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Unlocking Volatile Budgets and Saturation States in Eruptions of Varying Magnitude: Insights from Apatite at Santorini, Greece

^^ David J. Colby^^ 1, Madeleine C.S. Humphreys1, Charline Lormand2, Victoria C. Smith3, Cees-Jan De Hoog4, Georgios Vougioukalakis5

  • Affiliations: 1. Department of Earth Sciences, Durham University, Science Labs, Stockton Road, Durham, DH1 3LE, UK  2. Department of Earth Sciences, University of Geneva, UNIGE, Switzerland 3. Research Laboratory for Archaeology and the History of Art, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford OX1 3QY, UK 4. EIMF, School of Geosciences, University of Edinburgh, Edinburgh, EH9 3FE UK 5. Hellenic Survey of Geology and Mineral Exploration, 3rd Entrance Olympic village 13637, Aharne, Athens, Greece 

  • Presentation type: Talk

  • Presentation time: Thursday 11:00 - 11:15, Room S150

  • Programme No: 1.1.9

  • Theme 1 > Session 1

Abstract

Volatiles play a crucial role in magmatic systems and in conditioning them for remobilisation and eruption. Understanding changes in volatile concentrations and saturation state of a magma is essential for establishing the conditions necessary for explosive eruptions of varying magnitudes and probing the dynamics of complex mushy systems. Santorini (Greece) is an ideal location to investigate the changes in a magmatic system between Plinian and smaller inter-Plinian eruptions. Previous studies indicate most magmas at Santorini are volatile saturated, and modelling demonstrates that eruption dynamics are sensitive to the presence of exsolved gas. Here, we present new volatile data from apatite (H2O, Cl, F) for several Plinian and inter-Plinian eruptions from Santorini. Apatite provides a robust tool for tracking changes in volatile concentrations and the saturation state of magma. We utilise identified apatite volatile trends alongside an iterative forward model to estimate the initial volatile concentrations of the melt and the saturation conditions under which the magmas likely fractionated. Our data suggests that while magmas from some of the major Plinian eruptions were likely volatile saturated, this is not consistent. Apatite from inter-Plinian and intermediate composition eruptions seem to record volatile undersaturated conditions and were stored and fractionated at greater depths prior to eruption. Our modelling results of volatile concentrations align well with melt inclusion data, and the estimated required degree of crystallisation is consistent with phase equilibria studies. We further refine the halogen volumes released during large Plinian eruptions and present an updated model for the plumbing system at Santorini.