Preprints
https://doi.org/10.5194/gchron-2024-29
https://doi.org/10.5194/gchron-2024-29
14 Nov 2024
 | 14 Nov 2024
Status: this preprint is currently under review for the journal GChron.

A comparison between in situ monazite Lu–Hf and U–Pb geochronology

Alexander T. De Vries Van Leeuwen, Stijn Glorie, Martin Hand, Jacob Mulder, and Sarah E. Gilbert

Abstract. In complex metamorphic terranes, monazite U–Th–Pb dates can span a wide concordant range, leading to ambiguous geological interpretations (e.g., slow protracted cooling versus multiphase growth). We present in situ monazite Lu–Hf analysis as an independent chronometer to verify U–Th–Pb age interpretations. Monazite Lu–Hf dates were attained via laser ablation inductively coupled plasma mass spectrometry equipped with collision/reaction cell technology (LA-ICP-MS/MS). In situ Lu–Hf dates for potential reference monazites with uncertainties < 1.6 % agree with published U–Th–Pb dates, validating the approach. We demonstrate the method on complex metamorphic samples from the Arkaroola region of the northern Flinders Ranges, South Australia, which exhibit protracted thermal and monazite growth histories due to high geothermal gradient metamorphism. In situ Lu–Hf dates reproduce the main U–Pb monazite age populations, demonstrating the ability to reliably resolve multiple age populations from polymetamorphic monazite samples.

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Alexander T. De Vries Van Leeuwen, Stijn Glorie, Martin Hand, Jacob Mulder, and Sarah E. Gilbert

Status: open (until 26 Dec 2024)

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Alexander T. De Vries Van Leeuwen, Stijn Glorie, Martin Hand, Jacob Mulder, and Sarah E. Gilbert

Data sets

Monazite Lu–Hf and U–Pb data Alexander T. De Vries Van Leeuwen https://doi.org/10.25909/27441327.v1

Alexander T. De Vries Van Leeuwen, Stijn Glorie, Martin Hand, Jacob Mulder, and Sarah E. Gilbert

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Short summary
In this contribution we demonstrate in situ monazite Lu–Hf dating and compare results with U–Th–Pb dating. We present data from monazite reference materials and complex samples to demonstrate the viability of this method. We show that in situ Lu–Hf dating of monazite can resolve multiple age populations and may find use where the U–Th–Pb system is compromised by Pb-loss, non-radiogenic Pb contamination, excess 206 Pb, low U contents, or a combination of these factors.