遥感地质线性体与化探信息数字复合处理提取金矿控矿构造信息

从遥感图像获取的地质线性体与土壤岩石化探异常数据处理来进行定量分析提取具有控矿构造意义的遥感地质线性体,并从遥感地质环形体影像与化探金异常数据的关系,间接地分析环形体在成矿、控矿中的作用,为地面地质工作者提供找矿构造数值分析依据。研究结果与过去做过的大量地面成矿、控矿地质构造分析结果非常吻合。     

河北省内遥感线环形构造及化探异常信息的控矿特征

本文在河北省遥感地质解译和化探信息的基础上，对区内线、环形构造分布特征进行综合分析，提出了线环构造带、环形构造体系等概念，化探信息的提取主要是选用迭代法、主因子分析等方法来确定地球化学背景值和快速提取化探异常信息。通过对遥感和化探异常信息与成矿的相关分析，圈定找矿靶区，并对其控矿特征进行总结，指出了寻找大矿、特大矿的有利地段。     

多金属矿区遥感成矿预测初探

以浙江新昌拔茅火山岩区为试验区，着重探讨了由遥感TM图像中提取的线性休、环形体、控矿围岩、热液蚀变信息计算机综合处理方法，建立了一种无监遥感多金属成矿预测模型，并与有化探数据参与预测时的效果作了比较，论证了矿产勘查中遥感先行的可行性。     

基于遥感示矿信息的秘鲁阿雷基帕省南部斑岩铜矿遥感综合评价

在总结秘鲁南部地区斑岩铜矿成矿地质规律的基础上,分析了研究区控矿构造和赋矿岩层、矿化蚀变类型等成控矿地质特征;并根据研究区斑岩铜矿典型蚀变带蚀变矿物组合及其波谱特征,利用美国地质勘查局(USGS)波谱数据库,重建了斑岩铜矿典型蚀变带主要蚀变矿物在ASTER卫星数据B1～B9对应的反射率曲线,综合对比分析主要蚀变矿物的波谱曲线特征后,研发了基于ASTER数据B1467和B1348主成分分析模型,可分别提取典型蚀变带中泥化—绢英岩化类和青磐岩化蚀变矿物组合信息,并分别提取了研究区泥化—绢英岩化类和青磐岩化带蚀变矿物组合信息,为研究区斑岩型铜矿的遥感综合评价提供了重要的示矿标志;同时,采用人机交互遥感解译技术,获取了斑岩铜矿控矿构造、矿源层与赋矿岩石等示矿信息.最后,基于遥感技术获取的线性与环形控矿构造、矿源层与赋矿岩石、泥化—绢英岩化类和青磐岩化带蚀变矿物组合等遥感示矿信息,完成了研究区遥感找矿综合评价,圈定出遥感找矿有利区,经与已知斑岩铜矿床和物化探资料对比,以及高分辨卫星图像佐证,发现遥感评价结果具有很好的效果.     

遥感示矿信息在阿根廷西北部成矿预测的应用

针对我国矿产资源被不断勘探开发、国内经济发展需求不断加大使得大部分矿产资源供需形势十分严峻的问题,该文响应国家推出的"走出去"战略,选取国家境外地质矿产资源勘查重点地区阿根廷西北部作为研究对象进行成矿预测。阿根廷西北部的米纳皮基塔斯(Mina Pirquitas)地区是阿根廷重要的金、铜、锡、铅、锌、银矿采区,具有很大的找矿潜力。该文在充分收集相关地质矿产资料基础上,分别提取线环构造、矿源层、赋矿岩体和蚀变矿物异常等与成矿相关的遥感示矿信息,结合成矿地质特征和已知矿化点总结出研究区的遥感找矿特征,并据此圈定了7个遥感找矿有利区。经化探异常对比和实地核查验证,发现所圈定的找矿有利区与银、金化探异常基本一致,表明这些成矿有利区对找矿具有实际指导意义,可为进一步开展地面矿产资源勘查工作提供重要的参考,达到充分利用境外资源解决本国矿产资源紧缺问题的目的。     

