Japan Geoscience Union Meeting 2016

Presentation information

Oral

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

[S-CG56] Petrology, Mineralogy and Resource Geology

Thu. May 26, 2016 10:45 AM - 12:15 PM 201B (2F)

Convener:*Tatsuo Nozaki(Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology), Akira Miyake(Department of Geology and Mineralogy, Graduate School of Science, Kyoto University), Nobutaka Tsuchiya(Department of Geology, Faculty of Education, Iwate University), Satoshi SAITO(Graduate School of Science and Engineering, Ehime University), Chair:Nobutaka Tsuchiya(Department of Geology, Faculty of Education, Iwate University), Satoshi SAITO(Graduate School of Science and Engineering, Ehime University)

12:00 PM - 12:15 PM

[SCG56-08] Crystallization history and petrogenesisi of the Hikami granitic rocks, south Kitakami Mauntains, Japan

Jun Sasaki1, *Nobutaka Tsuchiya1, Tatsuro Adachi2, Nobuhiko Nakano2, Ippei Kitano2, Yasuhito Osanai2, Yoshiko Adachi3 (1.Department of Geology, Faculty of Education, Iwate University, 2.Department of Earth Sciences, Faculty of Social and Cultural Studies, Kyushu University, 3.Center for Transdisciplinary Research, Niigata University)

Keywords:Hikami granitic rocks, petrochemistry, Ordovician, Kitakami Mountains

Hikami granitic complex are divided into next ten rock types; hornblend-bearing granodiorite-tonalite (A-1, A-2, A-3 and A-4), hornblend-free granodiorite-tonalite (B, C, and D), and granodiorite associated with the Tsubnosawa metamorphic rocks (E, F and G). Zircon U-Pb ages were determined with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for each rock type, and solidification age of the Hikami granitic rocks are Ordvician age of around 450 Ma. Petrogenesis of felsic rocks B and C in the Hikami granitic complex can be explained by the fractional crystallization model from the common parental magma of rock type A-2. Difference between the trends of A-2 to B and C can be explained by the slightly different conditions of fractional crystallization. Source material of the Ordovician granites including Hikami granitic rocks is considered to be a basaltic to andesitic material in lower continental crust, which has Sr-Nd isotopic composition more depleted compared with the Tsubonosawa metamorphic rocks and more enriched conpared with the amphibolites in teh Kurosegawa belt (Osanai et al., 2000).