WRI-17 Post conference fieldtrip

P4: Ryoke metamorphic rocks: from accretionary complex to anatectic
migmatites
Updated 23 May 2023
Guided by Prof. Tetsuo Kawakami and Dr. Fumiko Higashino (Kyoto University, Japan)
In this field trip, we will visit the Ryoke belt exposed in Kyoto prefecture and Mie prefecture.
The Ryoke belt represents the crustal section that records plutono-metamorphism at theCretaceous Eurasian continental margin. We will observe progressive change of the MinoTamba accretionary complex into the high-temperature/low-pressure type Ryoke
metamorphic rocks (schists and anatectic migmatites), in addition to gneissose and massive
granitoids intruding into the metamorphic rocks.
We will leave Kyoto University at ~9:00 am on the first day (24 August), so staying at
Kyoto on 23 August is strongly recommended.

We will use two bans (8-9 persons each) for the trip. The ban has no extra space for large
luggage. Therefore, please bring compact luggage suitable for two-day trip. Ask yourhotel in Kyoto to keep large suitcases during the field trip. Please consult us if you want
us to keep the suitcases during the field trip.

Because the arrival to Kyoto University on the second day of the trip may vary dependingon traffic jams, we strongly recommend to reserve a hotel in Kyoto on the second day (25August).

Also note that August in Japan is very hot and humid.

The field trip may be canceled in case typhoon hits Kansai area (low possibility, though).

PLANFig. 1 Simplified geological map of the Kinki district showing the Waduka and Aoyama areas(Kawakami and Nishioka, 2012).
(Day-1)
We will visit the Wazuka area (Kyoto Prefecture). We start from observation ofunmetamorphosed accretionary wedge material exposed in Kyoto (Uji-city), followed by lowgrade pelitic schists, andalusite- and cordierite-bearing pelitic schists developed at the contact
metamorphic aureole around the massive granitoids. We will move to Iga-city and stay there.
Stop 1
Mino-Tamba Complex at Amagase-dam.
Wewillobserve

metamorphic

rocks,

protolith
theofRyoke

Mino-Tamba

Complex. In this outcrop, duplex structures
can be well observed (Kusunoki, 2020).

Stop 2
Lenses of green rock and limestone in lowgrade metapelites.

Stop 3
Bt-zone grade slates at Inu-uchi pass.
Stop 4
Contact metamorphic zone of Crd+And grade developed around the massive Bt granite (KoyaGranite).

Drive to Iga city (stay at a hotel).
(Day-2)
We will visit the Aoyama area (Mie Prefecture). We start from pelitic schists ofandalusite/sillimanite transition grade, followed by metatexite migmatites and diatexites. We
will also visit an outcrop of gneissose granitoid/massive granitoid contact. We will arrive atKyoto University after dusk.
Stop 5Pelitic schist at the low-T part of
the Grt-Crd zone containing Sil
transformedfromAnd.

Interboudin

partitions

filledwith

leucosomemaybeobserved, and magmatic And
maybefoundwithintheleucosome (Kawakami, 2002).
Tourmaline-out

isograd(Kawakami, 2001) lies near thislocality.

Stop 6
Lens-shaped leucosomes developed inmigmatites. (We will walk into anoutcrop in a river.)

Stop 7
Metatexite migmatites in the Grt-Crdzone (Kawakami, 2001) at Bano river.
These migmatites are likely affected by
the massive granitoid intrusions assuggested by bimodal age recorded inmonazite (Kawakami & Suzuki, 2011).

Stop 8
Diatexite migmatites in the GrtCrd zone (Kawakami, 2001) atOkuin river. Mafic lens may beobserved. Glass inclusions werefound in zircon from diatexite
migmatites (Kawakami et al.
2013). Most of the zircon
domains are considered to havegrown during the anatectic melt
crystallization

whengarnet

breaks down to release Zr(Kawakami et al. 2019).

Stop 9Contact between a gneissose granite(Joryu Tonalite) and a massive granite(Ao Granite).

Drive back to Kyoto University using highway.
References:
Kawakami, T. (2001). Tourmaline breakdown in the migmatite zone of the Ryoke
metamorphic belt, SW Japan. Journal of Metamorphic Geology, 19(1), 61–75.
Kawakami, T. (2002). Magmatic andalusite from the migmatite zone of the Aoyama area,
Ryoke metamorphic belt, SW Japan, and its importance in constructing the P-T path.
Journal of Mineralogical and Petrological Sciences, 97(5), 241–253.
Kawakami, T., Horie, K., Hokada, T., Hattori, K., & Hirata, T. (2019). Disequilibrium REE
compositions of garnet and zircon in migmatites reflecting different growth timings
during single metamorphism (Aoyama area, Ryoke belt, Japan). Lithos, 338–339, 189–203.
Kawakami, T., & Nishioka, Y. (2012). Metamorphic rocks and granitoids in the Aoyama area,
Ryoke belt, SW Japan. The Journal of the Geological Society of Japan, 118(Supplement).
Kawakami, T., & Suzuki, K. (2011). CHIME monazite dating as a tool to detect
polymetamorphism in high-temperature metamorphic terrane: Example from theAoyama area, Ryoke metamorphic belt, Southwest Japan. Island Arc, 20(3), 439–453.
Kawakami, T., Yamaguchi, I., Miyake, A., Shibata, T., Maki, K., Yokoyama, T. D., & Hirata,T. (2013). Behavior of zircon in the upper-amphibolite to granulite facies
schist/migmatite transition, Ryoke metamorphic belt, SW Japan: Constraints from themelt inclusions in zircon. Contributions to Mineralogy and Petrology, 165(3), 575–591.
Kusunoki, T.（2020）. Duplex structures in the Amagase Broken-formation, southeastern partof the Tamba Belt, Southwest Japan. GSJ News, 9, 157-167.