I-type and S-type granites in the Earth’s earliest continental crust

Abstract

AbstractThe composition and origin of Earth’s earliest continental crust remains enigmatic due to the absence of Hadean (>4 Ga) age rocks. Here we address this question by using machine learning to examine the provenance of the 4.4–3.3 Ga Jack Hills zircons, which constitute the best archive of Earth’s earliest continental crust. Our results reveal that although some Jack Hills zircons may be derived from trondhjemite-tonalite-granodiorite series rocks, which were common during the Archean (4–2.5 Ga), most (as high as ~70%) are sourced from igneous (I-) and sedimentary (S-) type granites. This finding provides clear evidence for rocks other than the trondhjemite-tonalite-granodiorite suite in the Earth’s earliest continental crust. Considering that I- and S-type granites are typical of modern convergent plate margins, the presence of a high proportion of Jack Hills zircons from these rocks supports the operation of a horizontal, mobile-lid tectonic regime in the early Earth.