Research

The timescales of magmatic processes prior to a caldera-forming eruption of Santorini

My Ph.D. was on the >10 km3, 22-ka Cape Riva eruption of Santorini, Greece. I looked at a series of lavas and minor pyroclastic deposits that erupted prior to the Cape Riva. This eruptive sequence had previously been described as “precursory leaks” from a slowly growing magma reservoir that went on to feed the Cape Riva eruption itself. However, I found that these “precursory leaks” are enriched in incompatible trace elements relative to the Cape Riva, showing that they must have evolved separately. 39Ar/40Ar dates and diffusion chronometry shows that the assembly of the Cape Riva reservoir was rapid, and much of the magma arrived in the shallow system a few decades before eruption.

Further reading:

How Long Does it Take to Build a Caldera-Sized Magma Reservoir? Earth Observatory of Singapore Blog, 03 May 2018

Fabbro, G. N., Druitt, T. H., & Scaillet, S. (2013). Evolution of the crustal magma plumbing system during the build-up to the 22-ka caldera-forming eruption of Santorini (Greece). Bulletin of Volcanology, 75(12), 1–22. https://doi.org/10.1007/s00445-013-0767-5
Fabbro, G. N., Druitt, T. H., & Costa, F. (2017). Storage and eruption of silicic magma across the transition from dominantly effusive to caldera-forming states at an arc volcano (Santorini, Greece). Journal of Petrology, 58(12), 2429–2464. https://doi.org/10.1093/petrology/egy013
Fabbro, G. N. (2014). The timescales of magmatic processes prior to a caldera-forming eruption (Ph.D.). Université Blaise Pascal, Clermont-Ferrand. Retrieved from http://www.theses.fr/2014CLF22452

A complete caldera cycle at Rabaul, Papua New Guinea

During my postdoctoral fellowship, I studied Rabaul, Papua New Guinea. I found that there was a major change in the shallow plumbing system after the most recent caldera-forming eruption. In the post-caldera system, there is frequent basaltic intrusion, as opposed to andesitic recharge prior to the caldera-forming eruption. This suggests that a silicic reservoir large enough to block the rise of basalt existed before the caldera-forming eruption, but a similar reservoir is not present today under Rabaul. Currently, I am studying the pre-caldera eruptions to track the composition of the recharge and the evolution of the silicic reservoir.

Further reading:

Sizing Up the Next Eruption. Earth Observatory of Singapore Blog, 15 Jul 2016.