1,1- 1Department of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom (thomas.pierce-jones@manchester.ac.uk)
- 2Department of Earth and Environmental Sciences, KU Leuven, Leuven, Belgium
- 3Department of Geology, Université de Liège, Liège, Belgium
The crystal content of lavas can be used to interpret their magmatic histories and to infer both the structure of magma reservoirs and the nature of the processes that operate within them. Magma reservoirs are increasingly viewed as complex, crystal-rich systems, often expressed in terms of a crystal mush paradigm, where melt is distributed within vertically extensive crystal frameworks [1]. Crystal mush models were primarily developed at volcanic arc systems, where magma flux and volatile content are high, sustaining trans-crustal mushes. It is uncertain whether such trans-crustal mushes are viable at ocean island volcanic systems, due to their generally lower magma fluxes and volatile contents. In some ocean island systems, such as the Eastern Volcanic Zone (EVZ) of Iceland, spatially and temporally proximal samples have a wide range of crystal contents. In the EVZ, plagioclase-phyric magmas are erupted alongside crystal-poor magmas. It is possible that the variation in crystal content reflects the level of interaction between the magma and a crystal mush structure, as portions of the mush are entrained during magma ascent [2].
In this study, we use the geochemistry and petrology of 32 basalt samples from the EVZ, which were mostly erupted beneath ice, to investigate the nature and cause of variation in crystal abundances and proportions. We combine whole-rock analyses from X-ray fluorescence, thin section textural observations from optical and electron imaging (backscattered electron imaging and scanning electron microscope energy dispersive spectroscopy), and geochemical microanalysis (electron probe microanalysis) to constrain magma storage conditions and examine the processes controlling crystal content. Our goal is to evaluate magma storage models of ocean island systems, using the EVZ as a case study of an ocean island system with relatively high magma flux.
References
[1] Sparks et al. (2019). Phil Trans R Soc A 377: 20180019; [2] Neave et al. (2014). J Pet 55(12): 2311-2346
How to cite: Pierce-Jones, T., Hartley, M. E., Namur, O., Vander Auwera, J., and Neave, D. A.: Variations in the crystal content of basalts from the Eastern Volcanic Zone of Iceland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1420, https://doi.org/10.5194/egusphere-egu26-1420, 2026.
