ISSN:0143-1161    

DOI:10.1080/01431168908903883

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Abstract. Some fractures in the crust are expressed at the surface as a field of point-like features that have developed in response to usually fluid processes within those fractures. We describe two complementary quantitative methods for analysing such point-like features from remotely-sensed imagery in terms of structural alignment. The two-point azimuth method is probabilistic and tests for the existence of regional and field-wide structural anisotropies. By contrast, the Hough transform method is deterministic and locates specific alignments. These methods have been applied to a Landsat Multispectral Scanner (MSS) image of the Pinacate Volcanic Field in north-west Mexico. The point-like features of interest are cinder cones and maars. The results reveal a northerly structural anisotropy and specific alignments, trending mainly northerly and north-northwesterly, have been mapped. This application was limited by the relatively coarse spatial resolution of the MSS image used. However, although only 71 per cent of the cones mapped on the ground were detected on the MSS image, joint analysis of the two data sets yielded comparable results and a significant improvement on previous qualitative analysis of the ground data. The dual method used here could be applied to other fields of geological point-like features.

ISSN:0143-1161    

DOI:10.1080/01431168908903885

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Abstract. Strategies and techniques for the use of airborne digital image data equivalent to the Landsat Thematic Mapper (TM) and from the NASA Thermal Infrared Multispectral Scanner (TIMS) in geological mapping are discussed. The test areas are in complex Archaean greenstone terrain that has been subject to deep lateritic weathering and subsequent incision. These are spectrally unlike areas that have been covered before, and the analysis is based on new reflected and emitted spectra of natural surfaces. The newly available Landsat TM data over most of Western Australia is seen to have unprecedented potential as an aid to geological mapping in such intractible terrains because of the consistent and clear discrimination of weathered rock surfaces and colluvial soils over a wide range of rock types, particularly in decorrelation stretched three-band and band ratio images. The discrimination is due to the fortuitous association of mixtures of weathering products rather than to the primary mineralogy of the rocks. TIMS data are less useful in bedrock mapping, but offer considerable advantages for mapping the distribution of different types of superficial cover.

ISSN:0143-1161    

DOI:10.1080/01431168908903886

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The geology of a structurally complex part of the Arabian Shield which has been subjected to four successive phases of deformation over a considerable period of time, has been extended by Landsat image analysis. The lithologies are Proterozoic metavolcanics, metasediments, gneisses and granites. Their macroscopic structures, identified on the ground by traditional geological mapping methods, have been extrapolated and hence new information about the regional tectonics has been obtained. Thus the use of multispectral satellite sensor image data has proved to be an excellent tool for geological mapping on a regional scale in crystalline basement terrains.

ISSN:0143-1161    

DOI:10.1080/01431168908903887

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Abstract. This paper describes the use of Landsat Thematic Mapper (TM) imagery for geological mapping in a tectonically-complex area of south-east Spain. The terrain includes the metamorphic basement rocks of the Betic Cordillera and the sedimentary strata of an intermontane basin. TM bands 1, 3 and 5 were used to produce a colour composite. Experimentation showed that this was the most effective band combination to discriminate rock types in the semi-arid study region. A combination of spectral and textural characteristics was used to identify and map rock types in the Nevado-Filabride and Alpujarride basement complexes, sedimentary strata in the Neogene Tabernas-Sorbas Basin and Quaternary drift deposits. Structural features were best shown by digital convolution using a directional filter. The enhanced images revealed a previously unreported fault and fracture belt on the northern side of the Tabernas Basin. The geological interpretation of enhanced TM imagery was locally checked in the field.

ISSN:0143-1161    

DOI:10.1080/01431168908903888

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Abstract. A study has been made of the response on TM imagery of a suite of undisturbed sub-economic prophyry copper deposits occurring in the coastal desert of Peru. The deposits are associated with low-grade, mainly propylitic alteration but give rise to strong anomalies on a Landsat Thematic Mapper (TM) band-ratio image. Field and mineralogical studies indicate that normal weathering within these alteration areas has been augmented by oxidation of sulphides and acid leaching of silicate minerals to produce clays and sulphates, including gypsum and natroalunite. It is this supergene assemblage, rather than the hypogene alteration minerals, that is responsible for the strong absorption in band 7 of the TM.

