Geology Reference
In-Depth Information
Shergottite
7942 g
Found January 13, 1980
22 × 17 × 14 cm
Weathering = Ae
the composition of trapped gases that match those measured by the
Viking
spacecraft at the surface of Mars. Their young ages (~180 Ma) indicate
they also came from a planet with young volcanism on its surface, like
Mars. in addition, plagioclase feldspar has been entirely converted to
the shock glass, maskelynite, demonstrating the high shock pressures
required to eject them from the surface of Mars. Studies of shergottites
have also revealed information about the interior (mantle and crust) of
Mars, thus helping constrain its conditions of formation.
Plate 70
MiNERALogy
SigNiFiCANCE
Lithology A is composed of a basaltic host (pyroxene,
maskelynite, high-Ti chromite, merrillite, minor Cl apatite,
ilmenite, pyrrhotite and mesostasis) containing xenocrysts
of olivine, Cr spinel, and low-Ca pyroxene (left). Lithology
B is homogeneous basalt containing augite laths in a
matrix of pigeonite-augite, maskelynite, ulvöspinel-ilmenite
intergrowth, whitlockite, Cl apatite, and mesostasis (right).
Lithology C is an assemblage of glass “pods” and thin,
interconnecting, glass veins.
EET A79001 is one of the largest martian meteorites and
contains three different lithologies, all of which have
made important contributions to our understanding of
martian geology. The black glassy pods (Lithology C) are
the source of trapped gas that provided a match and link
to Mars. The basaltic lithology (B), which makes up
about 10% of the meteorite's volume, is similar to other
basaltic shergottites and exhibits a direct contact with
the main lithology of the meteorite (A). Lithology A is
olivine-phyric textured but also contains many individuals
and clusters of xenocrysts of olivine (distinct from the
phenocrysts) and orthopyroxene. The latter provide some
additional information about the source magmatic history
of the parent melt.
References [639-700]
