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www.niger-meteorite-recon.de
Santa Vitoria do Palmar meteorite
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Picture 9. Densely packed chondrules on a polished end
section of the Santa Vitoria do Palmar meteorite. This sample was
taken from the 10.45 kg mass. Image courtesy of Meteorite Recon.
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Chemical petrographic analysis and classification
Although known as meteorite since at least 2003 Santa
Vitoria do Palmar did not find its way to a laboratory
before 2005. The fact that SVP today is classified
and published is due to the tireless efforts of Senór
Correia who contacted the author in November 2005 and
submitted a sample.
The polished endcut that was first
sent to Germany weighed 110 gm and was taken from the 10.450 kg mass
. The exterior exhibited a dark brown and moderately weathered rind.
The cut section displayed a remarkably unequilibrated
texture with a broad variety of chondrules. Almost all
of the known crystallisation patterns were present.
Everything pointed to a quite extraordinary type 3 chondrite.
The cut section also displayed large portions which were darkened due to shock metamorphism.
Some islands of lighter colored portions embedded in the shock blackenned matrix showed no change of colors at all.
The lower section of picture N° 9 shows such a portion.
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Picture 10. A radial chondrule under plain (right) and crossed polarized light (left) showing
fine pyroxene laths radiating from an eccentric nucleation point. Cut sections through the SVP meteorite
display an overwhelming variety of chondrule crystallisation patterns.
Photo courtesy of Dr. Daniel Acevedo from CANDIC/Argentina
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On behalf of the author a 20 gm sample and a
couple of macro images were sent to the Humboldt University in Berlin,
Germany, in early December 2005. The
mineralogical and petrographic analysis was conducted by
Dr. Ansgar Greshake, curator of the world famous meteorite
collection of the Berlin Museum of Natural History.
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Picture 11. SVP thinslide. Photo courtesy of Dr. A. Greshake MNB/Germany
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After thinsections were made and studied
it became evident that the Santa Vitoria do Palmar
meteorite has to be placed in the group of L3 chondrites.
Dr. Greshake’s decision was also the first scientific
confirmation, that the material found in Brazil was in fact
meteoritic.
In his classification report Dr. Greshake explains:
"Investigation of the thin section by
optical and scanning electron microscopy
revealed that the meteorite is an unbrecciated
ordinary chondrite consisting of well defined
chondrules covering a wide range of known chondrule
types set into a matrix of dominantly mineral
fragments and Fe,Ni-metal. Olivine and pyroxene
in chondrules and among the mineral fragments
are generally unequilibrated and individual
grains often show a pronounced compositional
zoning. Quantitative mineral analyses performed
with an electron microprobe attest a fayalite
(Fa) content in olivine of 0.5-35.2 mole%
and a ferrosilite (Fs) content in low-Ca
pyroxene of 0.5-31.6 mole%."
And he continues: "As a result
of shock metamorphism olivine shows
strong undulatory extinction and set
s of planar fractures; low-Ca pyroxene
is characterized by strong undulatory
extinction and irregular fractures.
As some olivine crystals already
display mosaicism, a shock stage
of S3/4 is assigned. Reflected
light microscopy showed that
metal in SVP is moderately
oxidized which corresponds
to the grade W2."
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Picture 12. The Correia mass weighing 10.450 kg . NMR Cubescale is 1cm. Photo courtesy of Lautaro Correia
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Current status, Distribution of individual masses
The writing of the submission
text to the Nomenclature Committee
of the Meteoritical Society
raised a question of particular interest
to all parties involved: Is there enough
evidence to link the findings of 2003 and
2004 with the fireball sighting of 1997? In
other words, is SVP to be considered a fall
or a find?
The weathering grade usually is an
appropriate indicator to shed some
light on the question of terrestrial
residence time. Unfortunately all
of the SVP finds were made in an area with an
exceptionally aggressive microclimate. The
sandy soil of the Mirim Lagoon shores is
humid and contains a high level of diluted
salts. The huge difference between summer and winter
temperatures as well as between day and night time
temperatures increases the effects of chemical and
mechanical weathering on an alien mineral embedded in
this harsh environment. According to the experts it
is most likely that a meteorite exposed to this environment
for a period of only six years will display the apparent
weathering phenomena found within the SVP material.
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Picture 13. Approximate find location of the 10.45 kg Correia masses. This is a flood
plane at the southern tip of the Mirim Lagoon which can be seen in the background.
Picture was taken viewing north. Image courtesy of Monzon Pereia.
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Only an isotope analysis which
still has to be conducted could
give a final determination on this
issue. The NomCom however decided that according
to their rules, they would only accepted the submission
as a find. This is by no means unusual
as the case of the Russian meteorite
Tsarev demonstrates. Although Russian newspapers
reported as early as 1921 on the Tsarev fall and
although the fall site had been known to the locals for decades, in
1978 Tsarev was officially recognised – as a find in
fact and not as a fall. As is the case with SVP, too
much time had passed between the sighting of the fireball
and the first discoveries.
Several masses of Santa Vitoria do Palmar are accessible
to science and the public today.
34.000 gm lost since 2004
8.100 gm with the Finder, Lautaro Correia, Santa Vitoria d.P., Brazil
4.340 gm Museo Municipal Cel. Tancredo F. de Mello, Brazil (RS)
1.570gm Museo Municipal Cel. Tancredo F. de Mello, Brazil (RS)
451gm Dr. Svend Buhl, Meteorite Recon, Hamburg, Germany
20 gm + polished thinslide Humboldt University, Museum of Natural History Berlin,
Approximately 1.100 gm in other museums and private collections worldwide.
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Picture 14. This is a 164 gm slice recently cut from the main mass. This section clearly shows the interesting mix of shock-darkened and unmetamorphosed
portions within the matrix. NMR scalecube is 1 cm. Photo courtesy of NigerMeteoriteRecon
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Conclusion
Due to the relatively large total known weight of 63 Kg,
due to the uncommon chondrule structures represented,
and certainly due to the well documented history of its discovery
the SVP meteorite is currently creating a significant interest
in the scientific community.
A number of publications from Brazil and Germany are being prepared, many
will follow. Since the first unsuccessful search for the meteorite led
by police chief Luiz Cavalheiro nine years have passed but due to the efforts
of Mr. Maciel, Monzon-Pereia and Correia samples of the new Brazilian meteorite
reached the laboratories of those in charge of decoding the enigmatic messengers
from space that we all pursue so hard. The community is also grateful to Dr.
Ansgar Greshake from the MNB for his thorough investigation and his painstaking
efforts to bring to light the circumstances of the finds. In March 2006 the National
Museum of Brazil in Rio de Janeiro officially confirmed Santa Vitoria do
Palmar as the 53rd Brazilian meteorite.
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Picture 15. The sign above the city portal of Santa Vitoria do Palmar reads
"33304 Amigos, Hospitalidade I Natureza". Obviously such hospitality also attracts visitors from space.
Image courtesy of Monzon Pereia.
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Click to continue
Part 1, "The 1997 fireball" |
Part 2, "First finds" |
Part 3, "Analysis" |
Part 4, "Map"
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© 2001-2008 NigerMeteoriteRecon
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