Transcript Experimental modeling of impact-induced hightemperature processing of silicates. Mikhail Gerasimov Space Research Institute, RAS, Moscow, Russia Yurii Dikov Institute of Ore Deposits, Petrography, Mineralogy and.

Experimental modeling of impact-induced hightemperature processing of silicates.
Mikhail Gerasimov Space Research Institute, RAS, Moscow,
Russia
Yurii Dikov
Institute of Ore Deposits, Petrography,
Mineralogy and Geochemistry, RAS,
Moscow, Russia
Oleg Yakovlev
Vernadsky Institute of Geochemistry and
Analytical Chemistry, RAS, Moscow, Russia
Schematic cratering process
pt
projectilemelt
melt
projectile
target
targetmelt
melt
Projectile/target mixing proportions?
Computational issues:
v imp < 25 km/s
m target melt < 10 m projectile
 vap < 50 %
melt projectile/melt target > 5 %
Geochemical observations:
(PGEs, Ni, Co, Cr, etc.)
individual samples of melt ~ 1 %
integral melt sheets « 1 %
What happens to chemical composition of colliding materials?
Projectile
material
+
Target
material
mixing
+
volatilization
Impactites
LIGHT-GAS-GUN (LGG) EXPERIMENTS.
Sample
Projectile trajectory
A SCHEME OF THE SAMPLE CHAMBER
Dust trap
Foils with grid system
Outflow
SIMULATION EXPERIMENTS WITH
LASER PULSE (LP) HEATING
Filter
Foil
Calorimeter
Nd-glass laser
Focussing lens
Sample
Quartz window
Sample chamber
Inflow of
purging gas
Si
0
100
10
20
30
LP experiment with augite.
Chemical composition of
crater melt and ejected droplets.
90
80
Starting
augite
70
40
50
60
Crater
melt
50
60
40
Droplets
70
30
80
20
90
10
100
Ca
Starting
augite
SiO2
TiO2
Al2O3
FeO
MgO
CaO
MnO
Na2O
49.29
1.13
9.98
8.22
13.09
15.46
0.07
2.75

50.05
1.19
11.05
6.28
14.79
15.13
0.13
1.28
0
0
10
20
30
40
50
60
Droplets
 Volatilization sequence  
37.68
1.73
17.56
4.20
16.90
20.54
0.17
1.15
34.16
2.38
24.41
2.63
7.89
26.94
0.10
1.28
23.29
3.38
31.39
1.51
3.91
35.58
0.12
0.71
15.64
4.47
43.20
1.76
4.79
28.43
0.30
1.39
70
80
90
100
Al
Transformation of silicates
chemical composition from
starting sample (filled symbols)
to condensed material (open
symbols) in LGG experiments
SiO2
0
100
15
85
acidic rocks
30
70
mafic rocks
45
LGG experiment
Fe-Ni meteorite (5.6 km/s)  granite
55
alkali rocks
ultramafic
rocks
40
SiO2
Al2O3
FeO
CaO
Na2O
K2O
granite
70.2
16.0
2.3
1.1
3.8
6.6
condensate
 50.7
 19.2

