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Central Snake River Plain Eruptive Products Are Hot and Dry -- Yet Saturated with Zircon: Why?

Julian-Christopher Storck1 , Ben Ellis1, Edgar Alejandro Cortes-Calderon1,2, Marcel Guillong1, Olivier Bachmann1

  • Affiliations: 1Department of Earth and Planetary Sciences, ETH Zürich, Clausiusstrasse 25, 8092 Zürich 2Imaging and Analysis Centre, Natural History Museum, Cromwell Road, London SW 75 BD, UK

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 56

  • Programme No: 1.7.43

  • Theme 1 > Session 7

Abstract

Zircon (ZrSiO₄) serves as a nearly ubiquitous monitor of conditions in evolved magmatic systems. However, in rocks from exceptionally hot and dry magmatic environments, such as those of the Columbia River -Snake River Plain-Yellowstone province, an unexpected abundance of zircon is observed despite high magmatic temperatures and low Zr contents. These conditions theoretically favor zircon undersaturation, raising the question of how significant zircon crystallization could occur in such chemically and thermally unfavorable environments. Addressing this paradox is the primary focus of this study. We present new time-temperature estimates derived from zircon U-Pb geochronology, mineral thermometry and bulk rock/glass thermodynamic modeling to reconstruct the final stages of the thermal history of one of the youngest and hottest (>900°C, two-pyroxene and ilm-mgt thermometry) eruptions in the Central Snake River Plain: the Castleford Crossing ignimbrite. These results are integrated within a broader context, incorporating data from three older ignimbrites in the same stratigraphic profile which are intensely welded and commonly rheomorphic. Furthermore, we explore theoretical considerations on the role of (post-)eruptive emplacement conditions, to align the high temperature mineral record along with zircon saturation under these extreme conditions.