Unconventional component of parent materials of moldavites Jiří MIZERA, Zdeněk ŘANDA , Jan...
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Unconventional component of parent materials of Unconventional component of parent materials of moldavites moldavites Jiří MIZERA, Zdeněk ŘANDA, Jan KAMENÍK Nuclear Physics Institute, Academy of Sciences of the Czech Republic Řež 130, 250 68, Czech Republic E-mail: [email protected] 3 rd International Nuclear Chemistry Congress Sicily – Italy 18 - 23 September 2011 Summary Summary 17 16 15 14 13 12 11 49 50 51 Longitude °E Latitude °N 17 16 15 14 13 12 11 49 50 51 Longitude °E Latitude °N Formation of the Central European tektites - moldavites - has unequivocally been associated with a large meteorite impact to Ries region in western Bavaria in Germany 14.5 million years ago. However, after several decades of investigation, unambiguous assigning all source materials of moldavites and processes of their chemical differentiation still remains open. Despite some similarity of chemical composition between moldavites and isochronous sediments from vicinity of the Ries crater, there are some significant differences in both major and trace element contents, which cannot be attributed solely to the variability of the sediments or later weathering processes. Some of these differences could be explained by an original hypothesis, according to which ash from biomass burned at the early stage of the meteorite impact contributed to the source materials. Analytical mode Sample mass Irradiation - decay - counting times Irrradiation operating parameters Elements determined Short-time INAA, activation with reactor-pile neutrons ~50 mg 1 - 12 - 12 min LVR-15 reactor 9 MW neutron fluence rates 3e13 - 5e12 n cm -2 s -1 (th – fast) Na, K, Mg, Ca, Ba, Al, Ti, V, Mn, Dy Short-time INAA, activation in Cd ~100 mg 0.75 - 13 - 13 min Si, U Long-time INAA, activation with reactor-pile neutrons - 1 st count - 2 nd count - 3 rd count 200-300 mg 2 h – 5 d – 20 min 2 h – 13 d – 45 min 2 h – 30 (80*) d – 2 h LVR-15 reactor 9 MW neutron fluence rates 8e13 - 2e13 n cm -2 s -1 (th - fast) Na, K, As, Sb, La, Sm, U Rb, Cs, Ca, Sr, Ba, Sb, Sc, Cr, Fe, Co, Zr, Hf, La, Ce, Nd, Sm, Eu, Yb, Lu, Th Rb, Cs, Sr, Ba, Sb, Sc, Cr, Fe, Co, Zn, Zr, Hf, Ta, Ce, Eu, Tb, Yb, Th, (Ir), *Gd, *Tm Long-time INAA, activation in Cd - 1 st count - 2 nd count - 3 rd count 200-300 mg 2 h – 4 d – 30 min 2 h – 7 d – 45 min 2 h – 25 d – 2 h LVR-15 reactor 9 MW neutron fluence rates 8e13 - 2e13 n cm -2 s -1 (th - fast) K, As, Ga, Br, Cu, Mo, W, Pr, Ho Rb, Ca, Ba, As, Sb, Br, Mo, Au, La, Nd, Sm, Yb, Lu, Th, U Rb,Cs, Ba, Sr, Sb, Sc, Cr, Fe, Co, Ni, Zn, Zr, Ag, Hf, Ta, (Ir), Ce, Nd, Eu, Gd, Tb, Tm, Yb IPAA - 1 st count - 2 nd cound - 3 rd count - 4 th count 1-2.5 g 6 h - 5-7 h - 15 min 6 h - 1 d – 30 min 6 h - 7 d – 1 h 6 h - 20 d – 5 h MT-25 microtron E = 22 MeV I = 15 A Sr, Ti Mg, Ca, Ba, Ti, Ni, Zr, Sm, Th Cs, Ca, Rb, Zr, Nb, Ce, Nd, Sm Na, Rb, Cs, Sr, Mn, Co, Y, Nb, Ce Geochemical characterization of a large collection of moldavites using instrumental neutron/photon activation analyses supported the hypothesis. As shown by the data acquired in the study, this unconventional “biogenic component” could be indicated by enrichment in elements essential for plants (e.g., K, Ca, Mg) and depletion of nonessential elements (e.g., Na, Rb, Sr, Ba), similarly to redistribution of these elements during their transfer from soil to plants. Differentiation similar to