Zircon in tephra as a novel tool to decrypt geologic and archaeological archives: a case study from Central America
Mineralogy, Petrology and Geochemistry
Final Report Abstract
Age and geochemical signatures of zircon extracted from Quaternary eruptions sourced in the Central American Volcanic Arc (CAVA) were investigated to explore their potential for tephra correlation. This approach is based on the largely unique zircon age spectrum for individual eruptions and volcanic centers, whereas conventional methods, typically based on analysis of major and trace components in glasses, often yield ambiguous results especially when originated from the same or adjacent eruptive centers. In contrast to glass, zircon is also highly resistant against weathering. Trace element compositions provide a temporally resolved record of the thermochemical evolution of magmas prior to eruption. This information is crucial to identify processes of magma recharge and assimilation of country rock in long-lived transcrustal magma systems, which critically influence the compositional gamut of magmas and thus their eruptive behavior and tephra dispersal. In this project, volcanic centers ranging in size from stratovolcanoes (Santa María-Santiaguito) to multicyclic calderas (Atitlán, Amatitlán, Coatepeque und Ilopango) were investigated. In a subproject, zircon from geoarchaoologically relevant clay (palygorskite) deposits in the Yucatan peninsula karst were studied to test whether zircon can be used to identify tephra sources over protracted geological storage under conditions of extreme weathering. Zircon petrochronology indicates that in all studied volcanic systems of Quaternary age, silicic magma started to accumulate many tens of thousands of years prior to eruption. During this duration, zircon typically crystallized in a semi-continuous fashion, with zircon crystallization age peaks close to the eruption often indicating progressive magma differentiation. Over this time span zircon recorded secular changes in magma chemistry and temperature (e.g., δ18O and REE, Hf, Ti-in-zircon) that can be correlated to recharge events, assimilation of crustal components, and major differentiation episodes. These changes are reflected at the zircon intra- and inter-grain scale indicating that variable thermal and compositional gradients prevailed in the magma reservoir over protracted timespans. Cannibalization of genetically-related hydrothermally-altered rocks was here first identified for Ilopango as an important factor in the magmatic differentiation of CAVA volcanic systems. Based on the comprehensive characterization of zircon ages and compositions, we were able to demonstrate the successful correlation of tephra over large distances (>300 km) with their source calderas. In the case of zircon from palygorskite, the previously unknown source was identified as volcanoes in an Eocene volcanic arc, likely to the west of the deposition center.
Publications
- (2019). Millennial to decadal magma evolution in an arc volcano from zircon and tephra of the 2016 Santiaguito eruption (Guatemala). Lithos, 340, 209-222
Cisneros de León, A., Schmitt, A. K., Storm, S., Weber, B., Schindlbeck-Belo, J. C., Trumbull, R. B., & Juárez, F.
(See online at https://doi.org/10.1016/j.lithos.2019.04.027) - (2019). Zircon in sak lu'um: Evidence of multiple Eocene silicic tephra layers as palygorskite precursors in the Yucatán peninsula, Mexico. Journal of South American Earth Sciences, 93, 394-411
Cisneros de León, A.., Schmitt, A. K., Roberge, J., Heiler, L., Ludwig, C., & Schmitt, F. H.
(See online at https://doi.org/10.1016/j.jsames.2019.05.005) - (2020). The Arce Tephra: Two subsequent paroxysmal Plinian eruptions from Coatepeque Caldera (El Salvador). Journal of Volcanology and Geothermal Research, 390, 106673
Kutterolf, S., Schindlbeck-Belo, J. C., Rohr, I., Rademacher, M., Cisneros de León, A., Eisele, S., Freundt, A., Hernandez, W.& Wang, K. L.
(See online at https://doi.org/10.1016/j.jvolgeores.2019.106673) - (2021). A history of violence: magma incubation, timing and tephra distribution of the Los Chocoyos supereruption (Atitlán Caldera, Guatemala). Journal of Quaternary Science, 36(2), 169-179
Cisneros de León, A., Schindlbeck‐Belo, J. C., Kutterolf, S., Danišík, M., Schmitt, A. K., Freundt, A., Pérez, W., Harvey, J.C., Wang, K. L. & Lee, H. Y.
(See online at https://doi.org/10.1002/jqs.3265) - (2021). Zircon and melt extraction from a long‐lived and vertically extensive magma system underneath Ilopango Caldera (El Salvador). Geochemistry, Geophysics, Geosystems, 22(5), e2020GC009507
Cisneros de León, A., Schmitt, A. K., Kutterolf, S., Schindlbeck-Belo, J. C., Hernández, W., Sims, K. W. W., Garrison, J., Kant, L. B., Weber, B., Wang, K. L. & Trumbull, R. B.
(See online at https://doi.org/10.1029/2020gc009507)
