Geology Reference
In-Depth Information
Aubrite
1163 g
Found January 6, 2005
12.0 × 7.0 × 7.0 cm
Weathering = A
oxygen isotopic value with Earth, Moon, and enstatite chondrites, and are
the most reduced basalts known. They contain unusual sulfides, low Feo
silicates, and sodic plagioclase feldspar. Some aubrites contain a basaltic
vitrophyre lithology that may represent a basaltic component from the
aubrite parent body. Their low Feo contents and small amount of metal
would give these samples a high albedo for a parent asteroid.
W
E
5000
4000
L
U
3000
64
40
2000
28
1000
0
0
20 0
60
80
10 0 20
140
Asteroid diameter in km
Plate 52
MiNERALogy
SigNiFiCANCE
LAR 04316 is composed of comminuted matrix of essen-
tially Feo-free enstatite (Fs
0-1
) and diopside (Fs
1
Wo
45
)
with grain sizes reaching 3 mm in diameter with rare
nickel-iron metal, schreibersite, troilite, daubreelite, and
alabandite. Two clasts described in the macroscopic
description, and apparently in contact in the piece, are an
aubrite basalt vitrophyre composed of enstatite (Fs
2
) and
forsterite (Fa
2
) in a matrix of feldspathic glass and a
metal-sulfide quench-textured clast (above right) with a
single 0.5 mm alabandite grain.
LAR 04316 is remarkable in containing a pyroxene-
plagioclase-metal-sulfide clast approximately 2 cm in
diameter that may record the earliest melting of an aster-
oidal body. Volcanoes on asteroids should have produced
sprays of droplets (pyroclasts) whose eruption velocity
exceeded the escape velocity of the parent asteroid. only
the largest such droplets, those in excess of 1 cm in diameter,
might have been preserved. The mineralogy and texture of
the clast in LAP 04316 suggests it might be a rare
example of these large pyroclasts. Modeling the physics
of eruption places upper and lower bounds on the size of
the parent asteroid (above left, [386]).
References [385-387]
