What tell us the presence
of carbon in the shock-generated Martian meteorite "Tissint"
about the genesis of the Shergottite
Unfortunately, the interpretation of
the scientific investigations goes in the wrong direction, as so often. Some
authors are not open to new thinking. They can not imagine that the peculiarities
found (especially carbon matter) are indications that the shergottite is a
rock material from the mantle-sphere of Mars that has reached explosively
A biotic origin of the carbon matter is doubtful, also the contamination
by carbonaceous chondrites. The carbon matter was original enclosed in veins.
The C isotopic compositions of the carbon matter are significantly different
to the Martian atmospheric CO2. The exceptionally young age of some Shergottites
(averaging 175 million years) proves that was still active volcanism on Mars
at that time. It is possible that the material direct entered into space.
The density of the Martian atmosphere at this time (Jurassic time on Earth)
was already very similar to today's. Due to differences in crystallization,
it is conceivable that a plug has initially formed in the crust, that was
then shoot by a new explosive magma thrust from the mantle to the surface.
The shock-induced, high-pressure phases in Martian meteorites are the
result of movements in the mantle magma. The high-P phases in Martian meteorites
include produced glass (maskelynite from plagioclase and pyroxene-composition
glass), ringwoodite (ɣ-polymorph
of olivine), akimotoite (ilmenite structure of pyroxene), lingunite (Na-hollandite
structure of plagioclase), majorite (garnet structure of pyroxene), tuite
of merrillite), stishovite (α-TiO2 structure of quartz) and silicate
perovskite (perovskite structure of pyroxene). Most of the high-P phases are
polymorphs (more densely packed structure) than low-P minerals. These high-P
phases are typically small and were only observed in isolated occurrences
in or near shock-induced melts within the meteorites.
NanoSIMS analysis of organic carbon from the Tissint Martian
meteorite: Evidence for the past existence of subsurface organic-bearing fluids
Yangting LIN et al. -- Meteoritics & Planetary Science 49, Nr 12, 2201–2218
(2014): doi: 10.1111/maps.12389
|"Tissint has been heavily shocked, producing
shock-melt veins and pockets and abundant fractures. It probably experienced
multiple shock events.
Two distinct petrographic settings of carbonaceous grains were
found in the adhesive-free section of Tissint. Most carbonaceous matter
occurs as fine veins fully filling fractures and cleavages in olivine
and pyroxene, but not in maskelynite. These fractures and cleavages terminate
at the boundaries of maskelynite, a typical shock feature reported in
The carbonaceous components are kerogen-like, based
on micro-Raman spectra and multielemental ratios, and were probably deposited
from fluids in shock-induced fractures in the parent rock of Tissint.
After precipitation of the organic matter, the rock experienced
another severe shock event, producing the melt veins that encapsulated
a part of the organic matter.
Two types of carbonaceous matter were analyzed with laser micro-Raman
spectroscopy. The Raman spectra exhibit a broad G-band centered at 1580
cm-1 and a smaller D-band at 1346 cm-1, similar
to those reported for carbon and clearly distinct from those of ordered
graphite. The kerogen-like carbon grains entrained in the shock-melt veins
have the same Raman spectra as those filling the fracture space, except
for the presence of a sharp band at 1327 cm-1, characteristic
of the diamond T2G mode and distinguished from the D-band at
1331 cm-1 of the synthetic diamond used to polish the sections.
This indicates a transformation of kerogen-like
carbon to diamond at high pressure by a shock event and confirms independent
observations in other samples of Tissint as well as in NWA-6162 and NWA-856
(El Goresy et al. 2013b).
We assert that the organic matter we found in Tissint is pristine
and is not terrestrial contamination.
We have confirmed this by the following lines of evidence: (1) it is deuterium-enriched;
(2) the presence of organic matter inclusions in shock-melt veins
indicates its formation before production of the veins by shock events
on Mars; (3) partial conversion of the organic
carbon inclusions entrained in the shock-melt veins to diamond also points
to strong pressure conditions."
|Representative Raman spectra of the carbonaceous matter
in the fractures (blue) and the shock-melt veins (red).
Note the sharp band at 1327-1 cm indicative of the T2G
diamond band in the carbonaceous inclusion in
the melt vein.
MULTIPLE SHOCK EVENTS AND DIAMOND FORMATION ON MARS
A. El Goresy et al -- 44th Lunar and Planetary Science Conference (2013),
"NWA-6162 and NWA-856: These shergottites enclose a unique
type of broad shock-melt veins with a novel assemblage containing rosette-like
objects surrounded by comb-structured net-like pattern. Each of the polygonal
comb-like entities contains a small (<2μm) inclusion of carbon.
Such bizarre carbon-bearing objects were never observed
before in any Martian meteorite. Preliminary laser micro-Raman investigations
showed that some of the carbon inclusions in NWA-6162 depict the T2G
band of diamond at 1327 cm-1 that shifted 5 wave numbers below
the characteristic Raman mode at 1331 cm-1 and further shifted
to 1324 cm-1 upon increase of the laser power thus confirming the
probable nano-sized diamond nature as previously demonstrated.
This is the first report of shock-induced diamond in
a Martian sample. We encountered in NWA-856 orderly arranged carbon
particles also in comb-like objects in rows in a shock-melt pool. Nature of
the carbon particles in Tissint, NWA 6162 and NWA 856 are under investigation
and are subject of further detailed Raman study and isotopic scrutiny by NanoSIMS
A view at high magnification of a shock
vein in Tissint depicting tightly packed anhedral fragmented
and mobilized majorite-pyropess + magnesiowüstite grains along with fragmented
carbon grains of stark variable sizes in their interstices.
A BSE-SEM view at high magnification of
a 2-3 μm wide shock melt vein in Tissint depicting liquidus
idiomorphic majorite-pyropess + magnesiowüstite crystals and a clot of
amoeboid-shaped carbon enclosing rounded majorite grains.
BSE-SEM view of an unusual comb-like texture
in Tissint containing carbon inclusion inside each polygonal
comb. Some of carbon particles are confirmed to be diamond.