[meteorite-list] Are chondrites sedimentary rocks?

From: Mark Ferguson <mafer_at_meteoritecentral.com>
Date: Thu Apr 22 10:16:37 2004
Message-ID: <01ff01c36dc0$5ecdcd40$6701a8c0_at_vs.shawcable.net>

Hi List

I just have to comment on this. Sedimentary rock, in any definition found in
geology and petrology books is matter which is laid down by either wind or
water, then compacted over time into a durable rock. This is not how
chondrules formed. Chondrules most likely are a coalescing of minute liquid
droplets into larger droplets which is very different from the sedimentary
process. It would be more accurate to liken it to the formation of a
chondrule to that of a rain drop, but that might well be to simple a process
to adequately describe chondrule formation since there are some high
temperatures and very different pressures indicated . But to use
sedimentation is not even close. Totally different mechanisms are involved,
that much is sure. For anyone to use totally different processes and
mechanisms is wrong for that only corrupts a new persons attempt understand
meteoritics.

Mark

----- Original Message -----
From: <bernd.pauli_at_paulinet.de>
To: <meteorite-list_at_meteoritecentral.com>
Sent: Wednesday, August 27, 2003 2:51 PM
Subject: [meteorite-list] Are chondrites sedimentary rocks?


> Martin wrote:
>
> > In the interview, Ebel makes two comments that made me wonder...
> > First, he mentions that "Most meteorites are pieces of asteroids.
> > A very few are comets."
>
> > My question is which "very few"? I figure the usual suspects are Orgueil
> > and Murchison, but some comet experts I have talked with discount them
> > and all other meteorites as being of cometary origin.
>
> .. do not forget Tagish Lake and to some extent Krymka (see David Weir's
> comments on Krymka on his website: " ... This material is enriched in
volatile
> siderophiles such as Ag, Tl, and Bi, and represents a late condensate from
> a metal-depleted region of the solar nebula, possibly related to cometary
> material."
>
> > The second thing that caught my eye was when Ebel said, "Chondrites are
> > really sedimentary rocks made up of dust and then chondrules, these
round
> > droplets that were once molten and now are little beads, many containing
> > glass, which were present in the solar system."
>
> He may have read O.R. Norton's comments in Joel Schiff's magazine:
>
> NORTON O.R. (1998) Are chondrites sedimentary
> rocks? (M! Feb. 1998, Vol. 4, No. 3, pp. 22-23).
>
> > My question here is if chondrites can
> > really be considered sedimentary rocks.
>
> The only references I have about sedimentary meteorites:
>
> TOMEOKA K. et al. (1997) Evidence for early sedimentary
> processes in a dark inclusion in the Vigarano CV3 chondrite
> (Meteoritics 32-4, 1997, A129).
>
> TOMEOKA K. et al. (1998) Arcuate band texture in a dark inclusion from
> the Vigarano CV3 chondrite: Possible evidence for early sedimentary
> processes (Meteoritics 33-3, 1998, 519-525).
>
> BRIDGES J.C. et al. (1998) Traces of Martian sediment in Nakhla
> and other SNC meteorites (Meteoritics 33-4, 1998, A023).
>
>
> Best wishes,
>
> Bernd
>
>
> To: martinh_at_isu.edu
> Cc: meteorite-list_at_meteoritecentral.com
>
>
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Received on Thu 28 Aug 2003 07:58:37 PM PDT