Impact Melt Breccias

A breccia (Latin word meaning “broken”), in general, is a rock that is a mixture of angular fragments from different types of rocks surrounded by a fine-grained "matrix" that may be similar to or different from the fragmented material. Breccias can be formed in many different geologic processes (tectonic, volcanic , sedimentary) and from a variety of materials.

An impact melt breccia is similar to a breccia, but slightly different in that the matrix cementing the fragments is from crystallized impact melt. The melt is the primary evidence for a cataclysmic impact event, where the heat generated from the impact shatters and melts the target rock. From a sample collected at the Haughton impact structure on Devon Island, Canada (top left photo below), small pale gray/white to dark gray/black fragments are mostly carbonate rock. Occasionally you'll see a fragment of gneiss that was excavated from 2 kilometers below the pre-impact surface, then brought to the surface, and mixed in with other rock fragments to form this new rock: impact melt breccia. This type of rock forms the crater-fill deposits at the Haughton impact structure.

See impact melt breccias in the Haughton impact structure