基于ERDAS地质信息提取功能的设计与实现

遥感地质信息提取主要包括遥感蚀变信息的提取、线性构造信息的提取和岩性信息的提取等几个方面。目前，遥感蚀变信息的提取、线性构造信息的提取技术已经取得了较大的进展，而岩性信息的提取研究还没有成熟的方法。本介绍了在ERDAS平台的基础上，结合前人的有关地质信息提取的成熟方法和我们新增加的提取方法，将这些遥感异常提取方法进行整合与二次开发，设计并实现了地质信息提取的模块化。     

ETM+和ASTER数据在遥感信息提取中的对比研究

遥感蚀变信息提取是找矿的一个重要技术手段。本文选择位于秘鲁南部阿雷基帕(AREQUIPA)省境内的萨卡纳(CERCANA)和伊卡(ICA)省境内的Moarcona铁矿区作为本文的两个研究区,从分析地物光谱出发,利用ETM+和ASTER卫星影像数据,通过主成份分析法和比值分析法分别对两个研究区进行泥化蚀变信息提取和铁染蚀变信息提取,并对两者的提取结果进行对比分析。最后结果表明,相较于ETM+数据,ASTER数据在矿化蚀变信息的提取方面具有更大的优势。     

埃塞俄比亚西部岩浆熔离型铁矿遥感找矿模型

为解决在地质资料匮乏的情况下发挥多源遥感数据优势开展地质找矿研究这一科学问题,以非洲埃塞俄比亚西部研究区为例,选取ASTER及ALOS PALSAR单极化雷达数据为数据源,针对研究区重点类型铁矿--岩浆熔离型铁矿建立了其遥感找矿模型,提取与成矿作用相关的蚀变、构造、岩体信息。研究基于ASTER遥感数据,通过比值、主成分方法进行蚀变信息提取研究,并基于ASTER及ALOS PALSAR单极化雷达融合数据进行控矿构造及赋矿岩体信息提取研究。最终通过综合分析,基于ArcGIS平台圈定了3处遥感找矿靶区。研究结果与1∶25万地球化学数据对比,具有很高一致性,表明遥感找矿模型能够快速、准确地进行找矿靶区预测。     

基于ETM的遥感矿化蚀变信息提取研究综述

随着遥感技术在各个领域作用的不断凸现,在遥感地质找矿中,遥感矿化蚀变信息的提取是遥感找矿重要的突破口。本文对遥感矿化蚀变信息提取研究历史进行了回顾和未来展望,并对常用的遥感矿化蚀变信息提取方法进行了简单介绍。     

高光谱遥感蚀变矿物信息提取研究综述北大核心CSCD

蚀变围岩是热液矿床形成的重要标志之一,围岩蚀变会产生蚀变矿物,其与围岩中的矿物在颜色、结构、化学成分等方面具有明显差异,这些差异可导致蚀变矿物在特定波长区间产生诊断性波谱特征。通常高光谱遥感指的是光谱分辨率在5~15 nm的成像遥感,而绝大多数蚀变矿物的诊断性波谱宽度在20~40 nm,因此利用高光谱遥感技术可以快速地提取蚀变矿物信息,依据蚀变矿物组合及分布特征,划分蚀变分带、圈定矿化异常等具有重要的找矿意义。文章基于现有研究成果,系统总结了典型蚀变矿物的波谱特征、高光谱遥感技术的发展历史、蚀变矿物信息提取方法、不同地表覆盖类型对蚀变矿物信息提取的影响以及蚀变矿物信息提取在不同矿床类型下找矿的应用,最后指出了高光谱蚀变矿物信息提取研究中存在的问题以及未来发展方向。     

利用ETM数据进行矿化蚀变信息提取的方法研究——以柴北缘地区为例

在柴北缘地区利用ETM数据进行遥感矿化蚀变信息提取方法研究主要基于三个方面：①研究区蚀变信息及背景干扰地物信息的光谱特征;②矿化蚀变信息提取的最佳变量集组合;③图像增强处理方法和流程。在综合分析研究的基础上,采用“图像掩膜→最佳变量组合→波段比值→主成分分析→阈值分割→多元数据综合分析及异常筛选”的方法和流程提取了柴北缘成矿带的矿化蚀变异常信息,为该区综合成矿预测提供了可靠依据。     

