Compositional variations in geological materials at the microscopic scale can contain a record of geological processes and the evolution of environments. Trace element variations during crystal growth bear important information on magma compositions and conditions during crystallization, complementing petrography and major element studies. In the last decades, among the most common analytical approaches, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) mapping turned out to be the most efficient given the ability to reveal complexities that are not visible under the microscope or detected by microbeam spot analyses. In this project I propose to apply the LA-ICP-MS mapping technique to phenocrystals of K-basaltic scoria clasts from Solchiaro eruption (Procida island, Campi Flegrei Volcanic District) with the aim to unravel the dynamic processes that operate within the Campi Flegrei Volcanic District plumbing system. The LA-ICP-MS mapping technique will also be used to determine the distribution of trace elements of minerals crystallized in time-series experiments previously carried out at pressure of 0.8 GPa, temperatures between 1030 and 1250 °C and water contents up to 4 wt.%, using as starting material a scoria clast from Solchiaro eruption with a chemical composition similar to those of the K-basaltic scoria clasts considered for the natural crystals. Trace elements LA-ICP-MS maps collected on both natural and experimental crystals will provide a powerful tool to i) reconstruct the evolutionary history of natural products, and ii) contribute, when combined with crystal growth rates estimations, in decoding the eruption-triggering mechanisms, depths and timescales.
LA-ICP-MS trace element mapping represents a fundamental tool capable of resolving internal mineral complexities, previously undetectable with major element or whole rock analysis (Ulrich et al., 2009; Ubide et al., 2015). To date, this technique was successfully applied by Ubide et al. (2018) to M. Etna products and by Astbury et al. (2018) to selected products of Astroni eruption (Campi Flegrei). So, in this research project I decided to extend the application of this technique to some natural and experimental products of Procida island (Campi Flegrei Volcanic District, CFVD), that are the most representative primitive composition of the entire CFVD, able to provide useful information about the deep feeding system, investigated in more detail only in recent years (Bonechi et al., 2017; Bonechi, 2020; Bonechi et al., 2020a, 2020b; Bonechi et al., 2021; Perinelli et al., 2019). This project turns out to be innovative for two main reason. The first reason is the investigation of some natural primitive products, never investigated before, able to provide unique information on the deep feeding system, not only of Procida island but of the entire CFVD. The second reason, instead, is the application of this technique for the first time to experimental products, whose investigation is made possible thanks to the ability of this technique to remove less than 1 µm of the examined area. This application, indeed, can provide interesting results under controlled conditions (e.g. temperature, pressure, time), which can be used as reference models to reconstruct the evolutionary history of natural products, together with thermobarometry, that is generally used to estimate the pressure and temperature conditions at which natural products crystallize. In addition, the data collected with this project, combined with data on crystal growth rates (Bonechi, 2020; Bonechi et al., 2020a), have potential to help decode eruption-triggering mechanisms, depths and timescales. Indeed, as suggested by Ubide et al. (2018), an improvement in constraining the movement of magma preceding past eruptions could advise future volcano monitoring efforts in relation to the origin of seismic or deformation signals and the time available for hazard evaluation and emergency planning.
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