Lough Sheelin Block

The Lough Sheelin block consists of five contiguous prospecting licences - 1051, 1053, 1991, 3925 & 3926 - covering an area of approximately 170.76 km2 of Counties Meath and Cavan in north-central Ireland. The block is located approximately 20km west of the giant Navan zinc/lead mine (c.100 million tonnes grading c.8% zinc / 1% lead) that is currently being operated by New Boliden.

The licence block is located along the southern edge of the Longford-Down Massif, where Lower Palaeozoic sediments are unconformably overlain by a transgressive sequence of Lower Carboniferous shallow water marine carbonates. The primary target horizon for zinc/lead mineralisation are the Navan Beds succession, which can be up to 140m thick in this area. The structural setting of the Lough Sheelin region is strongly analogous to the Navan area.

Mineralisation

Mineralisation discovered to date is best developed in the Top Micrite and in the Impure Micrite Siltstone Unit (IMSU) of the Navan Beds, but is also present in other units, especially the Marine Sandstone. The best and most extensive mineralisation discovered in this area to date is in the region around Drumlerry. However, extensive mineralisation in the form of traces of sphalerite, galena and barite has also been recorded in the Laminated Beds, shaly Pales and ABL throughout the Lough Sheelin region. Barite tends to occur in faults and fractures and is particularly hosted by the Lower Palaeozoics.

Drumlerry

The Lower Micrite is essentially barren except for traces of sphalerite. Slightly more phalerite with barite occurs in the Evaporite Micrite Unit. The best developed mineralisation occurs within the Top Micrite. This consists principally of veins of sphalerite, galena, pyrite and barite generally cross-cutting the bedding at dips averaging 70o.

The veins appear to have resulted from dissolution and replacement along stylolitic fractures and water escape structures. The margins of the veins commonly contain disseminations of sphalerite and other sulphides, which extend into the wall rock. Well-developed birdseye features were mostly filled with calcite prior to the sulphide phase, sometimes replaced by barite or pyrite.

Work carried out in 2007 and 2008 has been focused on the greater Drumlerry Target

Area, where historically low to medium grade Navan Beds hosted zinc / lead mineralisation had been discovered. The early work programme consisted of a Gradient Array Induced Polarisation geophysical surveying that was designed to enhance the fundamental geological and structural understanding of the area. The geophysics was followed up by a diamond drilling programme designed to test geological / structural targets. Intersection of low to medium grade zinc and lead sulphide mineralisation meant the drilling programme was extended.

The diamond drilling programme was carried out to test targets along the relatively poorly explored Drumlerry region. A total of eleven holes were completed during this phase of exploration, carried out between December 2007 and April 2008. The cumulative meterage drilled is 1391.50m. Results are summarised below.

The drillholes were very widely spaced (up to 650m apart) and intended to locate indications of significant mineralising processes, both in terms of grade and style of occurrence. The initial results from the first three holes of this drilling programme were disappointing with only small traces of zinc and lead sulphides intersected at the target horizon. However, towards the end of the programme three drillholes C-3925-5, 8 & 9 intersected significant grades and thicknesses of zinc and lead mineralisation, hosted within the Top Micrite formation of the Navan Beds.

The style of the mineralisation is a combination of disseminated and fracture fill sphalerite and galena with some replacement of coarser grained limestones. It should be noted that as yet the mineralisation intersected is uneconomic. However, the grade and style is considered to be highly significant and it is similar to what would be expected close to the margins of a deposit (i.e. within 1-2km). It can be clearly seen that the recent drilling is extending the zone of known mineralisation to the northwest and west. This mineralisation remains open, both to the northwest and southwest. A follow up programme is planned.

Back Print