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愛媛大学大学院理工学研究科
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研究室紹介南極の写真新着トピックス授業科研費新着研究成果最近の論文

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Labo1

第44次南極地域観測隊夏期(2002年 12月〜2003年1月)沿岸調査隊の記録 


SkallevigsHalsenShegget
氷河の融水を集めた湖畔にベースキャンプ設営.湖水は左中程の隘 路から一気に海へ落下する.スカーレン露岩域とスカーレン氷河が遠 望できる.氷河の向こうは氷の南極大陸が延々と広がっている.スカレビーグスハルゼン 030118南極の夏が終わろうとすると,低い太陽光がシェッゲの岩壁に映える.海面のチラチラしたチリのようなものは氷りだした細かい氷の核.030127

RiiserLarsenEmeyIceShelf
3日間吹き荒れたA級ブリーザードの後,くっきりとリーセルラルセン山 が遠望できた.調査予定日数オーバーのため上陸断念.無念なり!他日に捲土重来を期す.030222大音響とともに崩れるエメリー棚氷.棚氷上面のようすは,しらせの上部操舵室(通称鳥かご)からも視認できなかった.030302
PenguinsPenguins2
南極といえば,この人たち!アムンゼン湾明るい岬、ペンギンルッカリー.
SealsSeal (2)
アザラシ.海氷に穴をあけて,海に入る.厚さ1m以上もある海氷にどうやって穴をあけるのだろう?アムンゼン湾日向ぼっこを楽しむアザラシ君.


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岩鉱セミナー
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セミナーの熱い議論の後,ビールで喉を潤し,できあがった面々.

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授業


授業題目対象学生開講学期
地球科学T理学部1回生前学期
地学実験理学部3回生前学期
岩石学概論地球科学3回生前学期
岩石鉱物学実験T地球科学3回生前学期
岩石鉱物学実験U地球科学3回生後学期
地球科学課題研究地球科学3回生後学期
岩石鉱物学特論地球科学3回生後学期
地球科学機器分析実習地球科学4回生前学期
地球科学特別演習地球科学4回生通年
岩石学特論数理物質科学専攻
地球進化学コース1年
後学期
地球科学特別実験T数理物質科学専攻
地球進化学コース1年
前学期
地球科学特別実験U数理物質科学専攻
地球進化学コース1年
後学期
地球科学特別実験V数理物質科学専攻
地球進化学コース2年
前学期
地球科学プレゼンターション
特別実習I
数理物質科学専攻
地球進化学コース1年
後学期
地球科学プレゼンターション
特別実習II
数理物質科学専攻
地球進化学コース1年
前学期
地球科学プレゼンターション
特別実習III
数理物質科学専攻
地球進化学コース2年
後学期
地球科学プレゼンターション
特別実習IV
数理物質科学専攻
地球進化学コース2年
前学期
地球科学ゼミナールI数理物質科学専攻
地球進化学コース1年
後学期
地球科学ゼミナールII数理物質科学専攻
地球進化学コース1年
前学期
地球科学ゼミナールIII数理物質科学専攻
地球進化学コース2年
後学期
地球科学ゼミナールIV数理物質科学専攻
地球進化学コース2年
前学期
数理物質学特別研究数理物質科学専攻1〜3年通年
数理物質学特別演習数理物質科学専攻1〜3年通年
地球進化学特論U数理物質科学専攻1年後学期


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科研費の補助を受けている研究

現在、日本学術振興会から以下の研究課題について補助を受けている。
科学研究費補助金の補助により得られた研究成果は新着研究成果最近の論文に掲げた。

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新着研究成果

Högbomite from West Ongul Island, East Antarctica.
Kawasaki, T., Hamada, S., 2011. Goldschmidt Conference, 15 August, Prague, Czech Republic.

