campbell I.H., Gioncada A., Carrasco Godoy C.I., Pistolesi M., Masotta M. (2021)
Platinum-group element geochemistry of the shoshonitic igneous suite of Vulcano (Aeolian Arc, Italy): implications for chalcophile element fertility of arc magmas.
Contributions to Mineralogy and Petrology 176, 106.
Data di pubblicazione: 29/11/2021
PubAIV-ID-00040 - Articolo in Rivista (non-open access)

Platinum-group element (PGE) geochemistry of arc-related magmas can be used to constrain the timing of sulfide saturation, which plays a critical role in the chalcophile element fertility of evolving magmatic systems. In this study, we provide new major and trace elements, PGE, Re and Au data for the shoshonitic suite (from basalt to rhyolite) of the active volcanic system of Vulcano (Aeolian Islands, Italy), an excellent study case for investigating mineralizing processes in arc volcanoes. The most primitive magma erupted at Vulcano is characterized by fractionation of Ir-group PGE (Ir, Os, Ru) relative to the Pd-group PGE (Pd, Pt, Rh), which is attributed to the magma being saturated with a Pt-rich alloy and possibly spinel and Os–Ir alloy. A negative Au anomaly, shown by Vulcano magmas, suggests that the Au was lost to an early exsolved S– (and moderately Cl–) rich fluid phase that, upon migration to higher levels of the feeding system, could have enhanced the mineralizing potential of the magmatic system. The Pd content of Vulcano primitive magmas is high (~ 8 ppb) and comparable to values found in other arc-related mineralized systems. The early Pd depletion, relative to Au and Cu, during evolution towards more evolved magmas, suggests that the magmatic system reached sulfide saturation at about 4 wt.% MgO. Chalcophile element fractionation modeling shows that the immiscible sulfide mass proportion was initially very low (~ 0.0015%), and gradually increased to about 0.1% at about 2 wt.% MgO, causing a late depletion of the less compatible chalcophile elements, including Cu. A significant chalcophile metal depletion in the silicate melt occurred once sulfide saturation was achieved, well before hydrosaline fluid exsolution at 
Hughes G.E., Petrone C.M., Downes H., Varley N.R., Hammond S.J. (2021)
Mush remobilisation and mafic recharge: A study of the crystal cargo of the 2013–17 eruption at Volcán de Colima, Mexico.
Journal of Volcanology and Geothermal Research 416, 107296
Data di pubblicazione: 25/05/2021
PubAIV-ID-00035 - Articolo in rivista (non-open access)

Volcán de Colima is a highly active stratovolcano at the western end of the Trans-Mexican Volcanic Belt. Present day activity consists of lava dome growth and destruction cycles, lava flows, small explosions, and larger explosive Vulcanian eruptions. It has been postulated that an increased frequency of more mafic eruptions signals the run-up to the end of c. 100-year eruptive ‘cycles’, terminating with a Plinian eruption such as those in 1818 and 1913. It is therefore important to understand the role played by mafic recharge during interplinian activity. We present new petrological and geochemical data for lava and ash from the 2013–17 phase of eruption. The uniform paragenesis and geochemical homogeneity of bulk rocks indicate efficient long-term homogenisation of magmas within the plumbing system, similar to the previous 1998–2005 eruptive products. Mineral chemistry however preserves complex patterns of magma recharge and mixing. Chemical and textural information support the interpretation of two magmatic end-members – an evolved end-member, saturated with respect to Fe–Ti oxides and apatite and crystallising low-An plagioclase and pyroxenes in the Mg# 69–75 range; and a more primitive, mafic end-member, crystallising high-An plagioclase and pyroxenes in the Mg# 77–88 range. Pyroxene textures and zoning patterns suggest mixing of the mafic melts with the evolved magma and remobilisation of the crystal mush. Two-pyroxene geothermometry constrains magmatic temperatures to c. 980–1000 °C for the evolved end-member, and c. 1020–1080 °C for the mafic end-member. Pressure estimates suggest crystallisation at 4–6 kbar, or c. 12–18 km depth.We interpret this to reflect periodic injections of mafic melts and remobilised crystals into evolved reservoirs in a mushy magma storage system in the mid-crust, in agreement with geophysical data suggesting a semi-molten, partially crystallised body at this depth. An increase in reverse zoned crystals, indicative of mafic injection, from mid-2015 onwards suggests that these melts were injected into the system following the large eruption in July 2015. Our findings suggest that the intense July 2015 eruption may be linked to increased input of mafic magmas into the shallow system, indicating that mafic injections may be a key process governing the timing and style of interplinian eruption at Volcán de Colima.
Nicotra E., Viccaro M., Donato P., Acocella V., De Rosa R. (2021)
Catching the Main Ethiopian Rift evolving towards plate divergence.
Scientific Reports 11, 21821.
Data di pubblicazione: 08/11/2021
PubAIV-ID-00039 - Articolo in Rivista (open access)

