高光谱蚀变信息在金矿找矿预测中的应用研究——以北山方山口金矿线索为例

航空高光谱数据具有丰富的光谱信息和高空间分辨率,在矿化蚀变带识别中发挥着重要作用。成矿地质条件分析表明,北山成矿带方山口—老金场地区存在与中酸性岩体有关的金矿床成矿潜力。覆盖该区的航空高光谱(CASI/SASI)遥感数据蚀变矿物异常提取结果显示,区内发育高铝绢云母、中铝绢云母、低铝绢云母、褐铁矿、白云石、绿泥石、绿帘石和方解石等蚀变矿物。对金滩子金矿床光谱信息的剖析表明,"中—高铝绢云母+褐铁矿"为其标志性蚀变矿物组合;对区内高光谱异常信息进行筛选,圈定出方山口找矿预测区;对预测区内标志性蚀变矿物组合发育地段进行野外查证,发现3条金矿化黄铁绢英岩脉。实践表明,通过针对性地筛选高光谱蚀变矿物异常组合,可以有效地指导下一步的金矿找矿工作。     

绢云母的光谱特征变异分析及成像光谱地质成因信息提取

鉴于绢云母(和白云母)类粘土矿物对于研究与矿化紧密相关的中低温热液蚀变机制、与温压有关的地质成因过程等的重要意义,开展了绢云母的岩矿光谱特征变异分析和成像光谱矿物识别,并对岩石、矿物的试验室光谱和影像光谱所反映的地质成因信息的提取进行探讨。     

蚀变岩石和矿物光谱的切比雪夫比值函数波形分析

本文用切比雪夫比值函数对矿物学和岩石学剖面样品在2.O-2.5μm谱域的光谱进行波形分析。结果表明,波形分析技术在鉴别矿物、确定岩石绢云母化和碳酸岩化蚀变分带,及蚀变矿物相对含量等矿物学和岩石学的光谱研究中具有应用价值。     

基于ASTER遥感影像的西昆仑岩性信息提取方法研究

基于西昆仑西段布伦口地区各岩性段内岩石样品的矿物组成及其光谱特征分析,提取代表各岩性单元的岩性端元波谱曲线;对研究区内ASTER可见光(VNIR)和短波红外(SWIR)数据进行匹配滤波处理,成功提取了研究区内9种重要的岩性单元(包括古元古界布仑阔勒群的黑云石英岩、黑云斜长片麻岩、黑云石英片岩和黑云角闪斜长片麻岩,志留系温泉沟群的绿泥石绢云母板岩、黑色千枚岩和绢云母石英片岩,以及石英闪长岩和英云闪长岩)。经已知地质资料和野外查证资料分析证明,用上述方法提取岩性信息的结果可靠,能为岩性填图及矿床勘查工作提供参考。     

西藏Hyperion数据蚀变矿物识别初步研究

矿物识别是高光谱遥感技术研究的重要内容,也是高光谱最能发挥作用的领域。文章以最新获取的西藏驱龙地区卫星高光谱Hyperion数据为例,进行了星载高光谱数据蚀变矿物识别的初步研究。根据矿物光谱识别规则和识别谱系,初步识别并提取出高铝和低铝白云母化、高岭石化以及绿泥石化等蚀变矿物。与已知地质资料对照分析,所提取的蚀变信息与矿区地质情况基本吻合,同时发现一个新的类似的蚀变组合。     

高分五号高光谱影像矿物精细识别

矿物识别是高光谱遥感技术优势之一,已在地质矿产领域取得了显著应用效果。随着光谱分辨率的不断提高,高光谱遥感矿物识别逐渐从识别矿物种类向矿物亚类、矿物成分等精细信息识别发展,且随着应用实践的不断深入,对矿物精细信息的需求也越来越大。而光谱分辨率和矿物识别方法是制约高光谱矿物精细识别的主要因素。高分五号(GF-5)超高的光谱分辨率为矿物精细识别提供了可能。首先在分析总结已有高光谱矿物识别方法优缺性的基础上,提出了综合光谱特征增强匹配度和特征参量的矿物识别方法;其次,选取甘肃柳园和美国Cuprite两个研究较多的地区为研究对象,基于GF-5卫星数据开展了矿物精细识别,在完成矿物种类、亚类识别的基础上,进一步对绢云母成分信息进行了反演;最后,结合上述地区已有机载高光谱数据及填图结果开展对比分析。结果表明:GF-5矿物识别信息分布与机载HyMap、AVIRIS一致性很好,相较机载数据GF-5矿物识别平均正确率优于90%,说明本研究提出的矿物识别方法能够满足GF-5矿物精细识别,可为后续业务化应用提供技术支撑,同时认为超高的光谱分辨率使得GF-5在矿物成分信息识别上更具优势。     

