The composition and origin of Earth's early crust remains hotly debated. This study uses 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 crystallized. The results strongly indicate that the protolith for the Jack Hills zircons was an andesite formed in a modern subduction setting, not an intra-plate mafic rock, a TTG, or a Sudbury-like impact melt. No secular variation was found 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, suggesting an early onset of plate tectonics.

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