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Abstract paper: ASPHALTIC (BITUMINOUS) BRECCIAS WITH CARBOLITE (CARBON ALLOTROPE) AND BALLEN STRUCTURES IN SILICA AS INDICATIVE OF THERMAL SHOCK: MORE EVIDENCE OF A HOLOCENE METEORITE IMPACT EVENT IN THE CZECH REPUBLIC

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Abstract paper: ASPHALTIC (BITUMINOUS) BRECCIAS WITH CARBOLITE (CARBON ALLOTROPE) AND BALLEN STRUCTURES IN SILICA AS INDICATIVE OF THERMAL SHOCK: MORE EVIDENCE OF A HOLOCENE METEORITE IMPACT EVENT IN THE CZECH REPUBLIC

ASPHALTIC (BITUMINOUS) BRECCIAS WITH CARBOLITE (CARBON ALLOTROPE) AND BALLEN
STRUCTURES IN SILICA AS INDICATIVE OF THERMAL SHOCK: MORE EVIDENCE OF A
HOLOCENE METEORITE IMPACT EVENT IN THE CZECH REPUBLIC. M. Molnár1, P. Švanda2, L.
Beneš3, K. Ventura4, K. Ernstson5. 1Resselovo nám. 76, Chrudim 537 01, Czech Republic; molnar@ego93.com,
2,3,4University of Pardubice, Czech Republic; Pavel.Svanda@upce.cz Ludvik.Benes@upce.cz Karel.Ven-
tura@upce.cz, 5Faculty of Philosophy I, University of Würzburg, D-97074 Würzburg, Germany
(kernstson@ernstson.de).
Introduction: At the last year's LPSC a paper was
presented [1] that reported on a proposed Holocene
meteorite impact strewn field in the Czech Republic
documented by widespread finds of black, green and
white glasses, iron silicide particles, glass-like carbon,
pumice-like carbon matter and various forms of glassy
scoria. Meteorite impact was substantiated by typical
shock metamorphism. Remarkably no associated clear
impact craters could be established. Here we report on
the resumption of the field work revealing a new type
of spotty deposits of a so far completely unknown
aspaltitic (bituminous; in the following: asphaltic only)
breccia obviously adding to the earlier investigated
impact evidence.
Geologic setting: In the agricultural landscape of
the Elbe valley in the surroundings of Mochov and
Přerov nad Labem near Lysa nad Labem (Fig. 1) the
commonly light-colored Upper Cretaceous sandy marls
and clays locally alternate with superficially very dark
to black places which must not be confused with coal
marls exposed further away in the south. The peculiar
matter forming the uppermost cover and only
somtimes penetrating to somewhat greater depth is
mostly carbonaceous pointing to some kind of pyroly-
sis of organic matter. Typical constituents are asphaltic
boulders frequently forming real polymictic breccias
with sedimentary and crystalline fragments (Fig. 2).
Various strange mixtures of organic and inorganic mat-
ter add to a real "zoo" of peculiar samples (Fig. 3).
This asphaltic mass has apparently been frequently
confused with anthropogenic asphalt ignoring the very
details of facies and texture. Meanwhile similar oc-
curences have been reported from the whole territory
of Bohemia and Moravia.
Methods: The bituminous boulders were examined
by thin-section polarizing microscopy of the breccia
components and by XRD (D8 ADVANCE, Bruker
AXS) and SEM (TESCAN VEGA 3 EasyProbe with
EDX analyser) of the bituminous mass especially fo-
cussing on a conspicous type of tiny fibres. Diffracto-
grams were compared with a database of standards,
PDF-4 + database (CITACE).
Fig. 2. Cut face of a polymictic breccia with dominant-
ly quartzite components in asphaltic matrix. Fig. 3.
From the asphaltic breccia: p = glassy pumice-like
lamination within carbonaceous organic matter, g =
vesicular glass with mineral fragments. Photomicro-
graph, plane light.