Magmatism accompanies rifting along divergent plate boundaries, although its role before continental breakup remains poorly understood. For example, the magma-assisted Northern Main Ethiopian Rift (NMER) lacks current volcanism and clear tectono-magmatic relationships with its contiguous rift portions. Here we define its magmatic behaviour, identifying the most recent eruptive fissures (EF) whose aphyric basalts have a higher Ti content than those of older monogenetic scoria cones (MSC), which are porphyritic and plagioclase-dominated. Despite these differences, calculations highlight a similar parental melt for EF and MSC products, suggesting only a different evolutionary history after melt generation. While MSC magmas underwent a further step of storage at intermediate crustal levels, EF magmas rose directly from the base of the crust without contamination, even below older polygenetic volcanoes, suggesting rapid propagation of transcrustal dikes across solidified magma chambers. Whether this recent condition in the NMER is stable or transient, it indicates a transition from central polygenetic to linear fissure volcanism, indicative of increased tensile conditions and volcanism directly fed from the base of the crust, suggesting transition towards mature rifting.
Petrone C.M., Mangler M. (2021)
Timescales of Magma Dynamics.
Geophysical Monograph Series 264, Chapter 8
Data di pubblicazione: 21/05/2021
PubAIV-ID-00036 - Capitolo di un Libro (non-open access)

Time-related information of pre-eruptive magmatic processes is locked in the chemical profile of compositionally zoned minerals and can be retrieved by means of elemental diffusion chronometry. However, only the timescale of the outermost rim is commonly resolved, limiting our knowledge of timescales to those directly preceding the eruption. A major obstacle is the need to accurately constrain the temperatures at which diffusion occurred. Elemental diffusion chronostratigraphy can be fully resolved for crystals that have spent their lifetime in hot storage. Under this condition, crystals will be kept at the temperature of the eruptible magma(s), and diffusion timescales approximate the storage of the crystal in question in different melt environments. Hot storage conditions are typical of open-conduit systems in steady state and are driven by the regular supply of fresh hot magmas determining the constant presence of eruptible magma. Fe–Mg interdiffusion in pyroxene crystals from Stromboli and Popocatépetl are used to reconstruct elemental diffusion chronostratigraphies of single crystals and to discuss their implications for magma dynamics. Uncertainties introduced by temperature estimates and other input data, including experimentally derived values for the activation energy E and the pre-exponential factor D 0 , have large effects on the accuracy of modeled timescales, which need to be evaluated and mitigated. Elemental diffusion chronostratigraphy is an extremely powerful tool for obtaining time-related temporal information on the dynamics and histories of volcanic plumbing systems, providing in-depth knowledge of the magmatic system far beyond late-stage pre-eruptive processes.
Tematica 2: Dinamiche eruttive e di messa in posto
Dellino P., Dioguardi F., Rinaldi A., Sulpizio R., Mele D. (2021)
Inverting sediment bedforms for evaluating the hazard of dilute pyroclastic density currents in the field.
Scientific reports 11, 2104
Data di pubblicazione: 02/11/2021
PubAIV-ID-00038 - Articolo in rivista (open access)

Pyroclastic density currents are ground hugging gas-particle flows associated to explosive volcanic eruptions and moving down a volcano's slope, causing devastation and deaths. Because of the hostile nature they cannot be analyzed directly and most of their fluid dynamic behavior is reconstructed by the deposits left in the geological record, which frequently show peculiar structures such as ripples and dune bedforms. Here, a set of equations is simplified to link flow behavior to particle motion and deposition. This allows to construct a phase diagram by which impact parameters of dilute pyroclastic density currents, representing important factors of hazard, can be calculated by inverting bedforms wavelength and grain size, without the need of more complex models that require extensive work in the laboratory.
Tematica 3: Geologia e struttura dei vulcani
Marra F., Cardello G.L., Gaeta M., Jicha B.R., Montone P., Niespolo E.M., Nomade S., Palladino D.M., Pereira A., De Luca G., Florindo F., Frepoli A., Renne P.R., Sottili G. (2021)
The Volsci Volcanic Field (central Italy): eruptive history, magma system and implications on continental subduction processes.
International Journal of Earth Sciences, 110, 689-718.
Data di pubblicazione: 12/02/2021
PubAIV-ID-00037 - Articolo in rivista (non-open access)

Here, we report on the Quaternary Volsci Volcanic Field (VVF, central Italy). In light of new 40Ar/39Ar geochronological data and compositional characterization of juvenile eruptive products, we refne the history of VVF activity, and outline the
implications on the pre-eruptive magma system and the continental subduction processes involved. Diferent from the nearby volcanic districts of the Roman and Campanian Provinces, the VVF was characterized by small-volume (0.01–0.1 km3) eruptions from a network of monogenetic centers (mostly tuf rings and scoria cones, with subordinate lava occurrences), clustered along high-angle faults of lithospheric depth. Leucite-bearing, high-K (HKS) magmas (for which we report for the frst time the phlogopite phenocryst compositions) mostly fed the early phase of activity (∼761–539 ka), then primitive, plagioclase-bearing (KS) magmas appeared during the climactic phase (∼424–349 ka), partially overlapping with HKS ones, and then prevailed during the late phase of activity (∼300–231 ka). The fast ascent of primitive magma batches is typical of a tectonically controlled volcanic feld, where the very low magma fux is a passive byproduct of regional tectonic strain. We suggest that the dominant compressive stress feld acting at depth was accompanied by an extensional regime in the upper crust, associated with the gravity spreading of the Apennine chain, allowing the fast ascent of magma from the mantle source with limited stationing in shallow reservoirs.
Tematica 4: Monitoraggio, pericolosità e rischio vulcanico
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