Earth Science Conservation Review
| Cushendun - Caledonide Igneous Complex | Antrim |
| Site Type: | Quarry (working) |
| Site Status: | ESCR |
| Grid Reference: | D233340 |
| Google maps: | 55.13829,-6.06652 |
| Rocks | |
|---|---|
| Rock Age: | Ordovician, Precambrian (Dalradian) |
| Rock Type: | Granodiorite, Microgranite, Quartz porphyry, Dacite |
| Interest | |
| Other interest: | Caledonian, phenocrysts, Intrusion |
Introduction:
This site is in a quarry located ~2km northwest of Cushendun in County Antrim.
The first edition of the Cushendall (Sheet 14) one-inch to the mile geological map (Geological Survey of Ireland, 1886) shows an intrusive body of "quartziferous porphyry", emplaced in the schist country rocks. In the accompanying explanatory memoir, Symes and McHenry (1886) described the porphyry as having a gradational and foliated southwest boundary. The central and northwest portions are described as being more massive and intrusive looking. The rock is described as highly feldspathic with large crystals of orthoclase feldspar in a plagioclase, quartz and mica matrix.
Part of the intrusion is marked on the resurveyed second edition of Ballycastle (Sheet 8) one-inch to the mile geological map (Geological Survey of Northern Ireland, 1963). The rock type is referred to as a porphyritic microgranite in the accompanying memoir (Wilson and Robbie, 1966).
Resurvey of the Cushendall map has as yet not been undertaken. A detailed account of the intrusion and surrounding country rock was however reported by Harrison and Wilson (1978). This report describes the geological context, petrography, chemistry and petrogenesis, of what is considered to be a granodiorite intrusion chemically related to other late post-tectonic Caledonian acid intrusions from the United Kingdom. The report also contains details of dykes associated with the Cushendun intrusion. Geochemistry would appear to indicate magma generation at the base of the Earth's crust, probably in the roots of the Caledonian orogenic belt. A Rb/Sr date of 496±128Ma and a K/Ar date of 462±6 indicate emplacement significantly earlier than most Caledonian post-tectonic acid intrusions in Northern Ireland. The emplacement date appears to equate more closely with the Craigballyharky and Craigbardahessiagh complexes of County Tyrone.
The first edition of the Cushendall (Sheet 14) one-inch to the mile geological map (Geological Survey of Ireland, 1886) shows an intrusive body of "quartziferous porphyry", emplaced in the schist country rocks. In the accompanying explanatory memoir, Symes and McHenry (1886) described the porphyry as having a gradational and foliated southwest boundary. The central and northwest portions are described as being more massive and intrusive looking. The rock is described as highly feldspathic with large crystals of orthoclase feldspar in a plagioclase, quartz and mica matrix.
Part of the intrusion is marked on the resurveyed second edition of Ballycastle (Sheet 8) one-inch to the mile geological map (Geological Survey of Northern Ireland, 1963). The rock type is referred to as a porphyritic microgranite in the accompanying memoir (Wilson and Robbie, 1966).
Resurvey of the Cushendall map has as yet not been undertaken. A detailed account of the intrusion and surrounding country rock was however reported by Harrison and Wilson (1978). This report describes the geological context, petrography, chemistry and petrogenesis, of what is considered to be a granodiorite intrusion chemically related to other late post-tectonic Caledonian acid intrusions from the United Kingdom. The report also contains details of dykes associated with the Cushendun intrusion. Geochemistry would appear to indicate magma generation at the base of the Earth's crust, probably in the roots of the Caledonian orogenic belt. A Rb/Sr date of 496±128Ma and a K/Ar date of 462±6 indicate emplacement significantly earlier than most Caledonian post-tectonic acid intrusions in Northern Ireland. The emplacement date appears to equate more closely with the Craigballyharky and Craigbardahessiagh complexes of County Tyrone.
| Enlander, I., Dempster, M. & Doughty, P., 2024. Cushendun - Caledonide Igneous Complex, County Antrim, site summary. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/summary.php?item=594. Accessed on 2024-12-26 |
| Previous Site | Next Site |