The brecciated stony meteorites and meteorites containing foreign fragments

Abstract

It is pointed out that the breccias among stony meteorites are mainly of two kinds : (a) breccias in which the enclosed fragments are of the same material as the surrounding principal mass of the stone: it is proposed to call this kind of breccias “monomict breccias,” and (b) breccias in which the enclosed fragments are of a foreign material as compared with the surrounding principal mass of the stone: it is proposed to call these breccias “polymict breccias.” The brecciated stony meteorites have so far been only superficially studied. In the present investigation it is shown that the occurrence of “monomict breccias” is mainly limited to various kinds of “achondrites,” whereas “polymict breccias” occur among the achondrites (e.y. all Howardites are polymict breccias) as well as among the chondrites. A petrographic investigation of thin-sections of a great number of fragments contained in the different kinds of stony meteorites, shows that most stony meteorites, achondrites as well as chondritee, and also a number of types not known as yet aa separate meteorites, occur as fragments in “polymict” brecciated stony meteorites. This remarkable result of the investigation shows that rocks made up of most kinds of stony meteorites must have existed on the cosmic body where these polymict breccias were formed; and the investigation thus throws light on the origin of the stony meteorites.