Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

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

[S-CG60] Investigation of inputs to subduction zones: Influence of tectonic processes on the incoming plate

Mon. May 27, 2019 10:45 AM - 12:15 PM A05 (TOKYO BAY MAKUHARI HALL)

convener:Makoto Yamano(Earthquake Research Institute, the University of Tokyo), Tomoaki Morishita(School of Geoscience and Civil Engineering, College of Science and Technology, Kanazawa University), Gou Fujie(Japan Agency for Marine-Earth Science and Technology), Chairperson:Shigeaki Ono(Japan Agency for Marine-Earth Science and Technology)

10:45 AM - 11:00 AM

[SCG60-01] Geophysical-petrological studies of the Chile triple junction and their significance: MIRAI research cruise MR-1806Leg2

*Masataka Kinoshita1,5, Hikaru Iwamori1,5, Tomoaki Nishikawa2, Ryo Anma3, Sofia Lagarrigue4, Natsue Abe5, Yuka Yokoyama6, Andres Veloso Espinosa4, Alessandra Isabella Rivero Cortes7, Gabriela Pia Lazcano Prado7, Ivan Andres Arriagada Bascuñan7, Satoru Haraguchi5, Kosuke Ota9, Yuji Orihashi8, Kaishi Nakao8, Shogo Numata8, Hajime Shiobara1, Hiroko Sugioka10, Aki Ito5, Nicolás Pérez-Estay11 (1.Earthquake Research Institute, University of Tokyo, 2.DPRI, Kyoto Univ., 3.Tokushima Univ., 4.Pontificia Universidad Catolica de Chile, 5.JAMSTEC, 6.Tokai Univ., 7.Andres Bello University, 8.Hirosaki Univ., 9.AORI, Univ. Tokyo, 10.Graduate School of Science, Kobe Univ., 11.Ministerio de relaciones exteriores, Chile)

Keywords:heat flow, Chile Triple Junction

The Chile triple junction (CTJ) is a unique place where a spreading center of mid-ocean ridge is subducting near the Taitao peninsula. Around CTJ, presence of high heat flow on the continental slope (Cande et al., 1987, J. Geophys. Res.) and near-trench young granitic rocks on the Taitao peninsula (Anma and Orihashi, 2013, Geochem. J.) suggests the thermal and petrological impact of subducting ridge on the continental side. The tectonic history of the southeast Pacific since early Cenozoic to the present suggests that ridge subduction continuously occurred along the Chile trench, which migrated northward (Cande and Leslie, 1986, J. Geophys. Res.), which can contribute to growth of the continental crust (Iwamori, 2000, EPSL).
In January 2019, the MR18-06 cruise Leg 2 was conducted at the Chile Triple Junction, as a part of 'EPIC' expedition by using R.V Mirai of JAMSTEC. During the leg, we completed 4 SCS lines, 6 piston coring, 6 heat flow measurements, 2 dredges, and underway geophysics observations, as well as deployment of 13 OBSs. The primary object of heat flow measurement at CTJ is to better constrain the thermal regime around CTJ by adding new data right above CTJ. The key question is whether CTJ is thermally dominated by ridge activity (magmatic, tectonic, and/or hydrothermal) or by subduction initiation (tectonic thickening, accretion, and/or erosion). The ultimate goal is to model the temperature at the plate interface from the heat flow and other data, and to infer how the thermal regime at CTJ contributes the seismogenic behavior at the M~9 megathrust zone.
Our preliminary analysis shows high and variable heat flow around CTJ. It is generally consistent with previous heat flow along line 751 (Cande et al., 1987). With SCS and piston core data, a reasonable thermal model can be constructed around CTJ. (Acknowledgment) we thank the Hydrographic Department of Chile (SHOA), for allowing to enter the Chilean EEZ and territory for our survey.