11:45 AM - 12:00 PM
[SCG52-05] Petrochemistry and zircon U-Pb age of ``lateritic'' metamorphic rocks from the Kitakami Mountains
Keywords:laterite, metamorphic rocks, zircon U-Pb age, petrochemistry
U-Pb dating of zircons were carried out using Agilent 7500cx quadrupole inductively coupled plasma mass spectrometer (ICP-MS) with a New Wave Research UP-213 Nd-YAG UV (213 nm) laser ablation system (LA) installed at the Kyushu University. The operating parameters of analyses with LA-ICP-MS system are after Adachi et al. (2012). Zircon grains from the Shinkama metamorphic rocks are euhedral crystal (ca. 0.05mm) with remarkable oscillatory zoning, and define a concordant age of 126+/- 3Ma. On the other hand, zircon grains of subhedral crystal (larger than 0.1mm) with no oscillatory zoning, and define a concordant age of 326+/- 3Ma. The former age correspond to the contact metamorphism of Early Cretaceous, on the other hand, the latter corresopond to the hydrothermal alteration event of Carboniferous.