Geology of the Ryoke Belt in the eastern Kinki District, Japan:The phase-divisions and the mutual relations of the granitic rocks

Hayama, Yoshikazu; Yamada, Tetsuo; Itô, Makoto; Kutsukake, Toshio; Masaoka, Kunio; Miyakawa, Kunihiko; Mochizuki, Yasutoshi; Nakai, Yutaka; Tainosho, Yoshiaki; Yoshida, Masaru; Kawarabayashi, Ikuro; Tsumura, Yoshihiro

doi:10.5575/geosoc.88.451

Cited by 19 publications

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“…Therefore, the solidification age of granodiorites can be younger than the reported age, considering the possible presence of an inherited core. However, if we accept the conventional zircon U-Pb age at face value, it can be said that granitic activity continued at the Kinki district from 94 to 79.8 Ϯ 3.9 Ma, because the Ao granite is considered to be the youngest granite in the western Kinki district and the Joryu tonalite and Kimigano granodiorite are considered to be the second oldest from the intrusion relationship (Hayama et al 1982). Therefore, the length of the granitic activity in the Kinki district is between that of the western part (Iwakuni-Yanai, ca 95-85 Ma) and the eastern part (Mikawa-Komagane, ca 95-68 Ma) (Suzuki & Adachi 1998), and the data from the Kinki district is concordant with the tendency that the granitic activity was longer in the east than the west of the Ryoke belt.…”

Section: Discussionmentioning

confidence: 99%

“…The Aoyama area is one of the well‐studied areas in the Ryoke metamorphic belt, where high‐grade metasedimentary rocks are widely exposed (Yoshizawa et al . 1966; Hayama et al . 1982; Takahashi & Nishioka 1994; Kawakami 2001a) (Fig.…”

Section: Geological Outline Of Aoyama Areamentioning

confidence: 99%

“…1b), there are two large areas where Ryoke metamorphic rocks are widely exposed. Low-to high-grade metamorphic rocks are widely distributed in the Wazuka area (Wang et al 1986;Takeuchi & Wang 1999;Ozaki et al 2000), and high-grade metamorphic rocks are widely distributed in the Aoyama area (Hayama et al 1982;Takahashi & Nishioka 1994;Kawakami 2001aKawakami , b, 2002Kawakami , 2004Kawakami & Kobayashi 2006). The Older Ryoke granites with gneissose texture dominate to the south of the Ryoke metamorphic rocks (Yoshizawa et al 1966;Hayama et al 1982).…”

Section: Introductionmentioning

confidence: 99%

“…Two Older Ryoke granites, the Joryu tonalite and the Kimigano granodiorite ( Fig. 1b Ishizaka (1969), the sampling locality given in the paper is located in the distribution area of the Joryu tonalite by Hayama et al (1982). We follow in this paper the naming of Hayama et al (1982) for simplicity.…”

Section: Introductionmentioning

confidence: 99%

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CHIME monazite dating as a tool to detect polymetamorphism in high‐temperature metamorphic terrane: Example from the Aoyama area, Ryoke metamorphic belt, Southwest Japan

Kawakami

Suzuki

2011

Island Arc

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Chemical Th-U-total Pb isochron method (CHIME) monazite dating was carried out for pelitic-psammitic migmatites and the Ao granite (one of the Younger Ryoke granites) from the Aoyama area, Ryoke metamorphic belt, Southwest Japan. The Ao granite gives an unequivocal age of 79.8 Ϯ 3.9 Ma. The monazite grains in migmatites yield an age of 96.5 Ϯ 1.9 Ma with rims and patchy domains of 83.5 Ϯ 2.4 Ma. The 83.5 Ϯ 2.4-Ma overprinting on migmatites over the garnet-cordierite zone suggests a wide and combined effect of thermal input and fluid activity on the monazite grains caused by the contact metamorphism by the Younger Ryoke granites including the Ao granite. This contact metamorphism has not been detected from the major metamorphic mineral assemblage previously, possibly because the migmatites already possessed the high-temperature mineral assemblage before the granite intrusions and were immune from contact metamorphism in terms of major metamorphic minerals. However, monazite records contact metamorphism clearly. Therefore, the field mapping of the CHIME monazite age is a powerful tool for recognition of polymetamorphism in high-temperature metamorphic terrains where later thermal effects can not be easily detected by the growth of new major metamorphic minerals.

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Section: Discussionmentioning

confidence: 99%

Section: Geological Outline Of Aoyama Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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CHIME monazite dating as a tool to detect polymetamorphism in high‐temperature metamorphic terrane: Example from the Aoyama area, Ryoke metamorphic belt, Southwest Japan

Kawakami

Suzuki

2011

Island Arc

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“…Indeed, the belt is composed of abundant Late Cretaceous plutonic rocks occurring together with metamorphic rocks which record low‐ P , high‐ T metamorphic conditions on a regional scale (Miyashiro, ; Nakajima, ). The plutonic rocks have been classified into the Older and Younger Ryoke granitoids based on their structure and intrusive relationships (Hayama et al, ; Higashimoto, Nureki, Hara, Tsukuda, & Nakajima, ; Ryoke Research Group, ). The Older Ryoke granitoids show a gneissose structure which is concordant with the foliation of the host metamorphic rocks, whereas the Younger Ryoke granitoids are generally massive, discordantly cut the host‐rock foliation, and create contact aureoles of variable widths.…”

