Continental growth during migrating arc magmatism and terrane accretion at Sikhote-Alin (Russian Far East) and adjacent northeast Asia

Abstract

Net additions to the continental landmasses, or continental growth, is a process that has irrevocably shaped our environment throughout the Earth history. Studies of ancient orogens suggest that continental growth can be facilitated by plate tectonics-driven arc magmatism and material accretion along convergent margins. However, such details are not well-understood due to the geological complexity of ancient orogens. Specifically, the role of the magmatic arc and its contributions to growing an accretionary margin remains unclear. This study explores an under-studied, long-lived magmatic arc along a 1500 km-wide swath of the NE Asian continental margin between 42° to 52°N (i.e., Sikhote-Alin and adjacent NE China, Sakhalin, and Hokkaido). We present new igneous rock zircon U-Pb ages (n = 93) and geochemistry (n = 61) from Sikhote-Alin that complement limited published data (n > 60). We synthesize these data to reveal four episodes of arc magmatism at Sikhote-Alin, including (1) 134 to 120 Ma S-type, (2) 110 to 100 Ma I-type, (3) 95 to 52 Ma highly-evolved I-type, and (4) <46 Ma I-type. We then combine our new results with published data (n > 600) and geology from adjacent NE Asia to analyze overall magmatic trends during a ∼ 1500 km trenchward migration of arc magmatism driven by Jurassic to Cenozoic juvenile terrane accretion. The young, growing continental margin was modified by arc magmatism with chemical compositions determined by: (1) generation from a mantle wedge mixed with 1.3– 1.4% sediment component from the downgoing slab; and, (2) silica-enrichment from crustal magmatic differentiation. Here, convergent margin continental growth that involved crustal accretion and trenchward migrating arc magmatism show magma compositions that evolve from initial mantle source mixing followed by crustal differentiation.