[meteorite-list] Ni-free metal in diogenites

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 10:08:29 2004
Message-ID: <3D8CCF14.6683A86_at_lehrer.uni-karlsruhe.de>

Hello List,

While sifting through the literature to be better prepared for
what is awaiting me when Adam's and Greg's NWA 1459
arrives, I came upon this in ..., well, of course, in O.R.
Norton's CEM:

Norton O.R. (2002) The Cambridge Encyclopedia of Meteorites,
pp. 153-155:

"The hypersthene in diogenites is remarkably homogenous with over
90% having an average composition of Wo1En74Fs25 (1% wollastonite,
74% enstatite, 25% ferrosilite). The iron-rich hypersthene is about
25% ferrosillite (Fs(23-27)), a mineral rarely if ever found on Earth.
There are s m a l l amounts of anorthite, *FeNi* and FeS. The
t o t a l i r o n is about 12 wt% but o n l y 0.3 wt%(!) is
r e d u c e d m e t a l.

(!) Remember: Adam wrote about NWA 1459:

> In this case Ni-Free metal means 6/100th of one
> percent or 0.06%. In other words trace amounts

Diogenites are thought to have formed in the lower crust or upper
mantle of a differentiated asteroid, possibly the asteroid 4 Vesta.
If the l o w e r m a n t l e could be sampled, a nearly p u r e
o l i v i n e cumulate similar to terrestrial dunite is expected to
be encountered (see the section on brachinites, p. 163)."

It is getting more and more exciting !!!

Cheers,

Bernd
Received on Sat 21 Sep 2002 03:57:08 PM PDT