Characterization of ammonium-bearing alteration associated with epithermal precious metal mineralization

金属和矿物对社会的基础设施至关重要，也是许多提供我们生活方式的材料的关键，从汽车到智能手机。由于这些资源是不可再生的，必须发现新的矿藏，以维持我们的生活水平，并支持发展中经济体的增长。大多数贵重金属（金和银）和贱金属（铜、铅和锌）的矿床是由热液作用形成的，热水运来的金属沿着浅层地壳的裂缝沉淀。热水的循环将矿床周围岩石中的原始矿物改造成含水矿物。这种蚀变晕可能从矿床延伸数公里，这意味着这些蚀变晕——或矿化热液活动的足迹——在金属矿床勘探中是有用的。铵在红外范围内具有吸收特性**，可以用红外光谱仪识别。便携式红外光谱仪和岩心扫描仪现在被世界各地的金属勘探和采矿公司广泛使用，因为这些新技术易于使用且快速识别蚀变晕中常见的矿物。然而，这些仪器并不能表明矿物中铵的含量，这意味着低浓度的铵可能存在于离矿床较远的地方，而不是用红外光谱检测到的。蚀变矿物如云母和长石是常见的，含有钾，可以用铵代替。然而，目前尚不清楚钾被铵取代的程度和矿物组合与矿床的大小和类型之间的关系。为了回答这些问题，本研究提出**量化蚀变岩中矿物的铵和钾含量，识别矿物和结构，**并将所获得的含量和矿物学信息与**工业产生的光谱数据进行比较。MAG Silver是这项研究的行业合作伙伴，一直在勘探** *银金矿。本研究获得的信息可以提高矿床足迹的识别，从而有助于有效地发现隐伏矿床

Metals and minerals are critical for the infrastructure of society as well as for many materials that provide our**way of life, from cars to smart phones. Since these resources are non-renewable, new mineral deposits must be**discovered to maintain our living standards and to support the growth of developing economies. Most precious**(gold and silver) and base metal (copper, lead and zinc) deposits form by hydrothermal processes where hot**water transports metals that precipitate along fractures in the shallow crust. The circulation of hot water**modifies and alters original minerals to hydrous minerals in rocks around the deposits. Such halos of alteration**may extend several km from mineral deposits, meaning that these alteration halos - or footprint of mineralized**hydrothermal activity- are useful during exploration for metal deposits. Ammonium has an absorption feature**in the infrared range that allows it to be identified with an infrared spectrometer. A portable infrared**spectroscopy and a core scanner are now widely used by metal exploration and mining companies worldwide**because these new techniques are easy to use and quick to identify minerals common in alteration halos.**However, these instruments do not indicate the quantity of ammonium in the mineral, meaning that low**concentrations of ammonium may be present farther from mineral deposits than can be detected using infrared**spectroscopy. Alteration minerals such as mica and feldspar are common and contains potassium, which can be**replaced by ammonium. However, it is not known how the degree of potassium substitution by ammonium and**mineral assemblages are related to the size and type of deposits. To answer these questions, this study proposes**to quantify ammonium and potassium contents of minerals in altered rocks, to identify minerals and textures,**and to compare the contents and mineralogical information obtained with that of spectral data generated by**industry. MAG Silver, an Industry partner for the proposed study, has been conducting exploration for**silver-gold deposits. The information obtained in this study can improve identification of deposit footprints and**thus contribute to efficient discoveries of concealed mineral deposits.**