Japan Geoscience Union Meeting 2014

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Symbol S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT41_28AM1] Origin, Evolution, Destruction, and Recycling of Oceanic Plate

Mon. Apr 28, 2014 10:00 AM - 10:45 AM 314 (3F)

Convener:*Tomoaki Morishita(School of Natural System, Colleage of Science and Technology, Kanazawa University), Toshitsugu Yamazaki(Atmosphere and Ocean Research Institute, The University of Tokyo), Nobukazu Seama(Department of Earth and Planetary Sciences, Graduate School of Science, Kobe University), Ryo Anma(Faculty of Life and Environmental Science, University of Tsukuba), Hidenori Kumagai(Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology), Daisuke Nakamura(Okayama University), Chair:Tomoaki Morishita(School of Natural System, Colleage of Science and Technology, Kanazawa University)

10:00 AM - 10:15 AM

[SIT41-01] Microstructural and fabric characteristics of the uppermost mantle peridotites in the Taitao ophiolite, South America

*Yoshiaki YOSHIDA1, Katsuyoshi MICHIBAYASHI1, Ryo ANMA2 (1.Institute of Geosciences, Shizuoka University, 2.Faculty of Life and Environmental Science, University of Tsukuba)

Keywords:Taitao ophiolite, mantle section, peridotite, microstructure, olivine fabrics

The <6Ma young Taitao ophiolite, exposed at the westernmost promontory of the Taitao Peninsula, is located approximately 40 km southeast of the Chile triple junction and consists of a complete sequence of oceanic lithosphere, including ultramafic rocks, gabbros, a dyke complex and volcaniclastic rocks. The ophiolite is surrounded by several contemporaneous granite plutons intruded in between the ophiolite and the Pre-Jurassic metamorphic basement. Several studies have been carried out on the Taitao ophiolite and surrounding granites. Whereas they have focused mostly on petrology and geochemistry, we investigated microstructures and crystal-fabrics of the ultramafic rocks, aiming to understand the origin of the ophiolite. 6 out of 16 ultramafic rocks preserved peridotite textures despite of intense serpentinization and show mostly porphyroclastic textures consisting of pyroxene porphyroclasts with a fine-grained olivine-pyroxene matrix. Their olivine crystal-fabrics shows [100]{0kl} and [100](001) patterns. These indicate that the uppermost mantle section have remarkably been deformed before and/or during the obduction process after their formation beneath the mid-ocean ridge.