|Budget Amount *help
¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1995 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1994 : ¥1,100,000 (Direct Cost : ¥1,100,000)
In this research, three dimensional distributions of element compositions and Sr isotope ratios of single granitic pluton were analyzed for the purpose of investigating the structure of shallow magma body and its differentiation process during the cooling and solidification. The Sori pluton was selected for this study.
For the vertical distributions of element concentrations for bulk rocks, which are measured for boling core samples with 1500m depth in the middle of the pluton, SiO_2 wt%, Fe_2O_3, MgO,MnO,K_2O/Na_2O,Ba, Rb, Y,Zn, U,Th increase, while Al_2O_3, CaO,Na_2O,Sr decrease with increasing depth. This vertical distributions of compositions correlate well with the petrography of the rocks, but not agree with the vertical distributions of other plutons such as Ariake and Okueyama. In horizontal distributions, the same tendency of element concentrations with increasing depth was recognized from the margin toward the core of the pluton. The Sr isotope ratios of the rocks are concentrated in a very narrow range, indicating that the magma was derived from isotopically homogeneous source without marked contamination of wall rocks.
These distributions of element contents and petrographical characteristics for the Sori pluton are explained by in situ fractionation during the cooling and solidification from margin to inner part.
The other plutons in different tectonic settings, Mesozoic plutons in the Hida belt and Paleozoic and Precambrian plutons, are also studied for comparison of the structure and formation process of the plutons.