崇礼地球化学块体与遥感成矿信息集成研究

成矿元素浓集中心是成矿物质富集的表现,遥感纹理信息中线性构造是成矿物质运移储存的空间、环形构造是成矿物质活化的动力、蚀变遥感异常是热液矿床成矿发生的主要标志之一。本文以河北省张家口崇礼地区银地球化学块体,利用该区1／20万银地球化学数据、遥感线环构造解译及蚀变遥感异常提取成果,开展了银地球化学块体与遥感成矿信息集成研究。认为冀西北地区,北东向断裂构造、北东向区域蚀变异常带及银地球化学块体剩余金属量是该区银矿的主要找矿标志。     

豫西南地区铜,金矿产分布与遥感地质构造的联系

豫西南地区铜、金矿产的形成，主要受构造及岩浆活动的控制。矿床（点）的分布与断裂构造、古火山构造以及岩浆岩体有明显的成生联系。不同规模、不同型式的构造组合在导矿，容矿空间和矿床、矿体定位上有着各自的特点。本区遥感图像上揭示的不同级别、不同类型的线性影像构造、环形影像构造及组合构造与铜、金矿床（点）的分布关系，充分反映了该区铜、金矿的区域成矿规律。结合区域成矿背景，建立相应的遥感地质影像模型，可有效地在豫西南地区进行铜、金矿的成矿预测和矿产勘查。     

秘鲁中南部奥马斯地区铜多金属遥感找矿预测研究

利用ASTER多光谱卫星数据,根据研究区内蚀变矿物的波谱特性,采用特征波段组合的主成分分析方法进行蚀变矿物组合信息提取,分别提取了绢云母、高岭石、蒙脱石、伊利石和明矾石等Al-OH类蚀变矿物组合信息,以及绿泥石、绿帘石和碳酸盐化(方解石和白云石)等青磐岩化类蚀变矿物组合信息。同时采用人机交互解译技术在研究区开展了遥感地质解译,结合区域成矿地质特征,综合分析了研究区控矿线性构造、环形构造、赋矿岩层和蚀变矿物组合等遥感示矿信息,并基于遥感示矿信息进行了综合找矿预测,圈定出遥感找矿有利区,经地面水系沉积物化探填图和高分辨卫星影像佐证,研究表明圈定的遥感找矿有利区为研究区开展地面矿产勘查工作提供重要的参考依据。     

基于国产卫星数据的遥感找矿预测——以青海省柴北缘地区为例

针对国产卫星数据进行遥感蚀变矿物信息提取存在较大困难这一问题,以青海省柴北缘地区为例,对基于国产卫星数据的铁染蚀变信息提取及其在找矿预测中的应用进行了研究。在了解青海省柴北缘地区地质背景和主要控矿因素的基础上,开展了国产卫星数据在地质矿产信息提取过程中的应用研究。通过各类地质体的影像特征分析,实现了由宏观解译到微观解释,表明国产卫星数据不仅能够细分岩性-构造层,并具有识别细微的与成矿作用相关的岩性、破碎蚀变带、小的岩体或岩脉的能力。根据国产卫星的多光谱波段设置,利用比值法和主成分分析方法提取了铁质矿物异常信息。在岩性、构造、成控矿要素解译的基础上,结合同步提取的遥感异常进行成矿与控矿信息筛选,并叠加多种地学信息进行成矿预测。经实地验证,发现基于国产卫星数据获取的遥感示矿信息与区内矿化现象十分吻合,表明所圈定的遥感找矿远景区具有重要的找矿应用价值。     

基于国产卫星数据的遥感找矿预测———以青海省柴北缘地区为例

针对国产卫星数据进行遥感蚀变矿物信息提取存在较大困难这一问题,以青海省柴北缘地区为例,对基于国产卫星数据的铁染蚀变信息提取及其在找矿预测中的应用进行了研究。在了解青海省柴北缘地区地质背景和主要控矿因素的基础上,开展了国产卫星数据在地质矿产信息提取过程中的应用研究。通过各类地质体的影像特征分析,实现了由宏观解译到微观解释,表明国产卫星数据不仅能够细分岩性-构造层,并具有识别细微的与成矿作用相关的岩性、破碎蚀变带、小的岩体或岩脉的能力。根据国产卫星的多光谱波段设置,利用比值法和主成分分析方法提取了铁质矿物异常信息。在岩性、构造、成控矿要素解译的基础上,结合同步提取的遥感异常进行成矿与控矿信息筛选,并叠加多种地学信息进行成矿预测。经实地验证,发现基于国产卫星数据获取的遥感示矿信息与区内矿化现象十分吻合,表明所圈定的遥感找矿远景区具有重要的找矿应用价值。     

