Petrogenesis and Geochronology of the basement rocks of Zao Volcano and the surrounding areas

Abstract

The Zao volcano is located in the central part of Abukuma Belt, and basement rocks is composed of Hbl-Bt granodiorite. Results of petrography and geochemical data indicate fractional crystallization of Pl and Hbl. Zircon U-Pb age is 97.8 +/- 1.3 Ma and initial Sr ratios are 0.7070~0.7072. Generally, initial Sr ratios of granitic rocks of Abukuma Belt are 0.705-0.706. Therefore, forming process of Zao basement rocks are different from other areas, and it can explain by the AFC model with pelitic gneiss.