that occurring during the soil-plant interaction has been observed also for other, nonessential elements, e.g., U and Th. Correlations between the K/Na ratio and K/Rb, Ca/Sr, Ca/Ba, and U/Th ratios, as well as some other indicators of the “biogenic” component observed in moldavites from various parts of the Central European tektite strewn field are presented and discussed. Moldavites from Southern Bohemia. Experimental Experimental • collection of 103 moldavites from the major parts of the Central European tektite strewn field: Southern Bohemia (MSB, 59), Cheb Basin (MCB, 30), Moravia (MM, 13), Lusatia (ML, 1) • analyzed by INAA and IPAA using the LVR-15 reactor of the Nuclear Research Inst., Řež, plc., and the MT-25 microtron of the Nuclear Physics Inst. ASCR, respectively • selective irradiation with epithermal/fast neutrons in Cd shielding included – interferences from fission suppressed ( 95 Zr, 99 Mo, 140 La, 141 Ce, 147 Nd) • various irradiation - decay - counting modes applied • RM used for QC: USGS GSP-1 granodiorite, SARM GS- N granite The study has been supported by the Czech Science Foundation grant 205/09/0991. Central European tektite strewn field and its substrewn fields. 3 5 7 9 11 13 15 17 0 1 2 3 4 5 6 7 8 9 CaO +M gO (w t%) K/Na 3 5 7 9 11 13 15 17 6 7 8 9 10 11 12 13 14 Al 2 O 3 (w t%) K /Na MCB MSB MM ML 3 5 7 9 11 13 15 17 0.00 0.05 0.10 0.15 0.20 M nO (w t%) K/Na 3 5 7 9 11 13 15 17 72 74 76 78 80 82 84 86 SiO 2 (w t%) K /Na 3 5 7 9 11 13 15 17 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 K 2 O (w t%) K/Na 3 5 7 9 11 13 15 17 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Na 2 O (w t%) K/Na Results Results The current concept of moldavite parent materials assumes mixing of 3 components of the Miocene sediments - quartz sands, clayey soil, and a Ca-Mg component. The Ca-Mg component has newly been assigned (besides carbonates) to ash produced from burned biomass and soil during the meteoritic impact. Composition of plant ash is governed by Ca, Si, K, Mg, and Mn, and characterized by a high K/Na ratio. Correlations between the K/Na ratio and the major elements support this assignment, particularly in a part of the Cheb Basin moldavites. In plants, due to enrichment in essential elements and depletion of nonessential elements, besides K/Na also Si/Al, Ca/Al, K/Rb, Ca/Sr, and Ca/Ba ratios increase during transfer of the elements from soil to plants. Redistribution of some nonessential elements as U and Th also occurs by soil-plant interaction. Significant correlations between these ratios observed in moldavites might thus be an indicator of the * - counting with planar HPGe detector 0 50 100 150 200 250 300 350 400 3 5 7 9 11 13 15 17 K/N a C a/Sr 0 10 20 30 40 50 60 70 80 3 5 7 9 11 13 15 17 K/N a C a/Ba 0.15 0.20 0.25 0.30 0.35 0.40 0.45 3 5 7 9 11 13 15 17 K/N a U /Th 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 3 5 7 9 11 13 15 17 K/N a Ca/Al MCB MSB MM ML 4 5 6 7 8 9 10 11 3 5 7 9 11 13 15 17 K/N a Si/A l 190 210 230 250 270 290 3 5 7 9 11 13 15 17 K /Na K/Rb
description
Unconventional component of parent materials of moldavites Jiří MIZERA, Zdeněk ŘANDA , Jan KAMENÍK Nuclear Physics Institute, Academy of Sciences of the Czech Republic Řež 130, 250 68, Czech Republic E-mail: mizera @ujf.cas.cz. 3 rd International Nuclear Chemistry Congress Sicily – Italy - PowerPoint PPT Presentation
Transcript of Unconventional component of parent materials of moldavites Jiří MIZERA, Zdeněk ŘANDA , Jan...
