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Shimooka, Kazuya*; Ogita, Yasuhiro; Saito, Satoshi*
no journal, ,
We discovered a new poikilitic texture in the felsic rocks of Kajishima, Shisakajima, northeastern Ehime Prefecture, Japan. In this presentation, we carried out chemical compositions of the poikilitic texture, and whole-rock chemical compositions of the felsic rocks. Based on the results, we discussed the formation process of felsic rocks distribute on Kajishima.
Shimooka, Kazuya*; Ogita, Yasuhiro; Saito, Satoshi*
no journal, ,
We discovered a new poikilitic texture in the felsic rocks of Kajishima, Shisakajima, northeastern Ehime Prefecture, Japan. In this presentation, we carried out chemical compositions of the poikilitic texture, and whole-rock chemical compositions of the felsic rocks. Based on the results, we discussed the formation process of felsic rocks distribute on Kajishima.
Shimooka, Kazuya*; Tani, Kenichiro*; Takahashi, Toshiro*; Nagata, Mitsuhiro; Saito, Satoshi*
no journal, ,
Various types of Cretaceous gabbroic rocks are known to be distributed on Kajishima Island in the Setouchi Islands of southwestern Japan. The understanding of these rocks leads to the deep crust-mantle process of the continental margin. In this study, field -petrographic observation, whole rock Sr-Nd isotope analysis, zircon U-Pb dating and Hf isotope analysis of plutonic rocks distributed in Kajishima were carried out. The Sr-Nd-Hf isotope signatures between granite and gabbro in Kajishima are very similar, and field-petrographic observations suggest that the granitic interstitial melts, formed through extreme crystal fractionation of gabbroic magma or partial melting of gabbroic rocks, join together and form granitic rocks in Kajishima.
Shimooka, Kazuya*; Nagata, Mitsuhiro; Ogita, Yasuhiro; Takahashi, Toshiro*; Tani, Kenichiro*; Saito, Satoshi*
no journal, ,
The Kajishima is located in the northeastern part of Ehime Prefecture, where Cretaceous gabbros with dike-like granite are widely distributed. In this study, we clarified the granitic magma formation process during the Cretaceous flare-up event based on data on field occurrences, petrography, whole-rock geochemistry, Sr-Nd isotope composition, and zircon Hf isotopes. We newly found that many of gabbro and granite 
Nd (t) and zircon Hf (t) are negative. This suggests that the Cretaceous flare-ups enriched the mantle, the origin material of the gabbros. Furthermore, the zircon Hf isotopic composition of the plutonic rocks in this study is consistent with the isotopic compositions of previously reported Cretaceous plutonic rocks in the Eurasian margin. The Kajishima plutonic rocks can be considered representative of the Cretaceous plutonic rocks of the inner zone of southwestern Japan, and can be regarded as a geological unit that records the felsic magma formation process in the mafic lower crust.
Fukui, Toko*; Shimooka, Kazuya*; Ogita, Yasuhiro; Nagata, Mitsuhiro; Takahashi, Toshiro*; Saito, Satoshi*
no journal, ,
no abstracts in English
Shimooka, Kazuya*; Nagata, Mitsuhiro; Ogita, Yasuhiro; Takahashi, Toshiro*; Tani, Kenichiro*; Saito, Satoshi*
no journal, ,
Cretaceous igneous rocks in southwestern Japan are one of the geological units formed by flare-ups, but many aspects of their formation process remain unclear. In this study, we conducted field and mirror observation, whole-rock chemical analyses, and zircon Hf isotopic analysis for Cretaceous gabbro and granite in Kajishima, Ehime Prefecture. As a result, the granites in Kajishima are considered to have been formed by two melting processes: (1) Partial melting of gabbros to generate tonalite or granodiorite, and then (2) partial melting of the tonalite and granodiorite.