Geology Reference
In-Depth Information
L4 chondrite breccia
1094.57 g
Found January 9, 1988
10.0 × 8.0 × 8.0 cm
Weathering = A/B
nearly 20% of all ordinary chondrites are breccias, and brecciation is often
revealed only during study of the largest masses of some meteorites. Most
asteroids have regolith at their surface and regolith compacts to breccia,
so brecciated meteorites can lead to a better understanding of processes
affecting near-surface samples from asteroids.
Impact
Fragmentation
Reassembly
Plate 5
MiNERALogy
SigNiFiCANCE
MAC 87302 consists of olivine with a range of com-
positions (Fa
5-24
, with a distinct peak in compositions at
Fa
23-24
) and low-Ca pyroxene (Fs
1-21
, with a peak at Fs
20-21
)
with minor plagioclase, metal, and troilite. Most clasts
are similar in composition, although a few exhibit com-
positions more typical of H chondrites, and some olivine
grains within the melt clasts are reversely zoned.
MAC 87302 was the first sample recognized from a pair-
ing group of L chondrite regolith breccias recovered dur-
ing the 1987-1988 and 2002-2003 field seasons. Bearing
solar wind-implanted gases, these meteorites contain a
range of cognate xenoliths that include differing meta-
morphic types as well as impact melts [26]. The meteorite
may also sample H chondritic material, and thus may
represent a multilithologic asteroid body (rubble pile)
formed from fragmented and reassembled material
(bottom, [25]). Terrestrial age dating suggests that these
meteorites fell within the last 50 kyr.
References [24-26]
