著者

Kazuya SHIMOOKA Satoshi SAITO Kenichiro TANI

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.230224, (Released:2023-07-28)

被引用文献数

1

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We carried out zircon U-Pb dating of the Cretaceous gabbroic and granitic rocks exposed in the Kajishima to determine their magmatic ages. The plutonic rocks in the Kajishima are classified into seven lithologies: Hbl-bearing olivine norite, Type-1 Hbl-bearing troctolite, Type-2 Hbl-bearing troctolite, Type-1 pyroxene hornblende gabbronorite, and Type-2 pyroxene hornblende gabbronorite, massive granodiorite, and deformed granodiorite. The new zircon U-Pb ages are: 90.77 ± 0.99 Ma for the Type-2 Hbl-bearing troctolite, 92.35 ± 0.74 Ma for the Type-1 pyroxene hornblende gabbronorite, 91.33 ± 1.03 Ma for the massive granodiorite, and 84.11 ± 1.12 Ma for the deformed granodiorite. The new zircon U-Pb ages suggest multiple episodes of magmatic intrusion in Kajishima during ∼92 Ma and 84 Ma. Although two gabbroic rocks and a massive granodiorite show similar zircon U-Pb ages, subsequent granitic magmatism is unraveled in Kajishima, which is contrary to previous geological studies that postulated an evolution of all plutonic rocks from a single gabbroic parent magma.