基于在成分分析的植被掩模与模式滤波方法在中等植被区蚀变信息提取中的应用

植被干扰的消除对于应用TM图象进行蚀变信息提取是非常重要的。本文从矿物，岩石和植被在TM波段内的波谱响应分析入手，选择了TM5和TM1，TM5和TM7，TM4和TM3这三个组合分别来增强含铁矿物（主要是铁氧化物），含羟基矿物和碳酸盐矿物及植被信息。通过对比值，比值合成以及主成分分析等方法的比较，提出了一种适于中等植被覆盖区蚀变信息提取的新方法，即基于主成分分析的植被掩模和模式滤波相结合的方法。此方法在试验区进行蚀变信息提取中取得良好效果，它不仅识别出了与地表金矿化区一致的蚀变矿物富集区，而且对土石矿的一些矿脉也有较好反映。     

组合分析蚀变信息提取方法研究

目前主成分分析法、比值法、光谱角制图法等已广泛应用于遥感矿化蚀变信息提取中,且取得了很好的效果。根据研究区遥感数据特点,采用比值与主成分组合分析的方法,结合FLAASH大气校正、中值滤波以及彩色密度分割等图像处理方法,对新疆且末地区ASTER数据进行蚀变信息提取。经USGS标准矿物波谱库中典型矿物光谱的验证,组合分析方法能够去除数据冗余和噪声,有利于各类蚀变信息的提取。     

基于主成分分析的植被掩模与模式滤波方法在中等植被区蚀变信息提取中的应用

植被干扰的消除对于应用ＴＭ图象进行蚀变信息提取是非常重要的。本文从矿物、岩石和植被在ＴＭ波段内的波谱响应分析入手，选择了ＴＭ５和ＴＭ１，ＴＭ５和ＴＭ７，ＴＭ４和ＴＭ３这三个组合分别来增强含铁矿物（主要是铁氧化物）、含羟基矿物和碳酸盐矿物及植被信息。通过对比值、比值合成以及主成分分析等方法的比较，提出了一种适合于中等植被覆盖区蚀变信息提取的新方法，即基于主成分分析的植被掩模和模式滤波相结合的方法。此方法在试验区进行蚀变信息提取中取得良好效果，它不仅识别出了与地表金矿化区一致的蚀变矿物富集区，而且对于土石矿区的一些矿脉也有较好反映。     

地形对蚀变信息光谱影响研究与应用

通过加入地形因子进行相关光谱信息分区来提取蚀变信息,首先利用ASTER影像立体像对提取DEM,进行地形(坡向)划分,即分为阳坡、半阳坡、半阴坡、阴坡4类型,将相对应的区域统计其波谱信息,分为不同的波谱区,然后分别用主成分分析法提取蚀变信息。结果表明:波谱分区蚀变信息提取方法能够更加有效地识别出各个波谱区的蚀变异常信息,有效减小地形因素对蚀变信息提取结果的影响,并且在研究区得到很好的应用。     

Combined use of ASTER and ALI data for hydrothermal alteration mapping in the northwestern part of the Kerman magmatic arc,Iran

The study area is located in the Kerman magmatic arc in southern Iran, which is known for its world-class porphyry-type deposits. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Advanced Land Imager (ALI) visible–near-infrared to shortwave-infrared bands were used to investigate the spectral discrimination of hydrothermally altered rocks based on their mineral assemblages. Band ratioing, directed principal component analysis (DPCA), and the Spectral Angle Mapper (SAM) were applied on ASTER and ALI data for separating ferric iron-poor from ferric iron-rich phyllic alteration zones. The individual principal component images through DPCA could detect specific alteration zones dominated by minerals such as iron oxides, sericite, kaolinite, chlorite, and epidote. The phyllic zone associated with copper mineralization is generally rich in iron oxide minerals at the surface, which can be especially detected by ALI. The altered areas were sampled and studied using X-ray diffraction analysis, spectral measurements, chemical analysis, and thin-section studies. The results of this analysis have shown that more than 90% of the known copper mineralization falls within the ASTER/ALI-mapped alteration areas. These data can be useful for mapping alteration minerals related to porphyry deposits in other regions with similar geological settings.     