Abstract

Högbomite has been found within magnetite megacrysts (5 cm x 3 cm) from the upper amphibolite- to granulite-facies pegmatite cutting the medium-grained quartzo-feldspathic garnet-biotite gneiss at West Ongul Island, Lützow-Holm Complex, East Antarctica. Associated minerals included in magnetite are biotite, plagioclase, hercynite, sillimanite, corundum, quartz, rutile, ilmenite, hematite, and zircon. Högbomite occurs as very fine euhedral to subhedral crystal (5-20 μm) along grain boundaries between magnetite and ilmenite or less commonly enclosed in hercynite (Fig. 1) and in magnetite. Quartz is found in hercynite. Högbomite is in direct contact with hercynite. Ilmenite contains hematite exsolution lamellae. Hematite also forms exsolution lamellae in rutile, which is trapped in ilmenite. Corundum is in direct contact with magnetite, hercynite or sillimanite. Electron microprobe analyses of högbomite yield 2.6-7.9 wt% TiO
2, 60-64 wt% Al2O3, 0-0.1 wt% Cr2O3, 18-25 wt% Fe (as FeO), 0.3-0.6 wt% MnO, 2.9-4.4 wt% MgO, 4.8-10 wt% ZnO, 0.61-0.01 wt% SnO2, and 0.20-0.36 XMg. Hercynite varies 4.9-14 wt% ZnO and 0.23-0.36 XMg. Sillimanite contains 0.6-3.6 wt% Fe2O3 from rim to core and < 0.1 wt% TiO2. Textures and mineral chemistry suggest that the reaction, Mag + Ilm + H2O + O2 to Hög + Hc + Qtz, took place at retrograde stage (T < 600 °C) whereby magnetite and ilmenite contained impurities Si, Al, Zn and Mg. Hydrous and oxidized fluid, possibly supplied by crystallization process of pegmatite, were sufficiently enough to form högbomite and biotite. Subsequent cooling processes hematite crystallized as exsolution lamellae from ilmenite and rutile, and andalusite and corundum became Fe2O3-poor at the rim. The P-T path of the retrograde metamorphism is estimated from assemblages of Spl+Qtz, Spl+Hög, Ms+Pl, Ilm+Mag, Sil, And, Crn, Dsp, Rt, Ant (Fig. 2).
HogSplQtzMagWestOngulAl2SiO5PhaseDiagram
Figure 1: Backscattered image of högmatite + hercynite and hercynite + quartz in magnetite.Figure 2: Drawing of the possible P-T path from assemblage of Spl+Qtz, Ms+ Pl, Dsp, Crn, Sil, And, Rt, Ant, Mag.


Experimental study on the phase relations of granitic and andesitic crustal rocks at 8.0 GPa pressure. 9th International Eclogite Conference, 7 August, Mariánské Láznĕ, Czech Republic.
Kawasaki, T., Osanai, Y., 2011.

沈み込むプレートにより,地球深部にもたらされた地殻下部物質の変化を調べるために,北海道日高変成帯中軸部に産する泥質グラニュライト(Osanai et al., 1992; 表 1)を用いて,超高圧力条件(8.0 GPa)で再結晶化実験を行った.コーサイトエクロジャイトの鉱物組み合わせザクロ石+単斜輝石+藍晶石+コーサイト)をもつ実験生成物を得た(図1).これは,系中のほとんどのNa2O,K2O成分が単斜輝石に固溶したためである.衝突帯で形成される超高圧変成岩の大部分は花崗岩質岩である(Liou et al 1994; Schreyer 1995; Coleman Wang 1995; Chopin 2003).我々の予察的実験で明らかなように,花崗岩質岩は高圧力下で無水条件ではザクロ石+単斜輝石+藍晶石+コーサイトの鉱物組み合わせを持った岩石(エクロジャイト)になる.この岩石の主要構成鉱物である単斜輝石にほとんどのNa2O,K2O成分が溶け込むと同時に過剰のSiO2成分やAl2O3成分が固溶する.

