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Abstract The Challenger Deep is the deepest part of the world’s ocean at ~10.9 km. It constitutes the southern part of the Isu-Bonin-Mariana system, formed by intra-oceanic subduction of the Pacific plate. However, instead of consisting of Jurassic Pacific mid-ocean-ridge basalt (~150 m.y. old), samples collected in situ using the submersible Fendouzhe from the bottom of the Challenger Deep, and five other nearby sites on the subducting plate, reveal that the basalt is much younger, with U-Pb zircon and plagioclase 40Ar/39Ar crystallization ages of ca. 34–17 Ma. These are coeval with tholeiitic basalt on the nearby Caroline Plateau, with which they share a similar chemistry. The subducting plate has therefore been resurfaced by Cenozoic basalts generated by the Caroline hotspot, with only a thin veneer of overlying sediments. Numerical modeling indicates that subduction of an old plate with these characteristics may possibly account for the features exhibited by the Challenger Deep, including its slow convergence rate and induced slab rollback due to increased friction between the subducting and overriding plates, thereby producing the deepest trench on Earth.
Wu et al. (Thu,) studied this question.