TY - JOUR
T1 - An (U-Th)/He age for the small Monturaqui impact structure, Chile
AU - Ukstins, Ingrid A.
AU - Wartho, Jo Anne
AU - Cabrol, Nathalie A.
AU - Grin, Edmond A.
AU - van Soest, Matthijs C.
AU - Biren, Marc B.
AU - Hodges, Kip V.
AU - Chong, Guillermo
N1 - Funding Information:
IAU would like to acknowledge support from NSF grant EAR-1126728, NASA grant 06-PGG06-6, University of Iowa CLAS start-up funds and the University of Iowa Obermann Center for support during fieldwork and manuscript preparation. J-AW, MvS, MBB and KVH would like to acknowledge the support of NSF grant EAR-0948143. We would also like to thank Dr Henrietta E. Cathey (LeRoy Eyring Center for Solid State Science, ASU) for assistance in obtaining the secondary electron images presented in this paper. We also gratefully acknowledge the field assistance of Christy Kloberzanz, Sarah Byram and David W. Peate. We thank Barry Kohn and an anonymous reviewer for their careful reviews and the editorial handling of Robyn Pickering, which improved the quality of this research paper.
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2022/2
Y1 - 2022/2
N2 - Single-crystal (U-Th)/He dating of 32 apatite and zircon crystals from an impact breccia yielded a weighted mean age of 663 ± 28 ka (n = 3; 4.2 % 2σ uncertainties) for the Monturaqui impact structure, Chile. This ~350 m diameter simple crater preserves a small volume of impactite consisting of polymict breccias that are dominated by reworked target rock clasts. The small size, young age and limited availability of melt material for traditional geochronological techniques made Monturaqui a good test to define the lower limits of the (U-Th)/He system to successfully date impact events. Numerical modeling of 4He loss in apatite and zircon crystals shows that, for even small craters such as Monturaqui, the short-lived compressional stage and shock metamorphic stage can account for the observed partial to full resetting of (U-Th)/He ages in accessory minerals. Despite the distinctly different 4He diffusion parameters of apatite and zircon, the 2σ-overlapping youngest ages are recorded in both populations of minerals, which supports the inference that the weighted mean of the youngest (U-Th)/He population is the age of formation of this impact structure.
AB - Single-crystal (U-Th)/He dating of 32 apatite and zircon crystals from an impact breccia yielded a weighted mean age of 663 ± 28 ka (n = 3; 4.2 % 2σ uncertainties) for the Monturaqui impact structure, Chile. This ~350 m diameter simple crater preserves a small volume of impactite consisting of polymict breccias that are dominated by reworked target rock clasts. The small size, young age and limited availability of melt material for traditional geochronological techniques made Monturaqui a good test to define the lower limits of the (U-Th)/He system to successfully date impact events. Numerical modeling of 4He loss in apatite and zircon crystals shows that, for even small craters such as Monturaqui, the short-lived compressional stage and shock metamorphic stage can account for the observed partial to full resetting of (U-Th)/He ages in accessory minerals. Despite the distinctly different 4He diffusion parameters of apatite and zircon, the 2σ-overlapping youngest ages are recorded in both populations of minerals, which supports the inference that the weighted mean of the youngest (U-Th)/He population is the age of formation of this impact structure.
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U2 - 10.1016/j.quageo.2021.101217
DO - 10.1016/j.quageo.2021.101217
M3 - Article
AN - SCOPUS:85112808836
SN - 1871-1014
VL - 67
JO - Quaternary Geochronology
JF - Quaternary Geochronology
M1 - 101217
ER -