[S-CG52] 海洋底地球科学

[SCG52-09] A cold seep triggered by a hot ridge subduction

*LUCIA ALEJANDRA VILLAR-MUNOZ¹、Masataka Kinoshita²、Joaquim P. Bento³、Ivan Vargas-Cordero⁴、Eduardo Contreras-Reyes¹、Umberta Tinivella⁴、Michela Giustiniani⁴、Natsue Abe⁵、Ryo Anma⁶、Yuji Orihashi⁷、Hikaru Iwamori²、Tomoaki Nishikawa⁸、Eugenio Andres Veloso⁹、Satoru Haraguchi² (1.Departamento de Geofísica, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile.、2.Earthquake Research Institute, the University of Tokyo, Tokyo, 113-0032, Japan.、3.Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.、4.Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, 34010, Trieste, Italy. 、5.Mantle Drilling Promotion Office, MarE3, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan.、6.Graduate School of Technology, Industrial and Social Sciences, Tokushima University. 、7.Global Environment and Disaster Prevention, Graduate School of Science and Engineering, Hirosaki University, Hirosaki, Japan. 、8.Disaster Prevention Research Institute, Kyoto University, Japan.、9.Andean Geothermal Center of Excellence (CEGA), Santiago, Chile)

キーワード：Gas hydrates, Spreading centre, Submarine volcano, Heat flow

The Chile Triple Junction, where the hot active spreading centre of the Chile Rise system subducts beneath the South American plate, offers a unique opportunity to understand the influence of the anomalous thermal regime on an otherwise cold continental margin. Integrated analysis of various geophysical and geological datasets, such as bathymetry, heat flow measured directly by thermal probes and calculated from gas hydrate distribution limits, thermal conductivities, and piston cores, have improved the knowledge about the hydrogeological system. In addition, rock dredging has evidenced the volcanism associated with ridge subduction. Here, we argue that the localized high heat flow over the toe of the accretionary prism results from fluid advection promoted by pressure-driven discharge (i.e., dewatering/discharge caused by horizontal compression of accreted sediments) as reported previously. However, by computing the new heat flow values with legacy data in the study area, we raise the assumption that these anomalous heat flow values are also promoted by the eastern flank of the currently subducting Chile Rise. Part of the rift axis is located just below the toe of the wedge, where active deformation and vigorous fluid advection are most intense, enhanced by the proximity of the young volcanic chain. Our results provide valuable information to current and future studies related to hydrothermal circulation, seismicity, volcanism, gas hydrate stability, and fluid venting in this natural laboratory.