Geology Reference
In-Depth Information
Table 8.1.
List of ungrouped or anomalous meteorites.
ALH A80104
Post-eutectic crystallization iron meteorite?
EET 83230
High-Ni iron related in process to IVA irons
EET 96031 pairing group
Low-FeO chondrites
GRA 06128/06129
Albite-rich achondrites related to brachinites
GRO 95555
Unbrecciated, equigranular diogenite
ILD 83500
High-Ni iron related to South Byron trio and, possibly, the Milton pallasite
LAP 04757/04773
Low-FeO chondrites similar in bulk composition to H chondrites
LAP 03719
Unbrecciated, olivine-bearing aubrite
LAP 04840/10031/10033
Hornblende-phlogopite-bearing R6 chondrite
LAR 04315
Metal-sulfide-veined ureilite
LAR 06298/06299
Kg-sized LL chondrite impact melt breccias
LEW 85332
Low petrologic type, ungrouped carbonaceous chondrite
LEW 85369
Silicon-bearing iron meteorite
LEW 86211
Troilite-rich ungrouped iron meteorite
LEW 87051
Quenched angrite; main mass of 0.611 g
LEW 87232
Kakangari-like chondrite
LEW 87234 pairing group
Ungrouped type 3 enstatite chondrites rich in Ca-Al-rich chondrules
LEW 88055
Silicate-bearing iron meteorite related to aubrites
LEW 88631
Silicide-bearing iron meteorite
LEW 88774
Ureilite exhibiting coarse exsolution of augite in low-Ca pyroxene
MAC 87300/87301
C2 chondrite related to CM and CO groups
MAC 88107
C2 chondrite related to CM and CO groups
MET 01085
Olivine-free ureilite
MIL 03443
Dunite related to HED meteorites
MIL 090405 pairing group
Brachinite-like achondrites
MIL 090807/090978
Enstatite chondrite impact melts similar to Happy Canyon
MIL 11207
Hornblende-bearing R6 chondrite
QUE 93148
Coarse-grained olivine-pyroxene-metal; pyroxene pallasite?
QUE 94204 pairing group
Coarse-grained enstatite meteorites; impact melts or primitive achondrites?
QUE 94570
Low-FeO chondrite similar in bulk composition to L chondrites
RBT 04239/04255
Ungrouped olivine-rich achondrites similar to Divnoe
RKP A79015
Anomalous mesosiderite
LEW 87057/87220/87223) contained an unusually high
abundance of Ca- and Al-rich objects relative to other
enstatite chondrites, including chondrules that contain
primary (igneous) calcic plagioclase. This meteorite also
contains a high abundance of FeO-bearing pyroxene for
an enstatite chondrite [
Weisberg et al
., 2011].
Weisberg
and Righter
[2014 (this volume)] have noted the anoma-
lous nature of this meteorite grouping, suggesting they
don't fall within either the EH or EL group.
Grossman
et al
. [1995] reported that three analyses revealed no
resolvable excesses of
26
Mg indicative of the former
presence of
26
Al. These results are supportive of the hy-
pothesis that Al-rich chondrules formed after CAIs. Far
more commonly, a single interesting chondrule will be
noted in the initial description of a meteorite, without
subsequent study. A relevant example of this is found in
the LL6 chondrite Miller Range (MIL) 07065. The initial
description indicated the presence of a semicircular,
1-mm diameter skeletal spinel. Subsequent examination
by the author suggested that a circular area including
this grain is enriched in feldspar. Despite extensive
metamorphism, this suggests the possibility of an Al-rich
chondrule in which spinel was the liquidus phase and
rapid cooling or few nuclei produced a skeletal mor-
phology. Given the potential of these objects as
intermediate between chondrules and CAIs and
significant improvements in our ability to constrain
relative ages in the earliest history of the solar system,
revisiting these and other examples of Al-rich chondrules
in the Antarctic collection might prove fruitful.
8.3. NEBULAR OR PARENT BODY?
Given the complexity of meteorite petrogenesis, it is
of little surprise that the properties of some meteorites
cannot be confidently ascribed to a particular setting.
Attributing the properties of chondritic meteorites to
nebular or parent body settings are among the most dif-
ficult connections to establish. Two groupings of mete-
orites that illustrate this difficulty are Queen Alexandra
Range (QUE) 94570 and the LaPaz Icefield (LAP)
04773/04757 pairing groups (Plate 10). QUE 94570 was
