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Experimental modeling of impact-induced high-temperature processing of silicates .
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Experimental modeling of impact- induced high-temperature 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
description
Experimental modeling of impact-induced high-temperature processing of silicates. Mikhail Gerasimov Space Research Institute, RAS, Moscow, Russia Yurii DikovInstitute of Ore Deposits, Petrography, Mineralogy and Geochemistry, RAS, Moscow, Russia - PowerPoint PPT Presentation
Transcript of Experimental modeling of impact-induced high-temperature processing of silicates .
Experimental modeling of impact-induced high-temperature processing of silicates.
Experimental modeling of impact-induced high-temperature 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
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
vapor
melt
ejecta
isobars
tp
Schematic cratering process
target melt
projectile meltprojectile melt
target melttarget melt
projectile melt
Projectile/target mixing proportions?
Computational issues:
v imp < 25 km/sm 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?
Projectilematerial
Targetmaterial
mixing +
volatilization
Impactites
+
Nd-glass laser
Calorimeter
Focussing lens
Filter
Sample chamber
Inflow ofpurging gas
Outflow
Foil
Sample
Quartz window
Dust trap Foils with grid system
SampleProjectile trajectoryLIGHT-GAS-GUN (LGG) EXPERIMENTS.
A SCHEME OF THE SAMPLE CHAMBER
SIMULATION EXPERIMENTS WITHLASER PULSE (LP) HEATING
Starting Droplets augite Volatilization sequence
SiO2 49.29 50.05 37.68 34.16 23.29 15.64TiO2 1.13 1.19 1.73 2.38 3.38 4.47Al2O3 9.98 11.05 17.56 24.41 31.39 43.20FeO 8.22 6.28 4.20 2.63 1.51 1.76MgO 13.09 14.79 16.90 7.89 3.91 4.79CaO 15.46 15.13 20.54 26.94 35.58 28.43MnO 0.07 0.13 0.17 0.10 0.12 0.30Na2O 2.75 1.28 1.15 1.28 0.71 1.39
Al0 10 20 30 40 50 60 70 80 90 100
Si
0
10
20
30
40
50
60
70
80
90
100
Ca
0
10
20
30
40
50
60
70
80
90
100
Droplets
Cratermelt
Starting augiteLP experiment with augite.
Chemical composition of crater melt and ejected droplets.
SiO2
MgO+FeONa2O+K2O+Al2O3
ultramaficrocks
mafic rocks
acidic rocks
alkali rocks
0 15 30 45 6040
55
70
85
1000
15
30
45
60
Transformation of silicates chemical composition fromstarting sample (filled symbols) to condensed material (open symbols) in LGG experiments
LGG experimentFe-Ni meteorite (5.6 km/s) granite
granite condensateSiO2 70.2 50.7Al2O3 16.0 19.2FeO 2.3 1.1CaO 1.1 3.5Na2O 3.8 22.7K2O 6.6 2.7
No Sample K Na Al Si O
BE Al 2s73.3 ev
Phase NBE Si 2p102.1 ev
Phase QBE Si 2p103.6 ev
1 Ab96Ort4 - 3.9 4.3 4.3 23.0 64.52 Ab80Ort20 1.3 5.3 5.1 4.0 21.8 62.5
3 Ab80Ort20 1.0 5.2 4.9 4.6 21.7 62.6
4 Ab56Ort44 2.7 5.5 4.9 4.9 20.2 61.8
5 Ab56Ort44 2.2 5.0 4.9 5.1 20.3 62.5
Bulk compositions of condensed films (mol. %) obtained in LP experiments for target samples composed of some Ab-Ort proportions.
NaAlSi3O8 melt NaAlSiO4 vapor + 2 SiO2 vapor/melt
2.0
1.5
1.0
0.5
0 20 40 60 80 100Ab in Ab-Ort mixtures (mol %)
Al/Si (phase N)
KAl
Na
Si
Surface 20 6040 80 Bottom
5
10
15
25
30
20
conc
entr
atio
n, m
ol %
Depth inside condensed film, %
Depth-profiles of main elements through the thickness of condensed film obtained in LP experiments with Ab56Ort44 mixture
“Netheline” cluster Na : Al : Si = 1 : 1 : 1
Augite
Depth from the surface, %
Surface 20 40 60 80 Bottom
Co
nce
ntr
atio
n, a
t. %
1
2
3
4
5
Al
Na
Startingsamplevalues
Indarch EH4
Depth from the surface, %
Surface 20 40 60 80 Bottom
Co
nce
ntr
atio
n, a
t.%
0
1
2
3
Na
Al
Etter L5
Depth from the surface, %
Surface 20 40 60 80 BottomC
on
cen
trat
ion
, a
t.%
0
1
2
3
4
Na
Al
Tsarev L5
Depth from the surface, %
Surface 20 40 60 80 Bottom
Co
nce
ntr
atio
n, a
t. %
0
1
2
3
4
Na
Al
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.
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.
