Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG52] Petrology, Mineralogy & Resource Geology

Thu. May 30, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Tatsuo Nozaki(Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology), Satoshi SAITO(Graduate School of Science and Engineering, Ehime University), Koichi Momma(National Museum of Nature and Science), Nobutaka Tsuchiya(Department of Geology, Faculty of Education, Iwate University)

[SCG52-P09] Petrological study on the intrusive contact of a Setouchi volcanic rock dike in the Nakajima
Island, Ehime Prefecture

*Taiki Omori1, Satoshi SAITO2 (1.Department of Earth Science, Faculty of Science, Ehime University , 2.Department of Earth Science, Graduate Schoole of Science, Ehime University )

Keywords:Setouchi volcanic rocks, Nakajima Island, Ehime Prefecture

We performed a detailed petrological study on the intrusive contact between a Setouchi andesitic
dike and host Ryoke granitoids occurring in the Nakajima Island, Ehime Prefecture. At the
intrusive contact, the andesite contains many fragments of host granitoids. The bulk SiO2 contents
of the marginal andesite at the intrusive contact are markedly higher than those of internal
domain implying the mixing between the andesite intrusion and the host granitoids. Other bulk
chemical compositions such as MgO, CaO, Na2O, K2O, Cr and Zr also imply mixing of the host
granitoids into the andesite intrusion at the intrusive contact. However, the Al2O3 contents of the
marginal andesite can not be explained by bulk mixing of the host granitoids and the andesite
intrusion because the Al2O3 contents of the marginal andesite are higher than those of the host
granites and internal domain of the andesite intrusion. Assuming that the marginal andesite with
chilled margin texture retain original compositions of intrusive magma, we tested the major
element mass-balance modeling to explain chemical compositions of internal domain of the
andesite intrusion. The modeling reproduced the major element compositions of internal
andesites by adding ~7 % of host granite components and ~12 % of mafic phenocryst minerals
into the marginal andesite.