岐阜県高根地域に分布する美濃帯沢渡コンプレックスから得られた砕屑性ジルコンU-Pb年代

Detrital zircon U-Pb dates from the Sawando Complex of the Mino Terrane in the Takane area, Gifu Prefecture, Japan

箱岩 寛晶; 山田 来樹; 長田 充弘   ; 小北 康弘  ; 丹羽 正和   

Hakoiwa, Hiroaki; Yamada, Raiki; Nagata, Mitsuhiro; Ogita, Yasuhiro; Niwa, Masakazu

To expand radiometric age data of Jurassic accretionary complexes in Japan, we conducted zircon U-Pb dating for a sandstone sample from the Sawando Complex in the eastern Mino Terrane, using a multiple collector ICP-MS coupled with a multiple spot femtosecond laser system (msfsLA-MC-ICP-MS). 32 concordant data of 72 dated grains are classified into seven age groups: 1920-1850 Ma (Paleoproterozoic), 1110 Ma (Mesoproterozoic), 492 Ma (Cambrian), 442 Ma (Silurian), 262-260 Ma (Permian), 250-218 Ma (Triassic), and 186-168 Ma (Jurassic). The youngest single grain date (YSG) exhibits 168.0 6.9 Ma (2). Although YSG date is slightly order than the radiolarian ages reported by previous studies showing late Callovian to middle Oxfordian, it overlaps their ranges within an uncertainty.