Depth of the condensed film, %
Surface 20 40 60 80 Bottom
Mg
/Si,
ato
mic
ra
tio
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
- enstatite- olivine-serpentine
“Enstatite” cluster
Mg : Si = 1 : 1
Na
0
2000
4000
6000
8000
10000
initial melt cond
Na
initial melt cond0
2000
4000
6000
8000
K
initial melt cond0
400
800
1200
1600
K
initial melt cond0
400
800
Sc
initial melt cond0
4
8
12
Sc
initial melt cond048
12
162024
Co
initial melt cond0
300
600
900
Co
initial melt cond0
30
60
90
La
initial melt cond0
10
20
30
40
50
La
initial melt cond 0
0.3
0.6
0.9
1.2
1.5
Sm
initial melt cond 0
0.1
0.2
0.3
0.4
Sm
initial melt cond0
1
2
3
Eu
initial melt cond 0
0.03
0.06
0.09
0.12
Eu
initial melt cond 0
0.1
0.2
0.3
0.4
Ce
initial melt cond0
30
60
90
Ir
initial melt cond 0
0.2
0.4
0.6
0.8
Hf
initial melt cond0
1
2
3
4
Hf
initial melt cond0
2
4
6
8
U
initial melt cond 0
0.5
1.0
1.5
2.0
U
initial melt cond0
1
2
3
4
5
Dy
initial melt cond 0
0.3
0.6
0.9
1.2
Ga
initial melt cond0
2
4
6
8
Ga
initial melt cond0
5
10
15
20
Th
initial melt cond0
3
6
9
12
Tsarev (L5) Amphibole Tsarev (L5) Amphibole
Con
cent
rati
on, p
pm
INAA analysis of trace elements compositions in starting Tsarev (L5)
and amphibole samples and in their melts and condensates obtained in LP experiments
Sc
Sc
Sm
Eu
Eu
Th
Th YbYb
Sm
La
Ce
U
Ce
La
Rb
10-5 10-4 10-3 10-2 10-1
10-4
10-3
10-2
10-1
Target
Con
dens
ate
Ci/CNa
Ci/CNa
basalt target
granite target
Comparative composition of trace-elements in starting basalt and granite samplesand in their condensates formed during LGG experiments.
Concentrations of elements Ci are given relative to concentration of sodium, CNa.
LP experiment with olivine
LP experiment with olivine
Ni0 20 40 60 80 100
Si
0
20
40
60
80
100
Mg
0
20
40
60
80
100
condensate
starting kerolite
melt spherules
Ni0 20 40 60 80 100
Si
0
20
40
60
80
100
Mg
0
20
40
60
80
100
melt spherules
starting garnierite
condensate
Chemical composition (mol %) of starting kerolite (left) and garnierite (right) and of their experimentally produced condensates and melt spherules.
KeroliteSiO2 – 53,44 wt.%NiO – 11.32MgO – 22.59Fe2O3 – 0.24Al2O3 – 0.05H2O –12.58
GarnieriteSiO2 – 33,00 wt.% NiO – 44.50MgO – 4.52Fe2O3 – 1.08Al2O3 – 0.62CaO – 0.33H2O –16.42
Concentrations of Fe, S, P, and Ni in Pt-rich and in silicate droplets Concentrations of Fe, S, P, and Ni in Pt-rich and in silicate droplets
Al/Si
0 1 2
P/S
i
0
0.5
1
- silicate droplets- Pt-rich droplets
Al/Si
0 1 2
S/S
i
0
1
2
3
4
5
6
7
- silicate droplets- Pt-rich droplets
Al/Si
0 1 2
Ni/S
i
0
1
2
3
4
5
- silicate droplets- Pt-rich droplets
Al/Si
0 1 2
Fe
/Si
0
5
10
15
20
25
30
- silicate droplets- Pt-rich droplets
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.
- LP spherules- "pristine" glasses- average target- Murchison - Ti - basalt
Mg+Fe0 10 20 30 40 50 60 70 80 90 100
Si+Ti
0
10
20
30
40
50
60
70
80
90
100
Al+Ca
0
10
20
30
40
50
60
70
80
90
100
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
Mg/Al, wt. ratio
0 1 2 3 4 5
Al,
wt.
%
0
4
8
12
16 - LP spherules- "pristine" glasses- average target- Murchison - Ti - basalt
10.57
Al vs. Mg/Al in starting sample and in glass spherules in LP experiment with a mixture sample (Murchison+Ti-basalt (1:1))
SiO2, wt. %
30 35 40 45 50 55
TiO
2,
wt.
%
0
5
10
15
20
- "pristine" glasses- lunar basalts
Chemical trend for Ti during an impact of a chondritic projectile into lunar basalts
basaltsvolatilization
mixing
trend
SiO2, wt. %
30 35 40 45 50 55
Al 2
O3,
wt.
%
0
5
10
15
- 'pristine" glasses- lunar basalts
SiO2, wt. %
30 35 40 45 50 55
CaO
, w
t. %
0
5
10
15
- "pristine" glasses- lunar basalts
basaltsvolatilization
mixing
trend
Chemical trends for Al and Ca during an impact of a chondritic projectile into lunar basalts
basalts
volatilization
mixing trend
Chemical trends for Mg and Fe during an impact of a chondritic projectile into lunar basalts
SiO2, wt. %
30 35 40 45 50 55
Mg
O,
wt.
%
0
5
10
15
20
25
30
- "pristine" glasses- lunar basalts
SiO2, wt. %
30 35 40 45 50 55
Fe
O,
wt.
%
0
5
10
15
20
25
30
- "pristine" glasses- lunar basalts
basalts
volatiliza
tion
mixing
trend
SiO2, wt.%
30 40 50
Ca/
Al,
wt.
rat
io
0
1
2
3
- "pristine" glasses- lunar basalts
Ca/Al ratios vs. SiO2 in lunar «pristine» glasses (Delano, 1986) and in lunar basalts (Papike et al., 1998)
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.
