ESCR - Newry By-pass

Earth Science Conservation Review

Summary Full report
Newry By-pass	Armagh

Site number:	576
ESCC:	EO
Locality Type:	Roadside section	Status:	ASSI
Grid Reference:	J08032485 Centroid
Google maps:	54.16133,-6.34662
County:	Armagh	Council area:	Newry, Mourne & Down District Council
Period:	Devonian
Stages:	Lower Devonian
Lithostrat:	Newry Igneous Complex

Site Description
Highlights:
The Newry By-pass site offers access to a zone of contact between the middle and southwest plutons of the late Caledonian Newry Igneous Complex. The site contains evidence of the variety, and relative timing of intrusion of the igneous rock types that comprise the middle and southwest plutons of the late Caledonian Newry Igneous Complex.
Introduction:
The Newry By-pass site is a roadside section located approximately 3km south-southwest of Newry town centre and immediately northwest of the Dublin Road Bridge and roundabout. Exposure on the western (northbound) side of the dual carriageway is of most interest and includes a zone of contact between the southwest and middle plutons of the Newry Igneous Complex. The first edition of the Newry (Sheet 60) one-inch to the mile geological map (Geological Survey of Ireland, 1876) indicates granite that has been intruded by quartziferous porphyry and basic dykes. The accompanying memoir (Hull, 1881) provides a general description of granite in the Newry area, but provides no detail concerning this site. Petrology and classification of Newry granite by Reynolds (1934, 1936, 1943 and 1944) showed the rocks to be granodioritic in composition. Reynolds's classification and terminology still stand with modern schemes (Streckeisen, 1976). Systematic sampling, thin section petrology and geochemistry (Grant, 1961; Meighan and Neeson, 1979 Neeson, 1984) have revealed compositional zoning within the plutons of the Newry Igneous Complex. Granodiorite at the margin of the middle pluton is more acid than at the centre of the intrusion. This zoning pattern has been referred to as "reverse zoning". The opposite situation, "normal zoning", in which the centre of the pluton is more acid than the margin, is present in the southwest pluton. O'Conner (1975) published a whole-rock (Rb-Sr) isotope age of 399±21Ma for granodiorite from the southwest area of the Newry Igneous Complex. The most recently published map which covers this site is the second edition of the 1:250,000 scale Solid Geology Map of Northern Ireland (Geological Survey of Northern Ireland, 1997).
Description:
At this site, key contact relationships can be observed in the first 20m of section northwest of the Dublin Road Bridge and roundabout. The first 5m of section consists mainly of medium-grained, pinkish yellow granophyre which is in contact with fine-grained, biotite granodiorite of the southwest pluton (Hurley, pers. comm., 1999). The granophyre forms part of the more recent Tertiary (Palaeogene) Slieve Gullion Ring Dyke. Approximately 5m further north coarse-grained, hornblende granodiorite (Meighan, pers. comm., 1999) belonging to the middle pluton occurs (Hurley, pers. comm., 1999). Shear zones are abundant, and are found associated with the granodiorite of the middle pluton. Several dark green to black, fine-grained, basic dykes cut the granodiorite and granophyre. These dykes are composed of basalt and dolerite, and are of Palaeogene age. Veins of late Caledonian microgranite are present and are affected by shearing. Similar microgranite veins showing signs of shearing are interpreted as being younger and related to the Tertiary ring dyke. Very coarse-grained veins and pods of pegmatite, of late Caledonian age, are also seen.
Importance:
The Newry By-pass site is of national importance which offers access to an exposed contact between two of the plutons that comprise the Newry Igneous Complex. The variety and relative timing of intrusion of the southwestern pluton of the late Caledonian Newry Igneous Complex can be demonstrated at this site.
Interpretation:
The Newry By-pass exposes a complex contact zone between the southwest and middle plutons of the Newry Igneous Complex. Textural and compositional differences within the granodiorites allow differentiation of the two plutons. Shearing of granodiorites and associated microgranitic veins is most likely related to the intrusion of the southeast pluton and continued regional deformation (Cameron, 1981). Granophyre and basic dykes were intruded as a result of Palaeogene magmatism and will not be discussed further.
Conclusions:
The Newry By-pass site offers access to a contact between two of the plutons of the Newry Igneous Complex. At this site, it is possible to demonstrate the variety, and relative timing of intrusion, of igneous rock types which form the middle and southwest plutons.
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 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, Microgranite, Pegmatite
Structures:	Caledonian, pluton
Relations:	Intrusion

Access
Management:
This site is a roadside cutting and therefore great care and attention is required when visiting. Vehicles should not be parked on the hard shoulder of the carriageway. Hammering should be restricted. 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.

Access

Management:

This site is a roadside cutting and therefore great care and attention is required when visiting. Vehicles should not be parked on the hard shoulder of the carriageway. Hammering should be restricted.
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.


Map(s):	GEOLOGICAL SURVEY OF IRELAND, 1876. 1:63,360 Geological Sheet 60 (Newry). Dublin, Ordnance Survey for Geological Survey of Ireland. GEOLOGICAL SURVEY OF NORTHERN IRELAND, 1997. Northern Ireland. Solid Geology (2nd edition). 1:250,000. (Keyworth, Nottingham: British Geological Survey).
Record type:	ESCR report
Entered by:	E M Porter
Last updated:	03 MAR 2001

Enlander, I., Dempster, M. & Doughty, P., 2026. Newry By-pass, County Armagh, site details. [In] Earth Science Conservation Review.
https://www.habitas.org.uk/escr/site.php?item=576. Accessed on 2026-11-07.