[meteorite-list] Glass Bomb

From: Bernd Pauli HD <bernd.pauli_at_meteoritecentral.com>
Date: Thu Apr 22 09:43:33 2004
Message-ID: <3B5C4D0F.C6FDA701_at_lehrer1.rz.uni-karlsruhe.de>

William Russell wrote:

> What exactly is a Glass Bomb? I have one from
> Ries Crater in Germany but I do not know how
> it is different from other impact glass.


Hello Bill and List!

I will be sending you two JPEGs in a private mail showing a sattelite
view of the Ries Crater and another showing the place names mentioned
below!

Best wishes,

Bernd


Glass bombs or Flädle (Flädle or Fladen = pancake) come from the fields
surrounding Heerhof on the western crater rim about halfway between
Pflaumloch and Bopfingen. The internal texture (vesicles, flow lines)
and the forms of the bombs indicate that they were hurled through the
air at a high speed, in the form of liquid molten masses. They acquired
their outer shapes during this flight, and behaved like solids when they
were embedded in the suevite.

WOLF VON ENGELHARDT (1967) Chemical composition of
Ries glass bombs (GCA 67-8, 1967, pp. 1677-1689, excerpts):

Abstract

Thirty-two chemical analyses of glass bombs, taken from various
suevite localities within and outside the Ries crater, Germany are
presented. Two main glass types, (I: non-recrystallized, III: highly
recrystallized), and one intermediate (II: slightly recrystallized) can
be distinguished. All glass bombs originate from the same melt. The
textural differences between the types I, II, and III are due to locally
different cooling rates of the suevite. The melt was formed in the
impact crater by shock melting of a limited mass of magmatic or
metamorphic rocks of uniform granititic composition. Minor chemical
differences between the glasses are mainly caused by later oxidation
and leaching processes which were controlled by the degree of
recrystallization.

The differences in appearance of types I, II and III are due to
different cooling processes. All glass bombs were deposited at high
temperatures before crystallization started. The type I glasses were
cooled so fast that they consolidated without reerystallization. The
cooling rate of type III glasses was slower so that different kinds of
crystals could grow. This origin of the I, II and III glass types can be
deduced from the uniformity of chemical composition and the pattern of
distribution of the glasses. They occur in the suevite in such a way
that larger blocks contain either only type III glasses or only type I
(and II) glasses. Where vertical sections in suevite outcrops are
exposed, boundaries can be drawn separating areas containing type III
glasses from those containing type I (and II) glasses.
Received on Mon 23 Jul 2001 12:13:03 PM PDT