Numerous showings and some small gold deposits are known in the Sperrin Mountains, within the Neoproterozoic Dalradian sequences of Northern Ireland, UK. These include the Curraghinalt group of veins and the Kearney vein at Cavanacaw.
The geology of the area is composed of three main rock groups, namely:
1). The Neoproterozoic Dalradian in the Grampian terrane - 590 Ma metasediments and basic metaigneous rocks, including biotite to garnet grade semipelites, psammites, and chloritic-sericitic semipelites and an important pelite horizon, the Glengawna Formation which hosts much of the gold on the limbs of an inverted, gently dipping limb of a major overturned tight to isoclinal fold, the Sperrin Nappe. Immediatley to the south-east is the gently dipping, NE trending Omagh Thrust which separates the Neoproterozoic Dalradian from the underlying Ordovician Tyrone Igneous Complex
2). The Tyrone Igneous Complex, comprising the Ordovician Tyrone Ophiolite gabbros and the Tyrone Volcanic Group MORB composition pillow lavas in the Northwest Terrane which are cut by Ordovician porphyries, a tonalite body and calc-alkaline granites. This complex is underlain by the 640 Ma Neoproterozoic silimanite grade paragneiss and greenstones of the Central Inlier.
3). Widespread upper Palaeozoic sediments, of Devonian and Carboniferous age which overlie all of the above.
Mineralisation is structurally controlled by a lateral ramp associated with the Omagh Thrust and by the NNE aligned Omagh Lineament. The latter is expressed in the cover rocks by the distribution and orientation of faults and igneous intrusions, bedding and foliation.
The Curraghinhalt deposits occur as a series of NW trending, NE dipping gold bearing quartz veins from a few mms to 2.75 m in thickness, within semipelites, close to the contact with the Glengawna Formation and generally related to the Omagh Thrust.
At Cavanacaw gold mineralisation occurs in a steeply west dipping, north-south trending quartz vein complex that is around 1 km long. The Kearney Vein lies in a coplanar, NNE trending sinistral shear zone.
The multi vein Curraghinalt prospect contained 0.9 Mt @ 11.66 g/t Au in 2000.
The Kearney Vein at Cavanacaw contained 2 Mt @ 6.9 g/t Au in 2000.
(Source: Porter Geoconsultancy, http://www.portergeo.com.au/, 2000)