150 Geochronology of Critical Mineral Deposits with Special Reference to U-Th-Pb Dating of Common-Pb-Rich Minerals (Posters)

Radiometric dating of ore deposits containing critical minerals. Studies discussing analytical aspects of methods such as U-Th-Pb, Ar-Ar, Rb-Sr, Sm-Nd, Re-Os and/or using radiometric ages for ore genesis research or critical mineral resource evaluation.

Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Hydrothermal zircon geochronology from the Nechalacho REE deposit, NWT, Canada

Paper number: 150-2
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Rare earth elements (REEs) are vital to modern technologies such as renewable energy, electronics, and defense systems. The Nechalacho deposit in Canada is one of the few large scale REE and zirconium (Zr) sources in North America, containing important concentrations of both light and heavy REEs in a variety of ore minerals, mainly the hydrothermal bastnasite-Ce, in addition to parisite-Ce, with other REE hosts being eudialyte and zircon. Hydrothermal processes are likely fundamentally important for the ore-enrichment process in the Nechalacho deposit, and by inference other alkaline magmatic deposits globally.

Hydrothermal events are difficult the evaluate in alkaline magmatic REE deposits, and the Nechalacho deposit is no exception. There is increasing focus on dating non-traditional mineral phases such as bastnasite [1], and using microanalytical techniques focused on traditional phases such as hydrothermal zircon [2]. In the Nechalacho deposit specifically, there is currently uncertainty in the ages of hydrothermal zircon, and therefore it’s role in the REE enrichment processes. Initial whole-grain dissolution TIMS data [3] suggested that in addition to the magmatic 2.175 Ga age there existed a 2.09 Ga hydrothermal zircon age, though this conclusion was disputed by later in situ zircon geochronology and geochemistry [4].

We have documented one single large hydrothermal zircon that records a seeming 2.09 Ga age, corroborating bastnasite geochronology from the Nechalacho deposit that suggested hydrothermal processes enriched the deposit nearly 100 Ma after initial intrusion [1]. In this study, we present expanded evaluation of hydrothermal zircons from the Nechalacho deposit for their ages and trace element chemistry. We will present morphological data, EPMA major element chemistry, and correlated U-Pb ages from magmatic and hydrothermal zircons in order to determine the sequence of hydrothermal alteration in this important REE deposit. These method may help evaluate the role of magmatic versus hydrothermal origins of REE enrichment at Nechalacho and may help guide exploration strategies in similar REE-bearing systems.

 

1 - Legros, Hélène, et al.Lithos  (2025)

2 - Monnier, Loïs, et al. Geochimica et Cosmochimica Acta (2025).

3 - Bowring, S. A., et al. Canadian Journal of Earth Sciences (1984)

4 - Sheard, Emma R., et al. Economic Geology (2012)

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413999

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