板桥稀土矿遥感找矿信息提取与矿产预测研究

通过对离子吸附型稀土矿成矿规律的分析,从浙江省板桥地区的遥感地质特征研究入手,在研究区地表范围内进行稀土遥感找矿信息的提取。首先利用SPOT图像和DEM数据构建的坡度数据对与稀土成矿相关的地貌单元进行解译;然后通过光谱特征分析和基于ASTER图像的矿物遥感异常提取,获取与成矿相关的高岭土、绢云母、绿泥石等风化特征矿物的分布信息;最后叠合分析地貌、坡度及异常提取结果,进行稀土遥感找矿预测。与地质调查资料及化探数据的对比分析证实,上述方法对圈定1∶5万的大比例尺离子吸附型稀土矿分布范围是有效的,可为更详细的稀土矿产资源潜力评价提供依据。     

新疆白杨河铀铍矿区航空高光谱矿物填图及蚀变特征分析

以新疆白杨河铀铍矿区为研究区,通过建立航空高光谱数据CASI/SASI矿物填图处理流程,运用混合调制匹配滤波技术实现了多种蚀变矿物的填图。填图结果的野外验证表明,3种绢云母亚类的准确性高于85%,其他各类矿物的准确性高于90%。叠加研究区铀矿点资料,发现白杨河矿区赤铁矿化和高铝绢云母的空间分布特征与铀矿点分布高度相关,主要位于杨庄岩体与外围火山岩的北接触带附近,呈明显分带性。并且,高、中、低铝绢云母的空间分布指示矿床北部和南部的热液活动温度可能存在差异,区域上存在多期热液活动作用。这为矿区外围找矿预测和区域地质成因研究提供了参考和依据。     

基于ASTER数据的蚀变矿物信息提取——以哈密黄山铜镍矿区为例

在分析哈密黄山铜镍矿区典型地物波谱特征的基础上,设计了基于ASTER数据的蚀变信息提取流程,详细论述了对4组含不同离子或基团的常见蚀变矿物应用主成分分析(PCA)进行蚀变信息提取、采用光谱角制图法(spectral angle mapper,SAM)进行干扰异常筛选的“SAM去干扰异常主分量门限技术”.4组(9种)蚀变矿物包括:含Fe离子的矿物(针铁矿、赤铁矿)、含CO23-基团的矿物(方解石、白云石)、含Al - OH基团的矿物(白云母、蒙脱石、高岭石)以及含Mg - OH基团的矿物(绿泥石、绿帘石).蚀变矿物信息提取结果表明,“SAM去干扰异常主分量门限技术”方法可行,对ASTER数据的应用效果与实际情况比较吻合,充分证明ASTER在短波红外范围内具有很强的矿物刻画能力.     

基于TASI发射率数据的层状硅酸盐蚀变矿物提取识别

层状硅酸盐矿物光谱曲线特征具有较大相似性,在以往可见光-近红外遥感中的区分提取难度较大。本文采用的加拿大先进的热红外航空成像光谱仪(Thermal Airborne Hyperspectral Imager,简称TASI),可获取具有高分辨率的热红外高光谱数据。基于TASI数据并利用热红外波段的发射率光谱可探测出矿物Si-O键振动特征的优势,可做到矿物亚类的区分识别和矿物丰度信息的提取,使硅酸盐矿物亚类中的层状硅酸盐矿物区分提取的精确性得以提高。本文对甘肃北山柳园工作区进行了基于发射率光谱特征的层状硅酸盐蚀变矿物提取实验。通过分析从图像获取的端元光谱曲线特征,并与ASU光谱库标准光谱曲线进行对比,确定目标端元,成功区分出了绿泥石、高岭石等层状硅酸盐矿物,经野外实地验证后,确认所提取信息精确性较高。     

