Distinct tectono-magmatism on the margins of Rodinia and Gondwana

Abstract

The orogenic petrological processes associated with the amalgamation of Rodinia (ca. 1 Ga) and Gondwana (ca. 550 Ma) reflect distinct tectonic dynamics that might have contributed to the contrasting geochemical and biological evolution following the orogenies. In this study, we explore these differences using the time sequence analysis of geochemical proxies in the detrital zircons sourced from the margin of East Gondwana. The zircon Eu anomalies are stronger during the formation of Gondwana than Rodinia, indicating a thicker Gondwana crust than Rodinia; the hinterland of Rodinia (∼35 km) is significantly thinner than its core Grenville Province (55–60 km). The Ce to U and Ti ratio, U/Yb, and εHf(t) proxies suggest that the Rodinia assembly was dominated by non-arc intraplate magmatism, consistent with widespread high-temperature magmatism and protracted granulite-facies 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 orogenies leading to the assembly of Gondwana may have proceeded in a modern-style plate tectonic manner, resulting in rapid uplift at the Gondwana margin, where voluminous clastic sediments were subsequently recycled and contributed to the post-orogenic magmatism from ca. 500 Ma. This massive crustal reworking is reflected by negative εHf(t) values of zircons that contrast εHf(t)∼0 in the Mesoproterozoic. The emergence of extensive mountains accelerated erosion and delivered key nutrients that might have fueled the rapid diversification of life forms in the late Precambrian and early Paleozoic.