Ironstones (Iron Oxide-Silica) in the Irish Zn-Pb Deposits and Regional Iron Oxide-(Silica) Alteration of the Waulsortian Limestone in Southern Ireland
Published:January 01, 1995
M. W. Hitzman, G. Earls, E. Shearley, J. Kelly, M. Cruise, G. Sevastopulo, 1995. "Ironstones (Iron Oxide-Silica) in the Irish Zn-Pb Deposits and Regional Iron Oxide-(Silica) Alteration of the Waulsortian Limestone in Southern Ireland", Irish Carbonate-Hosted Zn-Pb Deposits, Kerr Anderson, John Ashton, Garth Earls,, Murray Ritzman, Simon Tear
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Iron oxide minerals occur in both Irish zinc-lead deposits and, in southern Ireland, in regionally extensive zones within Waulsortian Limestone (Fig. 1). The zinc-lead deposits contain zones consisting of ironstone (iron oxide + silica) bands which are generally surrounded by red to pink, hematized limestone and green, bleached or chloritic limestone. These zones range in size from very large at Tynagh (2400 x900m area; up to 50m thick) to extremely minor occurrences of isolated ironstone nodules or veins. In southern Ireland, regional iron oxide alteration zones contain red to pink, hematized, and locally silicified, limestone. One zone extends over 30km along strike. Textural evidence suggests that both the ironstones associated with zinc-lead deposits and the regionally extensive iron oxide zones formed by replacement of carbonate sediments. The relationship, if any, between the two iron oxide-rich styles of alteration is unclear.
Figures & Tables
Irish Carbonate-Hosted Zn-Pb Deposits
This paper describes the stratigraphy, basin evolution, and structural geology of Ireland so that the hydrothermal processes which formed the deposits can be placed in a geological context. Informal regional nomenclature are used throughout this paper to provide a clearer overview, rather than the myriad of existing local formation names (see Jones and Earls, this volume). The stratigraphy, together with series and stage designation and available radiometric ages, is presented in Figure 1.