基于遥感影像的线性构造自动提取

断裂带、断层等地质构造属于地质薄弱区,由于侵蚀等作用会形成线状地貌,表现出线性构造(lineament),可以通过遥感影像上的色调变化进行解译,进而了解断裂的空间展布,推测矿产资源的地下分布、判断地质稳定性。利用线段追踪法(Segment Tracing Algorithm,STA),首先以某一遥感像素为中心分若干个方向在给定大小的搜索窗口内搜索像素值的连续性,然后对连续性好的像素应用地质统计学按一定的阈值判定其是否为线素,再根据像素值在该方向上的变化进行脊谷判定,进而按照一定距离和角度标准把判别为山谷的像素连接成线性构造,最后将重复的线素删除,从而实现遥感影像的线性构造识别。从该方法在个旧锡矿遥感影像(DEM)的应用来看,STA识别的线性构造和实测断裂(层)的走向能较好的吻合,与实测断裂(层)之间的对应关系较好,但在线素连接上需要给定人为设置的参数,还需要进一步改进算法。     

Integration of Landsat imagery interpretation and geomagentic data on verification of deep‐seated transverse fault lineaments in SE Zagros,Iran

In this paper, Landsat images are used in the mapping of transverse fault lineaments in Zagros, Iran, and the origin of the fault lineaments as the result of basement reactivation faults is examined using geomagnetic maps. The area under investigation is located in the SE part of the Zagros Fold Belt (ZFB) and was affected by influence of concealed faults, or fault lineaments, during the late Alpine Zagros orogeny. Image interpretation of geological structures such as curvilinear geometry of fold hinges, en echelon pattern of surficial lineaments and younger folds, and breached salt plugs, has been used to map the fault lineaments. Two sets of strike‐lateral transverse fault lineaments have been detected. The first set, NW‐trending, was identified by right lateral curved geometry of the main fold hinges, generation of younger folds, and en echelon pattern of surficial lineaments. The second set, NE‐trending, was verified based on left lateral displacement of the structures and alignment of salt plugs pierced anticline hinges. The placement of Upper Proterozoic salt plugs on the surface along the fault lineaments, together with their correlation with the magnetic‐driven lineaments, implies that the fault lineaments have a basement origin. The trend of these fault lineaments can be correlated with the trend of basement faults in the northern margin of the Arabian plate. The key result of this study is that the fault lineaments identified by integration of remotely sensed data and geomagnetic maps are generated as first order wrench faults by reactivation of the N–S‐trending basement faults. The thick Hormoz Salt formations overlaying the basement do not allow the fault lineaments to emerge at the surface. Therefore, they can be mapped through regional remote sensing and their basement origin can only be recognized by their correlation with magnetic faults. It is also concluded that satellite imagery can greatly contribute to the structural mapping of the ZFB and is therefore a valuable aid for oil and gas exploration in analogous tectonic environments.     

Landsat TM analysis of fracture patterns: a case study from the Coastal Cordillera of northern Chile

