Magma–rock interactions: a review of their influence on magma rising processes with emphasis on short-timescale assimilation of carbonate rocks M. Knuever 1 *, R. Sulpizio 1 , D. Mele 1 and A. Costa 2 1 Università degli Studi di Bari Aldo Moro, Dipartimento di Scienze della Terra e Geoambientali, Via Edoardo Orabona 4, 70125 Bari (BA), Italy 2 Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Bologna, Via Franceschini 31, 40100 Bologna (BO), Italy MK, 0000-0002-7357-7375; RS, 0000-0002-3930-5421 *Correspondence: marco.knuever@uniba.it Abstract: The interaction of magma and wall-rocks is inevitable when magma is moving through Earth’s crust. These interactions happen on different timescales and especially the short-term interactions (seconds to days) during the final ascent of the magma can induce changes in eruption dynamics. However, information on this matter is scarce and scattered in different scientific fields. We conducted this review in order to present a full picture of the state of the art for short-timescale magma–wall-rock interactions. According to the three existing studies on short-term magma–carbonate interactions, magma viscosity is the most important controlling factor for carbonate assimilation. Lower viscosity magmas enhance CO 2 -bubble migration away from the reaction site, resulting in a higher carbonate assimilation rate. The released CO 2 plays an important role regarding erup- tion dynamics since a higher CO 2 release rate would result in accelerated magma ascent and may increase erup- tion intensity. Despite the importance for hazard assessment, important factors (pressure, magma composition, vapour phase solubilities, carbonate clast properties) for carbonate assimilation in general and CO 2 release rate in particular are not or only poorly constrained. This review presents the present-day knowledge of short-term magma–carbonate interaction that is relevant to establish the basis for future work concerning magma– wall-rock interactions. The migration of magma is always accompanied by interaction with the surrounding country rock. These interactions are not only mechanical (erosion and incorporation) or thermal, but also include chemical processes. In general, they can affect magma com- position, magma rheology, conduit geometry, degas- sing rate and so the dynamics of magma ascent (Costa et al. 2009a; Sottili et al. 2010; Freda et al. 2011; Blythe et al. 2015; Buono et al. 2020). The mechanical interaction of magma and wall- rock is evidenced in the field by the presence of crustal xenoliths in pyroclastic deposits and within volcanic products (e.g. cored bombs or xenoliths in lavas). Given the low temperature of wall-rock dur- ing entrapment (100–500°C; Sottili et al. 2010), incorporating wall-rocks might lead to a significant cooling of the host magma, inducing groundmass crystallization and enhancing bubble nucleation and growth (Glazner 2007; Freda et al. 2011). Among the various lithotypes possibly interact- ing with ascending magma, carbonate rocks (e.g. limestone, dolostone, marble) have a unique behav- iour due to the thermo-metamorphic reactions taking place. Of primary importance is the decomposition of calcium- (and magnesium-) carbonate crystals into CaO, MgO and CO 2 (Deegan et al. 2010; Jolis et al. 2013; Blythe et al. 2015; Whitley et al. 2019). The diffusion of Ca into the silicate melt can alter the chemical composition, density and vis- cosity of the magma, while the release of CO 2 increases vesicularity and, under proper physical conditions, its diffusion into the melt lowers water solubility (Papale and Polacci 1999). Besides car- bonate rocks, other sedimentary rocks (like sand- or mudstones) can also contain volatile-bearing (mostly H 2 O) mineral phases, whose decomposition would add volatiles to an ascending magma during interaction (Troll et al. 2012b; Wiesmaier et al. 2015). Any additional volatile phases might cause the transition from effusive to explosive eruptive behaviour (Dallai et al. 2011; Freda et al. 2011; Troll et al. 2012a; Pappalardo et al. 2018). Because of the described effects on eruption dynamics, volcanoes resting on carbonate basements need a surplus of research in order to understand their eruptive behaviour. Examples of such a setting include volcanic systems like Colli Albani (Italy; di Rocco et al. 2012; Cross et al. 2014), El Hierro (Canary Islands, Spain; Troll et al. 2012b), Etna (Italy; Chiodini et al. 2011; Wiesmaier et al. From: Di Capua, A., De Rosa, R., Kereszturi, G., Le Pera, E., Rosi, M. and Watt, S. F. L. (eds) Volcanic Processes in the Sedimentary Record: When Volcanoes Meet the Environment. Geological Society, London, Special Publications, 520, https://doi.org/10.1144/SP520-2021-177 © 2022 The Author(s). Published by The Geological Society of London. All rights reserved. For permissions: http://www.geolsoc.org.uk/permissions. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics by guest on June 1, 2022 http://sp.lyellcollection.org/ Downloaded from