Abstract
Crustal xenoliths embedded in lavas offer chances to provide information on the lithology of the volcano basement and the process occurring during magma ascent. In this work we studied seven xenoliths found among the scoriae ejected during several paroxysms occurred between 2011 and 2016 at the South East Crater (SEC) of Mount Etna volcano. These samples are characterized by massive presence of glass and vesicles resulting in a foam-like appearance of their texture. A detailed study of their textural and chemical features was carried out combining XRF, SEM-EDS, two-dimensional observation and Synchrotron X-ray microtomography (3D imaging). This multidisciplinary approach allowed us to identify and quantify the components of the samples, individuate the likely provenance rock, ascribable to the Numidian Flysch outcropping west of the Etnean edifice. 2D and 3D imaging were successfully applied to estimate the amount of the phases constituting the samples (grains + glass + vesicles) and the degree of partial melting that occurred during the interaction with the basaltic melt and gaseous phase. The sedimentary rocks underwent profound changes led by partial melting, gas fluxing, vesiculation and selective alkali enrichment. These processes could not be driven exclusively by the prolonged contact with the molten phase but must be considered as result of a significant contribution from the volatiles rising through the plumbing system and the sedimentary basement.
Highlights
In the last three decades attention for xenoliths of Mount Etna volcano (Sicily, Italy) has raised following the discovery of sedimentary-like rocks enclaves in historic lavas [Ferla et al, 1978; Michaud, 1995] and due to the occurrence of many quartzarenitic fragments during the eruptive events of 2001 and 20022003 [Monaco et al, 2005; Ferlito et al, 2008; 2009]
Besides the information that Etnean xenoliths have provided on the basement beneath the volcanic edifice, attention has been drawn to the hints that they might offer on the LANZAFAME ET AL
These peculiar and rare samples on one hand provide information about the sedimentary basement laying beneath the volcanic edifice, and on the other hand interact with the magmas in which they are embedded, undergoing textural and chemical modifications that can be used to understand the petrological processes occurring within the plumbing system
Summary
In the last three decades attention for xenoliths of Mount Etna volcano (Sicily, Italy) has raised following the discovery of sedimentary-like rocks enclaves in historic lavas [Ferla et al, 1978; Michaud, 1995] and due to the occurrence of many quartzarenitic fragments during the eruptive events of 2001 and 20022003 [Monaco et al, 2005; Ferlito et al, 2008; 2009]. The relevance of assimilation has been proposed to justify and explain the increase in K and other LILE of the trachybasaltic lavas emitted after the 1971 eruption [Joron and Treuil, 1984; Clocchiatti et al, 1988; Marty et al, 1994; Condomines et al, 1995; Michaud, 1995; Tonarini et al, 1995; Tanguy et al, 1997] These peculiar and rare samples on one hand provide information about the sedimentary basement laying beneath the volcanic edifice, and on the other hand interact with the magmas in which they are embedded, undergoing textural and chemical modifications that can be used to understand the petrological processes occurring within the plumbing system. The 3D approach has been demonstrated to be the best technique to unravel the complex spatial relations developed by vesicle/pore networks [Baker et al, 2012b; Zambrano et al, 2017]
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