Despite the substantial amount of research on the Cretaceous Samail ophiolite in Oman, the factors controlling the size and metal endowment of the mafic-hosted, Cu-Au(-Zn-Ag) volcanogenic massive sulfide (VMS) deposits remain elusive. This work shows that the volcanostratigraphic position, hydrothermal venting style, and oxidation processes are critical factors controlling the distinct features of the Shinas and Mandoos deposits.Mandoos is a large (8 Mt, 1.8 wt % Cu, 0.18 g/ton Au) orebody preserving abundant primary vent-related features formed via mound growth and collapse within a wide hydrothermal field, overlying a poorly developed stockwork. The smaller Shinas deposit (0.8 Mt, 2.6 wt % Cu, 0.63 g/t Au) represents a higher-temperature system evolving from low fS2/fO2 conditions, locally sealed by jaspers, to a mound growth stage with widespread subseafloor brecciation/replacement with associated zone refining. Mandoos formed at the onset of the postaxial stage (Geotimes-Tholeiitic Alley transition), and Shinas is hosted within the Alley units. Volcanism in Samail was seemingly continuous, and the low ɛ_Nd and Nb/Ta of the Shinas hanging-wall lavas record the onset of significant modifications of the mantle source during the postaxial stage.Mandoos is enriched in Te + As + Se ± Zn ± Ga ± Sb relative to Shinas, where higher Cu + Au + Tl ± Mo grades possibly reflect leaching of protoarc-like lavas. Rare earth element patterns in the ores mimicking the deposit footwall can be employed to constrain volcanostratigraphic positioning and indicate that the footwall lavas may also represent a source of metals. Formation of metal-rich ochres at the sea floor likely led to Cu + Au upgrading in the ores during seawater-induced oxidation, which was enhanced during subaerial gossan formation.

中文翻译：

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阿曼萨迈伊蛇绿岩镁铁质曼杜斯和希纳斯火山成因块状硫化物矿床的对比特征和火山地层学

尽管对阿曼白垩纪萨迈伊蛇绿岩进行了大量研究，但控制镁铁质、Cu-Au(-Zn-Ag)火山成因块状硫化物 (VMS) 矿床的尺寸和金属禀赋的因素仍然难以捉摸。这项工作表明，火山地层位置、热液喷发方式和氧化过程是控制Shinas 和 Mandoos 矿床独特特征的关键因素。Mandoos 是一个大型（8 Mt，1.8 wt % Cu，0.18 g/ton Au）保存矿体通过在广阔的热液场内的土丘生长和塌陷而形成的丰富的与主要喷口相关的特征，覆盖着发育不良的网状结构。较小的 Shinas 矿床（0.8 Mt，2.6 wt% Cu，0.63 g/t Au）代表了从低 fS2/fO2 条件演变而来的高温系统，局部被碧玉密封，到一个土丘生长阶段，伴随着广泛的海底角砾化/替换以及相关的区域精炼。Mandoos 形成于轴后阶段（Geotimes-Tholeiitic Alley 过渡）开始时，Shinas 位于 Alley 单元内。萨美伊的火山活动似乎是持续不断的，而且低 ɛ_{希纳斯上盘熔岩的Nd}和 Nb/Ta 记录了轴后阶段地幔源发生显着改变的开始。相对于希纳斯，曼杜斯富含 Te + As + Se ± Zn ± Ga ± Sb，其中 Cu + 含量更高Au + Tl ± Mo 品位可能反映了原弧状熔岩的浸出。矿石中模仿矿床下盘的稀土元素模式可用于限制火山地层定位，并表明下盘熔岩也可能代表金属来源。海底富含金属的赭石的形成可能导致海水诱导氧化过程中矿石中的铜+金升级，而这种氧化在陆上戈桑形成期间得到增强。