NW Pacific-Eurasia Subduction History and Continental Arc Evolution along NE Asia since Cretaceous Times

The Eurasian continental margin of NE Asia records abundant Mesozoic to present igneous activity in response to Pacific and Panthalassa (paleo-Pacific) subduction. Plate tectonic studies typically reconstruct long-lived plate convergence involving subduction of the Panthalassa/Pacific plates since 200 Ma. However, many first-order details of NW Panthalassa plate tectonic reconstructions remain controversial, including ridge-trench intersections and intra-oceanic arc accretions along Eurasia since the Early Cretaceous. In this dissertation, we investigate the Mesozoic to Cenozoic magmatic and plate tectonic history of the 31-52 N NE Asian continental active margin (Japan, Korea, NE China, and southern Russian Far East). We analyze igneous rock U-Pb geochronology and geochemistry (n=92) of Sikhote-Alin, Russia and add published data (n>800) to create a large regional magmatic database that is compared to published structural geology, stratigraphy, paleomagnetism, and an unpublished fully-kinematic ‘tomographic’ NE Asian-Pacific plate tectonic reconstruction. I show the following plate tectonic stages along NE Asia since the Cretaceous: (1) subduction of one or more marginal sea plates during the Early Cretaceous; (2) a ~130-100 Ma intra-oceanic arc accretion event that shows magmatism from subducted-slab melting; (3) ~100-50 Ma Izanagi slab subduction correlated to higher magmatic fluxes (up to 1000 km2 /Myr), high % SiO2 (mean 66-70 %), and enriched Nd(t) isotopic ratios (-15 to +2), that link to ultrafast subduction (12 to 24 cm/yr); (4) ~50 Ma Pacific-Izanagi spreading ridge subduction based on a 56-46 Ma arc magmatic hiatus; and. (5) ~50-0 Ma slower (2 to 8 cm/yr) Pacific plate subduction correlated to lower magmatic flux (~ 400 km2 /Myr), SiO2 (mean 56-63 %), and more depleted Nd(t) isotopic ratios (-5 to +10). Migration of the NE Asian continental arc ~2000 km outboard (eastward) since Jurassic times indicates continental growth within an accretionary orogen that is driven by long-lived ocean-continent subduction.