Laser ablation (in situ) Lu-Hf dating of magmatic fluorite and hydrothermal fluorite-bearing veins

Abstract

Fluorite (CaF₂) is a common hydrothermal mineral, which precipitates from fluorine-rich fluids with an exceptional capacity to transport metals and Rare Earth Elements (REEs). Hence, the ability to date fluorite has important implications for understanding the timing of metal transport in hydrothermal systems. Here we present, for the first time, fluorite Lu-Hf dates from fluorite-carbonate veins from the Olympic Cu-Au Province in South Australia. The fluorite dates were obtained in situ using the recently developed LA-ICP-MS/MS Lu-Hf dating method. A fluorite-calcite age of 1588 ± 19 Ma was obtained for the Torrens Dam prospect, consistent with the timing of the formation of the nearby Olympic Dam iron-oxide copper gold Breccia Complex. Veins in the overlying Neoproterozoic successions were dated at 502 ± 14 Ma, indicating a temporal link between Cu-sulphide remobilisation and the Delamerian Orogeny. Additionally, we present a multi-session reproducible date for magmatic fluorite from a monzogranite in the Pilbara Craton (Lu-Hf age of 2866 ± 19 Ma). This age is consistent with a garnet Lu-Hf age from the same sample (2850 ± 12 Ma) and holds potential to be developed into a secondary reference material for future fluorite Lu-Hf dating.