Aso-4火砕流堆積物中の花崗岩マイロナイト異質礫の岩石学と放射年代および荷尾杵花崗岩との対比

Abstract

Aso-pyroclastic flow is one of the largest volcanic activities in Japan and formed huge caldera of the Aso volcano at about , years b.p.. This pyroclastic flow brought about accidental clasts of granitic mylonite in the Aso-pyroclastic deposit in northern area of the caldera. These granitic mylonite clasts were investigated petrologically and geochronologically, and compared with the Nioki Granite in the Asaji area to the east of the volcano. The Aso-granitic clasts are characterized by garnet-muscovite bearing adamelite-granite, and all of them are moderately to strongly mylonitized and show porphyroclastic texture. Their SiO content ranges -wt.%. The range of garnet composition of the Aso-granitic clasts is Alm , Sps , Pyr .. , Grs . . . These mineral and chemical compositions are quite similar to those of the Nioki Granite. The K-Ar muscovite age for Asogranitic clasts is .. Ma, whereas Nioki Granite is . . Ma. The heat of magma of the volcano did not affect the K-Ar closure system for muscovite when the pyroclastic flow took place, because heating has not fundamentally shortened the fission tracks within zircon grains in the dated clast. Accordingly, the Aso-granitic mylonite clasts are correlative with the Nioki Granite, which is also weakly to moderately mylonitized. The intrusive age of the Nioki Granite is also determined using CHIME monazite dating, and the result is Ma. This suggests that subsurface ductile mylonite zone initiated around Ma of the major fault extends from Asaji area to the Aso volcano. This fault coincides with the Oita-Kumamoto Tectonic Line, along which the active fault segment has been known. The occurrence of E-W extending mylonite zone is also significant evidence in considering the western extension of the Median Tectonic Line in Kyushu. AbstractCThe Geological Society of Japan 2007 1

RETRACTED ARTICLE: Structural features and seismotectonic implications of coseismic surface ruptures produced by the 2016 Mw 7.1 Kumamoto earthquake

“…The Hinagu–Futagawa fault zone is the western extension of the Median Tectonic Line (e.g., Kamata and Kodama 1994 ; Takagi et al 2007 ; Matsumoto et al 2015 ), which is composed of the NNE-SSW- to NE-SW-striking Hinagu Fault and NE-SW- to ENE-WSW-striking Futagawa Fault, and extends for ∼81 km in the central Kyushu Island (Fig. 1 ).…”

Secular Variation of Early Cretaceous Granitoids in Kyushu, SW Japan: The Role of Mélange Rocks as a Possible Magma Source

“…Published age dates of the granitic rocks using various methods (K-Ar, Rb-Sr, Sm-Nd, CHIME, U-Pb) on whole rock and minerals range from 143 to 75 Ma, whereas the mafic rocks yielded ages (K-Ar, Rb-Sr, U-Pb) that are comparatively more restricted and were emplaced from 123 to 97 Ma (Hattori and Shibata, 1982;Sasada, 1987;Osanai et al, 1993;Nakajima et al, 1995;Kamei et al, 1997Kamei et al, , 2000Kamei et al, , 2004Matsuura, 1998;Hamamoto et al, 1999;Owada et al, 1999;Takagi et al, 2000Takagi et al, , 2007Sakashima et al, 2003;Nishimura et al, 2004;Fujii et al, 2008;Kouchi et al, 2011;Miyoshi et al, 2011;Adachi et al, 2012;Tiepolo et al, 2012;Miyazaki et al, 2018). In comparison, the dacite and andesite yielded K-Ar mineral ages of 107 ± 3 Ma (Imaoka et al, 1993) and from 110 to 102 Ma (Imaoka et al, 1993;Matsuura, 1998;Owada et al, 1999), respectively.…”

Submarine slope–fan sedimentation in an ancient forearc related to contemporaneous magmatism: The Upper Cretaceous Izumi Group, southwestern Japan

“…Abbreviations for stratigraphy: Coniac., Coniacian; Sant., Santonian. References for radiometric age data: [1] Aoki et al (), [2] Imaoka, Nakajima, and Itaya (), [3] Takagi et al (), [4] Takagi et al (), [5] Takagi, Soda, and Yoshimura (), [6] Kishi et al (), [7] Imaoka et al (), [8] Imaoka and Ikawa (), [9] Imaoka et al (), [10] Yuge, Imaoka, and Iizumi (), [11] Ikawa et al (), [12] Suzuki, Adachi, and Nureki (), [13] Suzuki and Adachi (), [14] Suzuki, Adachi, and Kajizuka (), [15] Umeda et al (), [16] Tazaki et al (), [17] Kagami et al (), [18] T. Sato et al (), [19] Aoki et al (), [20] Nakahata, Isozaki, and Tsutsumi (), [21] Sonehara and Yagi (), [22] Matsumoto, Sawada, and Kagami (), [23] K. Sato et al (), [24] A. Noda et al (), [25] A. Noda, Danhara, Iwano, and Hirata (2017a), [26] Nakajima et al (), [27] Iida et al (), [28] D. Sato, Matsuura, and Yamamoto (2016a), [29] D. Sato, Yamamoto, and Takagi (2016b), [30] D. Sato (), [31] Terakado and Nohda (), [32] D. Sato (), [33] H. Ito et al (), [34] Miyata (), [35] Shibata and Uchiumi (), [36] Seike et al (), [37] Morioka, Tainosho, and Kagami (), [38] Watanabe et al (), [39] Kawakami and Suzuki (). Detailed version of this figure is presented in supporting information…”