Dating deformation using crushed alkali feldspar: 40Ar/39Ar geochronology of shear zones in the Wyangala Batholith, NSW, Australia

摘要

Diffusion parameters have been estimated for K-feldspar in and adjacent to mylonite shear zones in the Wyangala Batholith. The parameters obtained suggest that deformation during mylonitisation would have caused argon systematics to reset because diffusion distances were reduced by cataclasis, deformation and6 or recrystallisation. However, the mineral lattice remained sufficiently retentive to allow subsequently produced radiogenic argon to be retained. ~(40)Ar/~(39)Ar geochronology is thus able to constrain operation of these biotite-grade ductile shear zones to the period from ca 380 Ma to ca 360 Ma, at the end of the Tabberabberan Orogeny.