Projects

Clontibret: Tullybuck-Lisglassan

The Tullybuck-Lisglassan prospect was originally discovered over a century ago, when stibnite-bearing veins were discovered, and the Tullybuck and Lisglassan shafts were sunk to investigate them. At this stage the prospect was called the Clontibret antimony mine.  Gold was discovered when back channel samples in the old workings were analysed in the 1950s. The prospect was subsequently drilled by Can Erin Mines in the 1950s, and by Munster Base Metals in the 1970s.  Both these companies intersected high grades of gold in narrow veins, but with frequently poor core recovery in those narrow zones. 

In the past the prospect area has been at a disadvantage because of difficult exploration conditions.  This is largely on account of the thick glacial till which covers most of the surrounding area, which effectively obscures the bedrock geology.  The other main reason is the very fine grained nature of the gold mineralisation at Tullybuck-Lisglassan, which is micron-sized (typically 1 to 5 microns).  Even though the shafts and levels of the old Clontibret mine passed directly through one gold bearing structure, the very fine grained gold mineralisation was not observed until the 1950s.  For these reasons, the presence of gold was only established at the prospect in recent decades. 

These mineralised structures are also fault structures that, near to surface, can be expected to be strongly weathered.  Consequently much of the earlier drilling was beset by poor core recoveries in the lode zones, which are of critical importance. It is likely that some of the previous drilling done in the 1950s has effectively under-sampled many of the high-grade mineralised structures.

With CDG exploration work now focusing on the resource potential of the prospect, the establishment of a geological model for the deposit was of critical importance. The model helps to explain the geological and grade variations of the deposit, increases confidence levels in resource / reserve calculations, and guides ongoing exploration work.