Abstract
Magmatism has profoundly influenced the evolution of the geosphere, hydrosphere, atmosphere, and biosphere in back-arc basins. However, the timing of the magmatism in the Okinawa Trough (OT) is not well constrained by the age spectra of zircons. Here, for the first time, we carry out an integrated study combining in situ analysis of zircon U–Th–Pb and Hf–O isotopes, and trace element compositions of zircons from the volcanic rocks from the southernmost part of the OT. We found that the young (< 100 ka) zircons in these volcanic rocks have old (108 Ma to 2.7 Ga) inherited cores, which were captured as the magma ascended through the rifting continental crust. In particular, the inherited Archean zircons strongly suggest that remnants of the old East Asian continental blocks underlie the embryonic crustal rifting zone. Moreover, the ages of most of the inherited zircons correspond to five supercontinent amalgamation events. Specifically, the Archaean inherited zircons, which have positive εHf(t) and low δ18O values, correspond to the formation of juvenile continental crust. In contrast, the negative εHf(t) and high δ18O values of the post-Archaean inherited zircons indicate that their parental magma contained recycled older crust due to the enhanced crust-mantle interactions during the evolution of the early continental crust. Therefore, the inherited zircons in the back-arc volcanic rocks not only reflect the evolution of the local magmatism, but they also contain a record of the Archaean crustal fragment and of several global continental amalgamation events.
Highlights
Magmatism has profoundly influenced the evolution of the geosphere, hydrosphere, atmosphere, and biosphere in back-arc basins
The Okinawa Trough (OT), which is located on the western Pacific active continental margin (Fig. S1), is a back-arc basin formed by the northwestward subduction of the Philippine Sea Plate beneath the Eurasian Plate, which initiated during the Middle to Late Miocene[1]
We used Quaternary magmatic zircons from the southernmost part of the OT (SPOT) volcanic rocks and old inherited zircon cores captured from the deep crust during mantle-derived magma ascent through the rifting upper crust to analyze the era of magmatic activity and reveal the nature of the basement rocks in this region, as well as the record of supercontinent amalgamation events
Summary
Magmatism has profoundly influenced the evolution of the geosphere, hydrosphere, atmosphere, and biosphere in back-arc basins. We found that the young (< 100 ka) zircons in these volcanic rocks have old (108 Ma to 2.7 Ga) inherited cores, which were captured as the magma ascended through the rifting continental crust. The inherited zircons in the back-arc volcanic rocks reflect the evolution of the local magmatism, but they contain a record of the Archaean crustal fragment and of several global continental amalgamation events. We used Quaternary magmatic zircons from the SPOT volcanic rocks and old inherited zircon cores captured from the deep crust during mantle-derived magma ascent through the rifting upper crust to analyze the era of magmatic activity and reveal the nature of the basement rocks in this region, as well as the record of supercontinent amalgamation events
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