The Tara Deep Zn-Pb deposit, at Navan, Ireland, includes sub-economic pyrite-rich mineralization extending laterally for about 2 x 2 km within the overlying Lower Viséan calc-turbidites, known as the ‘New-Thin Bedded Unit’. Here, we investigate the genesis of this pyritic mineralization and its links to the limestone-hosted Zn-Pb deposit lying 100 m below it.

Four mineral assemblages have been identified: 1) in black shales, laminated pyrite comprises thin framboid-rich layers with minor interstitial sphalerite, both showing variable but low-δ³⁴S values ranging from -37.4 to 3.3‰; 2) in calcarenite and calcsiltite layers, pyritized fossils are widely distributed and occur chiefly as biodebris replaced by low-δ³⁴S pyrite (mean values of -13.2‰); 3) a replacive assemblage occurs as late remobilizations exhibiting both crosscutting and bedding-parallel styles, overprinting the early laminated pyrite. It comprises mostly marcasite, with minor pyrite, sphalerite, chalcopyrite, galena, stibnite and Co-pentlandite, with high δ³⁴S values up to 24.5‰; and 4) in black shales, bedded sulfide-rich cherts comprising microcrystalline quartz lenses exhibit δ¹⁸O mean values of 25.3‰. Cherts are rimmed by dolomite, associated with marcasite, pyrite, sphalerite, chalcopyrite, galena, siegenite and stibnite also with high δ³⁴S values up to 44.2‰. In general terms, pyrite shows a relatively high Co/Ni ratio >1 and sphalerite Zn/Cd ratios vary from 268 to 364.

Textural analysis indicates overlapping of early-diagenetic and multi-phase hydrothermal sulfide mineralization. Development of laminated pyrite and pyritized calcarenites suggests that this mineralization was generated during early diagenesis, close to the seawater-sediment interface in oxygen-poor conditions under the influence of low-temperature hydrothermal fluid circulation. Later hydrothermal cherts and replacive sulfides suggest discharge of relatively warm hydrothermal fluids during early to mid-diagenesis, presumed to be linked to movements of nearby normal faults. Similarities in mineralogy and S isotope compositions suggest genetic links between the sub-economic pyritic mineralization and the underlying Tara Deep deposit, and consequently, that the former represents a geochemical halo with direct applicability in exploration for Zn-Pb deposits.

位于爱尔兰纳文的 Tara Deep Zn-Pb 矿床包括在上覆的下维塞安钙质浊积岩内横向延伸约 2 x 2 公里的次经济富含黄铁矿的矿化，被称为“新薄层状单元”。在这里，我们调查了这种黄铁矿矿化的成因及其与位于其下方 100 m 的石灰岩中的 Zn-Pb 矿床的联系。

已识别出四种矿物组合：1) 在黑色页岩中，层状黄铁矿由富含小叶状的薄层和少量间隙闪锌矿组成，两者均显示出变化但低的 δ ³⁴ S 值，范围为 -37.4 至 3.3‰；2）在方解石层和方解石层中，黄铁矿化化石分布广泛，主要以低δ ³⁴ S黄铁矿取代的生物碎屑形式出现（平均值为-13.2‰）；3）当晚期再活化表现出横切和层理平行样式时，会发生替换组合，叠印早期层状黄铁矿。它主要由白铁矿组成，还有少量的黄铁矿、闪锌矿、黄铜矿、方铅矿、辉锑矿和钴黄铁矿，δ ³⁴高S值高达24.5‰；4) 在黑色页岩中，含有微晶石英透镜的层状富含硫化物燧石表现出 δ ¹⁸ O 平均值为 25.3‰。燧石由白云石镶边，伴生白铁矿、黄铁矿、闪锌矿、黄铜矿、方铅矿、辉长岩和辉锑矿，δ ³⁴ S 值高达 44.2‰。一般而言，黄铁矿显示出相对较高的 Co/Ni 比率 >1，闪锌矿 Zn/Cd 比率从 268 到 364 不等。

构造分析表明早成岩和多相热液硫化物成矿重叠。层状黄铁矿和黄铁矿化钙磷灰石的发育表明，这种矿化是在早期成岩作用期间产生的，在低温热液循环的影响下，在缺氧条件下靠近海水-沉积物界面。后期的热液燧石和置换硫化物表明在早期至中期成岩作用中排放了相对温暖的热液流体，推测与附近正断层的运动有关。矿物学和 S 同位素组成的相似性表明次经济的黄铁矿矿化与下伏的 Tara Deep 矿床之间存在遗传联系，因此，