EGU2020-22291
https://doi.org/10.5194/egusphere-egu2020-22291
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Thermochemical modelling of zircon age distributions from Nevado de Toluca volcano, Trans Mexican Volcanic Belt

Gregor Weber1, Luca Caricchi1, Axel Schmitt2, and José Luis Arce3
Gregor Weber et al.
  • 1Department of Earth Sciences, University of Geneva, Rue des Maraîchers 13, 1205 Geneva (Gregor.Weber@unige.ch), (Luca.Caricchi@unige.ch)
  • 2Institut für Geowissenschaften, Universität Heidelberg, Im Neuenheimer Feld 236, 69120 Heidelberg (axel.schmitt@geow.uni-heidelberg.de)
  • 3Departamento de Geología Regional, Instituto de Geología, UNAM, Cd. Universitaria, Coyoacán, México D.F., 04510, Mexico (jlarce@geologia.unam.mx)

Understanding the assembly of eruptible magma in volcanic plumbing systems through time is key to the evaluation of hazard scenarios at potentially active volcanoes. In this respect, zircon geochronology provides a temporally resolvable record of the presence of magma. However, which specific processes and associated timescales are captured by zircon age distributions is not well constrained. Here we use zircon geochronology and geochemistry and thermal modelling of pulsed magma injection in the Earth crust to quantitatively invert zircon ages and recalculate magma fluxes and the rate of accumulation of eruptible magma in time. Zircon crystals have been analyzed from 4 late Pleistocene eruptions of Nevado de Toluca, a long-lived currently dormant dacitic stratovolcano in Central Mexico. 238U-230Th and 238U-206Pb age distributions show a protracted zircon crystallization history of ~900 ka in the magmatic plumbing system, a large fraction of the 1500 ka record of volcanic activity at the surface for this volcano. The 4 studied eruptions show similar broad age spectra, which are overlapping with each other and comparable peak zircon crystallization ages between 150 and 250 ka. Our dataset suggests that interstitial melt extraction (including zircon crystals) from highly crystallized resident magma and mixing thereof with fresh recharge magma surges is very efficient beneath Nevado de Toluca. Zircon trace element data, together with the geochronology show that the observed temporal trends in zircon geochemistry are consistent with tracking long-term assembly processes beneath the volcano operating over more than 1 million years. The combination of these results and thermal modelling allow us to quantify the rate of magma input, intrusive/extrusive ratio and the rate of accumulation of eruptible magma at Nevado de Toluca, which is essential to estimate the maximum potential size of the next eruption from this system.

How to cite: Weber, G., Caricchi, L., Schmitt, A., and Arce, J. L.: Thermochemical modelling of zircon age distributions from Nevado de Toluca volcano, Trans Mexican Volcanic Belt, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22291, https://doi.org/10.5194/egusphere-egu2020-22291, 2020

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Presentation version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-22291, Szabolcs Harangi, 05 May 2020

    Hi Gregor and Luca,

    very similar story as Ciomadul!... but much less magma flux,.. yet higher magma volume!

    What is the heat flux (geothermal gradient) in the area?

    Cheers, Réka and Szabi

    • AC1: Reply to CC1, Gregor Weber, 05 May 2020

      Hi, that is interesting. The geotherm is 40°C/km in the Toluca area. The volume that we caluclated is a maximum, so it could be less

      • CC2: Reply to AC1, Szabolcs Harangi, 05 May 2020

        Gregor, maybe a simple question: what is the magma flux in km3yr-1 unit in your case?

        • AC2: Reply to CC2, Gregor Weber, 05 May 2020

          It is between 0.0024 and 0.0069 km3/yr

  • CC3: Comment on EGU2020-22291, Szabolcs Harangi, 05 May 2020

    Thanks, looks pretty high! :-)

    • AC3: Reply to CC3, Gregor Weber, 05 May 2020

      You are welcome :) The flux has to be that high in order to reproduce the zircon age span and Ti temperatures

  • CC4: Comment on EGU2020-22291, Szabolcs Harangi, 05 May 2020

    very intersting work, Gregor! This also suggests that U-Pb dates of zircons are important to resolve the total time span of zircon crystallization and the lifetime fo the reservoir. In addition, would this mean that the entire magma storage is alive for 1 Myr and certain parts can be effectively rehomogenized before eruption? What is erupted volume of the Toluca volcano?

    • AC4: Reply to CC4, Gregor Weber, 05 May 2020

      Thank you very much! Yes, in order to reproduce the zircon population and temperatures the system has to be alive for at least 1.25 Ma. The zircon population seems to be well stirred as eruptions separated by tens of thousands of years sample the same long-term population. The absolute minimum erupted volume is 60 km3

  • CC5: Comment on EGU2020-22291, Szabolcs Harangi, 05 May 2020

    Yes, 60 km3 erupted volume is really high and could be consistent with the high magma flux and the large volume of magma in the reservoir! Happy to see another story on a long-dormant volcanic system! Thanks and best wishes from the Ciomadul volcano, another long-dormant volcanic system! :-)