Plate tectonic–like cycles since the Hadean: Initiated or inherited?

Abstract

Interpretation of Earth’s oldest preserved crustal archive, the Jack Hills zircon of Western Australia, has been controversial in terms of the onset of plate tectonics. We conduct time-series analysis on hafnium isotopes of the Jack Hills zircon and reveal an array of statistically significant cycles that are reminiscent of plate-tectonic subduction. At face value, such cycles may suggest early Earth conditions similar to those of today—the uniformitarian hypothesis that plate tectonics was essentially operational since “day one”. On the other hand, in the context of expected secular changes due to planetary evolution and geological observations, the cycles could instead imply that modern plate-tectonic subduction inherited mantle convective harmonics already facilitated by an early phase of stagnant-lid delamination—the “lid-to-plates” hypothesis. Either way, any model for the nature of plate tectonics must incorporate conditions operating during Hadean time, either by initiation of plate tectonics then or by later inheritance of preexisting cycles of mantle convection.

No evidence of supracrustal recycling in Si-O isotopes of Earth’s oldest rocks 4 Ga ago

“…3.8 to 3.7 Ga (table S6) ( 9 , 29 , 34 , 45 – 47 ) or even earlier at ca. 3.9 Ga ( 48 ). For example, by combining the Acasta and global Hf isotope data, zircon 176 Hf/ 177 Hf shifted to higher values in each craton at ca.…”

An evolutionary system of mineralogy, Part VII: The evolution of the igneous minerals (>2500 Ma)

“…All appear to have first formed close to ~3.0 Ga, possibly because they required the extensive fluid-rock interactions of the crust and upper mantle associated with subduction (although significant debates persist concerning the commencement, style, and rates of subduction on early Earth; e.g., Sizova et al 2010Sizova et al , 2014Johnson et al, 2017;Wan et al 2020;Korenaga, 2021;Mitchell et al, 2022). Each of these four types of exotic igneous mineralization added to the diversity, as well as the chemical and structural complexity, of Earth's minerals.…”

Barium content of Archaean continental crust reveals the onset of subduction was not global

“…Whenever a compositional proxy for subduction is introduced, its broader implications must be considered within a multi-proxy context. Based on different proxies, however, the timing of the onset of plate tectonics is contentious [48][49][50][54][55][56] . Most of the proxies either record the first appearance of specific rock types or metamorphic facies (e.g., blueschist, Precambrian paired metamorphism) 50,57,58 , or indirectly infer the nature of continental crust 48,49 .…”