Browsing by Author "Wu, Tsung Jui"
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Item NW Pacific-Eurasia Subduction History and Continental Arc Evolution along NE Asia since Cretaceous Times(2021-12) Wu, Tsung Jui; Wu, Jonny; Casey, John F.; Lapen, Thomas J.; Okamoto, KazuakiThe 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large regional magmatic database that is compared to published structural geology, stratigraphy, paleomagnetism, and an unpublished fully-kinematic ‘tomographic’ NE Asian-Pacific plate tectonic reconstruction.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.