レター
根田茂帯付加体中に挟在する石英閃緑岩岩塊の前期オルドビス紀ジルコン年代
キーワード:
quartz diorite,
tectonic block,
zircon,
U-Pb age,
Ordovician,
Nedamo Belt,
accretionary complex
2022 年 128 巻 1 号 p. 221-227
詳細
2022 年 128 巻 1 号 p. 221-227
The Nedamo Belt in the Kitakami Massif, NE Japan, contains early Carboniferous and Early Triassic accretionary complexes. Tectonic blocks containing plutonic rocks, ultramafic rocks and high-P/T schists occur in these complexes and characterize the Nedamo Belt. The plutonic rocks comprise hornblende gabbro and quartz diorite, and they have been identified at more than 50 localities. U-Pb dating of zircon from the quartz diorite using inductively coupled plasma-mass spectrometry yields an Early Ordovician age of ca. 480 Ma. Based on similarities in lithofacies and age, the plutonic rocks are correlative to the Kagura Igneous Rocks of one of the basement units in the South Kitakami Belt. This correlation may help in deducing the mechanism (e.g., large sinistral strike-slip fault) of emplacement of the tectonic blocks into the accretionary complexes of the Nedamo Belt.
