著者

Kenta YOSHIDA Naoki AOYAGI Ryoji KATO Takao HIRAJIMA

出版者

一般社団法人日本鉱物科学会

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.111, no.6, pp.398-404, 2016 (Released:2017-01-12)

参考文献数

35

被引用文献数

1 5

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Thermal structure of the Kebara Formation and its proximal areas in the western Kii Peninsula was examined by Raman spectra of carbonaceous material (RSCM) geothermometer for pelitic rocks. A mean temperature of 313 ± 5 °C is obtained for the Kebara Formation, which is comparable with that of the neighboring unit of the Mikabu belt (319 ± 5 °C). The Sanbagawa belt of the relevant area, within a few kilometers to the north of the Kebara Formation, shows a mean temperature of 285 ± 7 °C, which is slightly but evidently lower value than those of the above two units. Peak temperatures estimated from the Chichibu belt and Shimanto belt located to the south of the Kebara Formation are 289 ± 13 °C and 216 ± 24 °C, respectively. Published geochronological data of the Kebara Formation are slightly older than those of the Sanbagawa belt in the Kii Peninsula and are similar to those of the Mikabu belt in the relevant area. These two data sets (geothermometry and geochronology) suggest that the Kebara Formation is possibly correlated with the Mikabu belt, but is not coherent to the southern margin of the Sanbagawa belt in the western Kii Peninsula, in tectonic contact with each other.

著者

Yu ITAMI Daisuke NAKAMURA Atsushi YASUMOTO Takao HIRAJIMA Martin SVOJTKA

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.220221, 2022 (Released:2022-10-28)

参考文献数

52

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The origins of eclogite associated with garnet peridotite in continent–continent collision belts are still debated. We performed petrological studies of eclogites collected from a garnet peridotite block from Nové Dvory in the Gföhl Unit of the Moldanubian Zone in the Variscan orogenic belt, Czech Republic. The eclogite was divided into three types: one kyanite (Ky)–bearing and two Ky–free types. Garnet and omphacite in the Ky–bearing eclogite have lower Fe contents than those in the Ky–free eclogite. Furthermore, the Ky–free eclogite was divided into two types on the basis of Ca content in garnet: Ca–rich (Xgrs > 0.32) and Ca–poor (Xgrs < 0.32) types, except for Ca–poor rim compositions. Application of conventional geothermobarometers to the Ky–bearing type and the Ky–free type with Ca–rich garnet yielded similar pressure–temperature (P–T) conditions (3.2–4.8 GPa and 920–1160 °C) to those of previous studies, whereas the Ky–free type with Ca–poor garnet yielded slightly lower P–T conditions (3.1–3.4 GPa and 950–990 °C) than the other two types. The observed chemical variation of garnet is probably due to the difference in origins, whereby, according to our new results and previous findings, the Ky–bearing eclogite was derived from plagioclase–bearing crustal gabbro, whereas the Ky–free eclogite with Ca–rich garnet was derived from a crystal cumulate possibly in the mantle wedge. In the Ky–free eclogite samples with Ca–poor garnet, chemical compositions of garnet and omphacite are different from those in the other Ky–free samples, and those samples with Ca–poor garnet would have a different origin from the others. One of the Ky–free type with Ca–poor garnet retains garnet grains with chemical zonings probably created during the prograde history, although the eclogite underwent the extremely high temperature (~ 1000 °C) metamorphism. Calculated diffusion distances in garnet reach 0.5 mm during 2 million years, even if we adopted a low value of diffusion coefficient data. Thus, the residence time of the eclogite at the peak meatamorphic conditions would have been shorter than at least 2 million years. The subsequent decompression and cooling after the peak metamorphism were also probably very fast to avoid the chemical homogenization of garnet.

著者

Wataru YABUTA Takao HIRAJIMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.190831, (Released:2020-10-28)

被引用文献数

1

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We present the first report of okhotskite in a lawsonite–blueschist–subfacies metachert of the Hakoishi subunit, Kurosegawa Belt, Kyushu, Japan, which was metamorphosed at peak temperatures and pressures of 200–300 °C and 0.6–0.8 GPa. This okhotskite–bearing assemblage is particularly notable because it formed at higher pressures than that of previously documented okhotskite with available pressure estimations. Textural relationships indicate that okhotskite formed during peak metamorphism in equilibrium with piemontite, Na pyroxene, magnesioriebeckite, braunite, and hematite. Okhotskite shows a significant variation in Fe:Mn ratio (Fetot/Mntot = 0.13–0.56) and a following average empirical formula; (Ca7.62Mn2+0.16)Σ7.78(Mn2+2.71Mg1.29)Σ4.00(Mn3+4.13Fe3+2.26Al1.36V3+0.23Ti0.02)Σ8.00Si11.86O44.02(OH)16.98. Raman spectra of okhotskite are reported for the first time and show characteristic peaks at 362, 480, and 563 cm−1. The stability relationships between okhotskite and other Mn–bearing minerals, such as piemontite, sursassite, spessartine, braunite, and Mn–bearing lawsonite, are examined using a revised Schreinemakers’ analysis. The obtained petrogenetic grid provides tight constraints on the P–T relationship of natural mineral assemblages observed in Mn–bearing cherts within epidote–blueschist–grade and lawsonite–blueschist–grade. Furthermore, this petrogenetic grid predicts that the assemblage of okhotskite and Mn–bearing lawsonite should be stable at higher pressures. The higher–pressure stability suggests that highly oxidized Mn–bearing metacherts can transport water and buffer oxygen in the deeper parts of subduction zones, given that okhotskite and Mn–bearing lawsonite contain high water contents (6.9 and 11.3 wt% H2O, respectively) and trivalent manganese.

