An andesitic source for Jack Hills zircon supports onset of plate tectonics in the Hadean

Simon Turner; Simon Wilde; Gerhard Wörner; Bruce Schaefer; Yi-Jen Lai

doi:10.1038/s41467-020-14857-1

An andesitic source for Jack Hills zircon supports onset of plate tectonics in the Hadean

Nat Commun. 2020 Mar 6;11(1):1241. doi: 10.1038/s41467-020-14857-1.

Authors

Simon Turner¹, Simon Wilde², Gerhard Wörner³, Bruce Schaefer⁴, Yi-Jen Lai⁴

Affiliations

¹ Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW, 2109, Australia. simon.turner@mq.edu.au.
² Department of Applied Geology, Curtin University, PO Box U1987, Perth, WA, 6845, Australia.
³ Abteilung Geochemie, Geowissenschaftliches Zentrum Göttingen (GZG), 37077, Göttingen, Germany.
⁴ Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW, 2109, Australia.

Abstract

The composition and origin of Earth's early crust remains hotly debated. Here we use partition coefficients to invert the trace element composition of 4.3-3.3 Gyr Jack Hills zircons to calculate the composition of the melts from which they crystallised. Using this approach, the average SiO₂ content of these melts was 59 ± 6 wt. % with Th/Nb, Dy/Yb and Sr/Y ratios of 2.7 ± 1.9, 0.9 ± 0.2 and 1.6 ± 0.7, respectively. Such features strongly indicate that the protolith for the Jack Hills zircons was not an intra-plate mafic rock, nor a TTG (tondjhemite-tonalite-granodiorite) or a Sudbury-like impact melt. Instead, the inferred equilibrium melts are much more similar to andesites formed in modern subduction settings. We find no evidence for any secular variation between 4.3 and 3.3 Gyr implying little change in the composition or tectonic affinity of the Earth's early crust from the Hadean to Mesoarchaean.