Izanagi-Pacific ridge subduction revealed by a 56 to 46 Ma magmatic gap along the northeast Asian margin

Recent studies have debated the timing and spatial configuration of a possible intersection between the Pacific-Izanagi spreading ridge and the northeast Asian continental margin during Cretaceous or early Cenozoic times. Here we examine a newly compiled magmatic catalog of ~900 published Cretaceous to Miocene igneous rock radioisotopic values and ages from the northeast Asian margin for ridge subduction evidence. Our synthesis reveals that a nearsynchronous 56-46 Ma magmatic gap occurred across ~1500 km of the Eurasian continental margin between Japan and Sikhote-Alin, Russian Far East. The magmatic gap separated two distinct phases of igneous activity: (1) an older, Cretaceous to Paleocene pre-56 Ma episode that had relatively lower ε_Nd(t) (-15 to + 2), elevated (⁸⁷Sr/⁸⁶Sr)₀ (initial ratio, 0.704-0.714), and relatively higher magmatic fluxes (~1090 km²/m.y.); and (2) a younger, late Eocene to Miocene post-46 Ma phase that had relatively elevated ε_Nd(t) (-2 to + 10), lower (⁸⁷Sr/⁸⁶Sr)0 (0.702-0.707), and a lower 390 km²/m.y. magmatic flux. The 56-46 Ma magmatic gap links other geological evidence across northeast Asia to constrain an early Cenozoic, low-angle ridge-trench intersection that had profound consequences for the Eurasian continental margin, and possibly led to the ca. 53-47 Ma Pacific plate reorganization.