NE Asia arc magmatic tempos and their relationship to Western Pacific-Izanagi plate tectonics since Cretaceous times

Abstract:

Subduction-related continental arc magmatism is a major source of atmospheric CO₂ and may drive Earth icehouse-greenhouse changes. However, the first-order processes that drive continental arc evolution and episodicity (i.e. arc tempos) remain debated. Current models argue that arc tempos are primarily driven by: (1) Internal factors involving crustal thickening, melting, and/or delamination;(2) External factors such as plate convergence rates and mantle flow. Arc tempos at western North America and South America have been more closely linked to internal cyclical processes, including crustal root eclogitization, rather than external plate tectonics. On the other side of Pacific ocean, the extensive igneous rocks along the NE Asian margin since Cretaceous times are typically viewed as magmatic arcs produced by subduction of the western Pacific, Izanagi, and other plates. However, NE Asian plate tectonic reconstruction models during these periods are controversial. Furthermore, the NE Asian arc magmatic record has been less systematically cataloged relative to other regions. Therefore, it is still unknown whether any quantifiable relationship truly exists between the NE Asian arcs and plate tectonics.

Here we build a large (n>500) compilation of igneous rock ages and geochemistry along the NE Asian margin along Japan, Sikhote-Alin, and Korea. We compare the magmatism against our recently-developed ‘tomographic’ western Pacific-Izanagi plate reconstruction since ~100 Ma, which is a fully-kinematic model that implies spatiotemporal subduction rates along NE Asia.

Our analysis shows that Cretaceous NE Asian magmatism is dominated by higher average silica content (~69%) relative to other continental arcs. Significantly higher areal addition rates showed between 56 to 100 Ma (~1100 km2/m.y. ) relative to younger <50 Ma periods (~400 km2/m.y.). More vigorous and silicic magmatism generally correspond to fast (15±5 cm/yr) Izanagi-Eurasia plate convergence whereas less vigorous and silicic magmatism corresponds to slower (<10 cm/yr) Pacific-Eurasia plate convergence. A period of magmatic quiescence between 56 to 46 Ma corresponds to Izanagi-Pacific ridge subduction. We then attempt to deconvolve plate tectonics from NE Asian magmatism to discuss the possible role of arc ‘external processes’.