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Lead-zinc exploration drilling within the Limer-7 ick Basin (Southern Ireland) has revealed the deep inter-8 nal architecture and extra-crater deposits of five alkali-9 basaltic maar-diatremes. These were emplaced as part of 10 a regional northeast southwest tectonomagmatic trend 11 during the Lower Carboniferous Period. Field relation-12 ships and textural observations suggest that the diatremes 13 erupted into a shallow submarine environment. Limerick 14 trace element data indicates a genetic relationship between 15 the diatremes and extra-crater successions of the Knock-16 roe Formation, which records multiple diatreme filling 17 and emptying cycles. Deposition was controlled largely 18 by bathymetry defined by the surrounding Waulsortian 19 carbonate mounds. An initial non-diatreme forming erup-20 tion stage occurred at the water-sediment interface, with 21 magma-water interaction prevented by high magma ascent 22 rates. This was followed by seawater incursion and the 23 onset of phreatomagmatic activity. Magma-water interac-24 tion generated poorly vesicular blocky clasts, although the 25 co-occurrence of plastically deformed and highly vesicular 26 clasts indicates that phreatomagmatic and magmatic pro-27 cesses were not mutually exclusive. At a later stage, the 28 diatreme filled with a slurry of juvenile lapilli and coun-29 try rock lithic clasts, homogenised by the action of debris Q1 30

Irish-type mineralization is commonly attributed to fault-controlled mixing of a seawater-derived, sulfur-rich fluid and basement-derived, metal-rich fluid. However, maar-diatreme volcanoes discovered in close spatial and temporal association with Zn-Pb mineralization at Stonepark in the Limerick basin (southwest Ireland) bring a new dimension to established geologic models and may increase the deposit-scale prospectivity in one of the world's greatest Zn-Pb districts. Stonepark exhibits many incidences of dolomitic black matrix breccias with associated Zn-Pb mineralization, the latter typically occurring within 150 m of the diatremes. Highly negative δ 34 S pyrite values within country rock-dominated black matrix breccias (-12 to-34‰) are consistent with sulfide precipitation from bacteriogenic sulfur reduction in seawater-derived brines. However, δ 34 S values of Zn-Pb sulfides replacing black matrix breccias (-10 to 1‰) reflect multiple sulfur sources. Diatreme emplacement both greatly enhanced country rock fracture permeability and produced conduits that are filled with porous volcaniclastic material and extend down to basement rock types. Our δ 34 S data suggest that diatremes provide more efficient fluid pathways for basement-derived fluids. The diatremes introduce another potential sulfur source and facilitate a greater input of metal-rich basement-derived hydrothermal fluid into the system compared to other Irish-type deposits such as Navan and Lisheen, evidenced by Stonepark's more positive modal δ 34 S value of-4‰. Irish-type deposits are traditionally thought to form in association with extensional basement faults and are considered unrelated to extensive Carboniferous magmatism. Our results indicate that a direct link exists between diatreme volcanism and Zn-Pb mineralization at Limerick, prompting a reevaluation of the traditional Irish-type ore formation model, in regions where mineralization is spatially associated with volcanic pipes.

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