Results: Thin sections of polymictic breccias -
ballen silica. From the many studied thin sections we
mention the observation of typical but not in all cases
diagnostic shock effects in breccia clasts like multiple
sets of PDF in feldspar, diaplectic feldspar, extreme
fracturing of quartz grains, multiple sets PF in quartz,
kink bands in mica and ballen structures in silica. We
will only address the latter here, because an observa-
tion in the asphaltic breccia (Fig. 2) remarkably corre-
sponds to results of the XRD and SEM-EDX ensuing
analyses.
Ballen structures in silica form a characteristic tex-
ture in quartz that in general is considered a result from
various stages of phase transformation and recrystalli-
zation of amorphous silica like e.g., diaplectic glass
and hence are regarded as shock indicator (e.g., [2]). A
different model has recently been suggested [3] that
proposes a formation of ballen in quartz in an extreme
thermal shock event. We support this hypothesis: In
Fig. 4 A a quartz particle has completely been trans-
ferred to diaplectic glass that has in part aquired a
ballen texture with slightly polygonal shape of individ-
ual ballen. In a second grain (Fig. 4 B) the diaplectic
glass has got a brick wall texture only faintly remind-
ing of the commonly observed roundish ballen pattern.
Finally in Fig. 4 C the diaplectic glass casing the brick
wall ballen has degenerated into "ballen" lamellae. A
fracture-mechanical process of ballen formation is fur-
1423.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)
ther supported by Fig. 5. In a third grain of diaplectic
glass the ballen network appears to trace a planar frac-
ture (PF) pattern in the former quartz grain similar to
the brick wall pattern in Fig. 4, and the passage of the
ballen texture into sets of quartz PDF also underlines
the validity of the new hypothesis dispensing with
multiple phase changes. The postulated [3] strong
thermal shock from cold to hot and to cold again
matches well the observation in the asphaltic breccia
where the diaplectic, ballen-bearing silica grains are
regularly found in contact with melt glass (Fig. 5 C).
Fig. 4. Diaplectic glass from shocked quartz in the
asphaltic breccia. Photomicrographs of ballen struc-
tures, plane light and crossed polarizers (see text).
Fig. 5. Ballen and planar features (PF and PDF), plane
light (A, C) and crossed polarizers (see text).
Carbolite. Relatively abundant orange transparent
fibres in the asphaltic boulders attracted particular at-
tention (Fig. 6 A) and were found on both the boulder
weathered surface and on fracture surfaces. SEM-EDX
analysis show pure carbon and oxygen (Fig. 6 B), the
latter possibly a contaminant from the air. XRD exe-
cuted on the fibres after dissolution of the asphalt re-
vealed a small amount of crystalline quartz (JCPDS
No. 00-046-1045) and wider hexagonal carbon lines
(JCPDS No. 00-050-0926) with lattice parameters a =
11,928 Å and c = 10,620 Å (CITACE) [xy] and an
average crystallite size of 92 Å (Fig. 7). Two weak
diffraction lines did not match any standard.
With respect to the identified grid parameters, we
identified the fibres as carbolite. The synthesis and
characterization of this carbon allotrope was first de-
scribed in 1995 [4, 5]. The synthesis was conducted at
high rates of carbon vapour cooling. Carbolite synthe-
sis by hydrometallurgical processes at high tempera-
tures and pressures was introduced much later [6]. In
the above-stated publications, the prepared carbon qua-
si-1D is characterized as an orange semi-transparent
material. This is in good accordance with our observa-
tions. BSE featured additional information about the
surface texture of the fibres. We observed carbolite
fibres consisting of helically twisted strips with a con-
siderably larger width compared with their thickness
(Fig. 6 C).
Fig. 6. Carbolite from the studied area. A: photo-
optical. B: SEM-EDX. C: BSE.
Fig. 7. XRD spectrum for the carbolite fibres.