Cretaceous rocks on the continental margin of northern Chile record a complex geodynamic evolution. Cycles of transtensional and transpressional deformation and of extrusive and intrusive magmatism are linked to the development of crustal-scale lineaments. The Landsat Thematic Mapper is used here as a tool to define these structural features. Geocorrected data were digitally enhanced and lineaments plotted directly from a hard copy image, thereby excluding artificial or non-geological features that might degrade the subsequent structural analysis. The lineaments were then digitized and analysed using a Weighted Moving Average (WMA) technique to suppress noise and to enhance azimuthal variation. Statistical analysis of the data reveals three lineament populations. The first is a set of NNE-trending lineaments that belong to the margin-parallel, sinistral Atacama Fault System. The second is a series of NW-trending lineaments with a similar orientation to large-scale structures identified across the South American continental plate. The third is a widely spaced set of NE-trending lineaments. The key result of this study is that lineaments identified from remotely sensed data may have orientation patterns that differ considerably from those identified by traditional geological mapping and that full structural analysis of structurally complex crustal regions will likely be incomplete without a comprehensive analysis of remotely sensed data. Although the NW-trending structures are numerically dominant on the Landsat TM image, they are seldom recorded at map scale and are under-represented on published geological maps. Of the 275 faults marked on the published geological map sheets, 89 are N to NNE-trending and only 88 are NW-trending. By contrast, of 841 lineaments identified from the satellite image, 455 are NW-trending and 178 are N- to NNE-trending. The lack of prior recognition of the NW-trending structures means that their importance has been underestimated in reconstructions of the geodynamic evolution of the region. In addition, as major ore deposits in the region are frequently located at intersections between two fracture systems, the recognition here of the NW-trending set of structures should illuminate future mineral exploration programmes.     

Application of wavelet analysis to the study of spatial pattern of morphotectonic lineaments in digital terrain models. A case study

Tectonic faults are often associated with characteristic geomorphological features such as linear valleys, ridgelines and slope breaks that can be identified as lineaments in remotely sensed images or digital terrain models. Lineaments of tectonic origin are often characterised by periodicity and characteristic spatial pattern. Unlike traditional methods of autocorrelation, variogram, lineament density and Fourier analysis, wavelet analysis is capable of capturing and describing both periodicity and spatial pattern of lineaments. In this paper, a case study is shown for the application of wavelet analysis to morphotectonic lineament investigation. Results of wavelet analysis are compared to traditional methods. Although this study involves DEM-derived morphological lineaments, the presented wavelet analysis can be also used for lineaments derived from remotely sensed images. These results hold for this case study and provide a good assessment of the relative abilities of wavelet analysis, but it remains to be seen how effective it is for other data sources, areas and geological terrain.     

Effectiveness of SRTM and ALOS-PALSAR data for identifying morphostructural lineaments in northeastern Brazil

This work provides a comparison between ALOS (Advanced Land Observing Satellite) PALSAR (Phased Array type L-band Synthetic Aperture Radar) and DEM (Digital Elevation Model) SRTM (Shuttle Radar Topography Mission) data aiming to evaluate their efficiency to detect morphostructural lineaments. An area in Northeastern Brazil was selected to perform this investigation because of its unambiguous evidence of tectonic fault activity from the Precambrian to the Quaternary. DEM enhanced by shading schemes and palettes was integrated with images representative of morphometric variables as aspect and horizontal curvature in order to enable the recognition of linear features. Images derived from HIS transformation and arithmetic operations of fine beam dual (HH+HV) polarization PALSAR images were processed to provide RGB compositions. Comparisons among lineament maps based on these two remote-sensing products attest to the highest efficacy of SRTM data in detecting geologically meaningful lineaments in the study area. These indicate a main E–W trend and secondary, NE–SW and NW–SE trends, which conform to dominant directions of tectonic fault zones previously mapped in northeastern Brazil. Geomorphological and geological field investigations carried out in the course of the current research further contributed to showing the best performance of this product for unravelling details of three expressive tectonic structures in the study area. This study shows that lineament attenuation in PALSAR images augments proportionally with increased land use. Other important interferences that either rule out or significantly attenuate linear structures are imposed by natural characteristics of the L-band PALSAR sensor, including layover and high-look azimuth in equatorial latitude. The latter might have particularly attenuated detection of lineaments parallel to illumination azimuth. Taking into account these interferences in PALSAR images, integration of DEM-SRTM data used herein offers a much more robust tool to help carry out morphostructural studies in terrains displaying characteristics similar to the ones in the study area.     

