A New Moldavite Sub-Strewn Field in Lower Silesia, … › meetings › metsoc2016 › eposter ›...
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A New Moldavite Sub-Strewn Field in Lower Silesia, Poland R. Skála , Š. Jonášová , K. Žák , J. Ďurišová , T. Brachaniec & T. Magna 1,2 1,2 1 1 3 4 1 2 Institute of Geology, The Czech Academy of Sciences, Rozvojová 269, 16500 Prague 6, Czech Republic, Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 12843, Prague 2, Czech Republic, 3 Department of Geochemistry, Mineralogy and Petrology, Faculty of Earth Sciences, University of Silesia, Bedzinska st. 60, 41-200 Sosnowiec, Poland, Czech Geological Survey, Klárov 3, 11821 Prague 1, Czech Republic 4 0 25 50 75 100 km 2 0 0 k m 25 0 k m 30 0 km 35 0k m Ries Steinheim Mn N D L Ps P V B Wr 40 0 km 4 50 km 500 km 51 N ° 50 N ° 49 N ° 11°E 10°E 12°E 13°E 14°E 15°E 16°E 17°E 11°E 10°E 12°E 13°E 14°E 15°E 16°E 17°E 51 N ° 50 N ° 49 N ° G M R Lus Ch H SB Mor 100 μm 200 μm a b 1000 μm c 200 μm d Acknowledgements: This research was supported through the Czech Science Foundation (GAČR) project No. 13-22351S, the Institute of Geology of the CAS Research Plan RVO67985831, and the Polish National Science Centre grant No. 2014/13/N/ST10/04921. Introduction: Traditionally, the Central European tektites (CETs) a.k.a. moldavites occur in several small areas (sub-strewn fields) reflecting the paleogeography at the time of impact as well as further geological history of the area. These regions include south Bohemia and western Moravia [1, 2], Austria [3], Lusatia [4] and the Cheb Basin [5]. In addition to these larger accumulations several scattered finds were also reported [6–8]. None of these moldavite occur- rences exceeds the distance of ~420 km from the center of the Ries crater – the parent impact structure of CETs. Recently, Brachaniec et al. found [9–11] moldavites at three localities in Lower Silesia, Poland: sandpits close to villages Rusko and Mielęcin SW of Wrocław, and sandpits in Gozdnica, NW of Jelenia G ra. The former two occurrences are located at a distance of about 475 km from ó the Ries crater center significantly extending the entire CET strewn field ( ). Fig. 1 Brachaniec et al. reported electron microprobe analyses for several of the [9–11] found moldavites, limited to the determination of the major elements, and based on them together with the mass and size distribution of individual finds they con- cluded that Polish moldavites were re-deposited from the Lusatian sub-strewn field by fluvial transport in Late Miocene. Cs Rb Ba W Th U Nb Ta La Ce Pb Pr Sr P Nd Be Zr Hf Li Sm Eu Sn Ti Gd Tb Dy Y Ho Er Tm Yb Lu Sc V Zn Cu Co Cr Ni UCC-normalized contents Cs Rb Ba W Th U Nb Ta La Ce Pb Pr Sr P Nd Be Zr Hf Li Sm Eu Sn Ti Gd Tb Dy Y Ho Er Tm Yb Lu Sc V Zn Cu Co Cr Ni Cs Rb Ba W Th U Nb Ta La Ce Pb Pr Sr P Nd Be Zr Hf Li Sm Eu Sn Ti Gd Tb Dy Y Ho Er Tm Yb Lu Sc V Zn Cu Co Cr Ni 0.01 0.1 1 10 0.001 0.01 0.1 1 10 0.01 0.1 1 10 0.01 0.1 1 10 0.01 0.1 1 10 Lusatia Lange (1995) & = 6 n Austria Koeberl et al. (1988) Cheb Basin = 80 n Moravia n = 25 South Bohemia = 127 n Goals: Since the importance of the finds of CETs in Poland for delineating of the strewn field we decided to collect major-, minor-, and trace-element data for a fragment of one moldavite from sandpit near Rusko (sample NS-4). When com- pared with existing datasets from other sub-strewn fields these new data com- plemented with the critical revision of local stratigraphy and paleogeography may help to constrain the origin of Polish moldavites, i.e., if they were transported from the Lusatian sub-strewn field as suggested in [9–11] or if they were depos- ited here directly at the time of impact forming a new separate sub-strewn field. Methods: The sample surface as well as polished thin section were imaged using a scanning electron microscope TESCAN VEGA 3XM. Major-element data were collected with a CAMECA SX-100 electron probe microanalyzer. Trace- element concentrations were determined on a polished thin section using a high- resolution Thermo Finnigan Element 2 ICP-MS coupled to a 213 nm Nd:YAG laser ablation system UP-213 (New Wave Research). Results: The surface of the sample displays marked sculpturing ( ). Figs. 2a,b The polished section reveals presence of numerous bubbles and lechatelierite inclusions ( ). The specimen is chemically heterogeneous with overall Fig. 2c fluidal fabric ( ). Two types of glass are present ( ). The high-Si Fig. 2d Fig. 3 (76–82 wt. % SiO ) low-Ca–Mg glass volumetrically dominates whereas the low- 2 Si (~74 wt. % SiO ) high-Ca–Mg glass is present as thin schlieren. The majority of 2 analyses presented here matches common compositions of moldavites from other sub-strewn fields. The low-Si high-Ca–Mg schlieren, however, are a rather unique group at the edge or even outside the compositional fields defined by ~5000 electron-microprobe analyses of moldavites from other parts of the CET strewn field. Such a composition is duplicated by only several analyses of South Bohemian moldavites. Chondrite-normalized REE patterns of the specimen match South Bohemian and Cheb Basin moldavites. The spiderplots demonstrate considerable enrich- ments in Cs, Rb and Li and substantial depletion in W, Pb, Sr, P, Sn, Sc, V, Zn, Cu, Co, Cr and Ni compared to UCC ( ). Fig. 4 Discussion: Lange [4] and Bouška et al. [12] showed that the effective transport of tektites in water streams is limited to less than 10 km. Clearly, the Polish moldavites could have hardly resisted re-deposition from Lusatian sub-strewn field for over at least 50 km in case of Gozdnica locality or >160 km in case of Rusko and Mielęcin. In addition, L neither in the ate Miocene nor in the Pliocene there was a river heading from Lusatia to Lower Silesia that might have potential- ly transported moldavites. fluvial deposits of river courses hea- There are solely ding to the North. Conclusions: The chemical composition does not allow unambiguously linking the Polish moldavites to any other existing CET sub-strewn field. The morpho- logical character of Polish moldavites and paleogeography of Central Europe in the last 15 Ma suggest that they represent pieces fluvially re-deposited from a new so far unknown separate sub-strewn field located south of the place of their recent occurrence. Polish moldavite, present data North Stanisław, Brachaniec et al., 2014 Gozdnica, Brachaniec et al., 2015 Mielęcin, Brachaniec et al., 2015 North Stanisław, Brachaniec et al., 2015 DiVincenzo and Skála, 2009; ála Sk et al., 2009 and unpublished data Published data w/ 1-sigma error bars References: [1] Bouška V. 1972. Acta Universitatis Carolinae, Geologica 1972:1–29. [2] Trnka M. and Houzar S. 1991. Muzejní a Moravian Moldavites. vlastivědná společnost v Brně, Západomoravské muzeum v Třebíči, pp. 1–115 (in Czech). [3] Koeberl C. et al. 1988. : 325–332. [4] Lange J.-M. Meteoritics 23 1996. :498–510. [5] Bouška V. et al. 1995. Chemie der Erde Bulletin of the 56 Czech Geological Survey Geologický průzkum :73–80. [6] Žebera K. 1972. 70 14 :54–56 (in Czech). [7] Žák K. et al. 1999. Bulletin mineralogicko- petrologického oddělení Národního muzea (Praha) :242–243 (in Czech). [8] 7 Ložek V. and Žák K. 2011. :49–94 (in Czech). [9] Bohemia Centralis 31 Brachaniec T. et al. 2014. :1–8. [10] Meteoritics & Planetary Science 49 Brachaniec T. et al. 2015. :1697–1702. [11] Meteoritics & Planetary Science 50 Brachaniec T. et al. 2016. :99–105. Bouška V. et Acta Geologica Polonica 66 [12] al. 1968. :277–286. [13] Skála R. et al. Acta Universitatis Carolinae, Geologica 4 2009. : 1145–1179. [14] Di Vincenzo G. and Skála Geochim Cosmochim Acta 73 R. 2009. : 493–513. Geochim Cosmochim Acta 73 South Bohemia = 4066 n Moravia n = 424 Cheb Basin = 878 n Austria Koeberl et al. (1988) Lusatia Lange (1995) & = 25 n MgO (wt.%) 1 2 3 4 5 CaO (wt.%) 2 4 6 8 10 1.4 65 70 75 80 85 90 SiO (wt.%) 2 70 75 80 85 90 SiO (wt.%) 2 70 75 80 85 90 SiO (wt.%) 2 65 70 75 80 85 90 SiO (wt.%) 2 70 75 80 85 90 SiO (wt.