Unconventional component of parent materials of moldavitesUnconventional component of parent materials of moldavites
Jiří MIZERA, Zdeněk ŘANDA, Jan KAMENÍK
Nuclear Physics Institute, Academy of Sciences of the Czech RepublicŘež 130, 250 68, Czech Republic
E-mail: [email protected]
3rd International Nuclear Chemistry CongressSicily – Italy18 - 23 September 2011
SummarySummary
17161514131211
49
50
51
Longitude °E
Lat
itu
de
°N
17161514131211
49
50
51
Longitude °E
Lat
itu
de
°N
Formation of the Central European tektites - moldavites -
has unequivocally been associated with a large meteorite
impact to Ries region in western Bavaria in Germany 14.5
million years ago. However, after several decades of
investigation, unambiguous assigning all source materials
of moldavites and processes of their chemical
differentiation still remains open. Despite some similarity
of chemical composition between moldavites and
isochronous sediments from vicinity of the Ries crater,
there are some significant differences in both major and
trace element contents, which cannot be attributed solely
to the variability of the sediments or later weathering
processes. Some of these differences could be explained
by an original hypothesis, according to which ash from
biomass burned at the early stage of the meteorite impact
contributed to the source materials.
Analytical modeSample mass
Irradiation - decay - counting times
Irrradiation operating parameters
Elements determined
Short-time INAA, activation with reactor-
pile neutrons~50 mg 1 - 12 - 12 min LVR-15 reactor
9 MWneutron fluence rates3e13 - 5e12 n cm-2s-1
(th – fast)
Na, K, Mg, Ca, Ba, Al, Ti, V, Mn, Dy
Short-time INAA, activation in Cd
~100 mg 0.75 - 13 - 13 min Si, U
Long-time INAA, activation with reactor-
pile neutrons- 1st count- 2nd count- 3rd count
200-300 mg
2 h – 5 d – 20 min
2 h – 13 d – 45 min
2 h – 30 (80*) d – 2 h
LVR-15 reactor9 MW
neutron fluence rates8e13 - 2e13 n cm-2s-1
(th - fast)
Na, K, As, Sb, La, Sm, U
Rb, Cs, Ca, Sr, Ba, Sb, Sc, Cr, Fe, Co, Zr, Hf, La, Ce, Nd, Sm, Eu, Yb, Lu, Th
Rb, Cs, Sr, Ba, Sb, Sc, Cr, Fe, Co, Zn, Zr, Hf, Ta, Ce, Eu,
Tb, Yb, Th, (Ir), *Gd, *Tm
Long-time INAA,activation in Cd
- 1st count- 2nd count- 3rd count
200-300 mg
2 h – 4 d – 30 min
2 h – 7 d – 45 min
2 h – 25 d – 2 h
LVR-15 reactor9 MW
neutron fluence rates8e13 - 2e13 n cm-2s-1
(th - fast)
K, As, Ga, Br, Cu, Mo, W, Pr, Ho
Rb, Ca, Ba, As, Sb, Br, Mo, Au, La, Nd, Sm, Yb, Lu, Th, U
Rb,Cs, Ba, Sr, Sb, Sc, Cr, Fe, Co, Ni, Zn, Zr, Ag, Hf, Ta, (Ir), Ce, Nd, Eu, Gd, Tb, Tm, Yb
IPAA - 1st count - 2nd cound - 3rd count - 4th count
1-2.5 g
6 h - 5-7 h - 15 min6 h - 1 d – 30 min
6 h - 7 d – 1 h6 h - 20 d – 5 h
MT-25 microtronE = 22 MeV
I = 15 A
Sr, TiMg, Ca, Ba, Ti, Ni, Zr, Sm, Th
Cs, Ca, Rb, Zr, Nb, Ce, Nd, Sm Na, Rb, Cs, Sr, Mn, Co, Y, Nb, Ce
Geochemical characterization of a large collection of
moldavites using instrumental neutron/photon activation
analyses supported the hypothesis. As shown by the
data acquired in the study, this unconventional “biogenic
component” could be indicated by enrichment in
elements essential for plants (e.g., K, Ca, Mg) and
depletion of nonessential elements (e.g., Na, Rb, Sr, Ba),
similarly to redistribution of these elements during their
transfer from soil to plants. Differentiation similar to that
occurring during the soil-plant interaction has been
observed also for other, nonessential elements, e.g., U
and Th. Correlations between the K/Na ratio and K/Rb,
Ca/Sr, Ca/Ba, and U/Th ratios, as well as some other
indicators of the “biogenic” component observed in
moldavites from various parts of the Central European
tektite strewn field are presented and discussed.
