Constraining the recent plumbing system of Vulcano (Aeolian Arc, Italy) by textural, petrological, and fractal analysis: The 1739 A.D. Pietre Cotte lava flow

Abstract

[1] The 1739 A.D. Pietre Cotte lava flow is part of a sequence of low-explosive to weak effusion events occurred at La Fossa Cone, the active vent on Vulcano Island (Aeolian Arc, Italy). This lava is rhyolitic, texturally heterogeneous, and contains lati-trachytic enclaves. These compositions are recurrent in the La Fossa volcanic products and are representative of the recent Vulcano plumbing system. The host lava is vesicular, relatively phenocryst-free, and locally contains microlites and millimeter-sized spherulites. The enclaves are up to 10 cm in size, display angular to spherical shapes, and can form the core of spherulites. Enclaves mostly consist of plagioclase and augitic phenocrysts set in a weakly vesicular groundmass characterized by variable abundance of glass and feldspar microlites. Field, textural, and fractal data allow us to constrain the rheological features of the rhyolitic and lati-trachytic magmas. In situ major, trace, and volatile element analyses provide evidence for heterogeneities in the glassy matrix and zoning of phenocrysts. Processes of magma evolution have been quantitatively constrained by using the apparent distribution ratios of trace elements measured between mineral phases and glassy matrices. The collected data in combination with petrological and fluid inclusion data from the literature provides evidence for (1) a genetic relationship between the two magmas through assimilation fractional crystallization process; (2) a mingling mechanism between an uprising rhyolitic magma and a shallower partly crystallized lati-trachytic

Magmatic evolution and textural development of the 1739 CE Pietre Cotte lava flow, Vulcano, Italy

“…Magmatic evolution and textural development of the AD 1739 Pietre Cotte lava flow 3 1230 ±40 AD (Davì, 2007;Davì et al, 2009Davì et al, , 2010; date determined by archaeomagnetic dating of Arrighi et al 2006). Similar compositions and mingling textures have been identified in young rhyolitic lava flows on Vulcano, including the AD 1739 Pietre Cotte lava flow (Frazzetta et al, 1984; De Astis et al, 1997Astis et al, , 2013Piochi et al, 2009;Forni et al, 2015;Vetere et al, 2015;Nicotra et al, 2018).…”

Chapter 11 Geology, volcanic history and petrology of Vulcano (central Aeolian archipelago)

“…The large geochemical variations in the glass matrices of the enclaves, the coexistence of olivine and K-feldspar and the occurrence of pyroxene phenocrysts with normal and reverse zoning point to disequilibrium conditions during latite crystallization. Thefeatures of both magmas therefore suggest that each experienced a specific evolutionary history before the interaction when the lavas mingled, creating a lava characterized by features due to thermal exchange and re-equilibration between the blobs of latite magma in the rhyolitic host (Piochi et al 2009). …”

“…Some rock suites from La Fossa cone were therefore generated by FC with late removal of zircon, De Fino et al (1991) and Clocchiatti et al (1994) have already stressed the important role played by magma mixing processes at La Fossa. A recent study on both Pietre Cotte rhyolite lava flow and embedded latite-trachyte enclaves has shown the complex petrogenesis of La Fossa magmas induced by the interaction between various magmas, which produced a wide chemical variability and also affected the magma ascent dynamics (Piochi et al 2009). The variability in the rhyolite host-lava is generally due to K 2 O, REE, Nb, and Zr elements, and is mostly related to advanced FC process as testified by textural data.…”

The mixing of magmas in plutonic and volcanic environments: Analogies and differences

“…In rare cases similar morphologies have been recognized in volcanic rocks (e.g. Perugini et al, 2007, Piochi et al, 2009. Although their use as markers for the evolution of rheological contrast between magmas could be feasible, it is not clear if these morphologies in volcanic rocks can still be considered a primary feature related to the injection process, or if they are the result of additional deformation processes occurring between enclaves and the host magmas while moving toward the Earth's surface.…”