%) 2 Fig. 1. Map of Central Eu- rope illustrating the distribu- tion of major moldavite local- ities. Red stars indicate Pol- ish localities with moldavite finds: R = North Stanisław near Rusko, M = Mielęcin and G = Gozdnica. Green tri- angles show locations of se- lected moldavite occur- rences across CET strewn field whereas light green dia- monds stand for uncertain or unconfirmed finds. The Ries and Steinheim impact struc- tures are also shown. Sub- strewn fields: Ch = Cheb, H = Horn, Lus = Lusatia, Mor = Moravia, SB = South Bohe- mia. Fig. 2. Scanning electron microscope images of the surface (a,b) and polished section (c,d) of the moldavite from the North Stanisław sandpit. ome larger pits are possibly relics of for- S mer bubbles and may show fine striation on their walls highlighting the overall fluidal fabric (a). Youngest sculpturing is formed by small circular flat depressions mostly less than 5 μm in diameter ( ). entire area of the studied polished section illustrat the dis- b BSE image of the es tribution of lechatelierite inclusions and the overall fluidal fabric (c); detail of fluidal fabric with bright high-Ca–Mg lamellae is shown in (d). ▲ 3 Fig. The high-Si-low- Ca–Mg and low-Si-high- Ca–Mg chemical glass com- positions of the NS-4 molda- vite Harker dia- illustrated in grams. Shown for compari- son are data presented for other Polish moldavites [9- 10] [4] , Lusatian moldavites , and Austrian moldavites . [3] Data for South Bohemian, Mo- ravian, Cheb and partly Lusa- tian moldavites either come from Skála et al. and Di [13] Vincenzo and Skála or [14] they represent unpublished authors’ analyses. ◄ Fig. 4. Upper continental crust-normalized contents of minor and trace elements in the NS-4 moldavite (yellow field) compared to data for moldavites from the classical sub-strewn fields (light blue circles and connecting lines). Red arrows indicate ele- ments substantially depleted in the sample compared to UCC contents, green arrows denote enriched elements. Data for comparison are from the same sources as those in Fig. 3. For details see: DOI: 10.3190/jgeosci.214
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A New Moldavite Sub-Strewn Field in Lower Silesia, PolandR. Skála , Š. Jonášová , K. Žák , J. Ďurišová , T. Brachaniec & T. Magna1,2 1,2 1 1 3 4
1 2Institute of Geology, The Czech Academy of Sciences, Rozvojová 269, 16500 Prague 6, Czech Republic, Institute of Geochemistry,Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 12843, Prague 2, Czech Republic,
3Department of Geochemistry, Mineralogy and Petrology, Faculty of Earth Sciences, University of Silesia, Bedzinska st. 60, 41-200
Sosnowiec, Poland, Czech Geological Survey, Klárov 3, 11821 Prague 1, Czech Republic4
0 25 50 75 100 km
200 km
250 km
300 km350
km
Ries
Steinheim
Mn
N
D
L
Ps
P
V
B
Wr
400
km
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500
km
51 N°
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49 N°
11°E10°E 12°E 13°E 14°E 15°E 16°E 17°E
11°E10°E 12°E 13°E 14°E 15°E 16°E 17°E
51 N°
50 N°
49 N°
G
MR
Lus
Ch
HSB
Mor
100 μm200 μm
a b
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Acknowledgements: This research was supported through the Czech ScienceFoundation (GAČR) project No. 13-22351S, the Institute of Geology of the CASResearch Plan RVO67985831, and the Polish National Science Centre grantNo. 2014/13/N/ST10/04921.
Introduction: Traditionally, the Central European tektites (CETs) a.k.a.moldavites occur in several small areas (sub-strewn fields) reflecting thepaleogeography at the time of impact as well as further geological history of thearea. These regions include south Bohemia and western Moravia [1, 2], Austria[3], Lusatia [4] and the Cheb Basin [5]. In addition to these larger accumulationsseveral scattered finds were also reported [6–8]. None of these moldavite occur-rences exceeds the distance of ~420 km from the center of the Ries crater – theparent impact structure of CETs. Recently, Brachaniec et al. found[9–11]moldavites at three localities in Lower Silesia, Poland: sandpits close to villagesRusko and Mielęcin SW of Wrocław, and sandpits in Gozdnica, NW of JeleniaG ra. The former two occurrences are located at a distance of about 475 km fromóthe Ries crater center significantly extending the entire CET strewn field ( ).Fig. 1Brachaniec et al. reported electron microprobe analyses for several of the[9–11]found moldavites, limited to the determination of the major elements, and basedon them together with the mass and size distribution of individual finds they con-cluded that Polish moldavites were re-deposited from the Lusatian sub-strewnfield by fluvial transport in Late Miocene.