Lithologic mapping in the Oscar II Coast area,Graham Land,Antarctic Peninsula using ASTER data

The results of the first attempt to use Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data for the purposes of lithologic mapping on the Antarctic Peninsula are presented for an area on the Oscar II Coast, eastern Graham Land. This study included undertaking laboratory reflectance spectroscopy of ～70 rock samples from the study area and spectral lithologic analysis of two ASTER scenes. Spectra of the granitoids, silicic volcanic/volcaniclastic and terrestrial sedimentary rocks in the study area display a limited range of absorption features associated with muscovite, smectite and chlorite that are generally present as the alteration products of regional metamorphism. ASTER data analysis was undertaken using the reflective bands of the Level 1B registered radiance at-sensor data and the standard thermal infrared (TIR) emissivity product (AST05). For both wavelength regions, standard qualitative image processing methods were employed to define image end-members that were used as reference within Matched Filter (MF) processing procedures. The results were interpreted with reference to existing field observations, and photogeologic analysis of the ASTER visible to near-infrared (VNIR)/shortwave infrared (SWIR) data was used to resolve ambiguities in the spectral mapping results. The results have enabled the discrimination of most of the major lithologic groups within the study area as well as delineation of hydrothermal alteration zones of propylitic, and argillic grades associated with the Mesozoic Mapple Formation volcanics. The results have extended the mapped coverage of the Mapple Formation into un-investigated regions further north and validated previously inferred geological observations concerning other rocks throughout the study area. The outcomes will enable important revisions to be made to the existing geological map of the Oscar II Coast and demonstrate that ASTER data offers potential for improving geological mapping coverage across the Antarctic Peninsula.     

Mapping alteration minerals at Malmbjerg molybdenum deposit,central East Greenland,by Kohonen self-organizing maps and matched filter analysis of HyMap data

The Malmbjerg molybdenum deposit in central East Greenland is a world-class porphyry molybdenum deposit. The porphyry molybdenum deposit occurs within a granite stock intruded into sedimentary rocks. The Malmbjerg molybdenum deposit is associated with a pronounced zone of hydrothermal alteration. The reflectance spectra of rock samples from the Malmbjerg alteration assemblage show absorption features of a number of minerals including topaz, jarosite, goethite, muscovite, phengite, epidote, chlorite and smectite. This study investigated the Malmbjerg alteration assemblage using airborne imaging spectrometer data recorded by the HyMap imaging system. The HyMap data were analysed using an unsupervised classification based on Kohonen self-organizing maps and partial spectral unmixing based on the matched filter algorithm. The mapping results show the spatial distribution of jarosite, goethite, phengite, epidote/chlorite, smectite, topaz and non-altered sediments. The remote-sensing mapping results bring new information for the alteration assemblage at Malmbjerg, especially for the occurrence and the spatial distribution of a phengite zone in the altered sediments overlying the molybdenum deposit and for the propylitic alteration zone. The study is an example of detailed characterization by imaging spectrometry of alteration assemblages associated with porphyry molybdenum deposits. This research also shows the potential of imaging spectrometry as a tool for geological mapping and exploration in the Arctic regions of East Greenland.     

Heterogeneous object modeling through direct face neighborhood alteration

Two recent advances—the use of functionally gradient materials in parts and layered manufacturing technology—have brought to the forefront the need for design and fabrication methodologies for heterogeneous objects. However, current solid modeling systems, a core component of computer-aided design and fabrication tools, are typically purely geometry based, and only after the modeling of product geometry, can a part's non-geometric attributes such as material composition be modeled. This sequential order of modeling leads to unnecessary operations and over-segmented 3D regions during heterogeneous object modeling processes.