Characterizing hydrothermal alteration zones in Hamama area in the central Eastern Desert of Egypt by remotely sensed data

Abstract

Remote sensing techniques provide meaningful information to mineral exploration by identifying the hydrothermally altered minerals and the fracture/fault systems. In this article, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data were processed to detect the hydrothermal alteration zones in Hamama area in the central part of the Eastern Desert of Egypt. Band ratios and principal component analyses successfully revealed the extent and the geometry of the hydrothermal alteration zones that trend in an NE–SW direction. Matching pixel spectrum derived from Minimum Noise Fraction, Pixel Purity Index, and n-dimensional visualization with reference spectra allowed characterizing key hydrothermal alteration minerals, including chlorite, kaolinite-smectite, muscovite, and haematite, in a successive alteration pattern. Field investigations and X-Ray Diffraction analysis validated the results revealed by ASTER data. In addition, the present prospects of significant gold and massive sulphide mineralizations are consistent with the detected hydrothermal alteration zone.     

Mapping alteration mineral zones and lithological units in Antarctic regions using spectral bands of ASTER remote sensing data

Abstract

Geological mapping is one of the primary tasks of remote sensing. Remote sensing applications are especially useful when extreme environmental conditions inhibit direct survey such as in Antarctica. In this investigation, a satellite-based remote sensing approach was used for mapping alteration mineral zones and lithological units using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data in the Oscar II coast area, north-eastern Graham Land, Antarctic Peninsula. Specialized band ratios and band combinations were developed using visible and near infrared, shortwave infrared (SWIR) and thermal infrared spectral bands of ASTER for detecting alteration mineral assemblages and lithological units in Antarctic environments. Constrained Energy Minimization, Orthogonal Subspace Projection and Adaptive Coherence Estimator algorithms were tested to ASTER SWIR bands for detecting sub-pixels’ abundance of spectral features related to muscovite, kaolinite, illite, montmorillonite, epidote, chlorite and biotite. Results indicate valuable applicability of ASTER data for Antarctic geological mapping.     

Spatial distribution of altered minerals in the Gadag Schist Belt (GSB) of Karnataka,Southern India using hyperspectral remote sensing data

Spatial distribution of altered minerals in rocks and soils in the Gadag Schist Belt (GSB) is carried out using Hyperion data of March 2013. The entire spectral range is processed with emphasis on VNIR (0.4–1.0 μm) and SWIR regions (2.0–2.4 μm). Processing methodology includes Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes correction, minimum noise fraction transformation, spectral feature fitting (SFF) and spectral angle mapper (SAM) in conjunction with spectra collected, using an analytical spectral device spectroradiometer. A total of 155 bands were analysed to identify and map the major altered minerals by studying the absorption bands between the 0.4–1.0-μm and 2.0–2.3-μm wavelength regions. The most important and diagnostic spectral absorption features occur at 0.6–0.7 μm, 0.86 and at 0.9 μm in the VNIR region due to charge transfer of crystal field effect in the transition elements, whereas absorption near 2.1, 2.2, 2.25 and 2.33 μm in the SWIR region is related to the bending and stretching of the bonds in hydrous minerals (Al-OH, Fe-OH and Mg-OH), particularly in clay minerals. SAM and SFF techniques are implemented to identify the minerals present. A score of 0.33–1 was assigned for both SAM and SFF, where a value of 1 indicates the exact mineral type. However, endmember spectra were compared with United States Geological Survey and John Hopkins University spectral libraries for minerals and soils. Five minerals, i.e. kaolinite-5, kaolinite-2, muscovite, haematite, kaosmec and one soil, i.e. greyish brown loam have been identified. Greyish brown loam and kaosmec have been mapped as the major weathering/altered products present in soils and rocks of the GSB. This was followed by haematite and kaolinite. The SAM classifier was then applied on a Hyperion image to produce a mineral map. The dominant lithology of the area included greywacke, argillite and granite gneiss.     

基于ASTER影像的蚀变异常提取方法研究——以赞比亚谦比希铜矿床地区为例

基于赞比亚谦比希(Chambishi)铜矿带中的多种蚀变矿物及其在ASTER影像VNIR - SWIR谱带的特征光谱分析,采用相对波段吸收深度(Relative absorption- Band Depth,RBD)和波段比值的方法对蚀变信息进行增强处理.用波段比值ASTER 2/ASTER 1和ASTER 3的RBD...     