Abstract

    We carried out ultrahigh-pressure experiments on the granitic and andesitic crustal rocks at 8.0 GPa pressure at temperatures from 1100 °C to 1500 °C for 30 minutes to 8 hours under the dry conditions to study the phase relations of the ultrahigh-pressure eclogites, which deeply subduct into the Earth’s interior. We prepared two types of starting materials: (1) the pelitic granulite from Tertiary Hidaka metamorphic belt in Hokkaido (Osanai et al., 1992), bulk composition of which is equivalent to granitic crustal rocks; and: (2) the high-magnesian andesite from Miocene Setouchi volcanic belt in northeastern Shikoku (Kawasaki et al., 1993).
    We found the assemblage of coesite, kyanite, clinopyroxene significantly oversaturated in SiO
2 containing a large amount of jadeite and garnet deficient in Al2O3 with a fairy amount of pyroxene components in the granulite system. On the other hand, kyanite was absent and coesite was rare in the andesite system. The difference between the mineral assemblages in the two systems is dependent on the SiO2 and Al2O3 contents of the bulk composition. We obtained the following results from chemical analyses and microscopic observations of the run products:
    1. Contents of Na
2O and K2O in clinopyroxene at UHP conditions should be constrained by the bulk composition of the system.
    2. The amount of clinopyroxene increases with increasing SiO
2, simultaneously with decreasing Na2O and K2O.
    3. The tschermak content in clinopyroxene depends on the amount of kyanite in the system.
    4. Coesite and kyanite buffer the solubility of Na2O and K
2O in clinopyroxene at ultrahighpressure metamorphic conditions.
8GPa1500CIbuki8GPa1500C
Run product from the metapelite system obtained at 8.0 GPa and 1500 oC for 30 min.Run product from the high-Mg andesite system obtained at 8.0 GPa and 1500 oC for 30 min.
CrnWoPxlightcreamCrnPxJdlightcream
Al2O3-CaSiO3-MSiO3 plot of coexisting garnet and clinopyrox- ene and clinopyroxene.Al2O3-MSiO3-(Na,K)AlSi2O6 plot of coexisting garnet and clinopyroxene.



Experimental study of Fe2O3 solubility in silimanite and kyanite to calibrate the Fe3+-in-Al2SiO5 geothermometer for ultrahigh-temperature granulites.
Kawasaki, T., Osanai, Y., Ishizuka, H., 2011. 11th International Symposium on Antarctic Earth Sciences, 12 July, Edinburgh, Scotland.

Al2SiO5 物への Fe3+ 溶量を調べた.出発物質は(1)珪線石(東南極リュツオホルム岩体ルンドボークスヘッタで採取;0.6 wt% Fe2O3)とヘマタイト(混合比 95:5);(2) meta-ironstone (ナピア岩体リーセルラルセン山で採取)を使用した.これらを Pt および AuPd 試料容器内で約 1000 時間焼結した.実験温度は 1050ºC とした.実験生成物と実験結果を(Fig. 1)に示した.Al2SiO5 鉱物への Fe3+ の固溶量は圧力とともに増加した.また,共存相により Al2SiO5 鉱物の Fe3+ 固溶量は系統的異なる.ヘマタイトと共存する Al2SiO5 鉱物はイルメナイトと共存する Al2SiO5 鉱物よりも Fe3+ 固溶量は大きいという結果を得た.これは,酸素分圧とともに Al2SiO5 鉱物の Fe3+ 固溶量が増加することを示している.また,1 気圧大気中での焼結実験の結果から,温度とともに Fe3+ 固溶量は増加することが分かった.

Abstract
We report experimental results on the Fe3+ solubility in sillimanite at pressures from 1 atm in air up to 15 kbar and at temperatures from 800 to 1330 °C using an electric furnace and a piston-cylinder apparatus. For starting materials, we used (1) a mixture of the reagent-grade hematite gel and powdered sillimanite, containing 0.6 wt% Fe2O3, from Rundvågshetta in the Lützow-Holm Complex, East Antarctica, and (2) a powdered meta-ironstone composed of ilmenite, garnet, sillimanite (0.7 wt% 
Fe2O3) and quartz from Mt. Riiser-Larsen, Napier Complex, East Antarctica.
The mixture of sillimanite and hematite and the powdered metaironstone were reacted for 548‐3744 hours in the Pt and AuPd capsule, respectively. The 
Fe2O3 content of sillimanite increases from 1.0 wt% at 5 kbar to 2.4 wt% at 15 kbar in the sillimanite-hematite system (Fig. 1 Left) followed by the reaction Al2SiO5 (Sil) + Fe2O3 (Hem) = Fe2SiO5 (Sil) + Al2O3 (Crn). In the meta‐ironstone system Fe2O3 slightly increases from 1.0 wt% at 5 kbar to 1.5 wt% at 15 kbar (Fig. 1 Middle) by the buffering reaction Fe2O3 (Ilm) + SiO2 (Qtz) = Fe2SiO5 (Sil). The results indicate the Fe2O3 content in sillimanite increases with temperature, pressure and oxygen fugacity (Fig. 1 Right).


