Solidification pressures and ages recorded in mafic microgranular enclaves and their host granite; An Example of the world's youngest Kurobegawa granite

苦鉄質細粒包有岩とその母岩に記録された固結の圧力と年代; 世界一若い黒部川花崗岩の事例

鈴木 康太*; 河上 哲生*; 末岡 茂   ; 山崎 あゆ*; 鏡味 沙耶   ; 横山 立憲   ; 田上 高広*

Suzuki, Kota*; Kawakami, Tetsuo*; Sueoka, Shigeru; Yamazaki, Ayu*; Kagami, Saya; Yokoyama, Tatsunori; Tagami, Takahiro*

Solidification pressure conditions and U-Pb zircon ages were determined and compared between mafic microgranular enclaves (MMEs) and their host granite from two sample localities in the Kurobegawa Granite (Hida Mountain Range, central Japan). The ages for MMEs tend to be younger than the host granites, although they overlap within uncertainty. In both lithologies, zircon occurs as the matrix mineral and as inclusions in plagioclase rims. Meanwhile, only in the host granites, zircon also occurs as early phases in plagioclase cores. Such differences in mode of occurrence of zircon suggest that the age variation reflects the difference in the timing of zircon crystallization between the MMEs and the host granites. Therefore, the MMEs record the same solidification pressures as the host granites and better represent the final solidification timing of the Kurobegawa Granite.