Moldavites from Southern Bohemia.
ExperimentalExperimental
• collection of 103 moldavites from the major parts of the Central European tektite strewn field: Southern Bohemia (MSB, 59), Cheb Basin (MCB, 30), Moravia (MM, 13), Lusatia (ML, 1) • analyzed by INAA and IPAA using the LVR-15 reactor of the Nuclear Research Inst., Řež, plc., and the MT-25 microtron of the Nuclear Physics Inst. ASCR, respectively• selective irradiation with epithermal/fast neutrons in Cd shielding included – interferences from fission suppressed (95Zr, 99Mo, 140La, 141Ce, 147Nd) • various irradiation - decay - counting modes applied• RM used for QC: USGS GSP-1 granodiorite, SARM GS-N granite
The study has been supported by the Czech Science Foundation grant 205/09/0991.
Central European tektite strewn field and its substrewn fields.
3
5
7
9
11
13
15
17
0 1 2 3 4 5 6 7 8 9
CaO+MgO (wt%)
K/N
a
3
5
7
9
11
13
15
17
6 7 8 9 10 11 12 13 14
Al2O3 (wt%)
K/N
a
MCB
MSB
MM
ML
3
5
7
9
11
13
15
17
0.00 0.05 0.10 0.15 0.20
MnO (wt%)
K/N
a
3
5
7
9
11
13
15
17
72 74 76 78 80 82 84 86
SiO2 (wt%)
K/N
a
3
5
7
9
11
13
15
17
1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4
K2O (wt%)
K/N
a
3
5
7
9
11
13
15
17
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Na2O (wt%)
K/N
a
ResultsResults
The current concept of moldavite parent materials assumes mixing of 3 components of the Miocene sediments - quartz sands, clayey soil, and a Ca-Mg component. The Ca-Mg component has newly been assigned (besides carbonates) to ash produced from burned biomass and soil during the meteoritic impact. Composition of plant ash is governed by Ca, Si, K, Mg, and Mn, and characterized by a high K/Na ratio. Correlations between the K/Na ratio and the major elements support this assignment, particularly in a part of the Cheb Basin moldavites.
In plants, due to enrichment in essential elements and depletion of nonessential
elements, besides K/Na also Si/Al, Ca/Al, K/Rb, Ca/Sr, and Ca/Ba ratios increase
during transfer of the elements from soil to plants. Redistribution of some
nonessential elements as U and Th also occurs by soil-plant interaction. Significant
correlations between these ratios observed in moldavites might thus be an indicator
of the “biogenic” component in the parent materials of moldavites.
* - counting with planar HPGe detector
0
50
100
150
200
250
300
350
400
3 5 7 9 11 13 15 17
K/Na
Ca/
Sr
0
10
20
30
40
50
60
70
80
3 5 7 9 11 13 15 17
K/Na
Ca/
Ba
0.15
0.20
0.25
0.30
0.35
0.40
0.45
3 5 7 9 11 13 15 17
K/Na
U/T
h
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
3 5 7 9 11 13 15 17
K/Na
Ca
/Al
MCB
MSB
MM
ML
4
5
6
7
8
9
10
11
3 5 7 9 11 13 15 17
K/Na
Si/
Al
190
210
230
250
270
290
3 5 7 9 11 13 15 17
K/Na
K/R
b
