Clumped C–O isotope temperature constraints for carbonate precipitation associated with the Irish-type Lisheen and Navan Zn–Pb orebodies

Hollis, Steven P.; Menuge, Julian F.; Dennis, Paul F.; Güven, John; Doran, Aileen; Marca, Alina; Boyce, Adrian J.; Wilkinson, Jamie J.; Ashton, John H.; Roberts, Stephen

doi:10.1080/03717453.2017.1306258

Cited by 3 publications

(7 citation statements)

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“…Carbonate isotope measurements (δ 13 C and δ 18 O) of calcite and dolomite phases were obtained from both the Lisheen and Navan deposits [37,38]. Carbonate phases were characterized by traditional petrography and Scanning Electron Microscopy at University College Dublin, and imaged using a CITL mk5 cold cathode-luminescence stage mounted on a Nikon 50i microscope at Imperial College London (London, UK).…”

Section: Samples and Methodsmentioning

confidence: 99%

“…The C-O isotope variations at Lisheen can be explained primarily through processes of fluid-rock buffering [50]. Although the exact cause for early regional dolomitization is not known, measured δ 18 O values are consistent with fluid of high δ 18 O and temperatures of formation (~150-200 • C), confirmed by clumped C-O isotope analyses [37,38]. It is perhaps no surprise that δ 18 O values for subsequent black hydrothermal dolomite from BMBs are similar to that recorded by corroded clasts of the fine-grained regional dolomite that it contains (Figure 9a).…”

Section: C-o Isotopesmentioning

confidence: 96%

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Coupling Mineralogy, Textures, Stable and Radiogenic Isotopes in Identifying Ore-Forming Processes in Irish-Type Carbonate-Hosted Zn–Pb Deposits

et al. 2019

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Irish-type deposits comprise carbonate-hosted sphalerite- and galena-rich lenses concentrated near normal faults. We present new data from the Tara Deep resource and overlying mineralization, at Navan, and the Island Pod deposit and associated Main zone orebodies, at Lisheen. Tara Deep mineralization predominantly replaces Tournasian micrites and subordinate Visean sedimentary breccias. The mineralization is mainly composed of sphalerite, galena, marcasite and pyrite. A range of Cu- and Sb-bearing minerals occur as minor phases. At Tara Deep, paragenetically early sulfides exhibit negative δ34S values, with later phases displaying positive δ34S values, indicating both bacterial sulfate reduction (BSR) and hydrothermal sulfur sources, respectively. However, maximum δ34S values are heavier (25‰) than in the Main Navan orebody (17‰). These mineralogical and isotopic features suggest that Tara Deep represents near-feeder mineralization relative to the Navan Main orebody. The subeconomic mineralization hosted in the overlying Thin Bedded Unit (TBU) comprises sphalerite replacing framboidal pyrite, both exhibiting negative δ34S values (−37.4 to −8.3‰). These features indicate a BSR source of sulfur for TBU mineralization, which may represent seafloor exhalation of mineralizing fluids that formed the Tara Deep orebody. The Island Pod orebody, at Lisheen, shows a mineralogical paragenetic sequence and δ34S values broadly similar to other Lisheen orebodies. However, the lack of minor Cu, Ni, and Sb minerals suggests a setting more distal to hydrothermal metal feeder zones than the other Lisheen orebodies. Pb isotope data indicate a very homogeneous Lower Palaeozoic Pb source for all Navan orebodies. Lower Palaeozoic metal sources are also inferred for Lisheen, but with variations both within and between orebodies. Carbon and oxygen isotopic variations at Navan and Lisheen appear to result from fluid-carbonate rock buffering. The emerging spectrum of mineralogical and isotopic variations define proximal to distal characteristics of Irish-type systems and will assist in developing geochemical vectoring tools for exploration.

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Section: Samples and Methodsmentioning

confidence: 99%

Section: C-o Isotopesmentioning

confidence: 96%

Coupling Mineralogy, Textures, Stable and Radiogenic Isotopes in Identifying Ore-Forming Processes in Irish-Type Carbonate-Hosted Zn–Pb Deposits

et al. 2019

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“…• Compilations of galena Pb isotope ratio data (Everett et al, 2003;Hollis et al, 2019) show a perturbation correlating generally well with the SW area (Fig. 11).…”

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confidence: 84%

Irish-type Zn-Pb deposits - What are they and can we find more?

