Geology Reference
In-Depth Information
Ungrouped iron
2480.7 g
Donated by science field team
11.5 × 7.0 × 7.0 cm
Weathering = ?
part of the main magmatic groups of irons and are ungrouped. These sam-
ples offer a glimpse into other processes operating in the early solar system,
from impact melting, condensation, or as-yet poorly defined magmatic
groups. one such example is highlighted here, but there are many ungrouped
irons that have been studied from the U.S. Antarctic meteorite collection.
1mm
HOW 88403
Kamacite
Plessite
Kamacite
SiO 2
Chromite
Silicate
Trailite
Chromite
Plessite
Shereibersite
Taenite
200 µ m
20 µ m
Plate 80
MiNERALogy
SigNiFiCANCE
The appearance of HoW 88403 exterior surface suggests
a metal-sulfide eutectic, with ~2/3 metal and ~1/3 sulfide.
it is a fine-grained structure with individual sulfide cells
averaging 0.3 mm in diameter. A thin fusion crust is pre-
sent, underlain by a 2-3 mm heat-altered zone. The metal
matrix is ataxitic, decomposing into a very fine-grained
mixture of taenite and kamacite with abundant small
schreibersites [819]. Troilite is surrounded by discontin-
uous rims of schreibersite, and an occasional chromite
was observed in the sulfide [819].
The meteorite was found by a research group under the
direction of Dr. Charles Swithinbank on the blue icefield
at Mt. Howe, Antarctica. HoW 88403 is more reduced
than H chondrites, and likely formed by impact melting
on a chondritic parent body. Bulk composition suggests
that it was liquid above 1350°C, and estimated cooling
rates suggest that HoW 88403 formed buried but near
the surface of its parent body.
References [819-821]
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