[meteorite-list] Chondrulo-mania

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:08:29 2004
Message-ID: <3D8B7A28.6648F9B4_at_lehrer.uni-karlsruhe.de>

Hello List, hello Adam,

What a day! Thank you, Adam. I can hardly wait ... Phew!!!

This afternoon I was again chasing ... no, not butterflies but those
enigmatic chondrules with conspicuous, spherical or slightly oval
indentations (cp. O.R. Norton: Cambridge Encyclopedia of Meteorites,
p. 231) and I did find some more. This time in my Clovis #1 – H3.6 thin
section. Maybe some of you will enjoy this petrographic thin section
description and feel like looking at their Clovis #1 thin section or any
other low petrographic grade TS you have:

Rectangular thin section with abundant large and small chondrules. Two
chondrules have a chondrule crater each. A polysomatic BO chondrule
shows several almost parallel thin olivine bars at different angles to
each other resulting in different interference colors. There is another
small chondrule with a chondrule crater to the lower left of this BO
chondrule. In the lower part of the TS, there is a PO chondrule with a
perfect, euhedral olivine crystal. Nearby is a conspicuous pyroxene
chondrule whose closely packed, parallel pyroxene laths display only
first order colors: white, light- /medium- and dark gray and a rim of
large, boulder-like pyroxene grains. Superimposed on these pyroxene
laths are several white pyroxene grains that go to undulose extinction
with the pyroxene laths underneath. On the left are two small, barred
olivine chondrules showing a vivid turquoise interference color - the
lower one of these has a segment missing, its remaining rim and the
short stubby olivine bars go to extinction simultaneously. The rim of
the other BO chondrule to its upper left is not in optical continuity
with its olivine bars some of which are long and slender crossing the
entire chondrule from rim to rim. Its rim is discontinuous and looks
like the one in Fig. 10.18 in O.R. Norton's CEM, p. 231. Arranged
diametrically opposite to each other are two crater-like intrusions
which reveal some fine-grained metal (in reflected light) around
multiply twinned plagioclase crystals. In-between the two BO chondrules
but slightly above is a large pyroxene chondrule with intertwining laths
crossing at near 90° angles.


Best wishes,

Bernd
Received on Fri 20 Sep 2002 03:42:32 PM PDT