Navan Project

Overview

Ownership & Location

Minco, through its wholly-owned subsidiary Westland Exploration Limited, holds a 20% interest in Propsecting Licence (“PL”) 1440R (Tatestown), which is being explored under a joint venture with Boliden Tara Mines (80%). PL 1440R is located immediately adjacent to Boliden Tara’s large >125 million tonnes Tara zinc-lead mine at Navan, Co. Meath, and hosts part of the small Tatestown–Scallanstown zinc-lead mineral deposit.

Minco, through its wholly-owned subsidiary Minco Ireland, has entered into a second joint venture agreement with Boliden Tara on PL 3373 (Kells), contiguous to the west with PL 1440R. Under terms of this agreement, Minco can earn a 75% interest through expenditure of €250,000, in staged programmes, by 1 March 2024. Boliden Tara Mines has the right of off-take to purchase or toll process all ore that may be produced from the licence area.

The Navan Block consists of these two contiguous prospecting licences covering a surface area of 62.08km², immediately northwest of the town of Navan and approximately 50km to the northwest of Dublin.

Geology

The Navan Block is located on the northern boundary of the Irish Midlands Orefield, contiguous with the Tara-Boliden mine lease.  The stratigraphy can be correlated to the mine with Courceyan aged intertidal and shallow marine sediments resting on a major unconformity upon Lower Palaeozoic sediments and volcanics.  The Courceyan carbonate succession is overlain by a succession of deeper water marine limestones of Chadian and Arundian age, referred to locally as the Upper Dark Limestone.  A well-defined lithostratigraphy has been developed within this Upper Dark succession in the vicinity of the mine where the Upper Dark Limestone rests upon an angular erosion surface, or slide. 

The Navan Succession

The Navan Block straddles the southern margin of the Longford Down inlier.  Drilling consistently demonstrates a rapid, northwards thinning / wedging out of the Courceyan succession along the southern margin of the inlier indicating that this remained a topographically positive feature, indicating active basement structural control, during deposition of the Courceyan fluvial, intertidal and shallow marine basal succession.

The boundary Fault, considered a Variscan re-activation of the regional basement structure, is well defined by past drilling on Licence 1440R.  At outcrop, east of the Boolies Fault, it juxtaposes the northeast striking, west dipping Courceyan succession against Lower Palaeozoic basement.  To the west the Boundary Fault outcrops within the Limestone succession, generally within the outcrop of the Upper Dark Limestones.

On Licence 3373 the exact location of the Boundary Fault, due to the sparser drill coverage and its outcrop within the Upper Dark Limestones, is less well constrained.  Interpretation of drill data and seismic profiles has identified a series of offsets of the Boundary Fault by northeast striking faults similar to those seen in the immediate vicinity of the Navan mine.

Geology of the Navan Block

Mineralization

Localised low grade, zinc-lead mineralisation has been intersected by drilling hosted by the Navan Beds at a number of areas across the property. Minco consider this to be an indication of prospectivity of the Navan Block, in particular for potential satellite deposits to the Navan Mine, analogous to recently discovered Tara Deep Deposit. However, to date on the licence block only one significant mineral occurrence has been discovered, the Tatestown / Scallanstown Deposit.

The Tatestown / Scallanstown deposit was discovered by Irish base Metals in 1972. The mineralisation is hosted by Lower Carboniferous, shallow water carbonate facies and is generally stratiform, occurring as two horizons at or close to the top of the Micrite Unit. The mineralisation consists of sphalerite, galena,  pyrite / marcasite and barite that occurs as rhythmic colloform infill to fractures, voids and interparticle porosity. The mineralisation thickens and is preferentially enriched in the immediate vicinity of a northerlt dipping, east-west striking normal fault, which transacts the deposit.

Tatestown Scallanstown Deposit Location Map

History

In the Navan Area regional exploration for base metals on Prospecting Licences 1440R and 3373 began during the late 1960’s and intensified following discovery of the Navan orebody in 1970. Since then, exploration has focused exclusively on the search for zinc-lead mineralisation hosted by the Navan Beds, which host the Navan orebody.  Historic work was carried out by RioFinEx, Gortdrum Mines Ltd., Enfer Holdings Ltd., Irish Base Metals Limited, Westland Exploration Ltd., Kenmare Resources Plc. and Boliden Tara Mines.

Historical exploration on the Navan Block follows a typical pattern to the that observed elsewhere in the Irish Midlands Orefield with a primary focus on geochemistry, supported by mapping, prospecting and lithogeochemistry. This was followed up with geophysics and ultimately diamond drilling. Soil sampling was supported with DOB Sampling in selected areas, normally to confirm and check soil anomalies. Ground geophysical surveying has included Induced Polarisation, Turam EM, VLF/EM resistivity and gravity. From the late 1990’s a series of airborne surveys were carried out across the Irish Midlands Orefield by a range of private companies. In the Navan region an EM / Magnetic survey was flown by BHP. Licences 1440R and 3373 were traversed by three reflectoin seismic survey lines which have proven effective in defining the structural model within the underlying Lower Carboniferous stratigraphy.

In addition to the acquisition of data through drilling and geological, geochemical and geophiscal surveying, a large suite of studies, interpretations and modelling has been carried out on the data acquired from the Navan Block. This work has included:

Structural interpretation and modelling (numerous studies)

Lithogeochmical assessment of alteration and mineralisation

Interpretation of satellite imagery

Conceptual studies

Metalurgical studies

Micropalaeontological studies

Feasibility studies

Drilling commenced at Tatestown in 1973 and has continued in the general vicinity until the present day. It was during the tenure of Irish Base Metals Ltd / Westland Exploration Ltd. that the Tatestown / Scallanstown deposit was discovered. The Tatestown–Scallanstown deposit straddles the Blackwater River, which forms the licence boundary between PLs 1440R and 1496. Part of this deposit is located on PL 1440R, the remainder on the adjacent PL 1496, held solely by Boliden Tara Mines.

A historical resource was estimated at 3.6Mt grading 6.9% Zn + Pb (Andrew and Poustie, 1986). Minco has not done sufficient work to classify the histrocial estimates as current mineral resources or mineral reserves and is not treating the histroical estimate as a current mineral resource or mineral reserve. The author has not had access to the historic drilling around the Tatestown / Scallanstown deposit.

Following the discovery of the Tatestown / Scallanstown deposit in 1973, a large number of holes have been drilled in the eastern part of PL 1440R, between the Randalstown and Boolies Faults.  In contrast, only 42 diamond drill holes, for approximately 11,000 metres of drilling, have been completed over the balance of PL1440R to the west of the Boolies Fault.  Many of these drill holes were short and sited primarily to ascertain bedrock geology. The northern two kilometres of the north-south trending zone remains essentially unexplored on Licence 1440R, with just four, widely spaced intercepts comparable to those peripheral to the known deposit.

Since 1975, approximately 8000m of diamond drilling has been completed in 51 diamond drill holes on PL 3373.  Twenty six of these, had an average depth of 19.3 metres, were drilled primarily to ascertain bedrock geology. The historical work provides an extensive database upon which to focus exploration for deeper, geophysically and geochemically blind deposits down-dip to the south. 

Reports

•  Blaney, D. “Technical Report on the Irish Zinc Exploration Project of Minco Exploration Limited a subsidiary of Buchans Resources Limited” dated 29 October 2019

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