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Eight L-Group Chondrites: A Comparative Study
Ananda Dube, Becky j. Fredriksson, Eugene Jaroseiuich, Joseph A. Nelen,
Albert F. Noonan, Jane O'Keefe, and Kurt Fredriksson
ABSTRACT
The bulk chemical compositions of eight L-group
chondrites, Atarra, Cranganore, Karkh, Kuttippuram,
Mabwe-Khoywa, Mirzapur, Segowlie, and
Sultanpur, all falls and mostly from the collection
of the Geological Survey of India, Calcutta, have
been determined by classical wet chemical analysis.
In addition, the compositions and abundances of
individual mineral phases were determined with
electron-probe techniques.
Seven of the eight stones represent the petrographic
types 4, 5, and 6, while one, Mabwe-
Khoywa, cannot be classified because it is a polymict
breccia. Still, the practically identical bulk
and phase compositions imply a similar (chemically
identical) parent; thus any metamorphic
recrystallization must have occurred before the
various fragments accreted. Therefore, we interpret
these L-group chondrites, in addition to four of the
H-group previously reported, as products of multiple
impacts of various intensities on similar materials
if not on the same parent body.
Introduction
The eight hypersthene (L-group) chondrites, all
observed falls, described here were selected for
detailed studies because they represent wide ranges
in macroscopic texture, hardness, color, and visibil-
Ananda Dube, Geological Survey of India, Calcutta IB, India;
Becky J. Fredriksson, Eugene Jarosewich, Joseph A. Nelen,
Albert F. Noonan, and Kurt Fredriksson, Department of
Mineral Sciences, National Museum of Natural History,
Smithsonian Institution, Washington, D.C. 20360; Jane
O'Keefe, Geology Department, Rice University, Houston,
Texas 77001.
71
ity of chondrules. This is reflected to some degree in
their classifications by Hey (1966), Mason (1975),
and Wasson (1974). Two are black chondrites, L4
and L6 respectively; two are gray chondrites, both
L6; one is a brecciated white chondrite, L6; one is
a brecciated, veined intermediate chondrite, L5;
and one is a crystalline chondrite, L6. Mabwe-
Khoywa looks like a polymict breccia and has so
far only been classified as "L." All eight meteorites
were analyzed by classical wet chemical techniques
(Jarosewich, 1966). Major phase compositions were
determined by standard electron-probe techniques;
in addition, the abundances of the major phases
(modes) were determined by our previously described
microprobe technique (Fredriksson, et al.,
1975). Bulk chemical compositions are given in
Table 1; the compositions and abundances of the
major silicates appear in Table 2. The mode and
the norm (mineralogical composition calculated
from the chemical analysis) are presented in
Table 3.
These chondrites are listed, classified and/or
described by Cotter (1912), Hey (1966), Mason
(1975), Silberrad (1932); their olivine compositions
were given by Mason (1963, 1967). Detailed information
on the morphology and the distribution of
samples is given by Murthy, Srivastava, and Dube
(1969) for the Indian falls (all but Karkh and
Mabwe-Khoywa). In the following descriptions we
do not repeat such information, but give a few
more references as required. Rather, we present our
observations on a number of polished thin sections
(some ultrathin prepared by Mr. G. Moreland of
the Smithsonian Institution) and some additional
microprobe analyses not included in Tables 2 and
3. After the name of each chondrite we give pertinent
references followed by the composition of