Apatite Triple Dating (Lu–Hf, U–Pb, FT) Constrains Deformation and Cooling in the Coompana and Madura Provinces, Western Australia

Abstract

Combined apatite Lu–Hf, U–Pb, and fission track (AFT) triple dating affords the opportunity to investigate the ~60 and 730°C thermal history of a study area. Here, we apply apatite triple dating to resolve the tempo of multiple thermo-tectonic events within the Precambrian basement rocks of the Coompana (COP) and Madura (MAP) Provinces, Western Australia. Apatite Lu–Hf dates for the western COP (~1.52 Ga) and MAP (~1.36 Ga) agree with published Mesoproterozoic magmatic crystallization ages. Younger apatite U–Pb dates (~1.16–1.12 Ga) for the western COP and MAP suggest isotopic decoupling and radiogenic-Pb loss by volume diffusion in response to metamorphism at that time. Further East in the COP, the apatite Lu–Hf, and U–Pb dates are within uncertainty of each other and are interpreted to reflect recrystallization at ~1.20–1.14 Ga, coinciding with the late Mesoproterozoic Maralinga thermomagmatic event. The imprints of such an event were more pervasive towards the eastern COP, resulting in a thermally weakened crust in this area. AFT results constrain the subsequent Phanerozoic low-temperature history which has contrasting thermal trajectories on either side of the Mundrabilla Shear Zone (MSZ). Thermal history modeling suggests an early Carboniferous rapid cooling pulse (~360–330 Ma) for the COP, east of the MSZ, that is contemporaneous with the intraplate Devonian–Carboniferous Alice Springs Orogeny. In contrast, the MAP, west of the MSZ, records a protracted monotonic cooling history since the Middle Devonian, implying long-term crustal stability. The differences in low-temperature thermal histories may be preconditioned by the extent of thermal weakening during the late Mesoproterozoic, as indicated by the Lu–Hf and U–Pb results. Here, we show the value of apatite triple dating applied to grains recovered from drill core samples, demonstrating opportunities for understanding other poorly accessible terranes.