Cs
Rb
Ba W Th U
Nb
Ta
La
Ce
Pb
Pr
Sr P
Nd
Be Zr
Hf
Li
Sm Eu
Sn Ti
Gd
Tb
Dy Y
Ho
Er
Tm Yb
Lu
Sc V
Zn
Cu
Co
Cr
Ni
UC
C-n
orm
alize
dco
nte
nts
Cs
Rb
Ba W Th U
Nb
Ta
La
Ce
Pb
Pr
Sr P
Nd
Be Zr
Hf
Li
Sm Eu
Sn Ti
Gd
Tb
Dy Y
Ho
Er
Tm Yb
Lu
Sc V
Zn
Cu
Co
Cr
Ni
Cs
Rb
Ba W Th U
Nb
Ta
La
Ce
Pb
Pr
Sr P
Nd
Be Zr
Hf
Li
Sm Eu
Sn Ti
Gd
Tb
Dy Y
Ho
Er
Tm Yb
Lu
Sc V
Zn
Cu
Co
Cr
Ni
0.01
0.1
1
10
0.001
0.01
0.1
1
10
0.01
0.1
1
10
0.01
0.1
1
10
0.01
0.1
1
10
LusatiaLange (1995)
& = 6n
AustriaKoeberl et al. (1988)
Cheb Basin= 80n
Moravian = 25
South Bohemia= 127n
Goals: Since the importance of the finds of CETs in Poland for delineating of thestrewn field we decided to collect major-, minor-, and trace-element data for afragment of one moldavite from sandpit near Rusko (sample NS-4). When com-pared with existing datasets from other sub-strewn fields these new data com-plemented with the critical revision of local stratigraphy and paleogeographymay help to constrain the origin of Polish moldavites, i.e., if they were transportedfrom the Lusatian sub-strewn field as suggested in [9–11] or if they were depos-ited here directly at the time of impact forming a new separate sub-strewn field.
Methods: The sample surface as well as polished thin section were imagedusing a scanning electron microscope TESCAN VEGA3XM. Major-element datawere collected with a CAMECA SX-100 electron probe microanalyzer. Trace-element concentrations were determined on a polished thin section using a high-resolution Thermo Finnigan Element 2 ICP-MS coupled to a 213 nm Nd:YAGlaser ablation system UP-213 (New Wave Research).
Results: The surface of the sample displays marked sculpturing ( ).Figs. 2a,bThe polished section reveals presence of numerous bubbles and lechatelieriteinclusions ( ). The specimen is chemically heterogeneous with overallFig. 2cfluidal fabric ( ). Two types of glass are present ( ). The high-SiFig. 2d Fig. 3(76–82 wt. % SiO ) low-Ca–Mg glass volumetrically dominates whereas the low-2
Si (~74 wt. % SiO ) high-Ca–Mg glass is present as thin schlieren. The majority of2
analyses presented here matches common compositions of moldavites fromother sub-strewn fields. The low-Si high-Ca–Mg schlieren, however, are a ratherunique group at the edge or even outside the compositional fields defined by~5000 electron-microprobe analyses of moldavites from other parts of the CETstrewn field. Such a composition is duplicated by only several analyses of SouthBohemian moldavites.Chondrite-normalized REE patterns of the specimen match South Bohemianand Cheb Basin moldavites. The spiderplots demonstrate considerable enrich-ments in Cs, Rb and Li and substantial depletion in W, Pb, Sr, P, Sn, Sc, V, Zn, Cu,Co, Cr and Ni compared to UCC ( ).Fig. 4
Discussion: Lange [4] and Bouška et al. [12] showed that the effective transportof tektites in water streams is limited to less than 10 km. Clearly, the Polishmoldavites could have hardly resisted re-deposition from Lusatian sub-strewnfield for over at least 50 km in case of Gozdnica locality or >160 km in case ofRusko and Mielęcin. In addition, Lneither in the ate Miocene nor in the Pliocenethere was a river heading from Lusatia to Lower Silesia that might have potential-ly transported moldavites. fluvial deposits of river courses hea-There are solelyding to the North.
Conclusions: The chemical composition does not allow unambiguously linkingthe Polish moldavites to any other existing CET sub-strewn field. The morpho-logical character of Polish moldavites and paleogeography of Central Europe inthe last 15 Ma suggest that they represent pieces fluvially re-deposited from anew so far unknown separate sub-strewn field located south of the place of theirrecent occurrence.