To enable an efficient design of heterogeneous objects, we propose a novel method, direct face neighborhood operation. This approach combines the geometry and material decisions into a common computational framework as opposed to separate and sequential operations in existing modeling systems. We present theories and algorithms for direction face neighborhood alteration, which enables direct alteration of face neighborhood before 3D regions are formed. This alteration is based on set membership classification (SMC) and region material semantics. The SMC is computationally enhanced by the usage of topological characteristics of heterogeneous objects. After the SMC, boundary evaluation is performed according to the altered face neighborhood. In comparison with other solid modeling methods, the direct face neighborhood alteration method is computationally effective, allows direct B-Rep operations, and is efficient for persistent region naming. A prototype system has been implemented to validate the method and some examples are presented.     

A remote sensing approach to alteration mapping: AVIRIS data and extension-related potassium metasomatism,Socorro, New Mexico

Miocene crustal extension in the south-western United States was accompanied by potassium metasomatism, a type of alteration marked by addition of large amounts of potassium at the expense of other constituents, notably sodium. The fluids responsible for the potassic alteration may have played a role in triggering extensional fault motion; one way to determine this is to compare the geographic distribution of the alteration to fault and sedimentary facies maps. Despite the large impact on rock composition, however, the alteration is visually subtle and difficult to map in the field. In this paper we present a preliminary alteration map of the Lemitar Mountains near Socorro, New Mexico, within the Rio Grande rift. This map was created from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data. The potential to discriminate potassium metasomatism in Landsat Thematic Mapper satellite data is part of the motivation for this study, since such data are widely available. Although the potassic minerals do not exhibit spectral features in the visible and near-infrared, iron was mobilized during potassium metasomatism, and the distribution of haematite thus serves as a proxy for the potassium. Evidence supporting the proxy relationship between haematite and metasomatism include (a) published reports by previous workers stating that haematite is added to rocks during K-metasomatism; (b) limited chemical evidence that samples collected from areas displaying a distinctive spectral response are strongly metasomatized; (c) the presence of large amounts of haematite in metasomatized rocks, observed petrographically and with an EDAX microprobe; and (d) the coincidence of the southern edge of the K-anomaly in the Lemitar Mountains as defined by chemical analysis and the southernmost occurrence of the anomalous spectral response. No other significant source of haematite has been reported from this area. Manganese oxide, occurring as localized veins or as rock varnish, is black in colour and highly absorptive, resulting in a distinctly different spectral response than the metasomatism-related haematite. This work shows that K-metasomatism can be mapped using AVIRIS data. The spectral response is not subtle, and can be observed in Landsat Thematic Mapper data; it is likely that K-metasomatism can be mapped, at least to some significant degree, from the Landsat data. Ongoing work is focusing on calibrating the strength of the spectral response to the intensity of alteration.     

An investigation of mineralized zones revealed during geological mapping,Jabal Hamra Faddan—Wadi Araba,Jordan, using LandsatTM data

The study area is well known for the historical Cu/Mn mineralization at Khirbet El Nahas. A map of alteration zones was prepared by Kaufmann in 1988, based on Landsat-TM data. During 1 :50000 geological field mapping, with associated imagery studies, a moe specificdelineation of the metallically mineralized parts of the alteration zones was achieved and the structural control on the distribution of minerals was defined. Different Landsat-TM band combinations, including colour composite of bands 7, 4, and 2, high pass filtering of the colour composite of bands 7, 5 and 2, ratio and principal component colour composites, were used to enhance diagnostic features of mineralized zones, preform analysis of structural features and to verify the distribution of certain lithological units. A number of target areas were examined in the field and selectively sampled. As a result, previously known mineralized zones were defined and new mineralization areas were discovered.     

