[S-MP26] Supercontinents and Crustal Evolution

[SMP26-01] Vanished from the Face of the Earth: Unraveling Japan's Enigmatic Lost Continental crust

Álvaro Rubio³, *Daniel Pastor-Galan¹, Tatsuki Tsujimori² (1.IGEO-CSIC, 2.Tohoku University, 3.Universidad de Oviedo)

Keywords:Zircon, Japan, Continental Crust

Plate movement is attributed to oceanic lithosphere recycling in subduction zones, while continents are perceived as passive buoyant masses. Recent geochemical models suggest that continents have been cryptically recycled into the mantle leaving no obvious record of their existence. Should this hold true, our current models of Earth's evolution would be woefully incomplete, neglecting to account for this substantial loss. Forearc basins preserve a geological record specifically linked to arc magmatism, with lack of support from the continents providing crucial information about crustal growth, accretion, destruction, magmatism, and subduction dynamics. We evaluated the changes in NE Japan, a long-lived subduction system by analyzing detrital zircon provenance (U-Pb and Hf-isotope data) in its forearc units. We found 430 ± 20, 360 ± 10, 270 ± 20, 184 ± 12, 112 ± 22, 7 ± 7 Ma peaks and a loss of older zircon populations over time. Hf data show three shifts in isotopic enrichment, which correspond to changes in the dominant age peaks. Each isotopic shift aligns with periods of isolation of older sedimentary packages, during which no older detrital zircon is observed in subsequent stages. We interpret that magmatic flare-ups formed the peaks, protracted tectonic erosion progressively removed older zircon sources. And a late Carboniferous event triggered the complete removal of the Precambrian crust. Lastly, the Cretaceous melting of the entire Permian arc crust is likely linked to the subduction of the mid-oceanic ridge, marking the separation of the Izanagi and Pacific plates. NE Japan forearc provide compelling evidence of a missing piece of continent. The identification of a missing continent within NE Japan's forearc region has profound implications on future development of tectonic and paleogeographic models. We need to learn how to integrate the findings of lost continents into tectonic models to achieve a more comprehensive and refined paleogeographic depiction of our planet's past.


AR and DPG are funded by a Grant PID2021-128801NA-I00 funded by MCIN/AEI/10.13039/501100011033, a Ramón y Cajal Fellow RYC2019-028244-I funded by MCIN/AEI/ 10.13039/501100011033 and by the “European Social Fund Investing in your future”, and a Leonardo grant 2022 to researchers and cultural creators (LEO22-2-3010) from the bank BBVA.