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Lisheen - Main Zone, Derryville, Bog East, Bog Central, Bog West, Island Pod |
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Ireland |
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Zn Pb
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Super Porphyry Cu and Au
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The Lisheen carbonate hosted zinc-lead deposit is located in approximately 18 km south-west of the town of Rathdowney in south-central Ireland, and approximately 10 km south-west of the Galmoy deposit.
The Lisheen deposit, which was discovered in April 1990, is composed of several discrete, stratabound Zn-Pb orebodies that are strongly controlled by a left-stepping, ramp-relay fault array (Hitzman et al., 2002; Fusciardi et al., 2003; Kyne et al., 2019). Mining operations began in 1999 and closed in late 2015. The deposit was composed of six distinct orebodies: Main Zone, Derryville, Bog East, Bog Central, Bog West and Island Pod (Kyne et al., 2019). Additional subeconomic pods of mineralisation occur at Barnalisheen, Templetouhy and Bawnmore. These orebodies were distributed over a ENE-WSW elongated area of ~3500 x 1600 m, with the two largest orebodies, Main Zone and Derryville occupying an area of ~1600 m in diameter.
The Lisheen deposit is hosted by lower Carboniferous carbonates within the Rathdowney Trend in central Ireland. Within the deposit area there are three main units, the lower Argillaceous Bioclastic Limestone, the Waulsortian Limestone composed of biomicrites, argillites and micrites, and the overlying cherty calcarenites if the Crosspatrick Formation.
The ore is located along the western edge of a broad zone of dolomitisation within the Waulsortian and Crosspatrick Formations along the Rathdowney Trend. Ferroan dolomite zones over print the dolomitisation and partially envelope, but predate the sulphides.
Massive sulphides are localised immediately above the base of the Waulsortian as a series of stratabound lenses with zones of vein stockworks. Minor mineralisation extends down into the Argillaceous Bioclastic Limestone as disseminations accompanied by silicification and veining.
Mineralisation is interpreted to represent host rock replacement and open space fill. A black matrix breccia forms irregular zones, above, below and laterally to massive sulphides. This breccia is composed of angular to sub-rounded, irregular clasts of dark grey dolostone, set in a very dark grey to black, <1 to 15µm grain sized matrix of ferroan dolomite, non-ferroan dolomite and minor disseminated iron sulphides, with abundant microscopic voids.
Doran et al. (2022) studied mineralisation from the satellite Island Pod orebody (0.4 Mt @ 20% Zn, 1.6% Pb) on the northern periphery of the Lisheen cluster. This orebody comprises high-grade mineralisation that is less deformed than elsewhere in the Irish orefield, but may be the result of ore forming processes common to many of the deposits in the field. The Island Pod orebody is almost exclusively composed of pyrite, sphalerite and galena, with several stages of calcite and dolomite precipitation. The pre-ore, diagenetic pyrite is frequently overgrown by early main ore-stage pyrite, with both phases replaced by main ore-stage sphalerite. Early main ore-stage pyrite is commonly texturally zoned and exhibits chemical zoning patterns, reflecting episodic influxes of hydrothermal fluids contained variable concentrations of As, Co, Ni and Tl. The main ore stage was dominated by sphalerite and galena from mineralising fluids that were depleted in these trace elements (e.g., As, Co, Tl) compared to the early main ore stage. The mineralogy of the Island Pod orebody comprises multiple generations of pyrite, sphalerite and galena. Minor marcasite and the sulphosalts gratonite [Pb9As4S15] and jordanite [Pb14(As,Sb)6S23] are also present. Gangue minerals include dolomite and calcite, with quartz and illite laths only observed locally. Several generations of calcite and dolomite have been identified, including a calcite phase intergrown with colloform sphalerite, later calcite that cuts colloform sphalerite bands, pink dolomite and late infilling calcite (Doran et al., 2022).
The pre-mining resource has been stated (Guven, et al., 2007) at 17.9 Mt @15.8% Zn, 2.6% Pb, although alternative resources at a lower cut-off of 21 Mt @ 12% Zn, 2% Pb have also been published.
