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 similar to 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 similar to 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 epsilon(Nd(t)) (-15 to + 2), elevated (Sr-87/Sr-86)(0) (initial ratio, 0.704-0.714), and relatively higher magmatic fluxes (similar to 1090 km(2)/m.y.); and (2) a younger, late Eocene to Miocene post-46 Ma phase that had relatively elevated epsilon(Nd(t) )(-2 to + 10), lower (Sr-87/Sr-86)(0) (0.702-0.707), and a lower 390 km(2)/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.