Secular evolution of rhyolites: Insights into the onset of plate tectonics

Abstract. The emergence of plate tectonics is intimately linked to the stabilization of buoyant continental lithosphere, yet the timing of this transition remains contentious. Here, we analyze the secular geochemical evolution of rhyolites, a proxy for crustal differentiation, to constrain the onset of modern-style plate dynamics. A global compilation of 21,252 rhyolitic samples reveals statistically significant shifts in diagnostic geochemical indicators at ~2.7 Ga, most notably increased potassium (3–5 wt%) and intensified negative Eu anomalies (Eu/Eu* =0.3–0.6). These trends mirror Phanerozoic rhyolites and temporally coupled with supercraton assembly (Kenorland), peak crustal reworking rates and the oldest evidence of plate margin processes (e.g., passive margins, foreland basins). The ~2.7 Ga shift in rhyolite compositions, including elevated K₂O, pronounced Eu anomalies, and enriched Nd isotopes, reflects enhanced crustal reworking and the stabilization of rigid continental lithosphere. This transition is rooted in the long-term accumulation and maturation of tonalite-trondhjemite-granodiorite (TTG) suites, the primary building blocks of Archean felsic crust. This period coincides with structural records of large-scale horizontal lithospheric motion and the establishment of interconnected plate boundaries, confirming the emergence of conditions necessary for sustained plate tectonics. The geochemical proxies in rhyolites provide quantifiable evidence for continental rigidization, complementing structural and isotopic archives of early plate dynamics. We propose that the ~2.7 Ga surge in evolved rhyolites marks the stabilization of rigid continental lithosphere—a prerequisite for sustained plate tectonics. This study reconciles conflicting models by linking crustal maturation to the earliest definitive records of convergent margins, establishing ~2.7 Ga as a pivotal transition in Earth’s shift to modern geodynamics.