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Breccia dikes in the Azuara impact structure

Breccia-dike generations: The younger dike partly runs within the older one. Whitish Muschelkalk dike within Keuper dike in Carniolas host rock (also see Ernstson & Fiebag 1992). Monforte de Moyuela; coin diameter 23 mm. - Dikes-within-dikes are known also from the Vredefort impact structure.

Large breccia dike composed of Mesozoic (?Keuper) and ?Lower Tertiary material cutting through Paleozoic siltstones. Near Santuario Virgen de Herrera.

Extended breccia-dike system in Dogger limestones. The sharp-cut emplacement of the dikes excludes any karstification processes. - Barranco de Bocafóz, near Almonacid de la Cuba.

Polymict breccia dike cutting through Malmian limestones. The dike can be traced in the field over nearly 300 m. Three dike generations can be differentiated. Many components are themselves breccias. Azuara impact structure; north of Muniesa.

Breccia dikes cutting through brecciated (mortar texture) Muschelkalk limestone. Azuara impact structure; Monforte de Moyuela. Coin diameter 23 mm.

Breccia dikes in Malmian limestone. Note the sharp-edged splinters within the dike (arrows) incompatible with any karst phenomena. Fuendetodos; Azuara impact structure. Photo-cap diameter 50 mm.

Breccia dikes in Liassic limestone. Match-box length 40 mm. Blesa, Azuara impact structure.

System of breccia dikes and breccia pockets (dark) in light Malmian limestones. The origin of the dark material is unknown. Small quarry between Muniesa and Ventas de Muniesa. Hammer length 42 cm.

Crossing breccia dikes (dike generations) in Malmian limestone. The first emplaced dike (N – S trending) is cut by the younger dike showing ribbon texture probably originating from chemical interactions between dike material and the host rock. Azuara impact structure; near Ventas de Muniesa, Corral de Cámaras. Match-box length 40 mm.

Typical breccia pockets in rocks from the Azuara impact structure.

Liassic limestone, near Belchite

Malmian limestone, near Ventas de Muniesa and Muschelkalk limestone, near Olalla.

Breccia pipe injected from below into Palaeozoic schists. Note the ring-wall of uplifted country rock. Azuara impact structure; near Santa Cruz de Nogueras. Coin diameter 23 mm.

Azuara impact structure, near Nogueras: Photomicrograph of microscopic breccia dike with bifurcation; plane parallel light and crossed nicols. Sandstone fragment from a shocked polymict dike breccia. Note that the thin dike cuts through several quartz grains (arrows). - The field is 2.5 mm high.

Impact dike breccias from the Azuara and Charlevoix impact structures. Left: Azuara polymict dike breccia; near Santa Cruz de Nogueras. Note the grading of the components and the distinct flow texture. Right: Comparable texture in a dike breccia from the Charlevoix impact structure (sample supplied by J.Rondot). Similar breccias have been described to occur also in the Sierra Madera impact structure (Wilshire et al. 1972).

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