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https://hdl.handle.net/2440/137325
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Type: | Journal article |
Title: | Robust laser ablation Lu-Hf dating of apatite: an empirical evaluation |
Author: | Glorie, S. Hand, M. Mulder, J. Simpson, A. Emo, R. Kamber, B. Fernie, N. Nixon, A. Gilbert, S. |
Citation: | Geological Society Special Publication, 2024; 537(1):165-184 |
Publisher: | Geological Society |
Issue Date: | 2024 |
ISSN: | 0305-8719 2041-4927 |
Statement of Responsibility: | Stijn Glorie, Martin Hand, Jacob Mulder, Alexander Simpson, Robert B. Emo, Balz Kamber, Nicholas Fernie, Angus Nixon, and Sarah Gilbert |
Abstract: | Recent development in laser-ablation Lu-Hf dating has opened a new opportunity to rapidly obtain apatite ages that are potentially more robust to isotopic resetting compared to traditional U-Pb dating. However, the robustness of the apatite Lu-Hf system has not been systematically examined. To address this knowledge gap, we conducted four case studies to determine the resistivity of the apatite Lu-Hf system compared to the zircon and apatite U-Pb system. In all cases, the apatite U-Pb system records a secondary (metamorphic or metasomatic) overprint. The apatite Lu-Hf system, however, preserves primary crystallisation ages in unfoliated granitoids at temperatures of at least ∼660 °C. Above ∼730 °C, the Lu-Hf system records isotopic resetting by volume diffusion. Hence, in our observations for apatite of ‘typical’ volumes in granitoids (∼0.01-0.03 mm2), the closure temperature of the Lu-Hf system is between ∼660 and ∼730 °C, consistent with theoretical calculations. In foliated granites, the Lu-Hf system records the timing of recrystallisation, while the apatite U-Pb system tends to record younger cooling ages. We also present apatite Lu-Hf dates for lower crustal xenoliths erupted with young alkali basalts, demonstrating that the Lu-Hf system can retain a memory of primary ages when exposed to magmatic temperatures for a relatively short duration. Hence, the apatite Lu-Hf system is a new insightful addition to traditional zircon (or monazite) U-Pb dating, particularly when zircons/monazites are absent or difficult to interpret due to inheritance or when U and Pb isotopes display open system behaviour. The laser-ablation based Lu-Hf method allows campaign-style studies to be conducted at a similar rate to U-Pb studies, opening new opportunities for magmatic and metamorphic studies. |
Rights: | © 2023 The Geological Society of London |
DOI: | 10.1144/SP537-2022-205 |
Grant ID: | http://purl.org/au-research/grants/arc/DP200101881 |
Published version: | http://dx.doi.org/10.1144/sp537-2022-205 |
Appears in Collections: | Geology & Geophysics publications |
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