U-Pb zircon ages and Sr and Nd isotope compositions of the Soeda Granodiorite, northern Kyushu, Southwest Japan

Abstract

U-Pb zircon dating, rare earth elements (REE) analysis and Sr-Nd isotope analysis were conducted on samples from the Soeda Granodiorite in the eastern part of northern Kyushu, Southwest Japan. The Soeda Granodiorite is divided into two units, based on whole-rock Sr content: the Ochiai and Irahara Granodiorites. These granodiorites are composed mainly of medium-grained hornblende - biotite granodiorite to biotite granite. U-Pb zircon ages of 107.41 ± 0.82 Ma and 103.11 ± 0.69 Ma were obtained from the Ochiai and Irahara Granodiorites, respectively. These suggest that timing of intrusion of each of the granodiorite magmas were different. REE and Sr-Nd isotopic compositions of source magmas of the Ochiai and Irahara Granodiorites also differ.