Geology Reference
In-Depth Information
EL4 enstatite chondrite
1.2 g
Found January 24, 1995
1.5 × 1.0 × 0.5 cm
Weathering = C
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 include petrologic types 3 through 6, with
equilibrated type 6 chondrites providing constraints on the metamorphic
history of the EL chondrite. Enstatite chondrites also share the same
oxygen isotopic signature as the Earth, the Moon, and aubrites.
Plate 32
MiNERALogy
SigNiFiCANCE
QUE 94368 shows numerous chondrules and irregular
aggregates, up to 0.6 mm across, and mineral grains in a
moderate amount of dark matrix. The matrix contains a
minor amount of nickel-iron and sulfides. The chondrules,
aggregates, and mineral grains appear to consist entirely
of pyroxene. The pyroxene is close to MgSio
3
in composi-
tion, but a few more iron-rich grains were analyzed. The
nickel-iron contains 0.5%-0.7% Si and sometimes has
graphite associated or included within (left, [222]).
QUE 94368 was the first recognized EL4 chondrite,
thus helping to define the metamorphic history of
the EL chondrite parent body. Subsequently, sinoite
(right, [221]) was discovered in QUE 94368, indicative
of highly reduced conditions, by the equilibrium
Sio
2
+ 3Si + 2 N
2
(g) = 2Si
2
N
2
o.
References [221, 222]