SilHem11-1050Metaironstone11-1050FeinSilP
Fig. 1. Run products recrystallized at 11 kbar, 1050ºC for 1045 hours (Left: Al2SiO5-Fe2O3 system in Pt capsule; Middle: meta-ironstone in AuPd capsule) and experimental results at 1050ºC (Right).


Osumilite and spinel + quartz association in garnet-sillimanite gneiss from Rundvågshetta, Lützow-Holm Complex, East Antarctica
.

Toshisuke Kawasaki
, Nobuhiko Nakano, Yasuhito Osanai. 
Gondwana Research 19, 430-445, 2011.


東南極リュツオホルム岩体ルンドボ−クスヘッタのグラニュライト相変成岩のザクロ石斑状変晶中に包有された大隅石を初めて見出した.また,スピネル+石英の鉱物組み合わせもザクロ石斑状変晶中に見出した.大隅石やスピネル+石英の産状は,この地域が超高温変成作用を被り,時計回りに変成温度圧力が変化したことを示している.

This is the first report of osumilite occurring as fine isolated inclusions within garnet porphyroblasts, as observed in garnet-sillimanite gneiss from Rundvågshetta, Lützow-Holm Complex, East Antarctica. The osumilite is characterized by high Si content (10.60 and 10.95 atoms based on 30 oxygens per formula unit), low Al content (2.99 and 3.82), a high content of M site-occupying cations (2.51 and 3.03), and hig XMg values (about 0.81). We also report a spinel + quartz association found as inclusions within garnet porphyroblasts. Spinel grains, which are in direct contact with quartz and are spatially associated with sillimanite, show extremely high Zn contents (XZn=0.330.46) and high XMg values (0.450.54). The garnet is rimmed by sillimanite, K-feldspar, plagioclase, and quartz. Biotite and cordierite are found only as inclusions within garnet porphyroblasts, where biotite coexists with spinel-quartz or with rutile. Porphyroblastic garnet contains rutile needles and has low  XMg values (about 0.36). The sillimanite contains a high Fe content (about 1.2 wt% Fe2O3).  
Inclusion_BRVH_Inclusions_BSEI_E



The occurrence of osumilite and spinel + quartz indicates a clockwise pressuretemperature path of ultrahigh-temperature metamorphism, involving the following events: (1) the Rundvågshetta granulites suffered prograde metamorphism within the kyanite and sapphirine + quartz fields; (2) subsequent retrograde metamorphism, involving near-isothermal decompression, occurred in the orthopyroxene + sillimanite + quartz field; (3) the granulites passed through the garnet + cordierite + sillimanite + quartz field during decreasing temperature; (4) the granulites entered the osumilite stability field at around 8 kbar and 950 °C; and (5) the granulites retain a final record of retrograde metamorphism within the biotite + sillimanite + K-feldspar and quartz field at 6.1 kbar and about 830 °C.


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Ilmenite-rutile intergrowth in garnet-sillimanite gneiss from Skallevikshalsen, Lützow-Holm Complex, East Antarctica: Implications for ultrahigh-temperature metamorphism
Toshisuke Kawasaki, Chie Shirakawa, Nobuhiko NakanoYasuhito Osanai. Abstract of Annual Meeting 2009 of the Mineralogical Society, MAPT: MicroAnalysis of Processes and Time, Edinburgh, Scotland
東南極リュツオ岩体スカレビークスハルセンの珪線石ザクロ石片麻岩中にフェロシュードブルッカイトの組成を持ったイルメナイト+ルチルが共生したドメインを見つけた下図イルメナイト+ルチル共生部の一部はルチルに取り囲まれ,イルメナイトと直接している.FeO-TiO2系の相平衡図 (Lindsley, 1991) によると,フェロシュードブルッカイト+イルメナイト+ルチルの3相が共存する温度は,1気圧では,1140ºC以上の高温である.フェロシュードブルッカイトには,少量のMgO(3 wt%)を含んでいるので,Lindsley (1991) の相平衡図をそのままの形で適用することはできないが,この地域はすくなくとも1000ºC を超える超高温変成作用 (Kawakami and Motoyoshi 2004) を被ったことが明らかになった.

