Abstract

Petrographic and chemical data obtained from an occurrence of Sudbury breccia reveal that, although the gross compositions of matrix materials can be accounted for by mixing of comminuted host gabbro and quartzite, enrichments in K2O, Rb, TiO2, Zr, Y, Ba, Sr, and P2O5 also occur. These enrichments parallel those in "foreign" fragments of alkali gabbro and are quantitatively similar to, but quantitatively less than, those in some fenites. The Sudbury structure lies along the projection of a linear belt of alkali igneous intrusions and it is suggested that this occurrence of Sudbury breccia represents fragmented rock above an underlying fenite breccia and alkali igneous body. The data support an origin by processes related to a diatreme rather than extraterrestrial impact.

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