DISTINCT TECTONO-MAGMATISM ON RODINIA AND GONDWANA MARGINS

The petrological processes associated with the formation of Rodinia (~1 Ga) and Gondwana (~550 Ma) supercontinents reflect distinct tectonic dynamics that might have contributed to the contrasting geochemical and biological evolutions following the orogenies. In this study, we explore these differences using time sequence analysis of geochemical proxies in the detrital zircons sourced from the margin of East Gondwanan plates. The crustal thickness modeled by zircon Eu anomalies shows that the Gondwanan margin (~42 km) formed thicker crust than the Rodinian margin (~35 km), and the core of Rodinia was thicker (55–60 km) than its margin. The Ce to U and Ti ratios, U/Yb, and ε_Hf(t) proxies suggest that Rodinian assembly was dominated by non-arc intraplate magmatism, consistent with widespread high-temperature magmatism and protracted high-grade metamorphism. The thin crust and accordingly low-elevation terrain, possibly overriding an anomalously hot mantle, limited continental weathering flux, and primary productivity in the Mesoproterozoic oceans. By contrast, the Gondwanan orogenies may have proceeded in a modern-style plate tectonic manner, which resulted in rapid uplifting at the Gondwana margin, where voluminous clastic sediments were subsequently recycled and contributed to the post-orogenic magmatism from ~500 Ma. This massive crustal recycling is reflected by a substantial increase in zircon P concentration and negative ε_Hf(t) value, contrasting a broad decreasing trend and ε_Hf(t) ~ 0 in the Mesoproterozoic. The emergence of extensive mountains accelerated erosion and delivered key nutrients that might fuel the rapid diversification of life forms in the late Precambrian.