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Earth Science Conservation Review
| Cam Lough Quarry - Caledonide Igneous Complex | Armagh |
| Site number: | 577 | ||
| ESCC: | EA | ||
| Locality Type: | Quarry (disused) | Status: | ASSI |
| Grid Reference: | J03692459 Centroid | ||
| Google maps: | 54.15954,-6.41405 | ||
| County: | Armagh | Council area: | Newry, Mourne & Down District Council |
| Period: | Tertiary, Devonian, Silurian | ||
| Stages: | Lower Devonian, Palaeogene | ||
| Lithostrat: | Slieve Gullion Complex, Newry Igneous Complex | ||
| Site Description | |
|---|---|
| Highlights: | |
Cam Lough Quarry contains exposures of the complex contact relationships between metamorphosed Silurian country rock, and early microgranitic and sheeted granodioritic rock types of the southwest pluton of the late Caledonian Newry Igneous Complex. The cross cutting relationship with the Slieve Gullion Ring Dyke (Palaeogene) is also exposed in the quarry. | |
| Introduction: | |
Cam Lough Quarry is located on the eastern side of Cam Lough, approximately 2.5km south of Camlough. Access is via the C class Keggall Road that joins the Newry Road (A25) at Camlough. Geologically, the site is part of the northern margin of the southwest pluton that forms part of the late Caledonian Newry Igneous Complex. The first edition of the Castleblayney (Sheet 59) one-inch to the mile geological map (Geological Survey of Ireland, 1875) shows no evidence of a quarry at this site, but does indicate a quartziferous porphyry (elvanite) surrounded by narrow zones of contact metamorphosed Silurian country rock which are referred to as indurated. Away from the current extent of the quarry, foliated and porphyritic granites are indicated either side of the indurated Silurian bedrock. A body of syenitic granite is also shown on the map and described in the accompanying geological memoir (Egan, 1877) as being rich in hornblende. The contact between indurated country rock and granite dips steeply to the north-northwest and strikes close to parallel to bedding in the surrounding Silurian sediments. The country rock is recorded as "altered Silurian grit" and "micasized Silurian rocks" retaining original dips and displaying the characteristics of fused (mobilized) sediment as described later by Reynolds (1934; 1936; 1943 and 1944). Reynolds (1934; 1936) classified the granite as being granodioritic. It should be noted that Reynold's terminology still stands up within more modern schemes such as Streckeisen (1976). Systematic sampling, thin section petrology and geochemistry (Grant, 1961; Meighan and Neeson, 1979; Neeson, 1984) revealed composition zoning within the granodiorite pluton. The rocks at the margins of the southwest and northeast plutons are more basic than that exposed towards the centres of the intrusions. This zoning pattern has been described as "normal zoning". The opposite, "reverse zoning" situation is seen in the middle pluton. | |
| Description: | |
Cam Lough Quarry is located on the western side of Camlough Mountain, approximately 2.5km south of Camlough. The site contains evidence of the complex relationships between highly deformed (sheared) contact metamorphosed Silurian country rock and late Caledonian microgranite, granodiorite (biotite granite) and diorite of the southwest pluton of the Newry Igneous Complex. Although deformation makes identification difficult, it appears that biotite-hornfels is present as sheared stringers and clasts. Thin section petrography (Meighan, pers. comm., 1999) shows the granodiorites to be atypical being closer in composition to biotite granite than granodiorite. They show variable degrees of deformation from sheared stringers and deformed pods to relatively undeformed sheets. The deformation has led to the formation of a strong, almost vertical fabric that trends east-northeast parallel to the pluton boundary. Sheeted biotite granite bodies demonstrate cross cutting relationships with older rock types. The Tertiary (Palaeogene) Slieve Gullion Ring Dyke is spectacularly exposed and demonstrates a clear cross cutting relationship with older rock types. The dyke is composed of a porphyritic granophyre that has a sharp and partially faulted contact with Silurian and late Caledonian country rock. INTERPRETATION IMPORTANCE CONCLUSIONS Cam Lough Quarry demonstrates complex relationships between contact metamorphosed Silurian country rock, and the late Caledonian microgranite and granodiorite (biotite granite) of the southwest pluton of Newry Igneous Complex. The Tertiary (Palaeogene) Slieve Gullion Ring Dyke is well exposed cross cutting older rock types. | |
