For over four decades, spaceborne multispectral data have played a crucial role in supporting mineral exploration and geologic mapping. The spaceborne multispectral datasets, however, have a restricted number of bands with coarse spectral resolution and, thus are very limited in mineral mapping. The advent of high-quality spaceborne imaging spectroscopic data like the Environmental Mapping and Analysis Program (EnMAP), has bridged this gap initiating a new era in global hyperspectral mineral mapping. The EnMAP satellite, operational since November 2022, covers the spectral range of 420 and 2450 nm in 224 bands, offering a spatial resolution of 30 m and a mean spectral sampling distance of 8.1 and 12.5 nm in the visible-near infrared and shortwave infrared regions, respectively. In this paper, we demonstrate the enhanced mapping capabilities of EnMAP using datasets acquired over the Reko Diq mining district, a cluster of Miocene porphyries located in Pakistan's Chagai Belt hosting an undeveloped world-class porphyry Cu-Au ± Mo deposit. The EnMAP's Level 2A data product was processed using the polynomial fitting technique to characterize the diagnostic absorption features of the alteration minerals in the Reko Diq porphyry system. This involved retrieving the minimum wavelength, depth, width, and asymmetry parameters for key absorption features and employing them interactively for mineral characterization. A diverse array of minerals were successfully mapped over the study area and validated by ground spectroscopy. This includes abundance/composition maps for white micas, chlorite, epidote, calcite, kaolinite, gypsum, jarosite, and ferric and ferrous iron minerals. The minimum wavelength of white mica was found to vary between 2195 and 2210 nm, with the shorter wavelengths (Al-rich) white mica occurring proximal to the known mineralized zones. The potassic alteration cores and the outer propylitic zones were identified by the ferrous iron and chlorite-epidote-calcite mineral maps, respectively. This study demonstrated the superiority of EnMAP hyperspectral data in delineating the alteration mineralogy and zonation pattern of porphyry copper systems. This capability can potentially contribute to the exploration of new deposits in exposed terrains worldwide.

中文翻译：

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用于蚀变矿物测绘的星载 EnMAP 高光谱数据评估：以巴基斯坦 Reko Diq 斑岩铜[sbnd]金矿床为例


四十多年来，星载多光谱数据在支持矿产勘探和地质测绘方面发挥了至关重要的作用。然而，星载多光谱数据集的波段数量有限，光谱分辨率较粗，因此在矿物测绘方面非常有限。环境测绘和分析计划 (EnMAP) 等高质量星载成像光谱数据的出现弥补了这一差距，开启了全球高光谱矿物测绘的新时代。 EnMAP卫星于2022年11月开始运行，覆盖224个波段的420和2450 nm光谱范围，在可见光-近红外和短波红外区域提供30 m的空间分辨率和8.1和12.5 nm的平均光谱采样距离， 分别。在本文中，我们使用在 Reko Diq 矿区获取的数据集展示了 EnMAP 的增强绘图功能，该矿区是位于巴基斯坦 Chagai 带的中新世斑岩群，拥有未开发的世界级斑岩铜-金±钼矿床。 EnMAP 的 2A 级数据产品使用多项式拟合技术进行处理，以表征 Reko Diq 斑岩系统中蚀变矿物的诊断吸收特征。这涉及检索关键吸收特征的最小波长、深度、宽度和不对称参数，并将它们交互地用于矿物表征。成功地在研究区域绘制了一系列不同的矿物图，并通过地面光谱进行了验证。这包括白云母、绿泥石、绿帘石、方解石、高岭石、石膏、黄钾铁矾以及三价铁和二价铁矿物的丰度/成分图。 研究发现白云母的最小波长在 2195 至 2210 nm 之间变化，较短波长（富铝）白云母出现在已知矿化带附近。钾化岩心和外部青盘岩带分别通过二价铁和绿泥石-绿帘石-方解石矿物图来识别。这项研究证明了 EnMAP 高光谱数据在描绘斑岩铜系统的蚀变矿物学和分带模式方面的优越性。这种能力可能有助于在全球裸露地形中勘探新矿床。