Total production to mine closure in 2015 was 22.4 Mt @ 11.63% Zn, 1.96% Pb (Torremans et al., 2018), at an economic cutoff grade of 6 wt.% Zn + Pb, with a minimum mining thickness of 4.5 m (J. Güven, 2020).
The most recent source geological information used to prepare this decription was dated: 2022.
Record last updated: 14/1/2022
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Doran, A.L., Hollis, S.P., Menuge, J.F., Piercey, S.J., Boyce, A.J., Johnson, S., Guven, J. and Turner, O., 2022 - A Distal, High-Grade Irish-Type Orebody: Petrographic, Sulfur Isotope, and Sulfide Chemistry of the Island Pod Zn-Pb Orebody, Lisheen, Ireland: in Econ. Geol. v.117, pp. 305-326.
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Hitzman M W 1995 - Mineralisation in the Irish Zn-Pb-(Ba-Ag) Orefield: in Anderson K, Ashton J, Earls G, Hitzman M, Tear S (Eds.), Irish Carbonate Hosted Zn-Pb Deposits SEG Guidebook Series, Littleton, Colorado, USA v21 pp 25-61
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Hitzman M W 1995 - Geological setting of the Irish Zn-Pb-(Ba-Ag) Orefield: in Anderson K, Ashton J, Earls G, Hitzman M, Tear S (Eds.), Irish Carbonate Hosted Zn-Pb Deposits SEG Guidebook Series, Littleton, Colorado, USA v21 pp 3-23
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Hitzman M W, O Conner P, Schaffalitzky C, Beaty D W, Allan J R, Thompson T 1993 - Discovery and geology of the Lisheen Zn-Pb-Ag prospect, Rathdowney Trend, Ireland: in Bowden A A, Earls G, O Connor P G, Pyne J F (Eds.), The Irish Minerals Industry 1980-1990 Irish Association for Economic Geology, Dublin pp 227-246
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Hitzman M W, Redmond P B, Beaty D W 2002 - The Carbonate-hosted Lisheen Zn-Pb-Ag deposit, County Tipperary, Ireland: in Econ. Geol. v97 pp 1627-1655
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Johnston J D 1999 - Regional fluid flow and the genesis of Irish Carboniferous base metal deposits: in Mineralium Deposita v34 pp 571-598
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Pannalal S J, Symons DTA and Sangster DF, 2008 - Paleomagnetic Evidence for an Early Permian Age of the Lisheen Zn-Pb Deposit, Ireland : in Econ. Geol. v103 pp 1641-1655
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Shearley, E., Redmond, P., King, M., Goodman, R., 1996 - Geological controls on mineralization and dolomitization of the Lisheen Zn-Pb-Ag deposit, Co Tipperary, Ireland: in Strogen, P., Somerville, I.D., Jones, G.L.l., (Eds.), 1996 Recent Advances in Lower Carboniferous Geology Geol. Soc. Spec. Publ. No. 107 pp. 23-33
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Torremans, K., Kyne, R., Doyle, R., Guven, J.F. and Walsh, J.J., 2018 - Controls on Metal Distributions at the Lisheen and Silvermines Deposits: Insights into Fluid Flow Pathways in Irish-Type Zn-Pb Deposits: in Econ. Geol. v.113, pp. 1455-1477
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Wilkinson J J 2003 - On diagenesis, dolomitisation and mineralisation in the Irish Zn-Pb orefield: in Mineralium Deposita v38 pp 968-983
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Wilkinson J J, Eyre S L and Boyce A J 2005 - Ore-Forming Processes in Irish-Type Carbonate-hosted Zn-Pb Deposits: Evidence from Mineralogy, Chemistry and Isotopic Composition of Sulfides at the Lisheen Mine: in Econ. Geol. v100 pp 63-86
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Wilkinson JJ, 2010 - A Review of Fluid Inclusion Constraints on Mineralization in the Irish Ore Field and Implications for the Genesis of Sediment-Hosted Zn-Pb Deposits : in Econ. Geol. v105 pp. 417-442
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