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Earth Science Conservation Review
| Ballymagreehan Quarry | Down |
| Site number: | 571 | ||
| ESCC: | EA | ||
| Locality Type: | Quarry (working) | Status: | ESCR |
| Grid Reference: | J30453540 Centroid | ||
| Google maps: | 54.2513,-5.99931 | ||
| County: | Down | Council area: | Newry, Mourne & Down District Council |
| Period: | Devonian, Silurian | ||
| Stages: | Lower Devonian | ||
| Lithostrat: | Newry Igneous Complex | ||
| Site Description | |
|---|---|
| Highlights: | |
Ballymagreehan Quarry contains outcrop of strongly foliated granodiorite, part of the northeast pluton of the Newry Igneous Complex. The granodiorite is more basic than that exposed towards the centre of the pluton indicating that the intrusion is normally zoned. The granodiorite contains a range of igneous and 'sedimentary' inclusions known as enclaves. | |
| Introduction: | |
Ballymagreehan Quarry is located on the eastern flank of Tullynasoo Mountain close the southern margin of the Newry Igneous Complex. Access to the site is via a private road which runs off the Largy Road northwest of Altnadua Lough. The quarry was opened up some time after publication of the first edition of the Newry (Sheet 60) one-inch to the mile geological map (Geological Survey of Ireland, 1876) on which the area was mapped as "granite". Reynolds (1934; 1936) classified the main rock type at this site as granodiorite, i.e. consisting of quartz, plagioclase feldspar, alkali feldspar, biotite mica and some hornblende. Reynolds' classification and terminology still stand within modern classification schemes (Streckeisen, 1976). Systematic sampling, thin section petrology and geochemistry (Grant, 1961; Meighan and Neeson, 1979; Neeson, 1984) have revealed that the granodiorite at the margins of the northeast and southwest plutons is more basic the than rocks towards the centres of the intrusions. These plutons were described as displaying a "normal zoning" pattern. The opposite case occurs in the middle pluton, which has a more basic core and acid margins. This zoning pattern has been referred to as "reverse zoning". Along the margin of the granodiorite plutons within the Newry Igneous Complex there is commonly a foliation and alignment of minerals, particularly biotite mica, (Reynolds, 1934; Meighan & Neeson 1979). These fabrics are aligned parallel to contacts, a feature attributed to regional deformation and shouldering aside of country rock during diapiric emplacement (Murphy, 1987). Such a fabric is well developed within Ballymagreehan Quarry. A varied selection of enclaves (xenoliths) of igneous and sedimentary origin is found at this location (Meighan, pers. comm. 1999). The sedimentary enclaves are metamorphosed Silurian country rock and the igneous xenoliths represent fragments of earlier formed less evolved igneous rock types. Meighan & Neeson (1979) published a Rb-Sr age date of 399±3Ma for the granodiorite of the northeast pluton. Field relations indicate that this pluton was the first of the three major bodies that together form much of the Newry Igneous Complex. | |
| Description: | |
Medium- to coarse-grained granodiorite, part of the northeast pluton, is exposed in Ballymagreehan Quarry. The main mineral components (Meighan pers. comm., 1999) of the granodiorite are plagioclase and alkali feldspar, hornblende (with clinopyroxene cores), quartz and biotite mica. Granodiorites are therefore classified as I-type (igneous) rocks. Systematic sampling, thin section petrology and geochemistry across the Newry Igneous Complex (Neeson, unpublished; Grant, 1961; Meighan and Neeson, 1979) have revealed compositional variation within the granodiorite plutons. Granodiorite at the margins of the northeast pluton is more basic than that exposed towards the centre of the intrusion. A similar situation exists for the southwest pluton; these intrusions are described as displaying normal zoning. A strong foliation of minerals, particularly biotite, is present and strikes northeast to southwest, parallel to the main contact of granodiorite with Silurian country rock to the southeast. The foliation is also steeply inclined to the southeast. A varied selection of enclaves (xenoliths) of sedimentary and igneous origin is found at this location (Meighan, pers. comm.). Most enclaves have irregular rounded forms and in some cases have diffuse boundaries with the enclosing granodiorite. Some are flattened and aligned parallel to the foliation in the granodiorite. Igneous enclaves include dioritic and microdioritic compositions, and include ultramafic 'clots' (restite). All of the sedimentary xenoliths appear to be metamorphosed Silurian greywackes and shales. Pegmatite veins cut the granodiorite and have a distinctive light pink colouration and a coarse to very coarse-grained texture. The main mineral constituents are quartz, plagioclase feldspar, alkali feldspar, and biotite mica. | |
