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King Tut's Tektite - Part 4 of 4

BARAKAT A.A. et al. (1998) Meteoritic iron from the Libyan glass area,
SW Egypt - Great Sand Sea 003 (MAPS 33-4, 1998, A173-A175, excerpts):

Abstract:

A fragment of a weathered iron meteorite was collected from the Libyan
Desert glass area of southwestem Egypt in 1991 May.

Introduction:

Fragments of Libyan Desert glass, a natural material containing > 98%
SiO2, are scattered over an oval area measuring 150 x 53 km and located
between latitudes 25° 02'-26° 13’ N and longitudes 025° 24'-25° 55' E
(Spencer, 1939). This area, which is named the Libyan glass area, is
characterized by an extensive field of linear dunes of the Great Sand
Sea of the Westem Desert.
The origin of Libyan Desert glass has long been a topic of interest and
confusion since it was first discovered by an Egyptian desert survey
party under the leadership of Sir P.A. Clayton on 1932 December 29
(Clayton and Spencer, 1934). Several hypotheses have been introduced to
explain the origin of the Libyan glass, which was formed about 28.5 Ma
ago (Gentner et al., 1969). Both terrestrial and extraterrestrial
origins have been proposed as well as low- and high-temperature
formation processes. However, there is a general tendency to consider
the Libyan glass to be analogous to the impactites that are formed by
sudden melting and rapid cooling of country rocks during impacts of
large cosmic bodies (Cohen, 1959, 1961). The absence of meteoritic
fragments and (a) meteoritic crater(s) from this area and its near
vicinity have delayed the proof of this hypothesis. It has been
suggested that the original surface of the glass area (28.5 Ma ago) was
stratigraphically higher than the present ground surface (Weeks et al.,
1984) as erosion has removed a considerable vertical sequence of the
Nubia sandstone country rock. If so, then we should expect that the
structures resulting from meteorite impact have been obliterated.
In the meantime, the fragments of the meteorite that formed the glass
could be partly or completely disintegrated owing to the long period
that has passed since its fall.

Discussion:

Lack of definite proof that this meteorite has a terrestrial age 28.5 Ma
does not allow a direct connection between this meteorite and the
formation of the Libyan Desert glass. However, the author thinks that
this discovery will shed light on the origin of the Libyan Desert glass.
The shape of this specimen and the others that were left in the field
indicates that they were pieces torn or scaled off  a larger mass. It is
also evident that they have been broken up further and reduced in size
by oxidation. The author also believes that pieces of this meteorite
were the source of the magnetic microspherules that were observed in the
Libyan glass area during the 1996 March expedition (with the same
director and the same main members). A preliminary chemical analysis
revealed that some these microspherules are related to an iron meteorite
(Barakat et al., 1996). A detailed report on these microspherules will
be published elsewhere.

Best Easter wishes,

Bernd


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