@article{9c5b5126d45642ff8b03c35d0bd6ed71,
title = "Diachroneity of the Clearwater West and Clearwater East impact structures indicated by the (U–Th)/He dating method",
abstract = "The (U–Th)/He method has been applied to constrain the formation ages of the Clearwater West and East impact structures of Quebec, Canada. Zircons were separated from impact melt samples derived from a surface exposure at Clearwater West (32 km diameter), and from a drill core at Clearwater East (26 km diameter). The (U–Th)/He results indicate ages of 280±27 Ma (2σ, n=7) for Clearwater West, and 450±56 Ma (2σ, n=8) for Clearwater East. Our (U–Th)/He date for Clearwater West supports the findings of previous Rb–Sr (266±15 Ma; 2σ) and 40Ar/39Ar (280±4 Ma and 283.8±2.2 Ma, 2σ) impact melt studies. Our (U–Th)/He date for Clearwater East also overlaps with previously published 40Ar/39Ar dating results, which yielded U-shaped spectra, with {\textquoteleft}maximum{\textquoteright} and {\textquoteleft}best-estimate{\textquoteright} dates of ∼ 460–470 Ma. Our results support the contention, previously based solely on 40Ar/39Ar data, that the Clearwater West and East impact structures do not comprise an impact doublet that formed coevally from a binary asteroid pair.",
keywords = "helium diffusion, impact cratering, shock metamorphism, thermochronology",
author = "Biren, {M. B.} and {Van Soest}, Matthijs and Wartho, {J. A.} and Kip Hodges and Spray, {J. G.}",
note = "Funding Information: This research was funded largely by National Science Foundation grant EAR-0948143 (J.A. Wartho, M.C. van Soest and K.V. Hodges), with supplementary funding from a NASA SSERVI grant ( NNX14AG36A ) to K.V. Hodges. We thank Henrietta Cathey (ASU) for assistance with analytical field emission scanning electron microscopy and Cameron Mercer (ASU) for the use of his ArAR Calc 40 Ar/ 39 Ar age recalculator program used to convert published K–Ar and 40 Ar/ 39 Ar ages using different K decay constants and age standard data, available at the following link http://group18software.asu.edu . Ann Therriault and Richard Grieve of the Earth Materials Collections, Natural Resources Canada, are thanked for providing the Clearwater East impact melt sample material. The Clearwater West samples were obtained from the Canadian impact crater collection, which until recently, has been maintained by the Planetary and Space Science Centre (PASSC), University of New Brunswick, through grants awarded to JGS from the Canada Foundation for Innovation and Canadian Space Agency FAST program. Planetary and Space Science Centre publication number 82. We thank An Yin for editorial handling and Martin Schmieder and Kyle Min for their thoughtful and useful reviews. Publisher Copyright: {\textcopyright} 2016 Elsevier B.V.",
year = "2016",
month = nov,
day = "1",
doi = "10.1016/j.epsl.2016.07.053",
language = "English (US)",
volume = "453",
pages = "56--66",
journal = "Earth and Planetary Science Letters",
issn = "0012-821X",
publisher = "Elsevier",
}