Abstract
Trace elements Sr, Rb, and Ba were analyzed by X-ray fluorescence spectrometric method for 268 samples of the Funatsu granitic rocks collected from main 7 intrusions of the Hayatsukigawa, Kekachidake, Yatsuo, Funatsu, Shimonomoto, Okumayama, and Utsubo, Hida Mountains. It is worthy of note that, among the intrusions, the Hayatsukigawa intrusion is characterized by high Sr contents (250-950 ppm). The Hayatsukigawa intrusion consists mainly of fine-grained hornblende-biotite granodiorite (SiO2=66-74%) and intrudes into the Okumayama intrusion with abundant mafic Minerals (SiO2=63-68%). No systematic changes in major element contents, trace element contents and mineral compositions are observed between the two intrusions. The initial 87Sr/86Sr ratio of the Hayatsukigawa intrusion is higher than that of the Okumayama intrusion. It seems to be unreasonable to consider that the two plutons were differentiated from a magma. Trace elements in the Hayatsukigawa intrusion are clarified to be zonally distributed and the zonation can be explained mainly as the results of in situ fractional crystallization, suggesting that the assimilation hardly took place during the crystallization. Moreover, the low Rb contents (42-116 ppm) in the Hayatsukigawa intrusion also do not favor the crustal assimilation hypothesis. Therefore, high Sr contents and high initial 87Sr/86Sr ratio in the Hayatsukigawa intrusion are probably attributed to the partial melting of the source material characterized by high Sr-isotopic ratio.