1.1

3.5
 22.7

2.7
0
Na2O+K2O+Al2O3
15
30
45
60
60
MgO+FeO
“Netheline” cluster
Na : Al : Si = 1 : 1 : 1
NaAlSi3O8 melt  NaAlSiO4 vapor + 2 SiO2 vapor/melt
Bulk compositions of condensed films (mol. %) obtained in LP
experiments for target samples composed of some Ab-Ort proportions
Depth-profiles of main elements
through the thickness of condensed
film obtained in LP experiments
with Ab56Ort44 mixture
30
concentration, mol %
Si
No
Sample
K
Na
Al
BE Al 2s
73.3 ev
1
2
3
4
5
Ab96Ort4
Ab80Ort20
Ab80Ort20
Ab56Ort44
Ab56Ort44
1.3
1.0
2.7
2.2
3.9
5.3
5.2
5.5
5.0
4.3
5.1
4.9
4.9
4.9
Si
Phase N
BE Si 2p
102.1 ev
4.3
4.0
4.6
4.9
5.1
O
Phase Q
BE Si 2p
103.6 ev
23.0
21.8
21.7
20.2
20.3
25
Al/Si (phase N)
2.0
20
15
10
5
1.5
Na
Al
K
1.0
0.5
80 Bottom
Surface 20
40
60
Depth inside condensed film, %
0
20
40
100
80
60
Ab in Ab-Ort mixtures (mol %)
64.5
62.5
62.6
61.8
62.5
Augite
Depth-profiles of concentrations of Na and
Al through the thickness of condensed films
produced in LP experiments with augite and
meteorites: Indarch, Tsarev, and Etter.
Concentration, at. %
5
4
Al
Starting
sample
values
3
Na
2
1
Surface
20
40
60
80
Bottom
Depth from the surface, %
Tsarev L5
Indarch EH4
2
Al
1
4
4
3
3
Concentration, at.%
Na
Concentration, at. %
Concentration, at.%
3
Etter L5
2
Na
1
2
Na
1
Al
Al
0
0
Surface
20
40
60
80
Bottom
Depth from the surface, %
0
Surface
20
40
60
80
Depth from the surface, %
Bottom
Surface
20
40
60
80
Depth from the surface, %
Bottom
Profiles of Mg/Si ratios through the thickness of
condensed films in LP experiments with enstatite,
olivine, and serpentine. Simbols on the ordinate
indicate initial values.
“Enstatite” cluster
Mg : Si = 1 : 1
2.0
- enstatite
- olivine
-serpentine
1.8
Mg/Si, atomic ratio
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Surface
20
40
60
80
Bottom
Depth of the condensed film, %
Tsarev (L5)
10000
8000
8000
6000
6000
4000
Na 4000
2000
2000
0
Tsarev (L5)
Amphibole
90
60
Na
cond
0
initial melt
initial melt cond
cond
0.4
1600
800
1200
K
800
3
0.3
K
400
400
Sm
0.2
0
initial melt
cond
0
initial melt
4
8
3
6
2
0
initial melt cond
cond
Sm
1
0.1
0
Ce
30
0
initial melt
initial melt
cond
0.4
0.12
Concentration, ppm
INAA analysis of trace elements
compositions in starting Tsarev (L5)
and amphibole samples and in their
melts and condensates obtained in LP
experiments
Amphibole
Hf
2
Hf
4
2
1
initial melt
cond
Eu
0.06
0
initial melt cond
0
initial melt
initial melt
cond
5
2.0
U
1.0
0.5
0.9
3
U
2
0.3
0
initial melt
0
initial melt
cond
Dy
0.6
1
0
cond
1.2
4
1.5
Eu
0.2
0.1
0.03
0
0
0.3
0.09
cond
initial melt
cond
8
12
Th
6
cond
8
Sc
4
0
initial melt
1.5
50
1.2
40
La
0.6
0.3
cond
initial melt
cond
0.6
20
Ir
0.4
0.2
0
initial melt cond
Co
0
initial melt
La
60
30
0.8
0
initial melt
Co
0
30
cond
90
600
cond
10
0
initial melt
cond
300
initial melt
cond
0.9
Sc
Ga
10
0
initial melt
900
12
8
4
0
15
5
0
initial melt
24
20
16
12
Ga
4
2
3
0
20
6
9
initial melt
cond
cond
Comparative composition of trace-elements in starting basalt and granite samples
and in their condensates formed during LGG experiments.
Concentrations of elements Ci are given relative to concentration of sodium, CNa.
Ci/CNa
10-1
basalt target
granite target
Rb
La
Condensate
10-2
Ce
La
10-3
10-4
10-5
Sm Sm
U
Yb
Th Eu Yb
Sc
Eu
10-4
Ce
Th
Sc
10-2
10-3
Target
10-1
Ci/CNa
LP experiment with olivine
LP experiment with olivine
