The genesis and timing of molybdenum (Mo) mineralization in the Mada Ring Complex, north-central Nigeria, have been constrained using a combination of whole-rock elemental geochemistry, Nd-Sr isotopes, zircon U-Pb-Hf isotopes, and molybdenite Re-Os geochronological data. The Mada Ring Complex is one of fifty-three within-plate alkaline ring complexes with economically significant Sn and Nb production from largely alluvial placer deposits in north-central Nigeria. Molybdenum mineralization in the ring complex is dominantly disseminated with minor stockwork veins hosted within biotite granite. Integrated zircon U-Pb and molybdenite Re-Os geochronology constrain initial magma emplacement to between 152 and 151 (± 1) Ma and the Mo-mineralization event to ≤ 150 (± 1) Ma. The granites associated with Mo mineralization are highly silicic and display elevated whole-rock concentrations of Nb, Zr, Y, and REE (except Eu), as well as high 87Rb/86Sr ratios, but low concentrations of Sr, Ba, CaO, MgO, and TiO2, consistent with highly differentiated A-type granites. They yield moderately negative whole-rock εNd(t) (− 5.87 to − 5.47) and zircon εHf(t) (− 4.97 to − 10.06), suggesting that their parental magmas were largely derived from the lower crust with a contribution from the upper mantle. Magmatic oxygen fugacity (ƒO2) of the A-type granites (log FMQ = +1.16), constrained from zircon compositions, is lower than values reported from typical within-plate porphyry molybdenum deposits (log FMQ = +2 to + 3). However, compared to regional Sn ± Nb-mineralized A-type granites, the Mada A-type granites have higher ƒO2 and Ce4+/Ce3+, but are less differentiated.

中文翻译：

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尼日利亚中北部马达环杂岩中钼矿化的成因和时间：全岩地球化学、Nd-Sr 同位素、锆石 U-Pb-Hf 同位素和辉钼矿 Re-Os 系统学的见解

使用全岩元素地球化学、Nd-Sr 同位素、锆石 U-Pb-Hf 同位素和辉钼矿 Re 的组合，限制了尼日利亚中北部 Mada Ring Complex 中钼 (Mo) 成矿的成因和时间-Os 地质年代学数据。Mada 环复合体是 53 个板内碱性环复合体之一，在尼日利亚中北部主要是冲积砂矿床，具有重要的经济意义的锡和铌生产。环复合体中的钼矿化主要分布在黑云母花岗岩中的小网状脉中。综合锆石 U-Pb 和辉钼矿 Re-Os 年代学将初始岩浆侵位限制在 152 和 151 (± 1) Ma 之间，并将钼矿化事件限制在 ≤ 150 (± 1) Ma。与 Mo 矿化相关的花岗岩含硅量高，全岩中 Nb、Zr、Y 和 REE（Eu 除外）浓度升高，87Rb/86Sr 比值高，但 Sr、Ba、CaO、MgO 浓度低和 TiO2，与高度分化的 A 型花岗岩一致。它们产生中等负的全岩εNd(t) (- 5.87 to - 5.47) 和锆石εHf(t) (- 4.97 to - 10.06)，表明它们的母岩浆主要来自下地壳，上地壳也有贡献地幔。A 型花岗岩 (log FMQ = +1.16) 的岩浆氧逸度 (fO2)，受锆石成分的限制，低于典型的板内斑岩钼矿床报告的值（log FMQ = +2 至 +3）。然而，与区域性 Sn±Nb 矿化 A 型花岗岩相比，