Zircon U-Pb-Hf and geochemical analyses of paragneiss and granitic gneiss from Oki-Dogo Island, Southwest Japan and its tectonic implications

The paragneiss and migmatitic gneiss on Oki-Dogo Island, located in northern part of southwest Japan, have U-Pb ages ranging from Mesoarchean to Paleoproterozoic. The youngest population of detrital zircons from the paragneiss and migmatitic gneiss suggests a maximum depositional age of ca. 1.96 Ga. Further, the three granitic gneiss samples give zircon U-Pb ages of 1.97, 1.88, and 1.81 Ga. The bulk rock composition of the granitic gneiss samples followed a calc-alkaline trend and showed negative Nb, Ta, P, and Ti anomalies with low Sr/Y (<35), Nb/Th (<1), and Nb/Zr (<0.1) ratios, indicating that the protolith of the granitic gneiss formed in an arc-related setting. Zircons from the granitic rocks in Oki-Dogo Island have negative epsilon(Hf)(t) values with Mesoarchean to Neoarchean model ages (TDM2). The results of geochronological and geochemical analyses and those of previous studies indicate that Oki-Dogo Island underwent two arc-related magmatic events at ca. 1.97 Ga and ca. 1.88-1.81 Ga, which correspond well with those of the Yeongnam massif in South Korea. Thus, we suggest that northern part of southwest Japan (Oki-Dogo Island) was more closely related with the Yeongnam massif than with the North China Craton during the early Paleoproterozoic period. (C) 2021 Elsevier B.V. All rights reserved.