Preprints
https://doi.org/10.5194/gchron-2022-21
https://doi.org/10.5194/gchron-2022-21
 
16 Aug 2022
16 Aug 2022
Status: a revised version of this preprint was accepted for the journal GChron and is expected to appear here in due course.

In situ U-Pb dating of 4 billion year old carbonates in martian meteorite Allan Hills 84001

Romain Tartèse and Ian C. Lyon Romain Tartèse and Ian C. Lyon
  • Department of Earth and Environmental Sciences, The University of Manchester, Manchester, M13 9PL, UK

Abstract. In situ carbonate U-Pb dating studies have proliferated dramatically in recent years. Almost all these studies have targeted relatively young calcite up to Carboniferous in age. To assess the robustness of the carbonate U-Pb chronometer in deep-time, we carried out in situ U-Pb analyses in magnesite-ankerite-calcite carbonates in the martian meteorite Allan Hills (ALH) 84001. Carbonates in ALH 84001 formed at ca. 3.94 Ga, and there is little evidence that much happened to this rock since then, making it an ideal sample to test the robustness of the U-Pb system in old carbonates. We obtained a concordant date of 3941 ± 49/110 Ma (n = 14, MSWD = 2.0), which is identical to the step-leaching Rb/Sr date determined previously. These results thus confirm that old carbonates are amenable to U-Pb dating in samples that have had a relatively simple history post-carbonate formation.

Romain Tartèse and Ian C. Lyon

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2022-21', Graham Edwards, 07 Sep 2022
    • AC1: 'Reply on RC1', Romain Tartese, 16 Oct 2022
  • RC2: 'Comment on gchron-2022-21', Anonymous Referee #2, 12 Sep 2022
    • AC2: 'Reply on RC2', Romain Tartese, 16 Oct 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2022-21', Graham Edwards, 07 Sep 2022
    • AC1: 'Reply on RC1', Romain Tartese, 16 Oct 2022
  • RC2: 'Comment on gchron-2022-21', Anonymous Referee #2, 12 Sep 2022
    • AC2: 'Reply on RC2', Romain Tartese, 16 Oct 2022

Romain Tartèse and Ian C. Lyon

Romain Tartèse and Ian C. Lyon

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Short summary
Absolute chronological constraints are crucial in Earth and Planetary Science. In recent years, U-Pb dating of calcite has provided information on the timing of diagenesis, faulting, or hydrothermalism, for example. These studies have targeted relatively young carbonates up to 300 million years old. By dating 3.9 billion years old martian carbonates using the U-Pb chronometer, we show that this system can be robust in ancient samples that have had a relatively simple history.