Timing of Okhotsk Sea Plate Collision With Eurasia Plate: Zircon U‐Pb Age Constraints From the Sakhalin Island, Russian Far East
2018
Zhao, Pan | Alexandrov, Igor | Jahn, Bor‐ming | Ivin, Vitaly
The Late Mesozoic to Cenozoic evolution of Northeast Asia involves successive subduction of the Pacific oceanic crust and amalgamation of the Eurasia, North American, and Okhotsk Sea Plates. The timing of plate collision is essential for understanding the tectonic evolution of Northeast Asia. In this study, we focus on the Okhotsk Sea Plate collision with the Eurasia Plate along the Sakhalin Island, Russian Far East, which is a highly controversial problem, especially about the timing of collision. In order to determine exact timing for this collision, we report zircon U‐Pb data from both the East Sakhalin accretionary complex and postcollisional granitic plutons in the Sakhalin Island. Detrital zircon data from four metasedimentary rocks show that the Sikhote‐Alin orogenic belt is the main provenance for the East Sakhalin accretionary complex. Meanwhile, the youngest detrital zircon age constrains the maximum depositional age of East Sakhalin accretionary complex later than 49 Ma. Both Langeri and Val'za plutons are made of peraluminous S‐type granite. Four granitic samples yielded consistent ages at 36–38 Ma, indicating that both plutons were emplaced at the middle Eocene. Their generation is considered to have been derived through crustal anatexis of accretionary wedge in the lower crust shortly after tectonic thickening caused by the Okhotsk Sea Plate collision with the Eurasia Plate. Consequently, our age data constrain that the Okhotsk Sea Plate and Eurasia Plate collision occurred in the middle Eocene between 49 and 38 Ma. This age range is consistent with late Eocene uncomformity identified in the Sakhalin Island and Okhotsk Sea.
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