Classifying depth‐layered geological structures on Landsat TM images by gravity data: a case study of the western slope of Songliao Basin,northeast China

Geological structures on remotely sensed images, Landsat Thematic Mapper (TM) images in this case, can be classified by quantitative depth information on the basis of the comparison of results from Landsat TM images and geophysical data. Although the lineaments with different depths can be visually interpreted together on Landsat TM images, the depth information and geological significance of these lineaments are however hard to obtain solely from the Landsat TM images of a study area under a thick cover, and it is of much importance for hydrocarbon exploration in the Western Slope Belt of Songliao Basin, northeast China. During the present study, the 3‐dimensional field source information, including location and depth information, is derived from 3‐dimensional Euler deconvolution of gravity data in particular. As an example, it may be quantitatively classified into four groups of depth range: <100?m, 100–500?m, 500–1000?m, >1000?m. It is then superimposed onto the lineaments map from Landsat TM images using a geographical information system (GIS). With a comprehensive analysis of the superimposed maps, we obtain validation and quantitative depth information of the geological structures delineated on the Landsat TM images. Four depth‐layered maps of geological structures with different depths are presented here. It is concluded that the number of structures with depth greater than 1000?m on the Landsat TM images is fewer than those at the other three depth ranges. The detection of geological structures on Landsat TM images attributed to depth information derived from the geophysical data may also be possible by this approach.     

Computer vision-based framework for extracting tectonic lineaments from optical remote sensing data

ABSTRACT

The extraction of tectonic lineaments from digital satellite data is a fundamental application in remote sensing. The location of tectonic lineaments such as faults and dykes are of interest for a range of applications, particularly because of their association with hydrothermal mineralization. Although a wide range of applications have utilized computer vision techniques, a standard workflow for application of these techniques to tectonic lineament extraction is lacking. We present a framework for extracting tectonic lineaments using computer vision techniques. The proposed framework is a combination of edge detection and line extraction algorithms for extracting tectonic lineaments using optical remote sensing data. It features ancillary computer vision techniques for reducing data dimensionality, removing noise and enhancing the expression of lineaments. The efficiency of two convolutional filters are compared in terms of enhancing the lineaments. We test the proposed framework on Landsat 8 data of a mineral-rich portion of the Gascoyne Province in Western Australia. To validate the results, the extracted lineaments are compared to geologically mapped structures by the Geological Survey of Western Australia (GSWA). The results show that the best correlation between our extracted tectonic lineaments and the GSWA tectonic lineament map is achieved by applying a minimum noise fraction transformation and a Laplacian filter. Application of a directional filter shows a strong correlation with known sites of hydrothermal mineralization. Hence, our method using either filter can be used for mineral prospectivity mapping in other regions where faults are exposed and observable in optical remote sensing data.     

A comparative study of lineament analysis from different remote sensing imagery over areas in the Benue Valley and Jos Plateau Nigeria

A comparison is made between lineament analyses made from side-looking radar (SLAR)imagery, LANDSAT and aerial photographs from an area on the Lamurde anticline (Benue Valley) and from an area of ring dyke complexes (Jos Plateau), Nigeria. Fault lineaments are, in general, well expressed on side-looking airborne radar with the exception of those lineaments orientated parallel or subparallel to the radar look direction. Look direction and radar incidence angle influence lineament detectability. Specifically the lineaments oriented perpendicular to the Sun azimuth direction on the LANDSAT image were over-represented. LANDSAT, SLAR and aerial photographs can be used in a complementary way; the first two for reconnaisance-type surveys and lineament analysis, the third for detailed surveying.     

The spacing calculator software—A Visual Basic program to calculate spatial properties of lineaments

A software tool is presented which calculates the spatial properties azimuth, length, spacing, and frequency of lineaments that are defined by their starting and ending co-ordinates in a two-dimensional (2-D) planar co-ordinate system. A simple graphical interface with five display windows creates a user-friendly interactive environment. All lineaments are considered in the calculations, and no secondary sampling grid is needed for the elaboration of the spatial properties. Several rule-based decisions are made to determine the nearest lineament in the spacing calculation. As a default procedure, the programme defines a window that depends on the mode value of the length distribution of the lineaments in a study area. This makes the results more consistent, compared to the manual method of spacing calculation. Histograms are provided to illustrate and elaborate the distribution of the azimuth, length and spacing. The core of the tool is the spacing calculation between neighbouring parallel lineaments, which gives direct information about the variation of block sizes in a given category of structures. The 2-D lineament frequency is calculated for the actual area that is occupied by the lineaments.