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Earth Science Conservation Review
| Curraghinalt - site of local interest | Tyrone |
| Site number: | 722 | ||
| Locality Type: | Stream section | Status: | local interest |
| Grid Reference: | H571865 Centroid | ||
| Google maps: | 54.72371,-7.1138 | ||
| County: | Tyrone | Council area: | Fermanagh & Omagh District Council |
| Period: | Carboniferous, Ordovician, Precambrian | ||
| Site Description | |
|---|---|
| Highlights: | |
A reasonably accessible, pyritic quartz vein outcrop that is representative of an internationally known and thoroughly documented gold ore prospect. | |
| Description: | |
The site is located approximately 150m upstream of the Attys Bridge in the Curraghinalt Burn, which forms the boundary between Attagh and Curraghinalt Townlands 8km east of Gortin. The vein is exposed in the bed of the stream and samples can be obtained of coarse-grained pyritic quartz vein material. Gold is not generally visible in hand specimen. A bulk sample of vein material was removed from the east flank of the stream valley but the vein is no longer exposed in the pit, which has grassed over. Evidence from mineralogical studies and cathodoluminescence microscopy (Earls et al., 1996; Parnell et al., 2000; Wilkinson et al., 1999) indicates that several stages of cross-cutting quartz (Q2-Q4) were introduced during brittle deformation following the formation of early veining (Q1) due to defluidization during ductile deformation and metamorphism of the Dalradian host rocks. Volumetrically minor, early paragenetic (Q2) electrum is encapsulated within pyrite. However, most electrum occurs along pyrite crystal boundaries, or is related to cross-cutting fractures that also contain baryte, chalcopyrite, tetrahedrite, quartz and dolomite, that were formed during a secondary mineralising event (Q4). In one sample which was the subject of detailed study, the syn-pyrite and post-pyrite electrum have a different chemistry: earlier electrum has a lower silver content than that in cross-cutting veinlets. Volumetrically minor amounts of gold-bearing tellurides containing up to 5.9 at% Au were also observed as micron-scale crystals enclosed within pyrite. The most common is bismuth telluride, less common are gold-silver tellurides including hessite [Ag,Au]2Te, mercury telluride and the lead telluride, altaite [PbTe]. | |
| Importance: | |
The vein was one of the first bedrock occurrences of potentially economic gold mineralization discovered during commercial mineral exploration in Northern Ireland. It is representative of the 'lode gold' style of mineralization in the Curraghinalt prospect, which has been the subject of detailed geological and geochemical investigations widely reported in the international scientific literature. This locality is unimpressive except for professional geologists, for whom it is important as a representative of an internationally known gold prospect and of regional metallogeny. | |
| Interpretation: | |
Those involved in the gold metallogeny study (Earls et al., 1996; Parnell et al., 2000; Wilkinson et al., 1999) concluded that paragenetically early mineralization at Curraghinalt (Q2 and associated minerals) is Ordovician in age and that minerals were deposited by fluids of magmatic origin associated with the underthrusted Tyrone Volcanic Group pyroclastic and intrusive sequence. The barren Q3 veining occurred as these fluids mixed with lower temperature, lower salinity connate waters. Q4 and associated minerals - notably, the bulk of the electrum - seem likely to have precipitated during the Carboniferous from high salinity fluids (perhaps basinal brines) that penetrated the Dalradian metasedimentary pile during tensional tectonism associated with the Variscan Orogeny. This hitherto unexpected conclusion has interesting implications as it enhances the gold prospectivity of Carboniferous and other Upper Palaeozoic rocks in the north of Ireland. | |
| Notes: | |
See also ESCR Key Site 521 - Curraghinalt Burn, near Gortin [Mineralogy and Metallogenesis Block]. | |
| Keywords | |
|---|---|
| Minerals: | Gold, Pyrite, Quartz, Electrum |
| Rocks: | Psammite |
| Structures: | hydrothermal vein |
| Access | |
|---|---|
| Approach: | The site is located approximately 8km east of Gortin. |
| Record type: | SLNCI Report | ||
| Entered by: | E M Porter | ||
| Last updated: | 09/10/03 | ||
| Enlander, I., Dempster, M. & Doughty, P., 2026. Curraghinalt - site of local interest, County Tyrone, site details. [In] Earth Science Conservation Review. https://www.habitas.org.uk/escr/site.php?item=722. Accessed on 2026-11-06. |
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