Geology Reference
In-Depth Information
CR2 chondrite
103.67 g
Found December 22, 1992
5 × 4 × 2.5 cm
Weathering = B
CR chondrites are one of the most primitive carbonaceous chondrite
groups, but they also record moderate secondary aqueous alteration.
Unusual characteristics are their high (50%-60%) content of relatively
large (0.7 mm) chondrules, high metal contents (7%-8%), and hydrated
(phyllosilicate-rich) fine-grained matrix. Most chondrules are porphyritic
types, and many chondrules have metal and sulfide rims. The matrix con-
tains a wide range of minerals such as carbonates, sulfides, and magnetite,
as well as serpentine and saponite.
EET 92042,0
Deuterium/Hydrogen
δ D ‰
24000
21000
19000
16000
13000
10000
74 00
4600
1800
-1000
2 µ m
δ 15N ‰
Nitrogen isotopes
1500
1300
1100
940
760
580
400
210
31
2 µ m
-150
Plate 25
MiNERALogy
SigNiFiCANCE
olivine and orthopyroxene are Mg rich (Fa, Fs <4%),
solar FeNi metal, and metal rich (10%). The matrix
contains hydrous silicates, carbonates, and magnetite.
Plagioclase-bearing chondrules are also reported
(An 91-96 ).
EET 92042 is part of a large pairing group of CR2s found
in the Elephant Moraine region of Antarctica. High res-
olution isotopic measurements of H and N in the matrix
of this meteorite have revealed large isotopic anomalies
that are associated with insoluble organic matter (right,
[156]). other studies have revealed diverse and interesting
features such as amino acids, presolar grains, and metal
and sulfide rims on chondrules.
References [154-174]
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