TY - JOUR
T1 - An apatite to unravel petrogenic processes of the Nova-Bollinger Ni-Cu magmatic sulfide deposit, Western Australia
AU - Morrison, Jessica L.
AU - Kirkland, Christopher L.
AU - Fiorentini, Marco
AU - Beresford, Steve
AU - Polito, Paul
PY - 2022/2
Y1 - 2022/2
N2 - The trace element signature and U-Pb systematics of apatite are useful in identifying petrogenic processes and tracking crust through the ∼375–600 °C thermal interval. Furthermore, as apatite is more abundant in mafic rocks than other more conventional U-Pb chronometers (e.g. zircon), it may be better suited to constrain magmatic ore systems. This work focuses on a case study of apatite from the Nova-Bollinger Ni-Cu magmatic sulfide deposit in the Fraser Zone of the Albany Fraser Orogen, Western Australia. LA-ICP-MS analysis is used to characterise the U-Pb systematics and trace element chemistry of apatite across four rock types at Nova-Bollinger. These analyses are combined with whole-rock geochemistry and petrography to resolve the poorly understood thermal evolution of Nova-Bollinger after peak metamorphic conditions. Apatite U-Pb data indicate an initial 15 °C/my cooling rate to 1284 ± 12 Ma from peak metamorphic conditions of ∼850 °C at 1304 ± 22 Ma. After 1284 Ma the cooling rate dramatically slowed to 1.2 °C/my until at least 1225 ± 17 Ma. Most apatite retains an igneous trace element signature where thermal diffusion has not influenced trace element concentrations, suggesting that any exposure to temperatures above ∼670 °C was short-lived or trace element diffusion was slow. Furthermore, trace element chemistry discriminates apatite that crystallised from an evolved intercumulus disequilibrium liquid, and apatite that crystallised in equilibrium with the mineral assemblage of more fractionated rocks. The new results from this study highlight the change from a fast to slow cooling regime in this litho-tectonic zone, likely driven by ebbing regional magma emplacement. This new information enables better understanding of the tectono-magmatic evolution of the Proterozoic Nova-Bollinger deposit and the broader Fraser Zone.
AB - The trace element signature and U-Pb systematics of apatite are useful in identifying petrogenic processes and tracking crust through the ∼375–600 °C thermal interval. Furthermore, as apatite is more abundant in mafic rocks than other more conventional U-Pb chronometers (e.g. zircon), it may be better suited to constrain magmatic ore systems. This work focuses on a case study of apatite from the Nova-Bollinger Ni-Cu magmatic sulfide deposit in the Fraser Zone of the Albany Fraser Orogen, Western Australia. LA-ICP-MS analysis is used to characterise the U-Pb systematics and trace element chemistry of apatite across four rock types at Nova-Bollinger. These analyses are combined with whole-rock geochemistry and petrography to resolve the poorly understood thermal evolution of Nova-Bollinger after peak metamorphic conditions. Apatite U-Pb data indicate an initial 15 °C/my cooling rate to 1284 ± 12 Ma from peak metamorphic conditions of ∼850 °C at 1304 ± 22 Ma. After 1284 Ma the cooling rate dramatically slowed to 1.2 °C/my until at least 1225 ± 17 Ma. Most apatite retains an igneous trace element signature where thermal diffusion has not influenced trace element concentrations, suggesting that any exposure to temperatures above ∼670 °C was short-lived or trace element diffusion was slow. Furthermore, trace element chemistry discriminates apatite that crystallised from an evolved intercumulus disequilibrium liquid, and apatite that crystallised in equilibrium with the mineral assemblage of more fractionated rocks. The new results from this study highlight the change from a fast to slow cooling regime in this litho-tectonic zone, likely driven by ebbing regional magma emplacement. This new information enables better understanding of the tectono-magmatic evolution of the Proterozoic Nova-Bollinger deposit and the broader Fraser Zone.
KW - Apatite
KW - Fraser Zone
KW - Nova-Bollinger
KW - Thermochronology
KW - Trace elements
KW - U-Pb
UR - http://www.scopus.com/inward/record.url?scp=85121995509&partnerID=8YFLogxK
U2 - 10.1016/j.precamres.2021.106524
DO - 10.1016/j.precamres.2021.106524
M3 - Article
AN - SCOPUS:85121995509
SN - 0301-9268
VL - 369
JO - Precambrian Research
JF - Precambrian Research
M1 - 106524
ER -