An (U-Th)/He age for the small Monturaqui impact structure, Chile.

Ukstins, Ingrid, Wartho, Jo-Anne , Cabrol, Nathalie A., Grin, Edmond A., van Soest, Matthijs C., Biren, Marc B., Hodges, Kip V. and Chong, Guillermo (2022) An (U-Th)/He age for the small Monturaqui impact structure, Chile. Open Access Quaternary Geochronology, 67 . Art.Nr. 101217. DOI 10.1016/j.quageo.2021.101217.

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Supplementary data:

Abstract

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 modelling 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.

Document Type: Article
Keywords: Monturaqui, Chile, impact crater, (U-Th)/He dating, He loss modeling
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-MUHS Magmatic and Hydrothermal Systems
Main POF Topic: PT3: Restless Earth
Refereed: Yes
Open Access Journal?: No
Publisher: Elsevier
Date Deposited: 09 Aug 2021 06:14
Last Modified: 07 Feb 2024 15:40
URI: https://oceanrep.geomar.de/id/eprint/53710

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