Schematic cratering process

1
(No Transcript)
2
Schematic cratering process
3
(No Transcript)
4
Projectile/target mixing proportions? Computatio
nal issues v imp lt 25 km/s m target melt lt 10
m projectile ? vap lt 50 melt
projectile/melt target gt 5 Geochemical
observations (PGEs, Ni, Co, Cr,
etc.) individual samples of melt 1
integral melt sheets 1
5
What happens to chemical composition of colliding
materials?
6
LIGHT-GAS-GUN (LGG) EXPERIMENTS. A SCHEME OF THE
SAMPLE CHAMBER
SIMULATION EXPERIMENTS WITH LASER PULSE (LP)
HEATING
7
(No Transcript)
8
LP experiment with augite. Chemical composition
of crater melt and ejected droplets.
Starting
Droplets

augite ? ? Volatilization sequence ?
? SiO2 49.29 50.05 37.68 34.16 23.29 15.64 TiO
2 1.13 1.19 1.73 2.38 3.38 4.47 Al2O3 9.98 11.05 1
7.56 24.41 31.39 43.20 FeO 8.22 6.28 4.20 2.63 1.5
1 1.76 MgO 13.09 14.79 16.90 7.89 3.91 4.79 CaO 15
.46 15.13 20.54 26.94 35.58 28.43 MnO 0.07 0.13 0.
17 0.10 0.12 0.30 Na2O 2.75 1.28 1.15 1.28 0.71 1.
39
9
Transformation of silicates chemical composition
from starting sample (filled symbols) to
condensed material (open symbols) in LGG
experiments
LGG experiment Fe-Ni meteorite (5.6 km/s) ?
granite granite condensate SiO2 70.2
? 50.7 Al2O3 16.0 ? 19.2 FeO 2.3 ? 1.1 CaO 1.1
? 3.5 Na2O 3.8 ? 22.7 K2O 6.6 ? 2.7
10
Netheline cluster Na Al Si 1 1 1
NaAlSi3O8 melt ? NaAlSiO4 vapor 2 SiO2
vapor/melt
11
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.
12
Enstatite cluster Mg Si 1 1
13
INAA analysis of trace elements compositions in
starting Tsarev (L5) and amphibole samples and in
their melts and condensates obtained in LP
experiments
14
Comparative composition of trace-elements in
starting basalt and granite samples and in their
condensates formed during LGG experiments. Concent
rations of elements Ci are given relative to
concentration of sodium, CNa.
15
LP experiment with olivine
16
LP experiment with olivine
17
(No Transcript)
18
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
Garnierite SiO2 33,00 wt. NiO 44.50 MgO
4.52 Fe2O3 1.08 Al2O3 0.62 CaO 0.33 H2O
16.42
19
Concentrations of Fe, S, P, and Ni in Pt-rich and
in silicate droplets
20
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.
21
(No Transcript)
22
Al vs. Mg/Al in starting sample and in glass
spherules in LP experiment with a mixture sample
(MurchisonTi-basalt (11))
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
Ca/Al ratios vs. SiO2 in lunar pristine glasses
(Delano, 1986) and in lunar basalts (Papike et
al., 1998)
27
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.