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Impact Melt Breccias


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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

Example of an impact melt breccia in our Impact Rock Kits
Example of an impact melt breccia in our Impact Rock Kits
Photo: F. Chuang, Planetary Science Institute
Location:
Crater-fill deposits of the Haughton impact structure, Devon Island, Canada

Closeup view of impact melt breccias with large shatter cone piece
Closeup view of impact melt breccias with large shatter cone piece
Photo: G. Osinski, University of Western Ontario
Location:
Crater-fill deposits of the Haughton impact structure, Devon Island, Canada

Location of impact melt breccia samples collected in the field
Location of impact melt breccia samples collected in the field
Photo: G. Osinski, University of Western Ontario
Location:
Crater-fill deposits of the Haughton impact structure, Devon Island, Canada

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