Abstract
An ilmenite-rutile intergrowth in contact with rutile within ilmenite (Fig.1) is found in garnet-sillimanite gneiss from Skallevikshalsen, a locality that occurs within the ultrahigh-temperature (UHT) metamorphic region of the Lützow-Holm Complex, East Antarctica (Motoyoshi et al., Geol Soc Spec Publ, 43, 325-329, 1989; Hiroi et al., Geological evolution of Antarctica, 83-87, 1991; Motoyoshi & Ishikawa, Terra Antarct Publ Siena, 65-72, 1997; Kawakami & Motoyoshi, J. Mineral Petrol Sci, 99, 311-319, 2004). Skallevikshalsen is underlain by layers of orthopyroxene-hornblende gneiss, garnet-sillimanite gneiss, garnet-biotite gneiss, marble, skarn and metabasite (Yoshida et al Antarctic Geol Map Ser 9 National Institute of Polar Research, 1976). 

09MAPT_Abstract_Kawasaki_color2.jpg
Fig. 1. Photomicrograph of garnet-sillimanite gneiss (left) and back scattered electron image (BSEI) of ilmenite-rutile intergrowth (right) from Skallevikshalsen. Ilm+Rt, ilmenite-rutile intergrowth; other mineral abbreviations as per usual.

The gneiss consists of porphyroblastic garnet with needle rutile, sillimanite, K-feldspar, plagioclase and quartz. Ilmenite is found in contact with prismatic sillimanite, quartz, plagioclase and/or K-feldspar. An Fe-Mg-Ti compositional domain with a ferropseudobrookite composition and atomic Mg/(Mg+Fe) ratio of 0.2 is partially mantled by rutile within Mg-poor ilmenite (Fig. 1). Raman spectroscopy reveals that this Fe-Mg-Ti domain is comprised by an ilmenite-rutile intergrowth.

UHT metamorphism around Rundvågshetta in the Lützow-Holm Complex (Motoyoshi et al. 1989; Hiroi et al. 1991), took place at 1000-1040°C and 11.5-15 kbar (Kawasaki et al., Proc NIPR Symp Antarct Geosci, 6, 47-56, 1993; Kawasaki & Motoyoshi, Antarctica: Contributions to Global Earth Sciences, 23-36, 2006; Yoshimura et al., Geol Soc London Spec Publ, 308, 377-390, 2008). The present finding of ilmenite-rutile intergrowth and the phase-relation experiments on FeO-TiO2 minerals (Lindsley, Rev Mineral, 25, 69-106, 1991; Kawasaki et al, unpubl.) supports a clock-wise P-T path model (Motoyoshi & Ishikawa 1997) for UHT metamorphism in the Lützow-Holm Complex.


References
Lindsley 1991 in Oxide Minerals Rev Mineral 25 69-106

Kawakami & Motoyoshi 2004 Jour Mineral Petrol Sci 99 311-319

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Experimental study of Fe3+ solubility in cristobalite and its application to a metamorphosed quartz-magnetite rock from Mt. Riiser-Larsen area, Napier Complex, East Antarctica
Toshisuke Kawasaki, Hideo Ishizuka. Journal of Mineralogical and Petrological Sciences, 103, 255-265, 2008
クリストバライトなどシリカ鉱物中のFe2+含有量が温度変化に大きく依存することを1気圧における焼結 実験で示した.実験結果を東南極ナピア岩体リ−セルラルセン山地域の変成石英マグネタイト岩(meta-quartz-magnetite rock, meta-ironstone)に応用した.その結果,この変成石英マグネタイト岩は,5−15 キロバールの圧力条件で,994 −1095 ºC の温度範囲で変成作用を受けたと推測される.
Abstract
    This report concerns the Fe3+ solubility in cristobalite coexisting with hematite obtained from heating experiments in air at 990−1460 ºC in the SiO2Fe2O3 system. The ferric iron substitutes for the tetrahedral silicon in cristobalite and Si4+ also substitutes for the octahedral Fe3+ in hematite. Combining the chemical and P−T data of the quartz in the high-pressure eclogite from Sanbagawa belt, central Shikoku, Japan with the present experimental data, we found the content of ferric iron in quartz increases with increasing pressure and temperature: 

