Mica 40Ar/39Ar geochronology: Implications for LCT-pegmatite chronology

This dataset documents 40Ar/39Ar geochronology analyses of mica (muscovite and lepidolite) from lithium–caesium–tantalum (LCT) pegmatites investigated as part of the MRIWA M532 lithium project.

The overarching aim is to constrain the timing of LCT-pegmatite crystallisation and to establish robust crystallisation ages for lithium-bearing pegmatite systems. Previous attempts to apply 40Ar/39Ar geochronology to spodumene, the principal Li-bearing pyroxene in LCT pegmatites, indicated that measured ages predominantly record alteration (sericitisation) rather than primary crystallisation. Consequently, this study focuses on coarsely crystalline mica phases that form during pegmatite crystallisation and are therefore more suitable targets for 40Ar/39Ar dating. Muscovite and lepidolite separates from the same pegmatite samples were analysed to obtain crystallisation ages for LCT pegmatites. These ages are interpreted to represent the timing of pegmatitic melt solidification.

Together, this dataset provides a geochronological framework for LCT pegmatite formation within the study area and supports improved interpretation of isotopic ages from lithium-bearing pegmatite systems.

The 40Ar/39Ar geochronology analyses were supported through AuScope's National Argon Map initiative (January 2020 – June 2021).