[meteorite-list] Bull's-eye chondrule assumptions

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Mon Mar 21 13:24:57 2005
Message-ID: <DIIE.0000000900003528_at_paulinet.de>

John and Dawn wrote:

> We seem to have several of them in our new LL3

Christian responded and presented some stunning pictures:

> I have many of them: ...

Whereupon John and Dawn wrote:

> I really liked NWA 1770

I am in love with the perfect bull's eye in Christian's NWA 724!

> www.austromet.com/collection/NWA_0724_5.646g.jpg

Do I have any ideas on the formation of such chondrules?

Only some ideas, no references, no direct links: These chondrules
obviously occur only in unequilibrated chondrites of types H3.x,
L3.x, and LL3.x (by inference probably also in some E3 chondrites),
up to petrologic type 4.

Darker core material seems to be enveloped by a lighter-colored, in
some cases almost concentric ring of (fine-grained, dusty?) material.

The process that gave birth to such chondrules may have been either
accretionary or condensational and the environment may have been
dusty (which would point to early solar system processes).

Obviously only a limited number of chondrules underwent this process
so that the bull's-eye chondrule formation may have been a selective
process (time, distance from the protosun, dusty environment..I don't
know).

It would be interesting and helpful if someone detected such bull's-eye
chondrules in one of their thin sections so that we could draw further
conclusions on their mineralic compositions (core material, rim or seam
(?) material, high-temperature, low-temperature phases, etc.).

Esteemed list member Jeff Grossman wrote several papers on chondrule
formation, chondrule composition, zoned chondrules, etc. Maybe he can
enlighten us on these "Eyes of Taurus", the Bull, my Constellation :-)

Best wishes,

Bernd
Received on Wed 16 Mar 2005 04:48:50 PM PST