The scarce geological record of Earth’s infancy, particularly before 3 billion years ago (Ga), is restricted to cratons, many of which likely originated as volcano-plutonic plateaus in a non-mobile lid geodynamic regime. However, this scarcity is at odds with the significant volumes of continental crust at 3 Ga that multi-proxy models of mantle depletion and crustal growth predict. This challenges the notion that plateau-type cratonic nuclei represent the predominant tectonomagmatic settings operating on the early Earth. Reconciling this paradox necessitates a “silent majority” of missing off-craton Archean crust of an uncharacterized affinity. To investigate a potential rare remnant example of an Archean crust constructed away from cratonic nuclei, we report major and trace-element chemostratigraphic data from the 3.1 Ga Whundo Group of the Pilbara Craton, investigating the petrogenetic processes related to its formation. These data reveal three magmatic cycles of intercalated supracrustal successions comprising six groups: tholeiites, boninites, calc-alkaline BADR (basalt-andesite-dacite-rhyolite), high-magnesium ADR (including a subset of transitionally adakitic affinity), Nb-enriched basalts (NEB), and boninite-calc-alkaline hybrids. Th/Yb-Nb/Yb, Gd/YbN-Al/TiN, and Nd isotope systematics are inconsistent with contamination by felsic basement characteristic of cratonic cores, suggesting eruption onto thin, juvenile lithosphere that was only later incorporated into the Pilbara Craton.

Abstract Different mineral clocks in granite can provide age information reflecting various aspects of rock formation, including cooling or post-emplacement fluid–rock interaction. However, the dating tool chosen can yield inconclusive age information due to differences in closure temperatures and susceptibility to fluid alteration among chronometers. This has led to an inferred superiority of U–Pb in zircon over U–Pb in monazite or Rb–Sr in mica. Here, we investigate age systematics using Rb–Sr biotite grains, U–Pb in monazite and zircon in a Devonian granite from Australia. Single-grain laser ablation ICP-MS/MS biotite analyses are combined with zircon–monazite U–Pb ages and trace element systematics. Textural and trace element evidence combined with age systematics reveals a Rb–Sr closure age of c. 360–330 Ma relative to a putative 364 Ma emplacement age, suggesting hydrothermal alteration of the granite. Trace element systematics and magnetic susceptibility in biotite grains reflect their partial chemical reset and fluid overprint in the granite. However, similar systematics are also observed for zircon and monazite. Our multiple chronometer dating approach, studied with modern laser-ablation methods, highlights the need for detailed investigation of isotope and trace element systematics in single grains and that individual ages should be used cautiously when dating altered granitoids.

The ancient cores of modern continents, cratons, are the oldest blocks of "stable" lithosphere on Earth. Their long-term survival relies on the resistance of their underlying thick, strong, and buoyant mantle keels to subsequent recycling. However, the effect of substantial geographical variations in keel thickness on the post-assembly behaviour and mass movement within these continental cores remains unknown. Here, we demonstrate that the spatial distribution of fluid-reset in-situ Rb-Sr ages for Paleo-Mesoarchean (3.6–2.8 billion years ago; Ga) granitoids of the Pilbara Craton, Australia shows remarkable correlation with independently-constrained lithospheric thickness models. Without craton-wide heating/magmatic events, these anomalously young Rb-Sr ages document episodes of fluid infiltration into granitoid complexes as a response to lithospheric reactivation by far-field stresses. This correlation implies that craton-wide fluid mobilization triggered by extra-cratonic Neoarchean to Mesoproterozoic (2.8–1.0 Ga) tectonic events is facilitated by variations in lithospheric strength and thickness. Compared to areas of older overprints, the two-thirds of the craton comprised of younger reset ages is underlain by comparatively thin lithosphere with higher susceptibility to reactivation-assisted fluid flow. We propose that even the strongest, most pristine cratons are less stable and impermeable than previously thought, as demonstrated by the role of granitoid complexes and cratons as selective lithospheric "sponges" in response to minor tectonic forces. Therefore, variations in lithospheric thickness, likely attained before cratonization, exert a crucial control on billions of years of fluid movement, elemental redistribution and mineralization within ancient continental nuclei.

Secular trends in plutonic whole-rock geochemistry pose critical, although non-unique, constraints to early Earth tectonics. Here, we present a large whole-rock geochemical (879 collated samples) dataset for granitoids from the Pilbara Craton, Western Australia, applying it to test the link between secular trends and proposed tectonic mechanisms. We show that the spatio-temporal distribution of granitoid trace element geochemistry is constrained within discrete lithotectonic blocks supporting the reconstruction of its tectonomagmatic evolution. Time-sliced geochemical contour mapping of key petrogenetic ratios indicates the craton underwent rifting similar to 3.2 Ga (billion years ago), marking a transition from predominantly sodic magmatism to a broader magmatic compositional spectrum. Our results demonstrate that rift-assisted breakup of proto-cratons is a viable craton growth mechanism. We identify a possible evolutionary sequence beginning with drips and upwellings below a Paleoarchean mafic plateau, which is subsequently dismembered by rifting. These plateau fragments form rigid blocks in the Mesoarchean, between which weaker, thinner crust accommodates minor convergence and divergence manifested as short-lived mobile lid-like features before stabilization. We conclude that these features do not require an active lid, plate tectonic regime.