The use of hyperspectral reflectance in mineral exploration has been steadily increasing in recent decades. This study presents a novel approach that integrates geochemical and spectral proxies to delineate ore formation and alteration processes, which provide new spectral-based exploration parameters that can be used in real time. The precious metal-bearing, bimodal-felsic Northwest zone of the Lemarchant volcanogenic massive sulfide (VMS) deposits, Newfoundland, Canada, is used as a case study. Alteration associated with the Northwest zone includes intense and localized sulfide (pyrite, chalcopyrite, sphalerite, and galena) and barite enrichment, as well as quartz, white mica, and chlorite alteration. Zones of elevated Zn (>5,000 ppm) are associated with high chlorite carbonate pyrite index (CCPI), Ishikawa alteration index (AI), Ba/Sr, and low Na2O values and elevated SiO2 and K2O, Fe2O3, Na2O, and BaO contents, similar to global alteration signatures in VMS deposits. Mineralized areas contain phengitic white micas with 2,200-nm absorption features longer than 2,215 nm and Mg-rich chlorites with 2,250-nm absorption features shorter than 2,252 nm. Together, these data are consistent with the Northwest zone having undergone intense hydrothermal alteration during the mineralization event. A new lithology-normalized spectral alteration index (SAI) for white mica and chlorite was developed in order to map and characterize the alteration intensity surrounding the deposit. In addition, depth ratio parameters (2200D/2340D vs. 2250D/2340D) were used to characterize mineralogical changes and zonation. Together, these features document a paleofluid pathway with Mg chlorite alteration extending to at least 300 m away from the mineralization, outside the study area, within the andesitic and dacitic units. The use of hyperspectral reflectance coupled with geochemical alteration proxies permitted the identification of areas of intense alteration, the chemical affinities of the minerals, and their relationships to alteration processes (i.e., seawater alteration versus silicification), which would not be possible using geochemistry alone.

中文翻译：

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使用加拿大纽芬兰 Lemarchant 火山大规模硫化物矿床西北区的光谱蚀变指数和深度比追踪矿物学和蚀变强度

近几十年来，高光谱反射在矿产勘探中的使用一直在稳步增加。这项研究提出了一种新方法，该方法将地球化学和光谱代理相结合，以描绘成矿和蚀变过程，从而提供可实时使用的新的基于光谱的勘探参数。加拿大纽芬兰 Lemarchant 火山成因块状硫化物 (VMS) 矿床的含贵金属、双峰-长英质西北区被用作案例研究。与西北带相关的蚀变包括强烈和局部的硫化物（黄铁矿、黄铜矿、闪锌矿和方铅矿）和重晶石富集，以及石英、白云母和绿泥石蚀变。Zn 升高​​区 (>5,000 ppm) 与高绿泥石碳酸盐黄铁矿指数 (CCPI)、石川蚀变指数 (AI)、Ba/Sr、和低 Na2O 值以及升高的 SiO2 和 K2O、Fe2O3、Na2O 和 BaO 含量，类似于 VMS 矿床中的全球蚀变特征。矿化区域包含具有 2,200-nm 吸收特征长于 2,215 nm 的 phengitic 白色云母和具有 2,250-nm 吸收特征短于 2,252 nm 的富镁绿泥石。总之，这些数据与在矿化事件期间经历了强烈热液蚀变的西北带一致。开发了一种新的白云母和绿泥石岩性归一化光谱蚀变指数 (SAI)，以绘制和表征矿床周围的蚀变强度。此外，深度比参数（2200D/2340D 与 2250D/2340D）用于表征矿物学变化和分带。一起，这些特征记录了具有镁绿泥石蚀变的古流体通道，在研究区外的安山岩和英安岩单元内延伸至距矿化至少 300 m。使用高光谱反射率与地球化学蚀变代理相结合，可以识别强烈蚀变区域、矿物的化学亲和性以及它们与蚀变过程（即海水蚀变与硅化）的关系，而单独使用地球化学是不可能的。