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The synergistic use of multi-scale remote sensing data for the identification of hydrothermal alteration patterns in Los Frailes, Spain
International Journal of Applied Earth Observation and Geoinformation ( IF 7.5 ) Pub Date : 2022-09-28 , DOI: 10.1016/j.jag.2022.103034
Anne Blumberg, Martin C. Schodlok

Remote sensing data can be successfully applied in mineral resource prospecting and exploration. With the increasing number of remote sensing sensors and methods, the application of multi-scale remote sensing data has met a broad audience in the geological remote sensing community over the last few years. Multi-scale remote sensing data close the scale gap between distal (satellite) and proximal (laboratory) remote sensing data, offering both a general and detailed overview of the target and allowing a synergistic use. In this study, the volcano-sedimentary hosted massive sulphide ore deposit Los Frailes in the east of the Iberian Pyrite Belt (IPB) in Spain is investigated for the first time with multi-scale remote sensing techniques. A typical hydrothermal alteration zonation is associated to the massive sulphide ore body in Los Frailes, which is characterised by an inner chlorite-rich zonation showing a strong Fe-enrichment and a peripheral muscovite-rich zonation, which is moderately enriched in Fe. The characterisation of these zones support traditional mineral exploration techniques especially in the prospecting phase by detecting regions of interest, thereby reducing time and cost consumption. By evaluating the synergistic use of multi-scale remote sensing data for massive sulphide exploration, an enhanced application for the economic prospecting and exploration of mineral resources in Los Frailes is introduced. Optical data are used for the detection, identification and characterisation of chlorite and white mica occurrences and compositions. A drill core is analysed with the FieldSpec4 Hi-res hyperspectral point spectrometer. Rock samples are investigated in the laboratory using the SisuROCK hyperspectral core imaging station. AisaFENIX hyperspectral field-based and WorldView-3 multispectral satellite data of the open pit are analysed. The mineral(-group) identification and characterisation are performed with either spectral feature fitting methods (hyperspectral) or mineral indices (multispectral). Hyperspectral analyses show Mg-/Al-substitutions due to Fe-enrichment owing to wavelength shifts of the absorption maximum in chlorite and white mica, respectively. The identification and characterisation of the Fe-OH absorption feature of chlorite at around 2250 nm is more challenging compared to the Al-OH absorption feature of muscovite at around 2200 nm because the spectral signature is more subtle regarding the depth and width. However, the chloritic hydrothermal alteration zonation in the footwall is successfully detected in all scales. The hydrothermal muscovite-rich zonation in the footwall is barely outcropping in the pit and is not captured in the drill core. However, the muscovite-rich alteration zonation in the hanging wall is indicated in all scales. Discrepancies in the results arise mainly from different spectral and spatial resolutions of the sensors and differing data acquirement conditions, such as different surface exposures, viewing angles and illumination conditions. The results show that the multi-scale method offers great opportunities to localise potential prospecting and exploration targets in the Iberian Pyrite Belt. The synergistic use of the different remote sensing scales offers a complete picture of the target by gaining macroscopic to regional spectral information collectively, which is superior to using only one scale. The method is relatively fast and cost-effective, which makes the identification of potential exploration targets more efficient.



中文翻译:

多尺度遥感数据在西班牙洛斯弗莱莱斯热液蚀变模式识别中的协同应用

遥感数据可成功应用于矿产资源勘查勘探。随着遥感传感器和方法数量的不断增加,多尺度遥感数据的应用在过去几年中在地质遥感界遇到了广泛的受众。多尺度遥感数据缩小了远端(卫星)和近端(实验室)遥感数据之间的尺度差距,提供了目标的一般和详细概述,并允许协同使用。本研究首次利用多尺度遥感技术对西班牙伊比利亚黄铁矿带(IPB)东部的火山沉积岩托管的大规模硫化物矿床Los Frailes进行了调查。典型的热液蚀变带与洛斯弗莱莱斯的块状硫化物矿体有关,其特征是内部富含绿泥石的分带表现出强烈的富铁和外围富白云母的分带,其中中度富集铁。这些区域的特征支持传统的矿产勘探技术,特别是在勘探阶段,通过检测感兴趣的区域,从而减少时间和成本消耗。通过评估多尺度遥感数据在大规模硫化物勘探中的协同使用,介绍了在洛斯弗莱莱斯矿产资源的经济勘探和勘探的增强应用。光学数据用于检测、鉴定和表征绿泥石和白云母的出现和成分。使用 FieldSpec4 高分辨率高光谱点光谱仪分析钻芯。岩石样本在实验室中使用 SisuROCK 高光谱岩心成像站进行研究。分析了露天矿场基于 AisaFENIX 高光谱和 WorldView-3 多光谱卫星数据。使用光谱特征拟合方法(高光谱)或矿物指数(多光谱)进行矿物(组)识别和表征。高光谱分析显示,由于绿泥石和白云母的最大吸收波长发生变化,富铁导致镁/铝取代。与白云母在 2200 nm 附近的 Al-OH 吸收特征相比,绿泥石在 2250 nm 附近的 Fe-OH 吸收特征的识别和表征更具挑战性,因为光谱特征在深度和宽度方面更加微妙。然而,下盘的绿泥石热液蚀变带在各个尺度上都被成功探测到。下盘中富含热液白云母的地带在矿坑中几乎没有露头,也没有在钻芯中捕获。然而,在所有尺度上都显示出上盘中富含白云母的蚀变带。结果的差异主要来自传感器的不同光谱和空间分辨率以及不同的数据采集条件,例如不同的表面曝光、视角和照明条件。结果表明,多尺度方法为定位伊比利亚黄铁矿带的潜在勘探和勘探目标提供了很好的机会。不同遥感尺度的协同使用,通过集体获取宏观到区域的光谱信息,提供了目标的全貌,优于仅使用一个尺度。该方法相对快速且具有成本效益,这使得潜在勘探目标的识别更加高效。

更新日期:2022-09-29
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