- 著者
- Takehiro HIRAYAMA Tomoyuki SHIBATA Masako YOSHIKAWA Khadidja ABBOU–KÉBIR Kosuke KIMURA Yasuhito OSANAI Kaushik DAS Yasutaka HAYASAKA Keiji TAKEMURA
- 出版者
- Japan Association of Mineralogical Sciences
- 雑誌
- Journal of Mineralogical and Petrological Sciences (ISSN:13456296)
- 巻号頁・発行日
- vol.117, no.1, pp.211217b, 2022 (Released:2022-11-30)
- 参考文献数
- 40
- 被引用文献数
- 1
Granitic and gabbroic xenoliths have been found within dacitic lavas in the Hime–shima volcanic group (HVG) of northeastern Kyushu, Japan. The HVG is located near the boundary between the Ryoke and Sangun belts, suggesting that the HVG and associated crustal xenoliths may provide insights into the subsurface distribution of the Ryoke and Sangun belts in Kyushu. This study focuses on xenoliths obtained from the coastal boulders near the Kane Lava of the HVG. The HVG xenoliths consist of gabbro, gabbroic diorite, amphibolite, gneiss, basaltic andesite, and tuffaceous sandstone, with the latter two types resembling those found in the basement rocks of the HVG. The gabbroic xenoliths are geochemically similar to gabbros in the Ryoke belt. The U–Pb dating for zircon in the gneiss xenoliths yielded a metamorphic age of ~ 111 Ma with Th/U values <0.1, similar to the age obtained for metamorphic rocks in or of the Ryoke belt. The new data presented in this study indicate that the xenoliths in the HVG were derived from basement units associated with the Ryoke belt, which in turn, means that the HVG is tectonically underlain by the Ryoke belt. This also suggests that the Ryoke belt extends further north in Kyushu than was previously considered, as implied by the presence of this belt directly below the HVG.
- 著者
- Tomokazu HOKADA Tatsuro ADACHI Yasuhito OSANAI Nobuhiko NAKANO Sotaro BABA Tsuyoshi TOYOSHIMA
- 出版者
- Japan Association of Mineralogical Sciences
- 雑誌
- Journal of Mineralogical and Petrological Sciences (ISSN:13456296)
- 巻号頁・発行日
- vol.117, no.1, pp.220317, 2022 (Released:2022-08-20)
- 参考文献数
- 38
- 被引用文献数
- 3
We have found corundum in direct contact with quartz and biotite and as inclusions in garnet in the pelitic gneisses of northern Austkampane in the Northeastern (NE) Terrane of the Sør Rondane Mountains (SRM), East Antarctica. Our samples, which include corundum–bearing gneisses, show petrographic features such as staurolite inclusions in garnet, compositional zoning of orthoamphibole with Al decreasing toward the rims, and late–stage cordierite formation, and these features are characteristic of a clockwise P–T trajectory. The observations are consistent with the proposed regional clockwise P–T evolution of the NE Terrane in the SRM. The corundum and other inclusions observed in the garnet porphyroblasts are interpreted to have formed owing to either staurolite breakdown or metastable crystallization relative to kyanite prior to the peak metamorphism. The close association of biotite and quartz surrounding corundum inclusions suggests fluid– or melt–related processes. These petrographic features imply that the corundum and quartz (rarely observed in high–grade metamorphic rocks) formed as a result of metastable crystallization during the prograde stage of the clockwise P–T evolution of a continental collision zone.