光谱重建与光谱真实性检验中地物光谱的作用

 将地物光谱与高光谱重建、影像光谱真实性检验相结合,重点阐述地物光谱在高光谱数据预处理中的主要作用。以新疆东天 山航空HyMap数据为例,在光谱重建过程中导入数据区特征地物（白云母和高岭石）光谱,以对利用大气模型校正的视反射率影像光 谱进行平滑、去“伪”或增强处理。进一步利用2种矿物的特征光谱评价重建光谱的真实性,从数据源头确保高光谱遥感数据光谱特 性的准确与可靠。     

Mapping of bauxite mineral deposits in the northern region of Saudi Arabia by using Advanced Spaceborne Thermal Emission and Reflection Radiometer satellite data

Mineral deposit mapping is very essential for sustainable and eco-friendly exploitation of natural resources. The Kingdom of Saudi Arabia has abundant natural resources such as natural gas, oil and minerals. It reserves high quantity of minerals such as phosphates, bauxites, copper, gold and other industrial minerals. The red soil regions located in Hail and Qassim provinces of Saudi Arabia have rich amount of bauxite (major aluminum ore) deposits. In order to initiate the focus on mapping of mineral deposits along this area, standardized hyper-spectral analysis has been carried out by using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data. The spectral signature of gibbsite (major element in bauxite) samples is analyzed with reference to the spectral features of gibbsite in the visible near infrared and short-wave infrared bands electromagnetic spectrum. Advanced hyper-spectral transformations such as minimum noise fraction function and pixel purity index have been performed to identify the target end-member. The existence of the mineral is confirmed by comparing the spectral signatures of the end-member with the predefined spectral plots of ASTER and United States Geological Survey spectral libraries. Finally, the end-members are mapped and their abundance is estimated in 0–1 scale. The study has opened up new areas for mapping of bauxite deposits in the area and leads to eco-friendly exploitation of natural resources. It also validates the high potential of ASTER multispectral satellite data for the exploration and mapping of mineral resources.     

多元数据分析与遥感矿化蚀变信息提取模型

蚀变矿物的光谱行为造成了蚀变岩的光谱特征。利用典型岩石的多元数据分析，可以对蚀变矿物成份和光谱数据之间的关系作出定性和定量评价，进而建立遥感矿化蚀变信息提取模型。笔者利用青海某金多金属矿化区典型岩（矿）石样品的野外实测波谱数据和化学分析数据，进行了基于多元数据分析的遥感矿化蚀变信息提取模型研究，建立的比值组合线性回归模型较之单一比值方法具有更好的应用效果。     

Aqueous alteration mapping in Rishabdev ultramafic complex using imaging spectroscopy

Hyperspectral remote sensing/imaging spectroscopy has enabled precise identification and mapping of hydrothermal alteration mineral assemblages based on diagnostic absorption features of minerals. In the present study, we use Airborne Visible InfraRed Imaging Spectrometer-Next Generation (AVIRIS-NG) datasets acquired over Rishabdev ultramafic suite to derive surficial mineral map using least square based spectral shape matching in wavelength range of diagnostic absorption features of minerals. Resulting mineral map revealed presence of hydrothermally altered serpentine group of minerals and associated alteration products (talc and dolomite) along with clays and phyllosilicates. Mineral maps are validated using field spectral measurements and published geological map. Involvement of low temperature (<350 °C) hydrothermal fluid in serpentinization of ultramafic rocks in the region is inferred from analysis of deepest absorption features of muscovites at 2.20 μm, spectral abundance of lizardite and absence of prenhite-pumpyllite facies mineral assemblages. Talc was found to be the most common alteration product of serpentines followed by dolomites. Intense alteration of serpentines to talc along the fracture zone is attributed to the circulation of carbon dioxide rich hydrothermal fluids along these conduits. Kaolinite and halloysite are primarily associated with granites and are the result of hydrothermal alteration of plagioclase feldspar in granites while muscovite and illites are generally associated with phyllites and quartzites . The study demonstrates the potential of imaging spectroscopy for mapping hydrothermal alteration mineral assemblages in ultramafic complex.