EGU2020-4623, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-4623
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Eliminating Laser Induced Elemental U-Pb Fractionation using low sample volume multi-shot ablation protocols

Eoghan Corbett1,2, Antonio Simonetti2, Phil Shaw3, Loretta Corcoran2, Quentin Crowley1, and Brendan Hoare1
Eoghan Corbett et al.
  • 1Trinity College Dublin, Department of Geology, Ireland (corbetep@tcd.ie)
  • 2The University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences (CEEES), USA
  • 3Nu Instruments Ametek, UK

The interaction of incident laser radiation and sample substrate is complex and difficult to predict. Natural zircons areoften both structurally and chemically heterogeneous in 3-dimensional space. Encountering growth-related, structural micro-heterogeneities, inclusions and chemical complexities is almost inevitable when employing ‘conventional’ static, high-frequency laser sampling protocols often lasting several tens of seconds at a time.

 

A multi-shot approach to laser ablation by contrast implements a minimal sample exposure time to incident laser radiation by applying multiple 1 Hz shots in delayed succession to a single sampling site. This process can be conceptualised as a “slowing down” of a high-frequency (10-20 Hz) static Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis. Each laser pulse applied in this manner, produces signal peak which is distinct albeit transient. The ability to integrate and collate signal pulses for a small number of consecutive laser shots (10-30 shots), as opposed to continuously pulsing the laser, produces highly precise age determinations (<1% reproducibility, 2slevel) on small sample volumes (~695µm3 on 91500 zircon standard). The multi-shot LA-ICP-MS protocol employed here effectively eliminates ‘downhole’ fractionation as the resultant craters are extremely shallow (as shallow as ~553nm on 91500 zircon standard) and maintain an aspect ratio of <<1. Further benefits include a reduced probability of thermally induced effects (e.g., substrate melting), plasma loading, and the potential for signal mixing (with depth) in a heterogeneous sample.

How to cite: Corbett, E., Simonetti, A., Shaw, P., Corcoran, L., Crowley, Q., and Hoare, B.: Eliminating Laser Induced Elemental U-Pb Fractionation using low sample volume multi-shot ablation protocols, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4623, https://doi.org/10.5194/egusphere-egu2020-4623, 2020

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