[meteorite-list] Vaca Muerta euc- what is it?

From: almitt2 at localnet.com <almitt2_at_meteoritecentral.com>
Date: Mon, 18 Oct 2010 06:02:26 -0400
Message-ID: <20101018060226.qeop72so82048sko_at_webmail.localnet.com>

Hi Bernd and all,

Agreed, there is accessory amounts of olivine in mesosiderites but
these are very low amounts so the olivine seem to be mostly absent in
the formation. Most likely the amounts found were mixed in formation.
This also explaines the green olivine crystal(s) found in some of
Martinez Rodrigo's specimens. Could these be from the pallasite
producing part of an asteroid?

Always appreciate your input Bernd and you are a treasure to this list!

--AL Mitterling


Quoting bernd.pauli at paulinet.de:

> AL kindly wrote:
>
> "I believe there is an absence of olivine in mesosiderites."
>
> Objection, Your Honor!
>
> Norton O.R. (2002) The Cambridge Encyclopedia of Meteorites, p. 157:
>
> "Accessory amounts of olivine are also present in mesosiderites"
> "...the mineralogy of the silicate portion...is ...orthopyroxene and
> plagioclase with minor amounts of olivine."
>
> Norton O.R. (2008) Field Guide to Meteors and Meteorites, p.173:
>
> a) Figure 8.10: "Estherville...Silicates include olivine, pyroxene,
> and plagioclase..."
> b) Figure 8.11: "Vaca Muerta...Like Estherville, it contains eucritic
> pebbles and
> many silicate inclusions..."
>
> T.H. Burbine et al. (1996) Mantle material in the main belt:
> Battered to bits (Meteoritics 31-5, 1996, 607-620, p. 609):
>
> "Mesosiderites are stony-iron meteorites containing Ni-rich Fe metal
> and mafic
> silicates (Floran, 1978). The amount of metal has been found to vary from 17
> to 80 wt% but is usually between 40 to 60% (Mason and Jarosewich, 1973). The
> silicates are mainly orthopyroxene and plagioclase with lesser
> amounts of other
> silicates such as pigeonite and olivine (Floran, 1978)."
>
> By the way, a few years ago, Martinez Rodrigo offered thin Vaca Muerta slices
> with predominantly eucritic components and / or olivine crystals. Some of the
> olivine-rich slices were cut so thinly that they were even
> translucent when held
> up against the light.
>
> Best wishes,
>
> Bernd
Received on Mon 18 Oct 2010 06:02:26 AM PDT