ISSN:0143-1161    

DOI:10.1080/01431168908903889

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Abstract. Infrared spectroscopy takes advantage of the strengths and positions of absorption bands determined by composition and crystal structure of rocks and minerals to discriminate between them. The spectral features in thermal-infrared multispectral remotely-sensed data, however, may be influenced by the weathered, rough and/or varnished character of the target as well as by environmental factors such as temperature and atmospheric conditions. Hence we measuredin situthe absolute spectral radiance of naturally-occurring surfaces of common sedimentary and igneous rocks to document the strengths and positions of absorption features available to the remote sensing geologist. The spectral radiance measurements (5-14 μm) were made with a portable spectral radiometer designed and built by the Jet Propulsion Laboratory and the data were used to estimate the spectral emissivity of the rocks. In addition, spectral reflectance measurements (2-3-20 μm) were made in the laboratory of samples of outcrops and soils previously measuredin situ.The reflectance measurements were made with a commercial Fourier transform infrared (FTIR) spectrometer equipped with a ‘diffuse reflectance’ accessory. A modified stage facilitates the sampling of large surface areas (6 mm x 10 mm). The agreement between the two techniques is very good and either approach seems suitable for the purposes of studying the spectral character of remotely-sensed targets. The techniques differ, however, in that the field portable spectrometer has a much larger field of view and the in situ data more accurately measure the intensity of spectral features which are in part a function of temperature and atmospheric effects.

ISSN:0143-1161    

DOI:10.1080/01431168908903890

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Geobotanical remote sensing techniques have been applied in studies of the geological characteristics of the Assynt area of Sutherland, Scotland. Airborne Thematic Mapper (ATM( data were used to evaluate the geobotanical utility of the multispectral information recorded in the visible and reflected infrared bands with respect to mineral exploration. The main aims of this study were, first, to evaluate remote-sensing techniques for the detection of stressed vegetation due to underlying mineral deposits and, secondly, to study the possibilities of using ATM data for lithology and structural mapping under existing natural conditions. Of the eleven multi-spectral bands, differences in canopy physiognomy characteristics may partially control the spectral response in bands 5, 7 and 9. Band 7 in the near-infrared wavelength region, however, has the contrasting effect of apparently enhancing topography and reducing the spectral effect of vegetation. This permits the recognition of a number of linear features on the band 7 image which may be interpreted in terms of structural geology. Several small-scale previously unrecognized lineaments which run in the NWW-SEE direction parallel to other known basic dykes in Lewisian Gneiss have been recognized. Stressed vegetation near Ledmore, north-west of Loch Borrolan, has been identified.

ISSN:0143-1161    

DOI:10.1080/01431168908903891

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Manganese-sensitive forest and manganese-tolerant lee soybean cultivars were subjected to differential manganese stress in loring soil in a greenhouse experiment. Leaf temperature measurements were made using thermistors for forest and lee. Manganese-stressed plants had higher leaf temperatures than control plants in both forest and lee. Results of this experiment have potential applications in metal stress detection using remote sensing thermal infrared data over large areas of vegetation. This technique can be useful in reconnaissance mineral exploration in densely-vegetated regions where conventional ground-based methods are of little help.

ISSN:0143-1161    

DOI:10.1080/01431168908903892

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Abstract. Geological and radiometnc investigations for radioactive materials in the Wadi Alalla area revealed the presence of some uranium-mineralized veins in pink granite rocks forming the prominent masses of Gebel El Erediya and Gebel El Missikat. These veins are mostly composed of siliceous material showing some variations from proper silica or jasperoid veins to ferruginous and siliceous mylonites filling some fracture zones. However, not all siliceous veins in these granite masses are mineralized or radioactive. This paper deals mainly with the distribution pattern of the radioactive veins associated with the granite masses of Gebel El Erediya and Gebel El Missikat, their characteristic geological features and geometry, as well as their relationship with the major structural features of the Wadi Atalla area. It has been found that most of the radioactive veins in El Erediya pluton are of the fracture-filling type, predominantly of a NNW-SSE trend. The similar radioactive veins in El Missikat pluton are of a vein-type, the majority of which extend in an ENE-WSW direction. Structural analysis shows that this variation is mostly due to some rotational movement in clockwise direction along a major NW-SE fault line crossing the area and affecting both granite masses. This may be caused by the compressional stress having acted upon the area and the whole region for a considerable duration. The results of this work are also in favour of the close genetic relationship between these radioactive veins and their enclosing pink granite masses.

ISSN:0143-1161    

DOI:10.1080/01431168908903893

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor