Time-resolved X-ray diffraction
experiment of dehydration of
serpentine at high pressure
Toru INOUE 1, Isamu YOSHIMI 1, Akihiro YAMADA 1,
Tetsuo IRIFUNE 1, Takumi KIKEGAWA 2
(1 GRC, Ehime Univ., Japan, 2 KEK, Japan,)
1 mm
Diamond-platinum composite capsule
2007APS workshop
Phase diagram of antigorite
Ａ
Fo + En+ Fluid
Atg
5Mg6Si4O10(OH)8
→ 2Mg7Si2O8(OH)6 + 16MgSiO3 + 18H2O
ph A
B
A
phA +
En +
Fluid
Atg
En
Fluid
9.1 wt% water released
3.9wt% water transported
to deep mantle
Atg
B
Mg6Si4O10(OH)8
→ 2Mg2SiO4 + 2MgSiO3 + 4H2O
Modified from Komabayashi et al. (2005)
Atg: Antigorite, Fo: Forsterite
En: Enstatite, phA: Phase A
Fo
En
Fluid
13 wt% water released
⇒How about the reaction rate in
subducting slab (low temperature)?
There are many experimental studies
about the stability of antigorite (phase
equilibrium study) under pressure.
However, few study about time-resolved
study (reaction kinetics study) under
pressure.
（Perrillat et al.(2005) etc)
Time-resolved experiment of dehydration
of antigorite under pressure
Experiments
High pressure apparatus：
MAX80 (AR-NE5C in KEK)
Time-resolved experiment:
every 60 sec.
Anvil truncation: 4, 6 mm
X-ray diffraction： Energy
dispersive system by Ge-SSD
Sample: Natural antigorite
Ideal formula: Mg6Si4O10(OH)8
※Al2O3 1.5 wt%, FeO 2.6 wt%
P-T ：3-9 GPa, <1000℃
Pressure marker: NaCl (Decker, 1971)
Analyses of recovered sample:
SEM-EDS, FE-SEM,XRD
MAX80 cubic-type apparatus
(KEK, AR-NE5C)
NaCl + Au
Cell assembly
BN
Graphite
heater
TC
ZrO2
BN
Pt or Au cap
BN
BN
Boron
epoxy
LaCrO3
Pt or Au cap
Mo
(Pressure
Marker)
BN
Sample in
Diamond
sleeve
Diamond sleeve
～2.3 mm
1 mm
Diamond - Pt or Au composite capsule
Optical system (AR-NE5C)
Incident slit
(0.1×0.2 mm)
White X-ray
Receiving slit
(0.2×0.3 mm)
SD
S
Ge
Collimator
（ 0.1
mm ）
Diffraction
angle (2θ= 4°)
Pressure-transmitting media
Intensity
(Boron-epoxy)
0
20
40
60
Energy / KeV
80
100
120
MCA (2048 ch)
Phase diagram of Antigorite
900
AR068
AR072
En+Fo+Fl+(Chl)
800
AR075
AR079
Temperature (℃ )
700
A+En+Fl±
AR083*
AR086
Chu
600
AR088
AR089
Atg+(Tlc)
500
AR091
Tlc+En+
Fo+Fl
400
AR092
AR093
AR095
Atg
AR097*
300
AR098
AR111
200
AR113
100
1
2
3
4
5
6
7
8
9
10
Pressure (GPa)
Atg: Antigorite, Tlc: Talc, Fo: Forsterite, En: Enstatite, Chl: Chlorite, A: Phase A, Chu: Clinohumite
( ):Small amount, *: power estimate
40 min
0
10
30
50
70
90
Count
4000
2000
20 min
En(610)
Chl(003)
Atg(001)
6000
Atg(002)
En(610)
Fo(020)
Energy (keV)
0
10
30
50
70
90
Every 60 sec
5000
Atg(002)
10000
Atg(001)
Energy (keV)
Time
(min)
Count
Tlc(010)
1000
500
Atg(002)
Fo(020)
1500
Tlc(010)
Atg(001)
Atg(001)
Fo(020)
Chl(003)
Atg(002)
Count
2000
En(610)
5.2 GPa 650℃
2500
1 min
0
10
30
50
Energy (keV)
70
90
Avrami model
V = 1 – exp(- ktn)
t : time
V: transformed volume fraction (V=I/Imax)
k: rate constant
n: constant that depends on the reaction mechanism
ln{-ln(1-V)}
ln {-ln(1-V)} = nln(t) + ln(k)
slope ⇒ n
intercept ⇒ ln(k)
ln (t)
Interpretation of n value
n>1: the growth rate is large relative to nucleation rate
nucleus
volume fraction
nucleation controlling mechanism
time
growth controlling mechanism
nucleus
volume fraction
n≦1: the nucleation rate is large relative to growth rate
time
Fitting of Enstatite growth
2
3.9 GPa 700℃
1
n≒1.0
1
0.8
0
0.6
5.5 GPa
650℃
0.4
4.6 GPa 650℃
ln{-ln(1-V)}
Volume fraction
5.2 GPa 650℃
-1
n=0.9
-2
0.2
1.0
5.2 GPa 650℃
-3
0
5.5 GPa 650℃
1.3 1.3
4.6 GPa 650℃
3.9 GPa 700℃
-4
0
20
40
60
Time (min.)
80
100
-1
1
3
ln t
¾n≒1.0 growth controlling mechanism
5
Fitting of Forsterite growth
1
n≒2.5
1
5.5 GPa
650℃
0.8
0
ln{-ln(1-V )}
Volume fraction
2
3.9 GPa 700℃
0.6
4.6 GPa
650℃
0.4
n=2.4
-1
2.3
-2
0.2
5.5 GPa 650℃
2.7
-3
4.6 GPa 650℃
3.9 GPa 700℃
0
-4
0
20
40
60
80
100
1.0
1.5
2.0
2.5
ln t
3.0
3.5
Time (min.)
¾n≒2.5
nucleation controlling mechanism
4.0
4.5
BEI of recovered sample
5.5 GPa 650℃
Forsterite
Enstatite
Forsterite +
Enstatite
En: nucleation rate Æ high
growth controlling
Fo: nucleation rate Æ low
nucleation controlling
Enstatite
Pore
BEI of recovered sample
(4 GPa, 700℃, 15min keep)
Enstatite
Antigorite
Antigorite → Enstatite + Fluid
Mg/Si:1.5
1.0
Kawamoto et al. (2004)
>1.5
MgO-rich fluid (Mg/Si>1.5) is formed.
Phase diagram of Antigorite
900
AR068
AR072
En+Fo+Fl+(Chl)
800
AR075
AR079
Temperature (℃ )
700
A+En+Fl±
AR083*
AR086
Chu
600
AR088
AR089
Atg+(Tlc)
500
AR091
Tlc+En+
Fo+Fl
400
AR092
AR093
AR095
Atg
AR097*
300
AR098
AR111
200
AR113
100
1
2
3
Poli & Schmidt (2002)
4
5
6
7
8
9
10
Pressure (GPa)
Atg: Antigorite, Tlc: Talc, Fo: Forsterite, En: Enstatite, Chl: Chlorite, A: Phase A, Chu: Clinohumite
( ):Small amount, *: power estimate
Dehydration at 8.0 GPa, 500℃
Antigorite → Talc + Forsterite + Enstatite + Fluid
Mg3Si4O10(OH)2 4.7 wt% H2O
Tlc (030), En (221)
Tlc (010)
Tlc (001)
Atg (001) Atg (002)
Fo (002), En (321)
Tlc (111)
En (512)
Summary
„
„
„
„
We have conducted the time-resolved dehydration
experiments of Atg at high pressure and high
temperature by in situ X-ray diffraction using diamond
capsule.
Atg in subducted slab should quickly dehydrate when the
slab crosses the dehydration boundary of Atg. Thus
metastable Atg can not exist in subducted slab at around
650-700 ℃ and 3-5 GPa.
The nucleation rate was quite high for enstatite, but low
for forsterite by dehydration of Atg. This result also can
be confirmed from the observation that incubation
periods exist for forsterite formation.
Talc was formed above 6 GPa with dissociation of Atg,
and then the formation of phase A was observed in the
present experiments. Thus talc formation should be
important for dehydration sequence in low temperature
subducted slab.
Stability of hydrous phases in hydrous peridotite
○
Wd Rw
phE
Ser
○
Sb
○
phD
phA
Modified from Ohtani et al. (2004)
En+Fo
BEI
7.5 GPa, 550℃
Talc
BEI of recovered sample
(3.0 GPa, 675℃, 40min. keep)
Antigorite
Forsterite
Enstatite
Forsterite +
Enstatite
Forsterite +
Enstatite
Antigorite + Enstatite
Dehydration reaction at 3-6 GPa
Antigorite → Enstatite + Fluid
Mg/Si:
1.5
1.0
>1.5
MgO-rich supersaturated
solution
Enstatite
Antigorite
Antigorite
Forsterite
Enstatite
Forsterite + Enstatite
Forsterite is crystallized from MgO-rich supersaturated solution.
Antigorite phase diagram
Schmidt&Poli(1998) Peridotite-H2O
800
Temperature ( ℃)
Fo+En+Fluid(+Chl)
AR072
700
600This
AR068
study
AR075
Atg(+Tlc-like)
500
400
Perrillat et al.(2005)
300
Atg
200
Komabayashi et al. (2005)
MSH
100
2
3
4
Pressure (GPa)
5
6
実験方法
実験試料：京都府宮津市中ノ茶屋産
Antigorite
理想式 Mg6Si4O10(OH)8
※Al2O3 1.5 wt%, FeO 2.6 wt% を含む
実験装置：MAX80@KEK
アンビル先端サイズ：4, 6 mm
X線回折測定：Ge-SSD を用いたエネルギー分散
法
測定時間を50秒とし、60秒間隔ごとの時分割測定
圧力温度条件：3-9 GPa, -1000℃
圧力決定： NaCl マーカー (Decker, 1971)
回収試料の分析：SEM-EDS, FE-SEM,
微小部X線回
折装置
3-6 GPa おける脱水分解反応
650℃)
(5.2 GPa,
Antigorite → Forsterite + Enstatite + Fluid
Fo (020)
Chl (003) En (610)
Atg (001)
Atg (002)
Time
(min
)
Count
Tlc (010)
Energy (keV)
反応初期について
Antigorite → Forsterite + Enstatite + Fluid
Fo (020)
Chl (003) En (610)
Atg (001)
Atg (002)
Time
(min
)
Count
Tlc (010)
潜伏期間あり
Energy (keV) 潜伏期間なし
3.9 GPa
700℃
1
Forsterite+Enstatite+Fluidへの脱水分解
5.2 GPa
650℃
Volume fraction
0.8
0.6
5.5 GPa
650℃
0.4
4.6 GPa
650℃
0.2
Forsterite
0
3.9 GPa
700℃
5.5 GPa
650℃
1
Volume fraction
0.8
0.6
4.6 GPa
650℃
0.4
Komabayashi et al. (2005) に加筆
0.2
Enstatite
0
0
20
40
60
Time (min.)
80
100
高圧下におけるTalcの生成
Poli & Schmidt (2002)
Komabayashi et al. (2005) に加筆
本研究と類似する脱水分解境界をもつBose & Navrotsky (1998)は, 6.5
GPa 575℃でTalcらしき相を観察している
Temperature (℃)
Stability of antigorite (serpentine)
Fo+En+H2O
phA+En
+H2O
Atg
Pressure (GPa)
Modified from Komabayashi et al.(2005)
Hypocenter distributions in subduction zone
Komabayashi et al.
(2005)
Pressure (GPa)
Dehydration of antigorite (opened system)
Fo+En
Appearance of
Talc-like phase
Atg
Fo+tlc-like
Temperature(℃)
Modified from
Perrillat et al.
(2005)
Dehydration reaction of antigorite (<5 GPa)
Mg6Si4O10(OH)8 → 2Mg2SiO4 + 2MgSiO3 + 4H2O
Atg
Fo
En
Fluid
13 wt% water released
5Mg6Si4O10(OH)8→2Mg3Si4O10(OH)2 + 12Mg2SiO4 + 18H2O
Atg
H2O
13.0 wt%
Tlc
4.8 wt % H2O
Fo
1.3 wt%
11.7 wt% water released
Fluid
11.7 wt%
Dehydration reaction of antigorite (>5 GPa)
5Mg6Si4O10(OH)8→2Mg7Si2O8(OH)6 + 16MgSiO3 + 18H2O
Phase A
Atg
En
11.8 wt % H2O
H2O 13.0 wt%
3.9 wt%
Fluid
9.1 wt%
9.1 wt% water released
With increasing temperature
Mg7Si2O8(OH)6 + 3MgSiO3 →
Phase A
En
5Mg2SiO4 + 3H2O
Fo
Fluid
3.9 wt%
Remnant 3.9 wt% water released
Phase appearance or disappearance and hold time (min)
T ( ℃)
AR072
AR068
AR075
AR079
3.0 GP a
5.2 GP a
5.5 GP a
8.5 GP a
300
no (15)
no (15)
400
no (20)
no (25)
Tlc-like*: appear (50) no (35)
450
500
550
600
Atg: no
Tlc-like*: appear (30)
Tlc-like*: appear (30)
Atg: no
Atg: no
no (90)
no (80)
no (40)
Atg: disappear (90)
Tlc-like: appear
no (40)
Tlc-like: disappear (50)
En: appear
no (80)
no (60)
no (45)
no (50)
Tlc-like: increase (120) Atg: disappear (120)
Atg: disappear (90)
no (60)
Atg: decrease
Tlc-like*: disappear
Tlc-like*: disappear
Chl: appear
En: appear
En: appear
Ol: appear
650
Ol: appear
Atg: disappear (90)
700
Tlc-like*: disappear
En: appear
Ol: appear
Blue: appear or increase, red: disappear or decrease
Ant igor it e
500
400
① 550℃
300
200
100
20
Ant igor it e
40
② 600℃
200
100
0
0
P=5.2 GPa
300
count / ring current
600
0
60
0
Time (min)
20
60
Enst at it e
count / ring current
200
40
Time (min)
Ant igor it e
count / ring current
count / ring current
Antigorite dehydration
③ 650℃
100
60
③ 650℃
30
0
0
0
50
Time (min)
100
0
20
40
60
80
Time (min)
100
120
BEI at 5.2 GPa, 650℃ run product
Ol
En
Chl
Ol
AR068
20 mm
5.2 GPa
500℃:anneal
550⇒600⇒650⇒quench