Ashton,

Andrew,

Hitzman

2023

Irish-Type Zn-Pb Deposits Around the World

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Seven carbonate hosted Zn-Pb (+/-Ag, Ba) or Cu deposits have been mined in Lower Carboniferous limestones in Ireland since 1960 - representing a resource base of ca. 22 Mt of metal (Tynagh, Gortdrum, Magcobar, Silvermines, Navan, Galmoy and Lisheen). The orebodies are amenable to modern mining and metallurgical processes and exploration for further deposits continues. Several significant prospects remain unexploited with numerous smaller prospects and mineralized localities attesting to the metal endowment of the country (Pallas Green, Stonepark, Ballinalack, Kilbricken and Keel). These deposits share sufficient characteristics to be termed Irish-type Base Metal Deposits and define a metallogenic province of worldwide significance known as the Central Irish Ore-field. Early discoveries resulted from shallow soil geochemistry, Induced Polarization surveys, and follow-up of legacy mining or mineralized outcrops. More expensive, deeper penetration methods including deep drilling, airborne geophysics and seismic methods have been utilized extensively in more recent years - but thus far with variable success. Large amounts of ground remain unexplored at depth, but further discovery is extremely challenging. Following over 60 years of discovery and mining this contribution summarizes our knowledge of Irish-type deposits and their exploration with a view to generating new ideas for future discovery. The Tynagh, Silvermines, Lisheen and Galmoy deposits, all hosted in the Waulsortian Limestone, occur in a distinct area in the SW of the Orefield. Silvermines, Lisheen and Galmoy are remarkably similar, comprising several, tabular, stratabound, lenses containing locally massive and high-grade sphalerite-galena with substantial pyrite +/- barite. These deposits are hosted in the first clean limestone above basement in Lower Carboniferous limestones and dolomites and exhibit fine grained, replacive sulphides with significant breccia and crosscutting mineralization. Structurally all these deposits abut major syn-sedimentary faults usually trending NE or ENE. The Navan deposit occurs on the NE side of the Orefield and is hosted in stratigraphically lower, Pale Bed limestones, that are roughly age equivalent to the Waulsortian Limestone in the SW of the Orefield. Navan is much larger and more complex than the deposits in the SW Orefield but shares several of their key characteristics. A review of the characteristics of Irish-type deposits and exploration results suggests some important areas for future exploration and research. For example, most observers relate the location of Irish-type deposits to the regional distribution of host rocks and structures of a certain age. It is suggested that the spatial location of these deposits is more fundamentally controlled by deep structural heterogeneities related to the collisional zone between basement rock terranes termed the Iapetus Suture. Understanding the timing of fault development is likely key to further discovery at depth as the mineralizing feeder structures are located on faults that did not necessarily extend through post-Waulsortian aged strata. Several promising fields for research and development to help enable further discovery are discussed.

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“…The paucity of mineralization within the Waulsortian above the orebody at Lisheen and the absence of any substantial geochemical anomaly in soils that rest directly on it suggests that metals must have been very efficiently removed from the hydrothermal fluids before they progressed further up through the Waulsortian. Limited clumped C-O data from white matrix breccia dolomites indicates high but falling temperatures up section (Hollis et al, 2017), suggesting a hot fluid mixing with a colder fluid or thermally equilibrating, as it rises through the Waulsortian. In mineralized areas it is possible therefore that the white matrix breccia cements were, at least in part, precipitated from remnant hydrothermal fluids (Hollis et al, 2017;Yesares et al, 2019).…”

Section: Mineralizing Processes and Controls On Fluid Flowmentioning

confidence: 99%

“…Limited clumped C-O data from white matrix breccia dolomites indicates high but falling temperatures up section (Hollis et al, 2017), suggesting a hot fluid mixing with a colder fluid or thermally equilibrating, as it rises through the Waulsortian. In mineralized areas it is possible therefore that the white matrix breccia cements were, at least in part, precipitated from remnant hydrothermal fluids (Hollis et al, 2017;Yesares et al, 2019). Although containing and depositing minor metals in white matrix breccias proximal to the orebodies (e.g., Fig.…”

Section: Mineralizing Processes and Controls On Fluid Flowmentioning

confidence: 99%

The Rathdowney Trend, Ireland: Geological evolution and controls on Zn-Pb mineralization

Guven,

Torremans,

Johnson

et al. 2023

Irish-Type Zn-Pb Deposits Around the World

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The Rathdowney Trend in south-central Ireland, is a NE-SW trend of fault-controlled Zn-Pb deposits that includes the Galmoy and Lisheen orebodies. The deposits are broadly stratabound and flat-lying occurring at or near the base of the Waulsortian Limestone Formation - a 200m thick massive biomicrite that is regionally dolomitised. The ore is largely developed by replacement of a dark, hydrothermal dolomite and dolomitic breccia - the black matrix breccia that is intimately associated with the mineralization event. Faulting exerts a major control on the ore thickness and distribution. The largest structures provided conduits for hot, metal-bearing fluids from basement to enter the Waulsortian at discrete feeder zones. Metal distribution patterns indicate that fluids progressed northwards from these feeder zones, facilitated by a network of small-displacement, low-angle extensional structures developed at the base Waulsortian contact with the underlying Ballysteen Formation. Significant dissolution of carbonate by hydrothermal fluids was important in developing conduits and promoting fluid flow. Fluid inclusion and isotope studies indicate that mineralization resulted from the mixing of hot, metal-bearing fluids with colder, saline fluids bearing sulphur derived from the bacteriogenic reduction of Carboniferous seawater sulphate. Mineralization developed during growth of the fault systems associated with basin development. Hydrothermal activity initiated shortly after rifting commenced during mid to late-Waulsortian sedimentation.

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Clumped C–O isotope temperature constraints for carbonate precipitation associated with the Irish-type Lisheen and Navan Zn–Pb orebodies

Cited by 3 publications

References 0 publications

Coupling Mineralogy, Textures, Stable and Radiogenic Isotopes in Identifying Ore-Forming Processes in Irish-Type Carbonate-Hosted Zn–Pb Deposits

Coupling Mineralogy, Textures, Stable and Radiogenic Isotopes in Identifying Ore-Forming Processes in Irish-Type Carbonate-Hosted Zn–Pb Deposits

Irish-type Zn-Pb deposits - What are they and can we find more?

The Rathdowney Trend, Ireland: Geological evolution and controls on Zn-Pb mineralization

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