Granitoid Record of Magmatic-Arc Reorganization in the Koni–Pyagin Segment of the Northern Okhotsk Paleo-Pacific Margin

Granitoid plutons widespread in the Northern Okhotsk region reflect the main stages of tectonomagmatic evolution of the Koni–Pyagin segment of the Northeast Asian Paleo-Pacific margin. We present new zircon U–Pb geochronological and geochemical data including whole-rock major and trace-element analysis. Our U–Pb ages indicate three main stages of granitoid magmatism: Permian (Aichan complex, ca. 287–260 Ma), Early Cretaceous (Kongali complex, ca. 125 Ma), and Albian–Cenomanian (Magadan and Svetlaya complexes, ca. 107–104 Ma and ca. 101–95 Ma, respectively). These stages correspond to the formation of the Koni–Taigonos arc system, the Uda–Murgal and the Okhotsk–Chukotka volcanic belts. The studied rocks generally show calc-alkaline, subduction-related geochemical characteristics, although systematic compositional differences indicate variations in magma generation and evolution. Granitoids of the Svetlaya complex are characterized by adakite-like geochemical features such as higher Sr/Y and La/Yb ratios. Changes in the rate of magmatic activity from the Early Cretaceous to Late Cretaceous with the magmatic lull at 122-108 Ma reflect arc reorganization of the Paleo-Pacific margin during its long-term evolution.