基于ASTER数据的北山方山口地区蚀变矿物提取与找矿应用

针对北山方山口地区急需在老矿山深部及外围寻找新矿体的问题,以蚀变矿物为研究对象,通过ASTER遥感数据提取含Fe~(3+)、含Al-OH、含Mg-OH、含CO_3~(2-)和含石英的遥感蚀变异常,并结合野外验证和典型矿床的遥感剖析,总结遥感蚀变异常分布与区域成矿的关系,圈定遥感找矿预测区,为区域成矿规律研究提供依据。实验结果表明:研究区5种蚀变矿物提取结果正确率均超过80%,且遥感蚀变异常的分布与物化探异常具有较高的吻合度,已知金属矿(化)点也几乎都落在蚀变异常区内或边缘。遥感异常与成矿关系的分析表明以共生方式呈现的线性Fe~(3+)+(AlOH)+(Mg-OH)的蚀变矿物组合对研究区岩浆热液型矿化(特别是金矿化)有较好的指示意义。另外,基于相似类比法圈定的遥感找矿预测区也比较令人信服,在5处遥感找矿预测区内,野外查证已发现局部区域存在良好的矿化线索,这可为后续地质矿产调查提供有效指示信息。     

Mineralogical mapping of southern Namibia by application of continuum-removal MSAM method to the HyMap data

We applied the Modified Spectral Angle Mapper (MSAM) and continuum-removal methods to reflectance data obtained in the shortwave infrared regions by the airborne hyperspectral sensor, HyMap, to delineate distribution of the minerals related to hydrothermal alteration and pegmatite. The combination of these two methods was applied to remotely sensed hyperspectral data for the first time in this study. The effectiveness of this method, ‘continuum-removal MSAM’, was confirmed by comparing our mineral index maps with existing mineral maps of the Cuprite region, Nevada, USA. We then produced mineral index maps of southern Namibia using newly observed hyperspectral data. The existence of many pegmatite- and porphyry-type deposits is reported in this study area, where detailed mineralogical mapping based on remote-sensing data has not previously been conducted. Our mineral index maps are consistent with our field survey results, and also with X-ray diffraction analyses and spectral measurements of rock samples. In this study, the continuum-removal MSAM method successfully discriminated hydrothermal alteration minerals such as kaolinite and pyrophyllite, and pegmatite-related minerals such as high-aluminium muscovite and lepidolite in southern Namibia for the first time. The main advantages of our classification method are simplicity and high-precision identification of alteration minerals.     

基于ASTER数据的巴里坤地区蚀变矿物填图及找矿

ASTER图像被广泛应用于蚀变矿物填图中,但综合采用多种方法并对结果进行优选的研究鲜有报道。以新疆巴里坤县三道岭地区为研究区,综合采用比值法和主成分分析法处理ASTER数据进行蚀变矿物填图,利用已知矿点、小岩体、构造、化探异常等信息对各种方法提取的遥感异常结果进行对比、筛选,进而选取最优结果,之后结合地质、化探异常综合分析圈定了15处靶区,通过对其中9处靶区进行野外检查发现铜、金矿化点7处。结果表明多种蚀变矿物填图方法对比、优选较单一处理方法更为有效。     

Comparison of multi-temporal ASTER images for hydrothermal alteration mapping using a fractal-aided SAM method

The shortwave infrared (SWIR) spectral bands of four multi-temporal images acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra platform were analysed for evaluating the effects of acquisition properties and atmospheric pre-processing levels on the resulting hydrothermal alteration maps a using the fractal-aided Spectral Angle Mapper (SAM) method. Three ASTER level-1B products covering the Sar Cheshmeh area in Iran were used for hydrothermal alteration mapping. These images were converted to surface reflectance using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH) method. The low reflectance of band 5 of the level-1B products was compensated for by using the spectra of collected rock samples. Level-2 (AST2B05S) SWIR ASTER images that had already been processed were also used. Reference spectra of the main hydrothermal alteration types were extracted for each product. The threshold angles were determined using the real value–area (RV–A) fractal technique. Then, SAM classification was carried out to map hydrothermal alteration for every product. It is concluded that the level-1B products that had been converted to reflectances have a better spectral contrast than the AST2B05S product. Summer images with lower tilt angle and higher solar elevation should be used to increase the accuracy of the image classification and minimize the effect of vegetation on the spectra of index minerals. By comparing the resulting hydrothermal alteration maps with known alteration types using a confusion matrix, it was shown that the application of the RV–A fractal technique to produce less biased threshold angles increases the accuracy of SAM classification.