Hydrothermal mineral deposits are the primary source of many mineral commodities of global importance. Since hydrothermal alteration minerals associated with the formation of these mineral deposits are active in the visible and infrared range, the analysis of spectral absorption features can be used to identify the mineralogy associated with different alteration events. Some hydrothermal events are responsible for the occurrence of mineral commodities, while other events create hydrothermal alteration unrelated to the introduction of base and precious metals. Therefore, it is crucial to develop a mineral exploration strategy to rapidly identify and map the indicator minerals linked to a mineralising event. The separation of minerals of different alteration events which are spectrally active in the same overlapping range of the spectrum, is the challenge addressed in this study. High spatial resolution airborne and laboratory-based hyperspectral images are combined to detect and visualise textures of muscovite replacing pyrophyllite in the shortwave infrared (SWIR) imaging spectroscopy survey over the Buckskin Range, the volcanic-hosted lithocap part of the Yerington porphyry district, Nevada (USA).

Spectral wavelength maps in different SWIR ranges are used to map the hydrothermal alteration mineralogy at both laboratory (26 µm) and airborne (1 m) scales. The airborne spectral data define outward zoning from alunite ± pyrophyllite to muscovite characterized by variable wavelength positions of its Al-OH absorption feature. The wavelength range of 1650–1850 nm is used to differentiate zones of pyrophyllite predominance over alunite within the inner domain. The laboratory data improves the characterisation of the hydrothermal alteration mineralogy, which includes alunite, pyrophyllite, muscovite, dickite, chlorite, topaz and zunyite. The textural relationship of muscovite replacing pyrophyllite is addressed through the development of a novel spectral index, the pyrophyllite-muscovite index (PMI). The characterisation of the intergrowths of pyrophyllite and muscovite at the laboratory scale is based on two aspects: (1) the definition of pervasive versus veinlet-controlled textures and (2) a subtle shift detection in the wavelength position of the Al-OH absorption feature of muscovite from 2189 to 2195 nm. The combination of the spatial patterns with the textural relationship of the pyrophyllite-muscovite association allows the identification of areas which contain the muscovite replacement of pyrophyllite. The recognition of a late muscovite replacement of pyrophyllite suggests that advanced argillic alteration reflecting intense acid leaching is followed by late near-neutral pH magmatic-hydrothermal fluids, adding K⁺ and potentially other alkali elements and metals in the epithermal environment. As a result of this study, we document the hydrothermal muscovite-pyrophyllite intergrowth relationships in the study area, thus contributing to an improved understanding of the lithocap epithermal system and a better assessment of its exploration potential for Au, Ag and Cu mineralisation.

热液矿物沉积物是许多具有全球重要性的矿物商品的主要来源。由于与这些矿床的形成有关的热液蚀变矿物在可见光和红外范围内都具有活性，因此对光谱吸收特征的分析可用于识别与不同蚀变事件相关的矿物学。一些热液事件与矿物商品的发生有关，而另一些热液事件则引起与引入贱金属和贵金属无关的热液变化。因此，至关重要的是制定一种矿产勘探策略，以快速识别和绘制与成矿事件有关的指示矿物质。在相同的重叠光谱范围内分离具有光谱活性的不同蚀变事件的矿物，是这项研究解决的挑战。在内华达州耶灵顿斑岩区火山岩性岩盖部分的短波红外（SWIR）成像光谱调查中，结合高空间分辨率的机载和实验室高光谱图像来检测和可视化白云母代替叶蜡石的纹理美国）。

使用不同SWIR范围内的光谱波长图来绘制实验室（26 µm）和机载（1 m）标度上的热液蚀变矿物学图。空中光谱数据定义了以亚铝石±叶蜡石到白云母的向外分区，其特征在于Al-OH吸收特征的波长位置可变。1650–1850 nm的波长范围用于区分内部区域内叶蜡石占优势的区域，超过亚矾石。实验室数据改善了热液蚀变矿物学的特性，包括钠沸石，叶蜡石，白云母，地开石，绿泥石，黄玉和方沸石。白云母代替叶蜡石的结构关系通过开发新的光谱指数，即叶蜡石-白云母指数（PMI）得到解决。叶蜡石和白云母在实验室规模上的共生关系的表征基于两个方面：（1）渗透性纹理与细纹控制纹理的定义；（2）Al-OH吸收特征的波长位置的微妙位移检测2189至2195 nm的白云母 空间图案与叶蜡石-白云母缔合的组织关系的组合允许鉴定包含白蜡铁矿替代叶蜡石的区域。叶蜡石后期白云母替代的认识表明，反映强烈的酸浸的晚期泥质蚀变，随后是近中性pH岩浆-热液，随后加入钾 （1）渗透性纹理与细纹控制纹理的定义，以及（2）白云母在2189至2195 nm的Al-OH吸收特征的波长位置中的细微位移检测。空间图案与叶蜡石-白云母缔合的组织关系的组合允许鉴定包含白蜡铁矿替代叶蜡石的区域。叶蜡石后期白云母替代的认识表明，反映强烈的酸浸的晚期泥质蚀变，随后是近中性pH岩浆-热液，随后加入钾 （1）渗透性纹理与细纹控制纹理的定义，以及（2）白云母在2189至2195 nm的Al-OH吸收特征的波长位置中的细微位移检测。空间图案与叶蜡石-白云母缔合的组织关系的组合允许鉴定包含白蜡铁矿替代叶蜡石的区域。叶蜡石后期白云母替代的认识表明，反映强烈的酸浸的晚期泥质蚀变，随后是近中性pH岩浆-热液，随后加入钾 空间图案与叶蜡石-白云母缔合的组织关系的组合允许鉴定包含白蜡铁矿替代叶蜡石的区域。叶蜡石后期白云母替代的认识表明，反映强烈的酸浸的晚期泥质蚀变，随后是近中性pH岩浆-热液，随后加入钾 空间图案与叶蜡石-白云母缔合的组织关系的组合允许鉴定包含白蜡铁矿替代叶蜡石的区域。叶蜡石后期白云母替代的认识表明，反映强烈的酸浸的晚期泥质蚀变，随后是近中性pH岩浆-热液，随后加入钾⁺ 以及超热环境中潜在的其他碱金属元素和金属。这项研究的结果是，我们记录了研究区内热液白云母与叶蜡石的共生关系，从而有助于人们更好地了解岩盖超热系统，并更好地评估了其对金，银和铜矿化的勘探潜力。