Japan Geoscience Union Meeting 2018

Presentation information

[EJ] Oral

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

[S-CG58] Investigation of inputs to subduction zones: Influence of tectonic processes on the incoming plate

Wed. May 23, 2018 9:00 AM - 10:30 AM 302 (3F International Conference Hall, Makuhari Messe)

convener:Makoto Yamano(Earthquake Research Institute, the University of Tokyo), Tomoaki Morishita(School of Natural System, Colleage of Science and Technology, Kanazawa University), Gou Fujie(海洋研究開発機構), Chairperson:Obana Koichiro(Japan Agency for Marine-Earth Science and Technology), Morishita Tomoaki(Kanazawa University)

9:30 AM - 9:45 AM

[SCG58-03] Modification of the subducting plate by petit-spot volcanism: Impregnation of CO2-rich melt from the asthenosphere

★Invited Papers

*Shiki Machida1, Yuki Sato2, Naoto Hirano2,3 (1.Ocean Resources Research Center for Next Generation (ORCeNG), Chiba Institute of Technology, 2.Graduate School of Science, Tohoku University, 3.Center for Northeast Asian Studies (CNEAS), Tohoku University)

Keywords:CO2-rich silicate melt, metasomatic enrichment, oceanic lithosphere, petit-spot

Petit-spot is the definitive evidence for partial melting in the asthenosphere caused by Carbon dioxide (CO2) [1]. Recent our studies [1, 2, 3, 4] identified two types of eruption process of CO2-rich silicate melt from asthenosphere due to petit-spot volcanism, which corresponds to differences of the stress field of oceanic lithosphere. On the concavely flexed region, CO2-rich melt reacts [2] and equilibrates [1] with ambient peridotite in the lower lithosphere before eruption. In contrast, on the convexly flexed region, CO2-rich melt erupts directly from the asthenosphere [3]. Our results [3, 4] suggest that majority of petit-spot volcanoes in the western North Pacific correspond to the former type of process. We thus consider that petit-spot volcanism provides insights into understanding the nature of pre-subduction modification of oceanic lithosphere.
In this presentation, we review geochemical and geochronological variation of petit-spot lava and xenocryst therein from the western North Pacific, to discuss reaction processes between CO2-rich melt and oceanic lithosphere.

[1] Machida, et al. (2017) Nature Communications 8, 14302.
[2] Pilet, et al. (2016) Nature Geoscience 9, 898-903.
[3] Sato, et al. (2017) International Geology Review, doi: 10.1080/00206814.2017.1379912.
[4] Machida, et al. (2015) Earth and Planetary Science Letters 426, 267-279.