著者

Kenta YOSHIDA Takao HIRAJIMA

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.107, no.1, pp.50-55, 2012 (Released:2012-02-29)

参考文献数

21

被引用文献数

5 5

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Annular fluid inclusions were found in a foliation-parallel quartz vein intercalated with metapelites from the Besshi area of the Sanbagawa belt, SW Japan. The preserved “foam microstructure” of the quartz vein suggests low differential stress at high temperatures for its formation. Three types of fluid inclusions have been identified: the earliest one, FIA-I, is characterized by two phase inclusions arranged along intragranular planes and mainly composed of aqueous saline fluid and CH4 gas; FIA-II texturally comparable to FIA-I consists of CH4-N2-CO2-H2 gas phase inclusions with rare two-phase inclusions; the latest type, FIA-III, is characterized by arrangements along transgranular planes consisting of two-phase inclusions mainly composed of CH4-N2 vapor in aqueous saline fluid. Amongst them, FIA-I contains annular fluid inclusions, which are attributed to reequilibration due to a confining pressure increase, suggesting that the host rock underwent the compression after the entrapment of FIA-I. Textural observations and chemical characteristics show that FIA-I and -II were trapped during prograde or near the peak metamorphic stage, and that FIA-III was probably trapped at an early stage of the exhumation.

著者

Kenta YOSHIDA Takao HIRAJIMA

出版者

一般社団法人日本鉱物科学会

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.110, no.5, pp.197-213, 2015 (Released:2015-11-11)

参考文献数

49

被引用文献数

5

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Garnet with a complex compositional zoning was found from the northern edge of the Western Iratsu body in the Sanbagawa metamorphic belt of the Besshi district, southwest Japan. The studied garnet shows incipient Mn–reverse (increase) zoning from the center part and subsequent Mn–bell shape type (decrease) zoning towards the outer part, which is almost identical to the ‘Mn–caldera shaped zoning’ described by Xu et al. (1994) and Banno and Nakamura (2004). In order to display the chemical characteristics sterically, three–dimensional X–ray chemical mapping was performed for one very–coarse grain of garnet. The result clearly displays that there is a high–Mn layer with faceted euhedral shape of the garnet at the intermediate part, and that its composition continuously changes from the inside to the outside. Inclusion arrays in garnet getting across the high–Mn layer also suggest the continuous growth of the garnet. In the same sample, garnets without Mn–caldera shaped zoning are ubiquitously observed, which are relatively small in size up to 5 mm in diameter. Inclusion mineral assemblage in garnet and Raman barometry suggest the peak P–T conditions of the studied sample not having reached the eclogite facies, but being the epidote–amphibolite facies. The formation process of the ‘Mn–caldera shaped zoning’ can be best explained by the disequilibrium crystal growth under oversaturation of garnet in MnO–(MgO + FeO) binary system. Such oversaturation can be triggered by rapid heating. The finding of the remnant of rapid heating event would provide an important clue to discuss the exhumation history of the Sanbagawa metamorphic belt.

著者

Kenta Yoshida Rustam Orozbaev Takao Hirajima Akira Miyake Akira Tsuchiyama Apas Bakirov Akira Takasu Kadyrbek Sakiev

出版者

GEOCHEMICAL SOCIETY OF JAPAN

雑誌

GEOCHEMICAL JOURNAL (ISSN:00167002)

巻号頁・発行日

vol.52, no.1, pp.59-67, 2018 (Released:2018-02-02)

参考文献数

42

被引用文献数

5 5

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Direct chemical analysis of a single fluid inclusion was conducted by micro-excavation at cryo-temperatures. A scanning electron microscope (SEM) equipped with a focused ion beam (FIB), an energy dispersive X-ray spectrometer (EDS), and a cold stage, were used to analyze the chemical composition of the sample fluid inclusion, which was trapped in the ultrahigh-pressure (UHP) talc-garnet-chloritoid schist obtained from the Makbal metamorphic complex, Kyrgyz. Conventional techniques such as microthermometry and cryo-temperature and room-temperature Raman spectroscopy enabled the detection of NaCl and CaCl2 as solute species in the fluid inclusions, as well as high salinity of 20.5 mass% CaCl2 and 1.7 mass% NaCl with the assumption of a NaCl-CaCl2-H2O ternary system. However, additional chemical analysis using the present cryo-FIB-SEM-EDS system further revealed the presence of K as a solute element, which is hardly identified by conventional techniques. Petrographic examination of the fluid inclusions indicated that they had been trapped during the exhumation stage of the UHP talc-garnet-chloritoid schist, possibly originating from the decompression breakdown of lawsonite. The data acquired from the present study challenges previous reports of the existence of simple chemical system of aqueous fluids in high-pressure and UHP metamorphic terrane in eastern Asia. This is imperative because misidentification of solute species introduces errors into salinity estimation, resulting in inaccuracy propagation in quantitative analytical processes such as LA-ICP-MS. A detailed fluid inclusion petrography would thus require accurate quantitative analysis involving FIB-based sample-preparation and SEM-EDS analysis.

