In an attempt to clarify the significance of Pb model ages in Pb-Zn sedimentary deposits, we report high-precision Pb isotopic compositions for 64 galenas and 52 K-feldspars, the former from ores and the latter separated from granites. All samples are from Spain and the French Pyrenees. Lead from galena ores is of unequivocal continental origin. With few exceptions, Pb model ages systematically exceed emplacement ages by up to 400 Ma, a gap which is well outside the uncertainties of ~ 30 Ma assigned to the model. The histogram of the new high-precision Pb isotope data shows prominent peaks of galena Pb model ages at 94 ± 38 Ma and 392 ± 39 Ma. When the data are consolidated with literature data and examined in 3-dimensional Pb isotope space, cluster analysis identifies five groups. The model ages of the peaks occur, in order of decreasing peak intensity, at 395 ± 40 (Middle Devonian), 90 ± 34 Ma (Middle Cretaceous), and 613 ± 42 Ma (Neoproterozoic), with two minor peaks at 185 + 26 Ma (Jurassic) and 313 ± 41 (Upper Carboniferous). To a large extent, the model ages centered around these peaks correspond to distinct localities. The ages of the peaks do not coincide with any of the Betic, Variscan, or Pan-African tectonic events, which are the main tectonic episodes that shaped Iberian geology, but instead match well-known global oceanic anoxic events. It is argued that surges of metals weathered from continental surfaces scorched during anoxic events accumulated and combined in anoxic water masses with unoxidized marine sulfide released by submarine hydrothermal activity to precipitate the primary Pb-Zn stock. Frozen Pb isotope compositions require that galenas from black shales are the source of the final ores. The sulfides were later remobilized by large-scale convective circulation of basinal and hydrothermal fluids. The peaks of K-feldspar Pb model ages are distinct from those of galenas and do not correlate with magmatic emplacement ages. It is suggested that they instead reflect local circulation in Paleozoic sediments surrounding individual plutons. While Pb isotopes can be used as a regional provenance tool, such an approach requires that the data are considered in a fully 3-dimensional space.

为了阐明 Pb-Zn 沉积矿床中 Pb 模型年龄的重要性，我们报告了 64 个方铅矿和 52 个钾长石的高精度 Pb 同位素组成，前者来自矿石，后者来自花岗岩。所有样品均来自西班牙和法国比利牛斯山脉。方铅矿矿石中的铅具有明确的大陆来源。除了少数例外，Pb 模型年龄系统地超过侵位年龄高达 400 Ma，这一差距远远超出分配给模型的约 30 Ma 的不确定性。新的高精度铅同位素数据的直方图显示方铅矿铅模型年龄在 94 ± 38 Ma 和 392 ± 39 Ma 的显着峰。当数据与文献数据合并并在 3 维 Pb 同位素空间中检查时，聚类分析确定了五个组。出现峰的模型年龄，按峰值强度递减的顺序，在 395±40（中泥盆纪）、90±34 Ma（中白垩纪）和 613±42 Ma（新元古代），在 185 + 26 Ma（侏罗纪）和 313 ± 41 处有两个小峰（上石炭纪）。在很大程度上，以这些峰为中心的模型年龄对应于不同的位置。山峰的年龄与贝蒂奇、瓦里斯坎或泛非构造事件中的任何一个都不重合，这些事件是塑造伊比利亚地质的主要构造事件，而是与众所周知的全球海洋缺氧事件相匹配。有人认为，在缺氧事件期间，从大陆表面风化的金属浪涌在缺氧水团中积累并与海底热液活动释放的未氧化海洋硫化物结合，从而沉淀出主要的 Pb-Zn 储量。冷冻铅同位素组成要求黑色页岩中的方铅矿是最终矿石的来源。硫化物后来通过盆地和热液流体的大规模对流循环而重新流动。钾长石 Pb 模型年龄的峰值与方铅矿的峰值不同，并且与岩浆侵位年龄无关。有人认为它们反映了单个岩体周围古生代沉积物中的局部环流。虽然 Pb 同位素可用作区域来源工具，但这种方法要求在全 3 维空间中考虑数据。钾长石 Pb 模型年龄的峰值与方铅矿的峰值不同，并且与岩浆侵位年龄无关。有人认为它们反映了单个岩体周围古生代沉积物中的局部环流。虽然 Pb 同位素可用作区域来源工具，但这种方法要求在全 3 维空间中考虑数据。钾长石 Pb 模型年龄的峰值与方铅矿的峰值不同，并且与岩浆侵位年龄无关。有人认为它们反映了单个岩体周围古生代沉积物中的局部环流。虽然 Pb 同位素可用作区域来源工具，但这种方法要求在全 3 维空间中考虑数据。