Preprints
https://doi.org/10.5194/gchron-2021-46
https://doi.org/10.5194/gchron-2021-46
 
06 Jan 2022
06 Jan 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 Lu – Hf geochronology of calcite

Alexander Simpson1,2, Stijn Glorie1,2, Martin Hand1,2, Carl Spandler1, Sarah Gilbert3, and Brad Cave1 Alexander Simpson et al.
  • 1Department of Earth Sciences, School of Physical Sciences, The University of Adelaide, Adelaide SA-5005, Australia
  • 2Mineral Exploration Cooperative Research Centre (Minex CRC), The University of Adelaide, Adelaide SA-5005, Australia
  • 3Adelaide Microscopy, The University of Adelaide, Adelaide SA-5005, Australia

Abstract. The ability to constrain the age of calcite formation is of great utility to the Earth Science community, due to the ubiquity of calcite across a wide spectrum of geological systems. Here, we present the first in-situ laser ablation inductively coupled tandem mass spectrometry (LA-ICP-MS/MS) Lu–Hf ages for calcite, demonstrating geologically meaningful ages for IOCG and skarn mineralisation, carbonatite intrusion and low grade metamorphism. The analysed samples range in age between ca. 0.9 Ga and ca. 2 Ga with uncertainties between 1.4 % and 0.5 % obtained from calcite with Lu concentrations as low as ca. 0.5 ppm. The Lu–Hf system in calcite appears to be able to preserve primary precipitation ages over a significant amount of geological time, although further research is required to constrain the closure temperature. The in-situ approach allows calcite to be rapidly dated while maintaining its petrogenetic context with mineralization and other associated mineral processes. Therefore, LA-ICP-MS/MS Lu–Hf dating of calcite can be used to resolve the timing of complex mineral paragenetic sequences that are a feature of many ancient rock systems.

Alexander Simpson et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2021-46', Donald Davis, 24 Jan 2022
    • AC1: 'Reply on RC1', Alexander Simpson, 01 Feb 2022
  • RC2: 'Comment on gchron-2021-46', Nick Roberts, 04 Feb 2022
    • AC2: 'Reply on RC2', Alexander Simpson, 18 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2021-46', Donald Davis, 24 Jan 2022
    • AC1: 'Reply on RC1', Alexander Simpson, 01 Feb 2022
  • RC2: 'Comment on gchron-2021-46', Nick Roberts, 04 Feb 2022
    • AC2: 'Reply on RC2', Alexander Simpson, 18 Mar 2022

Alexander Simpson et al.

Data sets

Supplementary file 1 Lu Hf data tables Alexander Simpson https://adelaide.figshare.com/articles/dataset/Supplementary_file_1_calcite_Lu-Hf_data/17425541

Supplementary file 1 Lu Hf data tables Alexander Simpson https://adelaide.figshare.com/articles/dataset/Supplementary_file_1_calcite_Lu-Hf_data/17425541

Alexander Simpson et al.

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Short summary
The article demonstrates a new technique that can be used to determine the age of calcite crystallisation using the decay of 176Lu into 176Hf. The technique is novel because it a) Lu-Hf radiometric dating is rarely applied to calcite and b) this is the first instance where analysis has been conducted by ablating the sample with a laser beam rather than bulk dissolution. By using laser ablation the original context of the sample is preserved.