TY  - JOUR
A1  - Ogasawara, Masatsugu
A1  - Fukuyama, Mayuko
A1  - Horie, Kenji
A1  - Sumii, Tomoaki
A1  - Takehara, Mami
A1  - Sudo, Masafumi
T1  - SHRIMP U-Pb age of SoriZ93 zircon from the Sori Granodiorite, Northeast
 Japan: a potential reference zircon of Late Cretaceous age
T2  - ISLAND ARC
N2  - SoriZ93 zircon was separated from residual mineral fraction after the preparation of the SORI93 biotite standard from the Sori Granodiorite in the Ashio Mountains, Northeast Japan, and analyzed for its U-Pb age using a sensitive high resolution ion microprobe (SHRIMP). The zircon grains of SoriZ93 are prismatic with pyramidal ends or broken prismatic fragments. Most zircons are 100-250m long and 50-150m wide. The zircons are clear crystals and colorless to pale yellow, although some grains are brown with optically low transparency. Cathodoluminescence (CL) imaging of the SoriZ93 zircons showed a fine oscillatory zoning, which is a typical characteristic of zircons in granitic rocks. A xenocrystic core was not present in the zircons. Although some mineral inclusions were present in the zircons, it is possible to select a typical analytical area with a dimension of 30m necessary for the microbeam technique. The analytical results of the colorless zircons provided a weighted mean Pb-207 corrected Pb-206/U-238 age of 93.9 +/- 0.6Ma (95% confidence, MSWD=0.97). This Pb-206/U-238 age is 1.3m.y. older than the K-Ar age of the SORI93 biotite, indicating that the granodiorite cooled to a closure temperature of the K-Ar biotite system within a short time interval. Although some grains of the SoriZ93 zircons show high U concentration, a selection of colorless zircons provided the precise age to be used for the calibration and reference for zircons of the Late Cretaceous.
KW  - Late Cretaceous
KW  - SHRIMP U-Pb dating
KW  - Sori Granodiorite
KW  - SoriZ93
KW  - zircon standard
Y1  - 2013
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/34785
SN  - 1038-4871
VL  - 22
IS  - 3
SP  - 306
EP  - 317
PB  - WILEY-BLACKWELL
CY  - HOBOKEN
ER  -