In-situ observation of liquid immiscibility in the Fe-O-S - CARS
Transcript of In-situ observation of liquid immiscibility in the Fe-O-S - CARS
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In-situ observation of liquid immiscibility in the Fe-O-S system
at high pressure using an X-ray radiographic technique
Kyusei Tsuno(Bayerisches Geoinstitut, Universität Bayreuth)
Hidenori Terasaki, Eiji Ohtani, Akio Suzuki, Keisuke Nishida, Tatsuya Sakamaki
(Institute of Mineralogy, Petrology, and Economic Geology, Tohoku University)
Yuki Asahara, Ken-ichi Funakoshi(SPring-8, JASRI)
Takumi Kikegawa(Photon Factory, KEK)
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Liquid immiscibility in the Earth‘s core?
Presence of a thin layer in the outermost core?
During core formation,Light elements dissolved in liquid iron.
Inner core crystallization
Immiscibility develops?
Immiscible layer
Tanaka (2004; 2007)Eaton and Kendall (2006)
Tcore decrease
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Light element combinations in the core
Li and Fei (2003)
• Liquid immiscibility gapFe-S-Si system (Sanloup and Fei 2004)Fe-O-S system (Urakawa et al. 1987; Tsuno et al. 2007a)Fe-S-C system (Urakawa et al. 2005)
• Based on the textural observation and chemical analysis of the recovered samples.
Fe+
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Previous Fe-O-S experiments
Tsuno et al. (2007a)Urakawa et al. (1987)
L (i)
L (m)
L (m): Fe-S metallic liquidsL (i): Fe-O ionic liquids
Difference in textural interpretation of quench products
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Tsuno et al. (2007a)
• Difference of liquid immiscibility gap could be due to difference in textural interpretation of quench products.
• Our goal is therefore to observe liquid immiscibility in-situ at high P and T, and determine precise liquid immiscibility gaps
Purpose of this study
15 GPa
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Experimental methods
High pressure apparatus: Kawai-type multianvil presses1500-ton (SPEED-1500) on BL04B1 beamline (SPring-8)700-ton (MAX-III) on BL14C2 beamline (KEK-PF)
3000-ton (SPIRIT-3000) at Tohoku University
X-rays: White X-ray (SPring-8)35 keV monochromatic X-ray (KEK-PF)
Pressure calibration: equation of state of hBN
Starting materials: mixtures of Fe, FeS, and Fe0.91 O
Experimental conditions: 3 GPa, up to 2203 K
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Cell Assembly (TEL 12 mm)
X-ray
GasketsBoron epoxy is sandwiched by pyrophyllite.
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Beamlines
Incident Slit
MultianvilPress
Collimator SSDWhite X-ray
CCDCamera
SPring-8 BL04B1Receiving Slit
Funakoshi et al. (2002)
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Starting compositions
in atomic %
O: 13-27 atomic %S: 8-33 atomic %
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Radiography results (1): Fe65 O27 S8
500 µm
500 µm
500 µm
500 µm
500 µm
Immiscible liquids were quenched at room T.
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Radiographic images(a-c)Tsuno et al. (2007b)
500 µm Immiscible liquids disappered and a
miscible liquid was formed.
500 µm
Radiography results (2): Fe65 O27 S8
500 µm
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500 µm
500 µm
Two separated phases appeared from a miscible liquid during quenching.
Radiographic images(d-e)Tsuno et al. (2007b)
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Importance of in-situ observation
• Fe-S and Fe-O liquid phases observed in quenched run products can be interpreted as either
(a) quenched immiscible phases, or(b) exolution from miscible liquid.
• In-situ observations at high P and T necessary to determine immiscibility gap in Fe-light element systems.
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Liquid immiscibility gap shrinks with increasing temperature.
1883 K2013 K
Composition of immiscible liquids
Tsuno et al. (2007b)
Liquid immiscibility gap at 3 GPa
Starting composition
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• In-situ observations of immiscible and miscible liquids in the Fe-O-S system were performed using an X-ray radiographic method.
• Immiscible and miscible liquids at high P and T, and quench process were observed.
• Liquid immiscibility gap decreases with increasing temperature at 3 GPa.
• X-ray radiographic technique is useful in solving questions of liquid immiscibility.
Summary
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Contents
1. Introduction・ Liquid immiscibility in the Earth’s outer core?・ Element combination in the Fe-light elements systems.・ Significance of S and O in the core・ Purpose of this study
2. Experimental methods3. Results and discussion4. Summary of this talk
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Significance of S and O in the core
(1) S: 1.9 wt.% in the outer core
3.2 3.1 3.0 2.9 2.8 2.7 2.6
Silic
ate
Eart
h (n
orm
aliz
ed to
CI c
hond
rite
and
Mg)
1
0.1
0.01
0.001
McDonough (2003)
Log 50% condensation temperature (K) at 10-4 atm
1.9 wt.% S in the coreS
(2) O: most abundant in the bulk EarthO32.4 %
Fe28.1 %
Si17.2 %
Mg15.9 %
Allegre et al. (1995)
Bulk composition of the Earth
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Beamlines in SPring-8 and KEK-PFIncident Slit
MultianvilPress
Collimator SSDWhite X-ray
CCDCamera
MultianvilPress
CCDCamera
35 keV X-ray
SPring-8 BL04B1KEK-PF BL14C2
Funakoshi et al. (2002)
Receiving Slit
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500 µm
500 µm 500 µm
Immiscible melts can be quenched as two separated phases.
Tsuno et al. (2007b)
Increasing temperature
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Radiography results (2): Fe65 O27 S8
3 GPaUp to 2073 K
Room temperature
500 µm
500 µm
500 µm
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Liquid immiscibility gap in the Fe-O-S system at 3 GPa
2013 K 1883 K