Section: Introductionmentioning

confidence: 99%

Age gap between the intrusion of gneissose granitoids and regional high‐temperature metamorphism in the Ryoke belt (Mikawa area), central Japan

et al. 2017

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The relationships between the intrusion of gneissose granitoids and the attainment of regional high‐T conditions recorded in metamorphic rocks from the Ryoke belt of the Mikawa area, central Japan, are explored. Seven gneissose granitoid samples (tonalite, granodiorite, granite) were collected from three distinct plutonic bodies that are mapped as the so‐called “Older Ryoke granitoids.” Based on bulk‐rock compositions and U–Pb zircon ages obtained by laser ablation inductively coupled plasma mass spectrometry, the analyzed granitoids can be separated into two groups. Gneissose granitoids from the northern part of the area give weighted mean 206Pb/238U ages of 99 ±1 Ma (two samples) and 95 ±1 Ma (one sample), whereas those from the southern part yield 81 ±1 Ma (two samples) and 78–77 ±1 Ma (two samples). Regional comparisons allow correlation of the northern granitoids (99–95 Ma) with the Kiyosaki granodiorite, and mostly with the Kamihara tonalite found to the east. The southern granitoids are tentatively renamed as “78–75 Ma (Hbl)−Bt granite” and “81–75 Ma Hbl−Bt tonalite” (Hbl, hornblende; Bt, biotite). and seem to be broadly coeval members of the same magmatic suite. With respect to available age data, no gneissose granitoid from the Mikawa area shows a U–Pb zircon age which matches that of high‐T metamorphism (ca 87 Ma). The southern gneissose granitoids (81–75 Ma), although they occur in the highest‐grade metamorphic zone, do not seem to represent the heat source which produced the metamorphic field gradient with a low dP/dT slope.

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Behavior of zircon in the upper-amphibolite to granulite facies schist/migmatite transition, Ryoke metamorphic belt, SW Japan: constraints from the melt inclusions in zircon

Kawakami

Yamaguchi

Miyake

et al. 2012

Contrib Mineral Petrol

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23Behavior of zircon at the schist/migmatite transition is investigated. Syn-metamorphic 24 overgrowth is rare in zircon in schists, whereas zircon in migmatites has rims with low Th/U that 25 give 90.3 ± 2.2 Ma U-Pb concordia age. Between inherited core and the metamorphic rim, a thin, 26 dark-CL annulus containing melt inclusion is commonly developed, suggesting that it formed 27 contemporaneous with the rim in the presence of melt. In diatexites, the annulus is further truncated 28 by the brighter-CL overgrowth, suggesting the resorption and regrowth of the zircon after near-peak 29 metamorphism. Part of the zircon rim crystallized during the solidification of the melt in migmatites. 30Preservation of angular-shaped inherited core of 5-10 μm in zircon included in garnet suggests 31 that zircon of this size did not experience resorption but developed overgrowths during near-peak 32 metamorphism. The Ostwald ripening process consuming zircon less than 5-10 μm is required to 33 form new overgrowths. Curved crystal size distribution pattern for fine-grained zircons in a diatexite 34 sample may indicate the contribution of this process. Zircon less than 20 μm is confirmed to be an 35 important sink of Zr in metatexites, and ca. 35 μm zircon without detrital core are common in diatexites, supporting new nucleation of zircon in migmatites. 37In the Ryoke metamorphic belt at the Aoyama area, monazite from migmatites records the 38 prograde growth age of 96.5 ± 1.9 Ma. Using the difference of growth timing of monazite and zircon, 39 the duration of metamorphism higher than the amphibolite facies grade is estimated to be ca. 6 Myr. 40 41 Keywords: zircon, migmatite, melt inclusion, glass, crystal size distribution, duration of 42 metamorphism. 43 Vavra et al. 1999; Bowman et al. 2011). In the polymetamorphic orthogneiss from northern Labrador, 56 Canada, almost no zircon grows in the amphibolite facies gneisses, and it starts to grow near the 57 amphibolite-granulite facies transition (Schiøtte et al. 1989). Vavra et al. (1999) described the zoning 58 pattern of zircon from the amphibolite-granulite facies transition of the Ivrea Zone (Southern Alps) 59in detail. In the Ivrea Zone, this grade of metasediments accompanies partial melting, and all the 60 zircon overgrowth was supposed to have formed entirely in an anatectic environment. They observed 61 an angular shape of inherited core of zircon in metasediments and interpreted that it is not affected 62 by the partial dissolution process. Since dust-like tiny zircons are abundant in the metasediments, 63 they assumed the Ostwald ripening as a possible growth mechanism of zircon overgrowth, and 64 considered that such a process took place during the prograde metamorphism. They recognized three 65 patterns of zircon overgrowth based on morphology and internal structure as follows; (i) prismatic 66 (prism-blocked) with low Th/U ratio and dark-cathodoluminescence (dark-CL), (ii) stubby with 67 medium Th/U ratio, and (iii) isometric with high Th/U ratio and bright-CL. The f...

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Geology of the Ryoke Belt in the eastern Kinki District, Japan:The phase-divisions and the mutual relations of the granitic rocks

Cited by 19 publications

References 0 publications

CHIME monazite dating as a tool to detect polymetamorphism in high‐temperature metamorphic terrane: Example from the Aoyama area, Ryoke metamorphic belt, Southwest Japan

CHIME monazite dating as a tool to detect polymetamorphism in high‐temperature metamorphic terrane: Example from the Aoyama area, Ryoke metamorphic belt, Southwest Japan

Age gap between the intrusion of gneissose granitoids and regional high‐temperature metamorphism in the Ryoke belt (Mikawa area), central Japan

Behavior of zircon in the upper-amphibolite to granulite facies schist/migmatite transition, Ryoke metamorphic belt, SW Japan: constraints from the melt inclusions in zircon

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