著者

Adil KASYMBEKOV Akira TAKASU Md Fazle KABIR Shunsuke ENDO Apas B. BAKIROV Kadyrbek SAKIEV Rustam OROZBAEV Takao HIRAJIMA Kenta YOSHIDA

出版者

The Association for the Geological Collaboration in Japan

雑誌

地球科学 (ISSN:03666611)

巻号頁・発行日

vol.74, no.2, pp.47-64, 2020-05-25 (Released:2020-07-05)

参考文献数

43

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キルギス北部天山に分布する高圧-超高圧変成作用を受けたマクバル・コンプレックス(Makbal Complex)中のネルディ層(Neldy Formation)のざくろ石を含まない泥質片岩(KG1251)と含ざくろ石-クロリトイド泥質片岩(KG1244)の岩石記載と地質年代の測定を行った.KG1251 の主要造岩鉱物はフェンジャイト,緑泥石と石英であり,その他に少量の曹長石,チタン石,方解石,ルチル及び炭質物を含む.ピーク変成条件はT < 630 ℃,P = 0.9-1.7 GPa が見積もられた.片理を形成するフェンジャイトのK-Ar 年代は524 ± 13 Ma であり,これはこれまでに報告されているマクバル・コンプレックスのエクロジャイト及びざくろ石-クロリトイド-タルク片岩のピーク変成年代(ca. 500 Ma)と調和的である.KG1244 の主要構成鉱物は白色雲母(コアがフェンジャイト,リムが白雲母),緑泥石,石英であり,その他に少量のざくろ石,クロリトイド,曹長石,電気石,ジルコン,モナザイト,チタン石,ルチル,方解石及び炭質物を含む.ピーク変成条件はT = 485-545 ℃,P = 1.2-1.5 GPa の高圧型変成作用を示し,その後,T = ca. 500 ℃,P > 0.3 GPa の低圧型変成作用を受けた.この変成作用は花崗岩体の貫入にともなう接触変成作用と考えられた.本研究で得られた白色雲母のK-Ar 年代(474 ± 12 Ma)は,この地域に分布するオルドビス紀の花崗岩の年代(ca. 460 Ma)と調和的である.KG1251 及びKG1244 のネルディ層の泥質片岩の変成条件は,マクバル・コンプレックスの構造・層序学的に下部を占めるエクロジャイトやざくろ石-クロリトイド-タルク片岩に比べて有意に低圧であることが明らかになった.

著者

Kenichiro KAMIMURA Takao HIRAJIMA Yoshiyuki FUJIMOTO

出版者

一般社団法人日本鉱物科学会

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.1204050196-1204050196, (Released:2012-04-07)

被引用文献数

1 5

著者

Kenta YOSHIDA Takao HIRAJIMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.1202160190, (Released:2012-02-18)

被引用文献数

5 5

著者

Kenta YOSHIDA Yoshiteru SENGEN Shigeki TSUCHIYA Kouta MINAGAWA Tomoyuki KOBAYASHI Taketoshi MISHIMA Shinji OHSAWA Takao HIRAJIMA

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.106, no.3, pp.164-168, 2011 (Released:2011-07-05)

参考文献数

26

被引用文献数

5 5

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A remarkably high Li/B ratio has been recognized from a crush-leached fluid extracted from a foliation-parallel quartz vein, IR27, intercalated with a pelitic schist in the northern proximal to the Western Iratsu body of the Sambagawa metamorphic belt, SW Japan. Thin section observation shows that most quartz grains in the vein are polygonal and rarely show the undulatory extinction. These facts suggest that the quartz grains in the vein could be recrystallized under relatively high-T condition with the stress free environment, and that these fluid inclusions could be trapped during the peak metamorphic stage. Most fluid inclusions in the investigated sample are composed of liquid and vapor. Raman spectroscopy revealed that the liquid phase is aqueous fluid and the vapor is mainly a mixture of CH4 and N2. Their ice melting temperatures determined by microthermometry, ranging from -3.5 to -7.1 °C, show a striking contrast against the data of the fluid inclusions in later stage veins, ranging from -0.6 to -1.7 °C. However, the homogenization temperatures of IR27 are much lower than the peak metamorphic temperature of the host pelitic schist. The partition coefficients between the host rock and released fluid (Drock/fluid) calculated from P-T pseudosection show that DBrock/fluid tends to be higher than DLirock/fluid in a pelitic system, because of generally high modes of white mica in pelitic schists. The calculation suggests that the crush-leached fluid obtained from the quartz vein intercalated with the pelitic schist has higher Li/B ratio than fluids of those intercalated with the metabasite.