                        lnXFe= (−1092−5.254T+7.75P)/T

where 
XFe, T and P are the number of Fe atoms in quartz per formula unit based on a 2-oxygen atom normalization (cationic mole fraction of Fe), temperature in Kelvin and pressure in kbar, respectively. This new geothermometer is applied to the ultrahigh-temperature metamorphosed quartz-magnetite rock from Mt. Riiser-Larsen area, Napier Complex, East Antarctica, resulting that the metamorphic temperatures are estimated as about 994−1095 ºC
for pressures 5−15 kbar.
Fe_profile_in_QtzFe3_in_QtzcolorP-T5


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Empirical thermometer of TiO2 in quartz for ultrahigh-temperature granulites of East Antarctica
Toshisuke Kawasaki, Yasuhito Osanai. Geological Society of London, Special Publications, 308, 419-430, 2008
東南極ナピア岩体バント島に産する石英長石質片麻岩の石英斑状変晶には針状のルチルの離溶ラメラがみられる(写真a).この針状ルチルの離溶組織を含んだ 石英(TiO2 含有量は 0.082 wt%)を 1300 ºC で 39 日間焼結した(写真b).生成物のクリストバライトでは,反応部が未反応部を縞状に切っていた(写真b,c).反応部の TiO2 含有量は 0.149 wt% まで達していた.同時に焼結した TiO2−SiO2 系のクリストバライト(写真d)では,0.767 wt% の含有量を示した.温度上昇に伴いシリカ鉱物中の TiO2 量は増加するので,この増加量を推測するために地質学的記載岩石学的によく調べられている変成岩の石英を分析した.使用した変成岩は,愛媛県新居浜市東赤 石山の石英エクロジャイトや東南極リュッツオホルム岩体やナピア岩体の超高温変成岩類である.既存の石英温度計は,今回得られた新しい石英温度計よりも 200 ºC ほど高温の推定温度を与える.
Abstract
   Two preliminary experiments, heating of rutilated quartz grains with 0.082 wt% TiO2 in average from Bunt Island, Napier Complex, East Antarctica and the synthetic TiO2−SiO2 (rutile−cristobalite) system in the air at 1300 ºC for 39 days, showed increasing solubility of TiO2 in silica minerals with temperature. Bunt quartz was converted to cristobalite and traversed by many transparent seams with the disappearence of needles and spots of rutile.  Unreacted host grains retained many fine needles of rutile. Seams are rather homogeneous and slightly enriched in TiO2 up to 0.149 wt% in average, which is about one-fifth lower than that of the synthesized TiO2−SiO2 cristobalite with 0.767 wt% in average. Area analyses with an electron beam in the raster mode at magnification of 5000 gave 0.308 wt% TiO2 for the bulk composition of the Bunt quartz. This indicates that needles of rutile exsolved from the TiO2-saturated quartz at the cooling stage, more explicitly, during the retrograde metamorphism.
    Natural examples of quartz in geologically and petrologically well-characterized metamorphic rocks were chemically analyzed to examine the temperature controls on the Ti saturation level in quartz.  The TiO
2 content of quartz in equilibrium with rutile increases sensitively with the metamorphic temperature, which can be expressed as

 T-5895
where X means the mole fraction of TiO2 or the number of Ti atoms per formula unit based on a 2-oxygen atom normalization. This empirical equation is very useful to evaluate the metamorphic temperatures for ultrahigh-temperature granulites. The temperatures calculated by the existing Ti-in quartz thermometer are about 200 ºC higher than those estimated by the present thermometer potentially due to the underestimates of Ti-solubility in quartz in the previous calibration.
RtQtz_Fig4originalcolor

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Solubility of TiO2 in garnet and orthopyroxene: Ti thermometer for ultrahigh-temperature granulites

Toshisuke Kawasaki, Yoichi Motoyoshi. In Antarctica: A Keystone in a Changing World – Online Proceedings of 10th ISAES, edited by A. K. Cooper and C. R. Raymond et al.,USGS Open-File Report 2007-1047, Short Research Paper 038, 4 p.; doi 10.3133/of2007-1047.srp038, 2007
ルチルや石英と共存するザクロ石や斜方輝石への TiO2 の固溶度を 2 個の南極のグラニュライトを使って 7−20 kbar の圧力範囲および 850−1300 ºC の温度範囲で調べた.ザクロ石では,Ti は 4 配位の Si を置換するようだ.6 配位の Al-Al を M-Ti (M は Fe や Mg)で置換する積極的な証拠や,ザクロ石の 8 配位の歪んだ六面体のM-Mを □-Ti (□は空孔)で置換する証拠は超高温変成岩の温度圧力領域では見出せなかった.温度増加に伴いザクロ石中の TiO含 有量は増加するが,圧力の増加に伴い減少する.斜方輝石では,Ti は 4 配位と 6 配位の元素を置換し,温度や圧力と共に Ti は増加する.斜方輝石やザクロ石では,Ti 含有量の圧力依存性は温度依存性と比較するとあまり大きくない.
Abstract

