Protracted late Paleozoic volcanic arc activity along the Northeast Asian continental margin

초록

Northeast Asia is a complex tectonic collage bounded by Paleozoic-Mesozoic internal and peripheral orogens, whose distribution and continuity are obscured by later deformation and magmatic overprinting. Here we present zircon data from granites and xenoliths in the Yeongdeok area, southeastern Korea, which suggest the presence of a long-lived (ca. 30 Myr) late Paleozoic volcanic arc system. Zircon cores yield U-Pb ages of 278-255 Ma, while rim ages cluster around 250 Ma, corresponding to the emplacement of the Yeongdeok adakite pluton and associated hydrothermal alteration. The 18O depletion (delta 1(8)O = 4.7-0.6 parts per thousand) observed in many zircons, along with core-to-rim decreases, is interpreted as the result of recycling of hydrothermally altered volcanic carapace material. Negative zircon epsilon Hf(t) values commonly observed in the xenolith-hosted zircons contrast with the consistently positive values of the host Yeongdeok pluton. These unradiogenic Hf signatures resemble those of detrital zircons from the Pyeongan Supergroup, deposited in an arc-related foreland basin. Our findings suggest a protracted late Paleozoic volcanic arc system-now largely eroded except for its plutonic roots-and, when integrated with data from the northern North China Block and Hida Belt of southwest Japan, provide new constraints on the configuration of the Central Asian Orogenic Belt.

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