Detrital zircon resolve longevity and evolution of silicic magmatism in extinct volcanic centers: A case study from the East Fjords of Iceland

• Published in: Geosphere
• Main Authors: Carley, T.L., Miller, C.F., Sigmarsson, O., Coble, M.A., Fisher, C.M., Hanchar, J.M., Schmitt, A.K., Economos, R.C.
• Other Authors: Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet Saint-Étienne (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Institut national des sciences de l'Univers (INSU - CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology; Kækjuskörð; Sion; Torfajökull; Iceland
• Online Access: https://hal.uca.fr/hal-01713319; https://doi.org/10.1130/GES01467.1

International audience Breiðuvík and Kækjuskörð are two neighboring extinct eruptive centers in the East Fjords of Iceland. Together, they compose the second-largest volume of silicic rock in the country (after Torfajökull, an active volcanic system in southern Iceland). We use ages and compositions of detrital zircon collected from two riv-ers, the Stóraá and Krossá-Kækjudalsá, to investigate the origins and longevity of silicic magmatism at Breiðuvík-Kækjuskörð. Zircon populations from the two catchments have identical median U-Pb dates (12.9 Ma), O isotopes (d18O Vienna standard mean ocean water = 3.1‰ versus 3.3‰), and Hf isotopes (İHf = 14.7). We interpret coherence of zircon elemental and isotopic compositions to indicate that a signifi cant volume of relatively uniform silicic material was produced in close temporal and spatial proximity between 11.2 ± 0.7 Ma and 15.0 ± 0.9 Ma (all errors are 1ı), dominated by assimilation–fractional crystallization processes. To test the robustness of this longevity estimate, we applied Monte Carlo modeling to the Breiðuvík-Kækjuskörð detrital zircon results and found the age span to be statistically resolvable at ³2.8 m.y. While this lifespan is comparable to those of large mafi c-silicic volcanic systems that have described in other settings glob-ally, it is the longest reported estimate for any Icelandic volcano, where typical longevity is thought to be ~0.5–1.5 m.y. The ³2.8 m.y. lifespan we present for Breiðuvík-Kækjuskörð is a conservative assessment, because the dates used in this study only represent the zircon-saturated period of magmatic activity. This study demonstrates that detrital zircon analysis of volcanigenic sediment pro-vides an effi cient and powerful tool that can illuminate histories of zircon-satu-rated magmatism at targeted volcanic centers and systems. This approach can be particularly valuable in dominantly mafi c provinces where silicic material is subordinate (e.g., ocean islands, fl ood basalt provinces), where glaciation, ero-sion, or ...