Geology Reference
In-Depth Information
EL3 enstatite chondrite
1748.6 g
Found January 19, 1992
14.4 × 12.0 × 4.8 cm
Weathering = Ce
in  our meteorite collections and are composed of nearly pure Mg end-
member silicate minerals such as enstatite and metallic FeNi metal that
contains Si. EL chondrites also include petrologic types 3 through 6, with
unequilibrated type 3 chondrites providing insight into nebular processes in
a more reduced portion of the solar nebula. Enstatite chondrites also share
the same oxygen isotopic signature as the Earth, the Moon, and aubrites.
PCA91020,0
PCA91020,24
1 cm
1 cm
PCA91020 EL3
Shock stage S5
50 µ m
Metal-sulfide melt and silicate debris
Plate 30
MiNERALogy
SigNiFiCANCE
PCA 91020 contains abundant chondrules, ranging up to
1.8 mm in diameter; they consist of granular or radiating
pyroxene, sometimes with minor olivine. The matrix con-
sists of pyroxene grains, with 25%-30% nickel-iron metal
and a lesser amount of sulfides. Most of the pyroxene is
close to MgSio 3 in composition: mean Fs 1 , range Fs 0.2--3 ,
with Cao 0.1%-0.8%; olivine is forsterite (Feo 0.1%,
Cao 1.5%). The nickel-iron metal contains 0.3%-0.7% Si.
PCA 91020 is one of the most highly shocked enstatite
chondrites. it contains maskelynite, metal-troilite textures
(left, [201]) typical of rapid cooling from super-liquidus
temperatures, and also elliptical and elongated chondrules
and inclusions that are part of a foliation present in the
meteorite. given all of these unusual features, PCA 91020
records important information about shock processes
that operated on the enstatite chondrite parent bodies.
References [197-204]
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