| Importance: | |
Ballymagreehan Quarry is a site of national importance offering access to high quality exposure of foliated granodiorite which is part of the northeast pluton of the Newry Igneous Complex. The granodiorite is more basic than that exposed towards the centre of the pluton indicating the intrusion is "normally zoned". The presence of foliation within granodiorites in this area is attributed to regional deformation and shouldering aside of country rock during emplacement of the Newry Igneous Complex. A range of igneous and sedimentary enclaves is present that provides information concerning pluton emplacement and less evolved magma compositions. | |
| Interpretation: | |
Compositional differences between granodiorite at this site and those situated towards the centre of the northeast pluton (see Key Site 572 - Rathfriland) indicate normal zoning of the intrusion. Such zoning could be evidence of fractional crystallisation of magma after emplacement. Alternatively, several injections of magma might have been involved in the formation of the northeast pluton; a model that could pertain to the formation of each of the plutons that together constitute the Newry Igneous Complex (Meighan and Neeson, 1979). Foliation of granodiorites in this area is in keeping with the geological setting, i.e. a pluton margin (Reynolds, 1934; Meighan & Neeson 1979). Foliation is attributed to regional deformation and shouldering aside of country rock during emplacement of the Newry Igneous Complex (Cameron, 1981). Regional curvature of fabrics parallel to such margins lends weight to a diapiric intrusive model (Murphy, 1987). The 'sedimentary' and igneous enclaves found within the granodiorite have to some degree been transported by the granodiorites. Diffuse boundaries indicate a degree of assimilation of the enclaves in the granodiorite. Sedimentary' enclaves have almost certainly been derived from the surrounding metamorphosed Silurian country rock. Assimilation of the country rock could have resulted from fracturing in response to regional deformation. Less evolved magma compositions are likely to be represented by the igneous enclave varieties. Pegmatite veins are most likely the product of late stage segregation of magma during cooling of the northeast pluton. | |
| Conclusions: | |
Ballymagreehan Quarry is a site of national importance offering access to high quality exposure of foliated granodiorite close to the margin of the northeast pluton. Marginal granodiorite is more basic than that towards the centre of the pluton indicating the intrusion is "normally zoned". The presence of a foliation within granodiorites in this area is attributed to regional deformation and shouldering aside of country rock during emplacement of the Newry Igneous Complex. A range of igneous and sedimentary enclaves is present that provides information concerning pluton emplacement and less evolved magma compositions. | |
| 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 572 - Rathfriland Key Site 573 - Gransha Key Site 574 - Aughnagon Quarry Key Site 575 - Goraghwood Quarry Key Site 576 - Newry By-pass Key Site 577 - Cam Lough Quarry 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 |
| Structures: | Caledonian, pluton, enclave, normal zoning |
| Relations: | Intrusion |
| Access | |
|---|---|
| Approach: | Access to the site is via a private road which runs off the Largy Road northwest of Altnadua Lough. |
| Management: | |
This site is an active quarry with steep quarry faces and loose blocks; sensible safety precautions will be required. Landowner permission will be needed to gain access to this site. There is an abundance of rock exposure, consequently there is no need to restrict hammering or sampling at this site. 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. | |
| Uses | |
| Uses: | Active quarry |
| Map(s): | GEOLOGICAL SURVEY OF IRELAND, 1876. 1:63,360 Geological Sheet 60 (Newry). 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. Ballymagreehan Quarry, County Down, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=571. Accessed on 2026-11-05. |
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