Geology Reference
In-Depth Information
CM1/2 chondrite
3019 g
Found January 1, 1984
8.0 × 7.0 × 6.0 cm
Weathering = Be
The CM2 chondrites are the most common carbonaceous group and have
been at the center of many studies focused on aqueous alteration on their
parent bodies, and on the abundance and species of organic matter. They
are distinguished by their small (~300 micron) chondrules, accretionary
rims around chondrules, common calcium-aluminum-rich inclusions (CAi),
and amoeboid olivine aggregates (AoA), with little to no FeNi metal
and a high matrix (~70%) that contains phyllosilicates, carbonate, sulfides, and
magnetite. Alteration postdates primary features such as chondrules
and CAis, producing some impressive textures in CM2 chondrites.
ALH 83100
,1
1cm
(j)
(k)
Dolomite
Calcite
Dolomite
Calcite
Calcite
10
μ
m
100
μ
m
3
CAI (Bouvier et al., 2007)
CAI (Amelin et al., 2006)
CR2 Kaidun
CM2.4 Y- 791198
2
CM2.1 ALH 83100
CM2.1 ALH 84051
CM2.1 ALH 84034
CM2.1 QUE 93005
CI Orgueil dolomite
CI Orgueil breunnerite
CI Orgueil/Ivuna
1
0
Y- 791198
(CM2)
LEW90500
(CM2)
Murchison
(CM2)
ALH83100
(CM2)
Orgueil
(Cl1)
4556
4556
4560
4562
4564
Age (Ma)
4566
4568
4570
4572
Plate 13
MiNERALogy
SigNiFiCANCE
Mg-rich serpentine (62%), Fe-cronstedite (24%), olivine
(Fa
0-10
; 9%), magnetite (2%), sulfide (1%), calcite (1%).
ALH 83100 is a large sample and has been classified as
transitional between CM1 and CM2. Therefore, it has
received much attention and been the subject of many
studies. in particular, calcite grains in the matrix (middle,
[53]) have been dated using Mn-Cr chronology showing
the calcite formed early, but just after chondrules and CAis
(right, [53]). Amino acid studies show that ALH 83100
contains a similar load of amino acids to the CM fall,
Murchison (left, where alanine = stripes, β-alanine = white,
α-aminoisobutyric acid = black, and isovaline = gray; [56]).
References [51-63]
