[meteorite-list] Irons in Mauritania

From: Darryl S. Futrell <futrelds_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:59 2004
Message-ID: <02df01c07c3b$672b9cc0$a3e41e3f_at_pavilion>

-----Original Message-----
From: Bernd Pauli HD <bernd.pauli_at_lehrer1.rz.uni-karlsruhe.de>
To: Michel Franco <MICH-FRANCO_at_wanadoo.fr>
Cc: METEORITELIST <meteorite-list_at_meteoritecentral.com>
Date: Monday, January 08, 2001 3:14 PM
Subject: [meteorite-list] Irons in Mauritania


"The Aouelloul impactor is said to have been an iron - possibly a
pallasite"????
Said by whom? By a bunch of "impact geochemists" who continue to refuse the
overwhelming evidence that there are a number of impact craters formed by
large blocks of tektite glass (Aouelloul, Darwin, Zhamanshin, Ries, etc.)!
The Aouelloul impactor is said by certain researchers back decades ago to
have been an iron, because of the traces of siderophile elements in the
glass.
However, more recently, it has been demonstrated that these traces of
siderophile elements are way too low to be meteoritic. Instead, they are a
result of in-situ reduction of the host rock (or the e.t. magma that was the
original source of the glass - the latter is my tuppence worth).
>R. Ganapathy, and John W. Larimer, 1983, Nickel-iron spherules in tektites:
bob-meteoritic in origin. Earth and Planetary Sci. Lett. 65,225-228.
ALSO
J. A. O'Keefe, 1984, COMMENTS on the abstract by Ganapathy and Larimer
Nickel-iron spherules in tektites: non-meteoritic in origin. J. of
Non-Crystalline Solids 67, 371-374.

Aouelloul glass certainly is NOT an impact melt. Any comparison with real
impact melts makes that obvious. There is evidence that Aouelloul glass is
a type of tektite glass and represent remelted fragments of a glass
impactor.
J. A. O'Keefe, 1970, Physical chemistry of the Aouelloul crater glass. NASA
Goddard Preprint X-640-70-365, 27 pgs.

J. A. O'Keefe, 1971, Physical Chemistry of the Aouelloul glass. J.
Geophysic. Res. 76, 6428-6439.

J. A. O'Keefe, 1976, Tektites and their origin. Book, Elsevier, 254 pages.

J. A. O'Keefe, 1978, The tektite problem. Sci. Amer. 239, 116-125.

J. A. O'Keefe, 1987, Zhamanshin and Aouelloul: craters produced by impact of
tektite-like glasses? LASP (Laboratory for Astronomy and Solar Physics).
NASA Goddard Space Flight Center, 18 pgs.

J. A. O'Keefe, 1987, Zhamanshin and Aouelloul: craters produced by impact of
tektite-like glasses? Meteoritics 22, 219-228.

And then, there's my 1999 Rock and Gem article, which contains in the March
issue, a discussion of Aouelloul, Zhamanshin, and Darwin glasses (free
reprints available).

T. E. Bunch, and William A. Cassidy, 1972, Petrographic and electron
microprobe study of the Monturaqui impactite. Contr. Mineral. and Petrol.
36, 95-112. On page 111 they ask why is the Monturaqui impactite loaded
with spherules and fragments of the impacting iron (as is Wabar and Henbury,
for example-my comment) when the Ries crater glasses contain none. They
also mention Aouelloul glass as being comparable to Ries. They point out
that the profusion of nickel-iron spherules should be preserved in the glass
as long as the glass does not devitrify. The Aouelloul glass is not
devitrified, as is much of the Ries glass.

W. Campbell-Smith, and M. H. Hey, 1952, The silica glass from the crater of
Aouelloul. Bull. Inst. Fr. Afr. Noire 14, 762-776. There was also an
earlier 1952 all French paper in another French journal - ref. in O'Keefe's
1976 book). In at least one of these two papers, they raise the question
whether we are to regard the crater as being excavated by a block of glass,
or to regard the glass as being formed by meteorite impact on the local
sandstone.





">Michel Franco a écrit:
>
>> I have just received an info about the possible discovery of hexaedric
>> irons near one of the 2 mauritanian craters (Aouelloul or Tenoumer).
>
>
>Bonsoir Michel, Hello List,
>
>Could this be a revival of the Chinguetti story?
>But Chinguetti was supposed to be a mesosiderite!
>The coordinates given for the Chinguetti mass are
>the same as the coordinates for Aouelloul.
>The Aouelloul impactor is said to have been an iron
>- possibly a pallasite, so myth and folklore may have
>blended here. Just a guess!
>
>Best wishes,
>
>Bernd"
>
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Received on Thu 11 Jan 2001 08:59:39 PM PST