Chemical composition (mol %) of starting kerolite (left) and garnierite (right)
and of their experimentally produced condensates and melt spherules.
Kerolite
SiO2 – 53,44 wt.%
NiO – 11.32
MgO – 22.59
Fe2O3 – 0.24
Al2O3 – 0.05
H2O –12.58
Si
0
Si
60
0
100
20
40
starting kerolite
melt spherules
80
melt spherules
60
60
40
60
40
40
starting garnierite
condensate
80
Mg
0
80
20
100
20
40
Mg
60
0
100
20
80
100
Garnierite
SiO2 – 33,00 wt.%
NiO – 44.50
MgO – 4.52
Fe2O3 – 1.08
Al2O3 – 0.62
CaO – 0.33
H2O –16.42
condensate
20
0
80
20
100
40
0
Ni
60
80
100
Ni
Concentrations of Fe, S, P, and Ni in Pt-rich and in silicate droplets
1
30
- silicate droplets
- Pt-rich droplets
25
- silicate droplets
- Pt-rich droplets
P/Si
Fe/Si
20
15
0.5
10
5
0
0
0
1
2
0
Al/Si
1
2
Al/Si
5
7
- silicate droplets
- Pt-rich droplets
6
- silicate droplets
- Pt-rich droplets
4
4
Ni/Si
S/Si
5
3
3
2
2
1
1
0
0
0
1
Al/Si
2
0
1
Al/Si
2
Volatilization during an impact is a “non linear” process:
- volatilization of elements is dominated by formation of
clusters which assemble elements having different “classic”
volatility (“enstatite”, “netheline”, “wollastonite”, … clusters);
- thermal and chemical reduction of iron with subsequent
agglomeration of iron droplets and their dispersion from
silicate melts;
- scavenging of siderophile elements from silicate melts into
forming and dispersing metallic droplets;
- observed high volatility of “classically” refractory elements
such as REE, U, Th, Hf, Zr, etc.
Chemical composition of glass spherules obtained in LP
experiment with target mixture of Murchison +Ti-basalt (1:1) in
comparison with the composition of «pristine» glasses
Si+Ti
0
10
100
- LP spherules
- "pristine" glasses
- average target
- Murchison
- Ti - basalt
90
20
80
30
70
40
60
50
50
60
40
70
30
80
20
90
10
100
Al+Ca
0
0
10
20
30
40
50
60
70
80
90 100
Mg+Fe
Al vs. Mg/Al in starting sample and in glass spherules in LP
experiment with a mixture sample (Murchison+Ti-basalt (1:1))
-
Al, wt. %
16
12
LP spherules
"pristine" glasses
average target
Murchison
Ti - basalt
8
4
10.57
0
0
1
2
3
Mg/Al, wt. ratio
4
5
Chemical trend for Ti during an impact of a chondritic projectile
into lunar basalts
basalts
20
- "pristine" glasses
- lunar basalts
TiO2, wt. %
15
10
5
0
30
35
40
45
SiO2, wt. %
50
55
Chemical trends for Al and Ca during an impact of a chondritic
projectile into lunar basalts
mixing
basalts
15
CaO, wt. %
Al2O3, wt. %
15
10
5
10
5
- 'pristine" glasses
- lunar basalts
- "pristine" glasses
- lunar basalts
0
0
30
35
40
45
SiO2, wt. %
50
55
30
35
40
45
SiO2, wt. %
50
55
mixing
mixing
Chemical trends for Mg and Fe during an impact of a chondritic
projectile into lunar basalts
basalts
basalts
30
30
- "pristine" glasses
- lunar basalts
25
20
FeO, wt. %
MgO, wt. %
25
15
10
20
15
10
5
5
0
0
30
35
40
45
SiO2, wt. %
50
55
- "pristine" glasses
- lunar basalts
30
35
40
45
SiO2, wt. %
50
55
Ca/Al ratios vs. SiO2 in lunar «pristine» glasses (Delano, 1986)
and in lunar basalts (Papike et al., 1998)
3
Ca/Al, wt. ratio
- "pristine" glasses
- lunar basalts
2
1
0
30
40
SiO2, wt.%
50
Conclusions:
- the usage of siderophile elements is a powerful tool as an
indicator of the presence of meteoritic material but it can
provide an underestimation of proportion of the projectile
in the impact melt;
- we need an involvement of computational methods into the
problem of projectile/target mixing.