小秦岭杨砦峪金矿床黄铁矿中碲化物等矿物包裹体微区研究

The large Yangzhaiyu gold deposit is an example of the early Cretaceous gold mineralization event in the Xiaoqinling region. Despite the many studies for the early Cretaceous gold deposits in this region, controversy still exists on the source of the ore-forming fluid, and few studies have put emphasis on revealing the specific mechanism for native gold enrichment. Minerals hold crucial information on ore genesis. Pyrite from the Yangzhaiyu gold deposit carries abundant micro- to nanoscale telluride and other mineral inclusions. By carrying out nanoscale studies for these mineral inclusions through transmission electron microscopy and other microanalysis techniques, it is possible to observe nanoscale minerals, mineral associations, and other geological phenomena which have not been observed before. This will not only help to better understand the fluid source, the mechanism for native gold precipitation and enrichment, but also help to improve gold recovery rate and reduce environmental pollutions caused by toxic metals hosted in mineral inclusions. Besides the known telluride mineral species, we have observed a possible new mineral–AgTe3 at the Yangzhaiyu gold deposit, and we have obtained electron microprobe, electron back-scattering diffraction, and transmission electron microscopy selected area electron diffraction data for the Yangzhaiyu AgTe3. We aim to submit the Yangzhaiyu AgTe3 as a mineral species by interpreting the obtained data and comparing the crystallography and crystal structure data of the Yangzhaiyu AgTe3 with the synthetic AgTe3.

杨砦峪金矿床是小秦岭地区早白垩纪金矿的代表，前人对小秦岭早白垩纪金矿已开展了一些研究，但对成矿流体来源的认识还存在争议，对于可见自然金的富集机制，前人则鲜有关注。矿物记载了矿床的形成与变化过程，是揭示矿床成因的钥匙。申请者研究发现杨砦峪金矿的黄铁矿中含大量微米、纳米级的碲化物等矿物包裹体。本项目拟通过透射电镜等手段对这些矿物包裹体开展纳米尺度的研究，识别和记录前人未观察到的纳米级矿物、矿物组合和地质现象，为揭示成矿流体来源和金的富集机制提供新的矿物学证据，也为提高资源利用率和减少环境污染提供参考。除已知的碲化物种类化，申请者在杨砦峪金矿发现了一种疑似新矿物AgTe3；AgTe3以微米级矿物包裹体的形式分布于黄铁矿中。申请者已获得杨砦峪AgTe3的化学成分和晶体结构数据。本项目拟通过解析杨砦峪AgTe3的晶体结构并与已人工合成AgTe3的晶体结构开展对比，力争将杨砦峪AgTe3申请为新矿物。

成功申请新矿物lingbaoite（灵宝矿）。2019年5月23日，经过国际矿物学协会新矿物及矿物分类、命名专业委员会（Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association）两轮的严格审查、投票，经过主席Ritsuro Miyawaki最终批准，灵宝矿正式被认定为新矿物。新矿物编号2018-138，英文名lingbaoite，化学式AgTe3。灵宝矿发现于河南省灵宝市小秦岭金矿田S60号含金石英脉，该石英脉是小秦了地区代表性的含金石英脉，金储量约100吨（10g/t）。灵宝矿所属空间群为R3m，晶胞参数a = 8.60 (5) Å ，c = 5.40 (18) Å，V = 346 (9) Å3， Z = 3。灵宝矿反射色为金黄色，与自然金类似。该矿物仅显微可见，与针碲金银矿、六方碲银矿、黄铜矿、斑铜矿等矿物以复合矿物包裹体（<50 微米）的形式赋存于黄铁矿中，在含灵宝矿的黄铁矿样品中灵宝矿大量发育，最大的灵宝矿颗粒粒度为30 x 12微米。在银碲二元体系内，灵宝矿是第四个被发现的自然矿物，其它三个矿物分别为碲银矿（Ag2Te）、六方碲银矿（Ag5−xTe3）、粒碲银矿（AgTe）。灵宝矿样品现已存放于中国地质博物馆，编号M13812。本研究也指示小秦岭金矿具有岩浆热液成矿的特征。形成灵宝矿及共生矿物的流体显示出高的硫逸度及碲逸度（如灵宝矿、自然碲、针碲金银矿、斑铜矿），而流体高的硫逸度及碲逸度是岩浆热液的特征，这暗示小秦岭深部还有较大的金成矿潜力。碲在我国和美国均被列入关键金属名录，是支撑战略性新兴产业发展的重要原材料。而以灵宝矿为代表的碲化物在小秦岭含金石英脉中大量产物，初略估算在含金石英脉的富金地段，一吨金矿石中碲含量可达几十至几千克，碲元素大大富集，已达到金矿中伴生碲的矿石品位要求，如条件允许可考虑对碲资源进行综合利用。此外，许多碲化物（如与灵宝矿共生的针碲金银矿，又如碲金矿、碲金银矿等矿物）也是含金矿物。因此，对这些碲化物开展有效的处理和利用，不仅能提取碲金属资源，也能提高金的回收利用率。