In supergene Zn non-sulfide deposits, the Fe-oxy-hydroxides (FeO/OH) are mainly concentrated in the residual zones (gossan) on top of the oxidized ore bodies, although they can also be found throughout the whole weathering profile coexisting with the primary and secondary ore assemblages. Fe-oxy-hydroxides are rarely pure as they form in systems where a wide range of metals, most of them of economic importance (e.g., Zn, Pb, Co, REE, Sc, Ga, Ge, V, etc.), freely circulate and can be “captured” under specific conditions. Although their occurrence can be widespread, and they have a potential to scavenge and accumulate critical metals, FeO/OH are considered gangue phases during the existing processing routes of Zn non-sulfide ores. Moreover, very little is known about the role of the deposit type on the geochemistry of FeO/OH formed in a specific association. Therefore, this paper provides a comprehensive assessment of the trace element footprint of FeO/OH from a number of Zn non-sulfide deposits, in order to define parameters controlling the metals’ enrichment process in the mineral phase. To achieve this, we selected FeO/OH-bearing mineralized samples from four supergene Zn non-sulfide ores in diverse settings, namely Hakkari (Turkey), Jabali (Yemen), Cristal (Peru) and Kabwe (Zambia). The petrography of FeO/OH was investigated by means of scanning electron microscope energy dispersive analysis (SEM-EDS), while the trace element composition was assessed using laser ablation-ICP-MS (LA-ICP-MS). Statistical analyses performed on LA-ICP-MS data defined several interelement associations, which can be ascribed to the different nature of the studied deposits, the dominant ore-formation process and subsequent evolution of the deposits and the environmental conditions under which FeO/OH phases were formed. Based on our results, the main new inferences are: (A) Zinc, Si, Pb, Ga and Ge enrichment in FeO/OH is favored in ores where the direct replacement of sulfides is the dominant process and/or where the pyrite is abundant (e.g., Cristal and Hakkari). (B) When the dissolution of the host-rock is a key process during the supergene ore formation (i.e., Jabali), the buffering toward basic pH of the solutions favors the uptake in FeO/OH of elements leached from the host carbonate rock (i.e., Mn), whilst restricting the uptake of elements derived from the dissolution of sulfides (i.e., Zn, Pb, Ga and Ge), as well as silica. (C) The input of exotic phases can produce significant enrichment in “unconventional” metals in FeO/OH (i.e., Cr and Co at Kabwe; Y at Cristal) depending on whether the optimal pH-Eh conditions are attained. (D) In the Kabwe deposit, FeO/OH records heterogeneous geochemical conditions within the system: where locally basic conditions prevailed during the alteration process, the V and U concentration in FeO/OH is favored; yet conversely, more acidic weathering produced Zn- and Si-bearing FeO/OH.

中文翻译：

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遗传过程对超锌非硫化锌矿床中氢氧化铁地球化学的影响

在超锌非硫化锌矿床中，氧化铁氢氧化物（FeO / OH）主要集中在氧化矿体顶部的残留区（戈桑），尽管在整个风化剖面中也可以发现它们与初级和次级矿石组合。羟基氧化铁很少会纯净，因为它们会在多种金属中自由生成的系统中自由生成，其中大多数具有经济重要性（例如，Zn，Pb，Co，REE，Sc，Ga，Ge，V等）可以在特定条件下“捕获”。尽管它们的发生可能很普遍，并且具有清除和积累关键金属的潜力，但在现有的非硫化锌矿石加工路线中，FeO / OH被认为是脉石相。此外，关于沉积物类型对以特定结合形式形成的FeO / OH的地球化学的作用了解甚少。因此，本文对许多非锌硫化物沉积物中FeO / OH的痕量元素足迹进行了综合评估，以定义控制矿物相中金属富集过程的参数。为了实现这一目标，我们从Hakkari（土耳其），Jabali（也门），Cristal（秘鲁）和Kabwe（赞比亚）的四个不同环境中的四个超基锌非硫化锌矿石中选择了含FeO / OH的矿化样品。通过扫描电子显微镜能量色散分析（SEM-EDS）研究了FeO / OH的岩石学，同时使用激光烧蚀-ICP-MS（LA-ICP-MS）评估了痕量元素的组成。对LA-ICP-MS数据进行的统计分析定义了几种元素间的联系，这可以归因于所研究矿床的不同性质，主要的成矿过程和矿床的后续演化以及FeO / OH相所处的环境条件形成了。根据我们的结果，主要的新推论是：（A）FeO / OH的锌，Si，Pb，Ga和Ge富集在矿石中以硫化物的直接替代是主要过程和/或在黄铁矿中含量丰富的矿石中更为有利（例如Cristal和Hakkari）。（B）当基质岩的溶解是表生矿形成过程中的关键过程（即Jabali）时，溶液向碱性pH的缓冲作用有利于从基质碳酸盐岩中浸出的元素被FeO / OH吸收（即Mn），同时限制了由硫化物溶解产生的元素（即Zn，Pb，Ga和Ge）以及二氧化硅的吸收。（C）异质相的输入可以使FeO / OH中的“非常规”金属（即Kabwe中的Cr和Co； Cristal中的Y）中的“非常规”金属大量富集，这取决于是否达到了最佳的pH-Eh条件。（D）在Kabwe矿床中，FeO / OH记录了系统中的非均质地球化学条件：在蚀变过程中普遍存在局部碱性条件的情况下，FeO / OH中的V和U浓度有利；相反，更酸性的风化会生成含锌和硅的FeO / OH。取决于是否达到最佳pH-Eh条件。（D）在Kabwe矿床中，FeO / OH记录了系统中的非均质地球化学条件：在蚀变过程中普遍存在局部碱性条件的情况下，FeO / OH中的V和U浓度有利；相反，更酸性的风化会生成含锌和硅的FeO / OH。取决于是否达到最佳pH-Eh条件。（D）在Kabwe矿床中，FeO / OH记录了系统中的非均质地球化学条件：在蚀变过程中普遍存在局部碱性条件的情况下，FeO / OH中的V和U浓度有利；相反，更酸性的风化会生成含锌和硅的FeO / OH。