Tellurium in natural and synthetic pyrite: Ore-formation and economic implication

碲（Te）由于其在快速增长的绿色能源技术领域的应用而被欧盟归类为高度重要的能源关键元素。目前，大多数Te是作为有色金属开采的副产品回收的，主要是通过精炼铜来回收的，基于目前的提取方法，几乎没有机会增加Te的供应。 因此，Te的短缺可能会在不久的将来达到，由于其不断增长的需求。热液黄铁矿中的碲达到8，000 ppm，并且通常与其他微量元素一起富集，例如As和Au（高达4.8 wt. %和11，OOOppm）。黄铁矿在各种流体条件下都是稳定的，包括低温和高温，可变的fO 2和pH条件。因此，黄铁矿的微量元素化学可用于确定关键的成矿作用的碲，这是迄今为止约束不足。由于其普遍存在和浓缩微量元素的能力，黄铁矿可能被认为是碲的经济重要宿主。因此，未来Te的供应可能通过加工包括黄铁矿在内的矿物来解决。然而，人们对碲在矿石加工过程中的行为并不十分了解，如果不回收并将其送往尾矿，可能会产生生态毒理学影响。该项目旨在通过提供有关浅成热液和卡林型系统中Te矿石形成的详细了解来缩小这些知识差距;建议采用两种不同的矿化类型来达到经济的Te浓度。国家的最先进的分析技术将用于一个完整的结构和化学特性的碲在黄铁矿下降到微米和纳米尺度。这使得开发一个坚实的工具来定义的纳入机制的碲在黄铁矿无论是作为一个结构上绑定的元素或作为微米到纳米级的夹杂物。相定量将结合矿物和散装矿石碲化学定量证明，黄铁矿是这些矿床的主要碲主机之一。微量元素填图将进行调查可能的晶内碲的变化（即分带）在黄铁矿，这将被用来确定关键的成矿过程，最终提出一个新的微观分析勘探工具的碲。受控实验室条件下的热液实验将有助于确定流体参数（例如，温度、pH、fO_2）控制着Te在黄铁矿中的分布。从已知的Te组合物的流体合成的实验黄铁矿的组合物允许定义在黄铁矿流体系统中的第一Te能斯特分配系数（KD）。因此，自然和合成系统的结合使用将允许，第一次，提供一个定量的了解有关的沉淀和纳入机制的碲在黄铁矿;一个无处不在的矿物托管的经济利益不断增长的元素。

Tellurium (Te) is classified by the European Union as an energy critical element of high importance due to its application in the rapidly growing sector of green energy technologies. Currently, most Te is recovered as a by-product from non-ferrous metal mining, principally by refining of Cu providing little opportunity to increase the Te supply based on current extraction methods. Hence, a shortage in Te is likely to be reached in the near future due to its increasing demand. Tellurium in hydrothermal pyrite reaches 8,000 ppm and is typically enriched together with other trace elements, such as As and Au (up to 4.8 wt. % and 11,000 ppm). Pyrite is stable under a wide range of fluid conditions including low and high temperatures, variable fO2 and pH conditions. Thus, the trace element chemistry of pyrite can be used to define the key ore-forming processes of Te, which are poorly constrained to date. Due to its ubiquity and ability to concentrate trace elements, pyrite may be considered as an economically important host for Te. Hence, the future supply of Te may be resolved by the processing of minerals including pyrite. However, the behaviour of Te during the ore-processing is not well understood and if not recovered and sent to tailings it may have an eco-toxicological impact. This project aims to close these knowledge gaps by providing a detailed understanding about Te ore formation in epithermal and Carlin-type systems; two distinct mineralisation-styles suggested to reach economic Te concentrations. State-of-the-art analytical techniques will be used for a full structural and chemical characterisation of Te in pyrite down to the micro- and nano-scale. This allows to develop a solid tool to define the incorporation mechanisms of Te in pyrite either as a structurally bound element or as micro- to nano-sized inclusions. Phase quantification will be combined with mineral and bulk ore Te chemistry to quantitively demonstrate that pyrite is one of the major Te hosts in these deposits. Trace element mapping will be performed to investigate possible intra-crystalline Te variations (i.e. zoning) in pyrite, which will be used to define key ore-forming processes to finally present a new micro-analytical exploration tool for Te. Hydrothermal experiments under controlled laboratory conditions will help to define fluid parameters (e.g., temperature, pH, fO2) controlling the distribution of Te in pyrite. The composition of experimental pyrite synthesized from a fluid of known Te composition allows to define the first Te Nernst partition coefficients (KD) in the pyrite-fluid system. Consequently, the combined use of natural and synthetic systems will allow, for the first time, to provide a quantitative understanding about the precipitation and incorporation mechanisms of Te in pyrite; a ubiquitous mineral hosting an element of growing economic interest.