Intrusive tuffs of west Cork, Ireland
Minor intrusions in west Cork include pipes and dykes believed to have originated by a process of fluidization. These bodies are described, emphasis being placed on features known to be characteristic of fluidization. The intrusions are pipes or dykes with sharp contacts with the country-rock, which plunge vertically or at high angles. Some show a zonal form based on the xenolith content; xenoliths moved upwards in the central zones but there is evidence of downward movement in some of the outer zones. Matrices are devoid of igneous material. The west Cork bodies are distinctive in occurring between phases of deformation of a fold-belt and in having their positions controlled by pre-existing structures. Petrologically they are distinguished by having a carbonate content that is variable but attains a maximum of 95 per cent. The bodies are compared with certain carbonatites that are held to be high-level developments of kimberlite pipes.