| Importance: | |
Cam Lough Quarry is a site of national importance. It contains evidence of the complex relationships between contact metamorphosed Silurian country rock, and late Caledonian microgranitic and granodiorites (biotite granites) of the southwest pluton of the Newry Igneous Complex. The site also contains exposure of the Tertiary (Palaeogene) Slieve Gullion Ring Dyke, which can be seen cross cutting all of the older rock types. The rocks of the Newry Igneous complex are considered to be prospective for a number of minerals including base metals and gold. Licensed mineral exploration and production has previously been carried out in Counties Armagh and Down. The area which includes this site is likely to attract further exploration activity | |
| Interpretation: | |
At this site, heat from the southwest pluton of the Newry Igneous Complex has caused contact metamorphism in the Silurian greywackes and shales forming rock types known as hornfels and fused (mobilized) sediment. Sediments have been intruded by melt and recrystallized giving rise to the relationships observed. The complex cross-cutting relationships observed between microgranite and various granodiorite sheets indicates contemporaneous intrusion and regional deformation (Cameron, 1981). The microgranite and granodioritic sheets are considered to represent the early stages of intrusion of the southwest pluton of the Newry Igneous Complex. Diorite is most likely associated with the basic body located to the southeast of the quarry. The presence of a strong vertical fabric in this area is attributed to regional deformation, and to shouldering aside of country rock during emplacement of the Newry Igneous Complex. Fabrics are aligned parallel to the main contact lending weight to a diapiric intrusive model of formation (Murphy, 1987). The Tertiary (Palaeogene) Slieve Gullion Ring Dyke has a circular outcrop and was intruded into existing country rock along a ring fault. At Cam Lough Quarry, it would appear to have been intruded along a pre-existing line of weakness within Silurian and late Caledonian country rock | |
| Notes: | |
For information and references on other sites within the Newry Igneous Complex see the following sites: Key Site 568 - Ardglass, Co Down Key Site 569 - Slieve Croob Key Site 570 - Shannaghan Hill Key Site 571 - Ballymagreehan Quarry Key Site 572 - Rathfriland Key Site 573 - Gransha Key Site 574 - Aughnagon Quarry Key Site 575 - Goraghwood Quarry Key Site 576 - Newry By-pass Key Site 578 - Kearney Point Key Site 579 - Ballyhalbert Pier For general information and references on the Caledonian Igneous Complexes of N. Ireland, and for directions to other regional sites, see the following site: Key Site 595 - Introduction to the Caledonian Igneous Complexes of N. Ireland | |
| Keywords | |
|---|---|
| Rocks: | Granodiorite, Greywacke, Hornfels, Microgranite, Shale |
| Structures: | Caledonian, ring-dyke, pluton |
| Relations: | Intrusion, Contact metamorphism |
| Access | |
|---|---|
| Approach: | Access is via the C class Keggall Road that joins the Newry Road (A25) at Camlough. |
| Management: | |
Cam Lough Quarry is disused and somewhat overgrown; it is also subject to fly tipping. Rock surfaces are slippery and overlooked by steep quarry faces. Landowner permission will be needed to gain access. There is no need to restrict hammering or sampling at this site. | |
| Map(s): | GEOLOGICAL SURVEY OF IRELAND, 1875. 1:63,360 Geological Sheet 59 (Castleblayney). (Dublin, Ordnance Survey for Geological Survey of Ireland). | ||
| Record type: | ESCR report | ||
| Entered by: | E M Porter | ||
| Last updated: | 03 MAR 2001 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Cam Lough Quarry - Caledonide Igneous Complex, County Armagh, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=577. Accessed on 2026-11-05. |
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