Conclusions: The sythesis of two completely dif-
fering approaches to peculiar observations features a
model of an extreme thermal shock signature in an
asphaltic breccia that explains both the formation of
the carbon allotrope carbolite, hitherto unknown from
a natural environment, and the formation of silica dia-
plectic glass with ballen structures from an impact
shock event. The observations add to earlier field and
lab work [1] and strengthen the hypothesis of a young
meteorite impact event that has affected larger parts of
the Czech Republic. Details of this event remain rather
enigmatic which concerns both the lack of a definite
impact location with a formation of e.g., a crater struc-
ture, and the formation of the here discussed peculiar
asphaltic breccia. Natural asphalt or bitumen deposits
to have possibly supplied the breciia matrix are un-
known in the regions under discussion. A meteoritic
near-surface strong air burst event may vaguely be
considered that caused brecciation, shock metamor-
phism and formation of melt rocks and glasses [1] in
the surficial geologic strata. Such an air burst could
possibly have produced the asphaltic matter by a kind
of pyrolysis of the target vegetation.
References: [1] Molnár, M. et al. (2017) LPSC
XLVIII, Abstract #1920. [2] Ferrière L. et al. (2009)
Eur. J. Min, 21, 203-217. [3] Chanou, A. et al. (2015).
Bridging the Gap III, Abstract 1112. [4] Tanuma, S.
and Palnichenko, A. (1995) J. Mater. Res. 10(5),1120
1125. [5] Tanuma, S. et al. (1995) Synthetic Met-
als, 71, 1841-844. [6] Kozhbakhteev, E. M. (2013)
Russ. J. Inorg. Chem., 58(12), 1542-1546.
1423.pdf49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)
Article
The fundamental approach for the confirmation of any terrestrial meteorite impact structure is the identification of diagnostic shock metamorphic features, together with the physical and chemical characterization of impactites and target lithologies. However, for many of the approximately 200 confirmed impact structures known on Earth to date, multiple scale‐independent tell‐tale impact signatures have not been recorded. Especially some of the pre‐Paleozoic impact structures reported so far have yielded limited shock diagnostic evidence. The rocks of the Dhala structure in India, a deeply eroded Paleoproterozoic impact structure, exhibit a range of diagnostic shock features, and there is even evidence for traces of the impactor. This study provides a detailed look at shocked samples from the Dhala structure, and the shock metamorphic evidence recorded within them. It also includes a first report of shatter cones that form in the shock pressure range from ~2 to 30 GPa, data on feather features (FFs), crystallographic indexing of planar deformation features, first‐ever electron backscatter diffraction data for ballen quartz, and further analysis of shocked zircon. The discovery of FFs in quartz from a sample of the MCB‐10 drill core (497.50 m depth) provides a comparatively lower estimate of shock pressure (~7–10 GPa), whereas melting of a basement granitoid infers at least 50–60 GPa shock pressure. Thus, the Dhala impactites register a strongly heterogeneous shock pressure distribution between <2 and >60 GPa. The present comprehensive review of impact effects should lay to rest the nonimpact genesis of the Dhala structure proposed by some earlier workers from India.
Bridging the Gap III, Abstract 1112
  • S Tanuma
  • A Palnichenko
Bridging the Gap III, Abstract 1112. [4] Tanuma, S. and Palnichenko, A. (1995) J. Mater. Res. 10(5),1120
LPSC XLVIII, Abstract #1920
  • M Molnár
References: [1] Molnár, M. et al. (2017) LPSC XLVIII, Abstract #1920. [2] Ferrière L. et al. (2009)
Bridging the Gap III, Abstract 1112
  • J Eur
  • Min
  • A Chanou
Eur. J. Min, 21, 203-217. [3] Chanou, A. et al. (2015). Bridging the Gap III, Abstract 1112. [4] Tanuma, S. and Palnichenko, A. (1995) J. Mater. Res. 10(5),1120
  • J Russ
Russ. J. Inorg. Chem., 58(12), 1542-1546. 1423.pdf 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083)