Polish moldavite, present data
North Stanisław, Brachaniec et al., 2014
Gozdnica, Brachaniec et al., 2015
Mielęcin, Brachaniec et al., 2015
North Stanisław, Brachaniec et al., 2015DiVincenzo and Skála, 2009;
álaSk et al., 2009and unpublished dataPublished data w/ 1-sigma error bars
References: [1] Bouška V. 1972. Acta Universitatis Carolinae, Geologica1972:1–29. [2] Trnka M. and Houzar S. 1991. Muzejní aMoravian Moldavites.vlastivědná společnost v Brně, Západomoravské muzeum v Třebíči, pp. 1–115(in Czech). [3] Koeberl C. et al. 1988. : 325–332. [4] Lange J.-M.Meteoritics 231996. :498–510. [5] Bouška V. et al. 1995.Chemie der Erde Bulletin of the56Czech Geological Survey Geologický průzkum:73–80. [6] Žebera K. 1972.7014:54–56 (in Czech). [7] Žák K. et al. 1999. Bulletin mineralogicko-petrologického oddělení Národního muzea (Praha) :242–243 (in Czech). [8]7Ložek V. and Žák K. 2011. :49–94 (in Czech). [9]Bohemia Centralis 31Brachaniec T. et al. 2014. :1–8. [10]Meteoritics & Planetary Science 49Brachaniec T. et al. 2015. :1697–1702. [11]Meteoritics & Planetary Science 50Brachaniec T. et al. 2016. :99–105. Bouška V. etActa Geologica Polonica 66 [12]al. 1968. :277–286. [13] Skála R. et al.Acta Universitatis Carolinae, Geologica 42009. : 1145–1179. [14] Di Vincenzo G. and SkálaGeochim Cosmochim Acta 73R. 2009. : 493–513.Geochim CosmochimActa 73
South Bohemia= 4066n
Moravian = 424
Cheb Basin= 878n
AustriaKoeberl et al. (1988)
LusatiaLange (1995)
& = 25n
MgO
(w
t.%
)
1
2
3
4
5
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O (
wt.
%)
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4
6
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65 70 75 80 85 90
SiO (wt.%)2
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SiO (wt.%)2
70 75 80 85 90
SiO (wt.%)2
65 70 75 80 85 90
SiO (wt.%)2
70 75 80 85 90
SiO (wt.%)2
Fig. 1. Map of Central Eu-rope illustrating the distribu-tion of major moldavite local-ities. Red stars indicate Pol-ish localities with moldavitefinds: R = North Stanisławnear Rusko, M = Mielęcinand G = Gozdnica. Green tri-angles show locations of se-lected moldavite occur-rences across CET strewnfield whereas light green dia-monds stand for uncertain orunconfirmed finds. The Riesand Steinheim impact struc-tures are also shown. Sub-strewn fields: Ch = Cheb, H =Horn, Lus = Lusatia, Mor =Moravia, SB = South Bohe-mia.
Fig. 2. Scanning electron microscope images of the surface (a,b) and polished section (c,d)of the moldavite from the North Stanisław sandpit. ome larger pits are possibly relics of for-Smer bubbles and may show fine striation on their walls highlighting the overall fluidal fabric(a). Youngest sculpturing is formed by small circular flat depressions mostly less than 5 μmin diameter ( ). entire area of the studied polished section illustrat the dis-b BSE image of the estribution of lechatelierite inclusions and the overall fluidal fabric (c); detail of fluidal fabric withbright high-Ca–Mg lamellae is shown in (d).
▲ 3Fig. The high-Si-low-Ca–Mg and low-Si-high-Ca–Mg chemical glass com-positions of the NS-4 molda-vite Harker dia-illustrated ingrams. Shown for compari-son are data presented forother Polish moldavites [9-10] [4], Lusatian moldavites ,and Austrian moldavites .[3]Data for South Bohemian, Mo-ravian, Cheb and partly Lusa-tian moldavites either comefrom Skála et al. and Di[13]Vincenzo and Skála or[14]they represent unpublishedauthors’analyses.◄ Fig. 4. Upper continentalcrust-normalized contents ofminor and trace elements inthe NS-4 moldavite (yellowfield) compared to data formoldavites from the classicalsub-strewn fields (light bluecircles and connecting lines).Red arrows indicate ele-ments substantially depletedin the sample compared toUCC contents, green arrowsdenote enriched elements.Data for comparison are fromthe same sources as those inFig. 3.
For details see: DOI: 10.3190/jgeosci.214