    We report the TiO2 solubility in garnet and orthopyroxene coexisting with rutile calibrated from the experimental data at pressures 7−20 kbar and temperatures 850−1300
ºC in the two Antarctic granulite systems. The Ti would substitute for the tetrahedral Si, whereas we could not find positive evidence of the coupled substitution of M-Ti (M is Mg or Fe) for Al-Al in octahedral sites as well as the interstitial substitution of □-Ti (□ is a vacancy) for M-M in triangular-dodecahedral sites of garnet at ultrahigh-temperature (UHT) metamorphic conditions. The TiO2 content of garnet increases with temperature and decreases with pressure. In orthopyroxene Ti substitutes for the atoms in the tetrahedral and octahedral sites. The Ti content of orthopyroxene increases with temperature and increases with pressure.
The titanium solubility in garnet and orthopyroxene is not so sensitive to pressure change as compared with temperature dependence given by following empirical equations:

T-15366

where X is the mole fraction of Ti or Si on the tetrahedral sites and temperature is given in Kelvin.

     Ti_in_GrtOpx

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最近の論文

  1. Kawasaki, T., Hamada, S., 2011. Högbomite from West Ongul Island, East Antarctica. Mineralogical Magazine, Vol. 75 (3), 1161-1161.
  2. Kawasaki, T., Nakano, N., Osanai, Y. 2011. Osumilite and spinel + quartz association in garnet-sillimanite gneiss from Rundvågshetta, Lützow-Holm Complex, East Antarctica. Gondwana Research, 19, 430-445.
  3. T. Kawasaki , N. Nakano and Y. Osanai (2008): Metamorphic P-T path of Rundvågshetta, Lützow-Holm Complex, East Antarctica inferred from inclusions of osumilite and spinel + quartz within garnet porphyroblasts of garnet-sillimanite-quartz gneiss. International Association of Gondwana Research Conference, Series, 7, 11-22. 
  4. T. Kawasaki and H. Ishizuka (2008): Experimental study of Fe3+ solubility in cristobalite and its application to a metamorphosed quartz-magnetite rock from Mt. Riiser-Larsen area, Napier Complex, East Antarctica. Journal of Mineralogical and Petrological Sciences, 103, 255-265.
  5. T. Kawasaki and Y. Osanai (2008): Empirical thermometer of TiO2 in quartz for ultrahigh-temperature granulites of East Antarctica. In: Geodynamic Evolution of East Antarctica: a Key to the East West Gondwana Connection (eds. M. Satish-Kumar, Y. Motoyoshi, Y. Osanai, Y. Hiroi and K. Shiraishi), Geological Society of London, Special Publications, 308, 419-430. 
  6. K. Sato, T. Miyamoto and T. Kawasaki (2008): Fe2+-Mg partitioning experiments between orthopyroxene and spinel using ultrahigh-temperature granulite from the Napier Complex, East Antarctica. In: Geodynamic Evolution of East Antarctica: a Key to the East West Gondwana Connection (eds. M. Satish-Kumar, Y. Motoyoshi, Y. Osanai, Y. Hiroi and K. Shiraishi), Geological Society of London, Special Publications, 308, 431-447. 
  7. T. Kawasaki (2007): Experimental study of Fe3+ solubility in silica minerals. International Association of Gondwana Research Conference, Series, 4, 81-82. 
  8. T. Kawasaki and Y. Motoyoshi (2007): Solubility of TiO2 in garnet and orthopyroxene: Ti thermometer for ultrahigh-temperature granulites. In: Antarctica: A Keystone in a Changing World (eds. A.K. Cooper et al.), USGS Open-File Report 2007-1047, Short Research Paper, 038, 4pp; doi 10.3133/of2007-1047.srp038
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