JpGU-AGU Joint Meeting 2017

講演情報

[EE] ポスター発表

セッション記号 S (固体地球科学) » S-MP 岩石学・鉱物学

[S-MP41] [EE] Oceanic and Continental Subduction Processes

2017年5月22日(月) 10:45 〜 12:15 ポスター会場 (国際展示場 7ホール)

コンビーナ:Hafiz Ur REHMAN(Department of Earth and Environmental Sciences, Graduate School of Science and Engineering, Kagoshima University)、辻森 樹(東北大学)、Chin Ho Tsai(National Dong Hwa University)

[SMP41-P05] New geochronological constrains on high-pressure meta-plagiogranites in the Yuli belt, Taiwan: results from LA-ICP-MS zircon dating

*Lo Wen-Han1Tsai Chin-Ho1Liu Chiao1 (1.Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien, Taiwan)

キーワード:ophiolite, mélange, high-pressure metamorphism

We analyzed zircon separated from high-pressure meta-plagiogranites in the Chinshuichi mélange unit with LA-ICP-MS facilities. The mélange contains blocks of serpentinite, meta-gabbro, pillow-structured metabasite, epidote amphibolite and meta-plagiogranite in a matrix of meta-sediments. The meta-plagiogranites commonly contain meta-mafic enclaves, indicating an intrusive protolith origin. Glaucophane and omphacite occur in some of the meta-plagiogranites (Keyser et al., 2016). From the LA-ICP-MS analyses, three samples yielded mean 206Pb/238U dates of 13.1 ± 1.9 Ma, 15.7 ± 0.4 Ma and 16.3 ± 1.4 Ma. On the basis of zircon petrographic features (e.g. no obvious overgrowth in CL images), we conclude that the dates represent timing of magmatic crystallization of the meta-plagiogranites. These zircon ages place geochronological constraints on a late-stage shallow intrusion in a mid-Miocene oceanic section, which is likely of origin from the South China Sea domain.