New insights into early Earth mantle evolution, with implications for ancient continental growth

Summary

Improved characterisation of the >3.5 Ga mantle depletion history is crucial to advance our understanding of early Earth’s crust forming events. To date, a linear evolution of a depleted mantle from 4.5 Ga to the present day is used in crustal growth calculations. However, evidence for an undepleted >3.5 Ga mantle is growing, and the current rock record is in stark contrast to the amount of stabilised crust at 3.5 Ga that recent models infer.

This project focuses on three key aspects: (I) Hf isotope characterisation of the c. 3.5 Ga mantle underneath the Pilbara Craton; (II) clarifying the existence of a crustal precursor to the Pilbara Craton and (III) the origin of decoupled Hf–Nd isotope compositions. The analytical work will mainly take place at the host UWA, while final synthesising work and complementary analyses will be done at NRM, Stockholm.

The research will incorporate and benefit from: (I) Expertise regarding mineral separation and isotopic work gained during my Ph.D in Lund. (II) Analytical capabilities and expertise in novel analytical techniques at UWA and NRM. (III) The experience at UWA from recent work within the field of isotope-geochemistry in general and specifically within the field area of interest. Using the novel approach of coupled baddeleyite and zircon U–Pb–Hf–Nd isotope data from the oldest units of the Pilbara Craton in Western Australia, allows for characterisation of the >3.5 Ga mantle and enables improved constraints to above outlined work.

Project funded by the Swedish Research Council (Vetenskapsrådet)

Project participants at the museum

• Martin Whitehouse

External project participants

• Anthony Kemp, University of Western Australia
• Andreas Petersson (Project leader)