GEO-CM: Trace metals in sphalerite from polymetallic, porphyry-lode mineral deposits of southwest Montana

闪锌矿是锌的主要矿石矿物，并且它经常含有高浓度的其他金属作为杂质，其中许多被美国地质调查局指定为“关键矿物”。 关键矿物包括对国家经济和安全至关重要的金属，但目前必须从其他国家进口。蒙大拿州比尤特的矿山富含铜、银、铅、锌和锰。 菲利普斯堡矿区位于比尤特西北60公里处，面积较小，但有许多共同的地质特征。对比特和菲利普斯堡闪锌矿样品的初步分析表明，它们都高度富集关键金属镓、铟、锗和钨，以及铜和银。最近的研究表明，闪锌矿是最丰富的这些金属杂质荧光明亮的红色下手持紫外灯。 这一现象可以提供一种低成本和简单的方法来分选具有不同浓度的微量金属的闪锌矿矿石。 这项研究的第一个目标是分析来自比尤特和菲利普斯堡的样品，以绘制出每个矿区规模（几平方英里，深达1英里）的闪锌矿中金属杂质的分布图。 第二个目标是在实验室中制造出含有与天然样品中相同微量金属的闪锌矿颗粒。 然后，研究人员将比较人造和天然标本的荧光行为。 该项目将在蒙大拿理工大学（MTU）培训经济地质学领域的本科生和研究生。 MTU是EPSCoR州的主要本科院校（PUI）。 该项目的结果可能会揭示闪锌矿和其他矿石矿物可用于研究矿床的新方法。 本研究对发光闪锌矿在材料科学与工程中的应用也有一定的应用价值。 蒙大拿州的比尤特是科迪勒拉式分区斑岩矿脉存款的典型例子，也是全国最大的铜、锌、银和锰的历史生产者之一。 这项研究将利用Anaconda研究实验室（ARL）收集，这是一套从Butte和蒙大拿州其他矿山收集的超过50，000个手样本，存档在蒙大拿理工学院校园。 利用ARL藏品，以及来自活跃的大陆斑岩铜钼矿的新样本，研究人员将收集一套200个抛光矿石标本，其中含有闪锌矿和其他硫化物矿物，这些矿石标本来自整个Butte地区的已知地点，深度可达5000英尺。在表面之下。 闪锌矿样品将通过光学显微镜、光致发光光谱（PLS）、拉曼光谱、激光烧蚀ICP-MS、电子探针显微分析（EPMA）和高光谱阴极发光（HP-CL）进行分析，以揭示微量元素分布的空间和时间模式，从微米尺度到千米尺度。 机器学习工具将用于识别闪锌矿数据库中元素之间的相关性，这将有助于阐明微量元素进入ZnS结构的潜在机制。 例如，研究人员假设上述深红色荧光与闪锌矿晶格中Cu（+1），Ga（+3）和W（+6）对Zn（+2）的耦合取代有关。 他们将使用水热方法合成已知微量元素组成的闪锌矿，并比较合成和天然样本的HP-CL、拉曼和偏最小二乘特征。 最后，他们将与能够使用XANES的同步加速器实验室建立合作关系，以验证金属掺杂ZnS和天然闪锌矿样品中钨和其他微量元素的氧化态。 该项目将支持蒙大拿理工大学经济地质学的前沿研究和研究生培训，该大学前身为蒙大拿矿业学院，是EPSCoR州的一所主要本科院校（PUI）。 该项目的结果可能揭示闪锌矿和其他矿石矿物可用于研究矿床的新方法，并可能在材料科学和工程中应用发光ZnS。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Sphalerite is the primary ore mineral of zinc, and it oftens contains elevated concentrations of other metals as impurities, many of which are designated as “critical minerals” by the U.S. Geological Survey. Critical minerals include metals that are important to the country’s economy and security, but must currently be imported from other countries. Mines in Butte, Montana are rich in copper, silver, lead, zinc and manganese. The Philipsburg mining district is located 60 km northwest of Butte is smaller but shares many geologic features. Preliminary analyses of sphalerite samples from Butte and Philipsburg show that they are both highly enriched in the critical metals gallium, indium, germanium, and tungsten, as well as copper and silver. Recent research has shown that sphalerite that is richest in these metal impurities fluoresces bright red under a hand-held UV lamp. This phenomenon could provide a low-cost and simple way to sort sphalerite ores with different concentrations of trace metals. The first goal of this study is to analyze samples from Butte and Philipsburg to map out the distribution of metal impurities in sphalerite at the scale of each mining district (several square miles by up to 1 mile deep). The second objective is to make sphalerite grains in the laboratory that contain the same trace metals that are found in the natural specimens. The researchers will then compare the fluorescence behavior of the man-made and natural specimens. This project will train undergraduate and graduate students in the field of economic geology at Montana Technological University (MTU). MTU is a primarily undergraduate institution (PUI) in an EPSCoR state. Results from this project may reveal new ways that sphalerite and other ore minerals can be used to study mineral deposits. This research may also have applications to the use of luminescent sphalerite in materials science and engineering. Butte, Montana is the type example of a zoned, Cordilleran-style, porphyry-lode deposit, as well as being one of the nation’s top historic producers of Cu, Zn, Ag, and Mn. This study will take advantage of the Anaconda Research Lab (ARL) Collection, a set of over 50,000 hand samples collected from Butte and other mines in Montana that is archived at Montana Tech campus. Using the ARL Collection, as well as new samples from the active Continental porphyry Cu-Mo mine, the researchers will assemble a suite of 200 polished ore specimens containing sphalerite and other sulfide minerals from known locations across the entire Butte district, to depths of up to 5000 ft. below the surface. The sphalerite samples will be analyzed by optical microscopy, photoluminescence spectroscopy (PLS), Raman spectroscopy, laser ablation ICP-MS, electron probe microanalysis (EPMA) and hyperspectral cathodoluminescence (HP-CL) to reveal spatial and temporal patterns in trace element distribution, from the micron scale to the km scale. Machine learning tools will be used to identify correlations between elements in the sphalerite database that will help illuminate the underlying mechanisms by which trace elements enter the ZnS structure. For example, the researchers hypothesize that the deep red fluorescence mentioned above is linked to coupled substitution of Cu(+1), Ga(+3), and W(+6) for Zn(+2) in the sphalerite lattice. They will synthesize sphalerite of known trace element compositions using hydrothermal methods and compare the HP-CL, Raman, and PLS signatures of the synthetic and natural specimens. Finally, they will establish collaboration with a synchrotron laboratory capable of using XANES to verify the oxidation state of tungsten and other trace elements in their metal-doped ZnS and natural sphalerite samples. This project will support cutting-edge research and graduate-student training in economic geology at Montana Technological University, formerly the Montana School of Mines, a primarily undergraduate institution (PUI) in an EPSCoR state. Results from this project may reveal new ways that sphalerite and other ore minerals can be used to study mineral deposits, and may have applications to the use of luminescent ZnS in materials science and engineering.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.