Preprints
https://doi.org/10.5194/gchron-2023-20
https://doi.org/10.5194/gchron-2023-20
25 Aug 2023
 | 25 Aug 2023
Status: a revised version of this preprint was accepted for the journal GChron and is expected to appear here in due course.

Increased accuracy and precision in igneous and detrital zircon geochronology using CA-LA-ICPMS

Erin Elizabeth Donaghy, Michael P. Eddy, Federico Moreno, and Mauricio Ibañez-Mejia

Abstract. Detrital zircon geochronology by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a widely-used tool for determining maximum depositional ages, sediment provenance, and reconstructing sediment routing pathways. Although the accuracy and precision of U-Pb geochronology measurements has improved over the past two decades, Pb-loss continues to impact the ability to resolve zircon age populations by biasing affected zircon toward younger apparent ages. Chemical abrasion (CA) has been shown to reduce or eliminate the effects of Pb-loss in zircon U-Pb geochronology, but has yet to be widely applied to large-n detrital zircon analyses. Here, we assess the efficacy of the chemical abrasion treatment on zircon prior to analysis by LA-ICP-MS and discuss the advantages and limitations of this technique in relation to detrital zircon geochronology. We show that i) CA does not systematically bias LA-ICP-MS U-Pb dates for thirteen reference materials that span a wide variety of crystallization dates and U concentrations; ii) CA-LA-ICP-MS U-Pb zircon geochronology can reduce, or eliminate, Pb-loss in samples that have experienced significant radiation damage; and iii) bulk CA prior to detrital zircon U-Pb geochronology by LA-ICP-MS improves the resolution of Neoproterozoic to present zircon age populations and the percentage of concordant analyses in Mesoproterozoic and older age populations. The selective dissolution of zircon that has experienced high degrees of radiation damage suggests that some detrital zircon age populations could be destroyed or have their abundance significantly modified during this process. However, we did not identify this potential effect in either of the detrital zircon samples that were analyzed as part of this study. We conclude that pre-treatment of detrital zircon by bulk CA may be useful for applications that require increased resolution of detrital zircon populations.

Erin Elizabeth Donaghy, Michael P. Eddy, Federico Moreno, and Mauricio Ibañez-Mejia

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on gchron-2023-20', Trystan Herriott, 19 Sep 2023
    • RC2: 'Reply on CC1', Marcel Guillong, 20 Sep 2023
      • CC2: 'Reply on RC2', Trystan Herriott, 20 Sep 2023
      • AC2: 'Reply on RC2', Erin Donaghy, 19 Dec 2023
    • AC4: 'Reply on CC1', Erin Donaghy, 19 Dec 2023
  • RC1: 'Comment on gchron-2023-20', Marcel Guillong, 20 Sep 2023
    • AC3: 'Reply on RC1', Erin Donaghy, 19 Dec 2023
  • RC3: 'Comment on gchron-2023-20', David M. Chew, 29 Sep 2023
    • AC1: 'Reply on RC3', Erin Donaghy, 19 Dec 2023
  • RC4: 'Comment on gchron-2023-20', Matthew Horstwood, 01 Nov 2023
    • AC5: 'Reply on RC4', Erin Donaghy, 19 Dec 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on gchron-2023-20', Trystan Herriott, 19 Sep 2023
    • RC2: 'Reply on CC1', Marcel Guillong, 20 Sep 2023
      • CC2: 'Reply on RC2', Trystan Herriott, 20 Sep 2023
      • AC2: 'Reply on RC2', Erin Donaghy, 19 Dec 2023
    • AC4: 'Reply on CC1', Erin Donaghy, 19 Dec 2023
  • RC1: 'Comment on gchron-2023-20', Marcel Guillong, 20 Sep 2023
    • AC3: 'Reply on RC1', Erin Donaghy, 19 Dec 2023
  • RC3: 'Comment on gchron-2023-20', David M. Chew, 29 Sep 2023
    • AC1: 'Reply on RC3', Erin Donaghy, 19 Dec 2023
  • RC4: 'Comment on gchron-2023-20', Matthew Horstwood, 01 Nov 2023
    • AC5: 'Reply on RC4', Erin Donaghy, 19 Dec 2023
Erin Elizabeth Donaghy, Michael P. Eddy, Federico Moreno, and Mauricio Ibañez-Mejia
Erin Elizabeth Donaghy, Michael P. Eddy, Federico Moreno, and Mauricio Ibañez-Mejia

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Editor
This study is an important contribution to high precision geochronology. The study highlights the criteria for selecting the most suitable zircon material and it analytical treatment to obtain precise and accurate mineral ages.
Short summary
Chemical abrasion (CA) is a technique that reduces or eliminates the effects of Pb-loss in zircon U-Pb geochronology. However, CA has yet to be applied to large-n detrital zircon (DZ) analyses. We show that CA does not negatively impact or systematically bias U-Pb dates and improves concordance, precision, and accuracy. When applied to DZ samples prior to laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), CA improves the resolution of DZ age populations.