magmatic & volcanic systems
Magmatic systems and subduction zones are key pathways connecting the deep Earth to its atmosphere, hydrosphere, and biosphere. Magmatism and subduction thus play key roles in Earth-system evolution and the development of continents, plate tectonics, and life on Earth. At smaller spatiotemporal scales, the processes occurring during the formation and evolution of magma chambers (e.g., assimilation, partial melting, magmatic differentiation) have large cascading effects on the nature, frequency, and violence of volcanic eruptions, which in turn can have significant impacts on human society. My research focuses on two main questions: (i) How can non-traditional stable isotopes inform us about magma chamber/volcanic processes? And (ii) what are the characteristics and fluxes of surficial materials recycled into the deep Earth today and through geologic time?
I have developed and pioneered the use of stable and radiogenic Ca isotopes in high-temperature systems, which are becoming increasingly useful tools for understanding magmatic and hydrothermal processes on Earth (e.g., Smart et al., 2021; Brown et al., 2020; Ionov et al., 2019; Mills et al., 2018). For example, I showed for the first time that disequilibrium Ca isotope fractionations between crystals and melt can be used to quantify crystal growth rates in volcanic and sub-volcanic systems, which can then be linked to magmatic recharge and volcanic eruption timescales. Using this novel geospeedometer, combined with crystal-size distribution analyses (CSD), I showed that both mafic and silicic systems can be primed for eruption in similarly short time periods (days-to-weeks), contrary to previous assumptions (Antonelli et al., 2019a, PNAS). The next step in this research is to develop in-situ stable Ca isotope measurements by SIMS to fully understand the growth timescales of volcanic crystals and crystal populations. I wrote two successful grant proposals (ETH Postdoctoral Fellowship and Marie Curie Fellowship) on this topic, and I am currently working on developing these measurements [collaborating with O. Bachmann, A. McCarthy, and A.-S. Bouvier (ETH-Zurich & U Lausanne)].
Sediment incorporation has a profound effect on the composition and oxidation state of magmas and their associated economic potentials. Surface materials can undoubtedly be recycled and stored in the mantle before re-erupting at the surface (Cabral,…, Antonelli et al., 2013, Nature), yet, a large number of Ca isotope publications invoke sedimentary carbonate incorporation as the dominant/only explanation for δ44Ca variations in magmas, without accounting for the various processes that can affect mass-dependent stable isotope ratios in high-temperature settings. To begin addressing these issues, I am currently working on a project aimed at understanding the effects of sediment incorporation on the δ44Ca of arc magmas (gabbro to granite) using samples from a well-constrained crustal section in the Famatina Arc, S. America, in collaboration with O. Bachmann. I have also shown that radiogenic Ca isotope measurements can be used to constrain the amount of juvenile mantle vs. reworked continental crust in arc systems (Cornet,…, Antonelli et al., under review).
Vulcano Island, Italy.
Photo Credit: E. Nordquist
Stromboli Volcano, Italy.
Photo Credit: E. Nordquist
Volcanic caldera on São Miguel Island, Azores. Photo Credit: N. Malartre.
Cornet, J., Wotzlaw, J.-F., Laurent, O., Antonelli, M.A., Otamendi, J., Bergantz, G., Bachmann, O. “Reworking of subducted sediments in arc magmas controls the isotopic diversity of continents” (resubmitted w/ minor revisions).
Antonelli, M.A. & Simon, J.T. (2020) “Calcium isotopes in high temperature terrestrial processes” Chemical Geology 548,119651.
Antonelli, M.A., Mittal, T., McCarthy, A., Tripoli, B., Watkins, J.M., DePaolo, D.J. (2019) “Ca isotopes record rapid crystal growth in volcanic and sub-volcanic systems” Proceedings of the National Academy of Sciences, USA, 116(41) 20315-20321.
Cabral, R.A., Jackson, M.G., Rosa-Koga, E.F., Koga, K.T., Whitehouse, M.J., Antonelli, M.A., Farquhar, J., Day, J.M.D., Hauri, E.H. (2013) “Anomalous Sulfur Isotopes in Plume Lavas Reveal Deep Mantle Storage of Archaean Crust” Nature 496, no. 7446, 490-493.