Archean to early Mesoproterozoic crustal evolution of the Yangtze Craton: Insights from U-Pb-Hf-O isotopic and trace elemental compositions of detrital zircon

Abstract

Detrital zircons from ancient sedimentary rocks provide essential evidence for deciphering the early crustal evolution of Earth, particularly in ancient cratons with limited ancient rock records. The Yangtze Craton in South China has limited exposure of Archean-Paleoproterozoic rocks, while abundant Paleo-Mesoproterozoic sedimentary units in the southwestern Yangtze Craton contains voluminous Archean detrital zircons. In this study, new U-Pb-Hf-O isotopic and trace elements data of detrital zircons and whole-rock elemental data from the Dongchuan and Hekou Groups are conducted. Three distinct detrital zircon age populations at 2.85 ∼ 2.6 Ga, 2.45 ∼ 2.2 Ga, and 2.0 ∼ 1.75 Ga are identified. Almost all zircons exhibit depleted LREEs, enriched HREEs, pronounced negative Eu anomalies, and positive Ce anomalies, suggesting a magmatic origin. The comparison of U-Pb-Hf isotopic data of detrital zircons with magmatic zircons within the Yangtze basement rocks, coupled with the angular morphology of the zircons, collectively suggest that the provenance originates within the Yangtze Craton rather than exotic terranes. At ca. 2.85 Ga and 2.1 Ga, mean δ¹⁸O values of detrital zircons are 5.8 ‰ and 5.5 ‰, respectively, with corresponding median ε_Hf(t) values of + 4.16 and −0.59. Subsequently, the δ¹⁸O values began to increase markedly, whereas ε_Hf(t) values declined during the same interval. Zircon trace element signatures point to their origin in S-type granites linked to orogenic events, with zircon Eu anomalies indicating crustal thickening at 2.85 Ga and 2.1 Ga, which coincides with the evolutionary trends observed in zircon O-Hf isotopes and resonates with supercontinent cycles. Crust growth curve calculations reveal that the growth of continent nuclei in Yangtze Craton can be tracked back to the late Hadean, reaching nearly 80 % of its present volume during the Meso-Neoarchean, with a subsequent decrease in growth rates. This growth pattern aligns with evolution trends of global crust growth curve, indicating a gradual growth and stabilization of continental crust during the Archean period.