International Joint Workshop on
Slow-to-Fast Earthquakes 2025

Post-meeting Field Trip (September. 27)

Fluid–Rock Interactions in Deep Slow Earthquake Regions of Subduction Zones: Geological Records from the Sanbagawa Metamorphic Belt

沈み込み帯の深部スロー地震発生領域での岩石―流体相互作用：三波川変成帯からの地質記録

Field Trip Overview

A one-day geological field trip to the Sanbagawa Metamorphic Belt will be conducted following the plenary session. The Sanbagawa Belt, located in southwest Japan, is a high-pressure metamorphic belt formed in a Cretaceous subduction zone. Its pressure–temperature (P–T) conditions are comparable to those in warm subduction zones, such as the Nankai Trough. During the trip, we will observe various fluid–rock interactions, including:　abundant quartz veins (Stop 2),　a metasomatic boundary between mantle wedge–derived serpentinite and metasedimentary rocks (Stop 3), and　hydration of eclogitic rocks (Stop 4).

Important Details:

• Meeting Point: 9:00 AM, September 27 (Saturday), at the Harimayabashi bus terminal, close to the CUL-PORT (the venue for the meeting).

• Capacity: TBD

• Participation Fee: TBD (meals are not included).

• Guides: Atsushi Okamoto (Tohoku U), Masaoki Uno (UTokyo) 

• Field Gear: At Stops, you will walk along the rocky riverside. Long sleeves, long pants, and trekking shoes are required.

• We will cancel the trip in case of heavy rain.

Field Trip Highlights:

1.  At the Nankoku Service Area of the Kochi Expressway (Stop 1), a monument made of stone from the Sambagawa metamorphic rock will be observed.

2.  At Tomisato (Stop 2), abundant quartz veins cutting through pelitic schists will be observed under greenschist-facies metamorphic conditions.

3.  At Tomisato (Stop 3), metasomatic reaction zones between serpentinite and pelitic schist will be examined.

4.  At Nikubuchi (Stop 4), boulders of garnet amphibolite—formed through the hydration of eclogitic rocks—will be collected along the river.