Discrimination Of Rock Types Research Articles

Reservoir Rock Discrimination Based on Integrated Image Logs and Petrographic Analysis: A Case Study from the Early Miocene Nukhul Carbonate, Southern Gulf of Suez, Egypt

AbstractThe discrimination of rock types within the limestones and dolostones of the Nukhul Formation in the West Younis Field (Gulf of Suez Basin, Egypt) presents significant challenges due to their multi-scale compositional and diagenetic heterogeneity, diverse pore types, complex microstructures, and limited core data. This study aims to characterize the carbonate reservoir of the Early Miocene sediments and establish distinct reservoir rock types by employing textural analysis, geological interpretations (i.e., structural interpretation, fracture analysis, reservoir characteristics) using advanced imaging tools, and petrophysical measurements to model porosity/permeability profiles across the reservoir. A new dataset was obtained from the latest exploratory well in the West Younis Field, incorporating microresistivity and acoustic image logs, well logs, nuclear magnetic resonance (NMR) tools, and drill cutting petrographic analysis. The integration of these datasets provided a comprehensive understanding of the properties of the Early Miocene carbonate reservoir. Based on image logs, the carbonate facies were divided into four reservoir units. Petrographic evaluation further classified two facies (A and B) based on diagenetic factors controlling reservoir quality. The results revealed the occurrence of multiple phases of dolomitization, which influenced the reservoir quality. Early-stage dolomitization enhanced reservoir quality, while late-stage idiotopic dolomite crystal growth diminished it. The study also provided comprehensive information on the original rock fabric/texture, diagenetic processes, porosity types and origins, as well as the spatial distribution of pores (permeability index) within this complex carbonate reservoir. By employing an integrated technique, this study successfully differentiated the carbonate reservoir into distinct rock types, leading to improved reservoir characterization and field development. Additionally, the findings contribute valuable insights for the development and exploration of the Early Miocene carbonate section in the southern Gulf of Suez.

Discrimination of Mineralized Rock Types in a Copper-Rich Volcanogenic Massive Sulfide Deposit Through Fast Independent Component and Factor Analysis

Multivariate methods are useful for simplifying the interpretation of variables in geochemical data and are widely used to uncover relationships between elements that are associated with geological and mineralization processes. Among these approaches, factor analysis (FA) is one of the most popular, whereas independent component analysis (ICA) has only been employed in a few cases. This study compared the effectiveness of these methods in distinguishing rock types and detecting mineralization signatures based on data on core samples obtained from the Nohkouhi copper deposit. The FA and ICA discriminated four known rock categories, namely barren rhyodacite, mineralized rhyodacite, barren black shale, and mineralized black shale. Stepwise linear discriminant analysis was used to compare the results of the FA and ICA and select components that effectively enable the discrimination of rock types and mineralization. First, rock types were distinguished with reference to the scores calculated via FA and ICA. The results showed that the FA and ICA achieved overall accuracy levels of 94% and 96% in rock-type discrimination, respectively. Second, each rock type was classified as either mineralized or barren. The FA exhibited classification accuracies of 76% for black shales and 70% for rhyodacites, whereas the ICA yielded classification accuracies of 79% and 88% for the two rock types, respectively.

Validating (MNF) transform to determine the least inherent dimensionality of ASTER image data of some uranium localities at Central Eastern Desert, Egypt

One of the main determinations of geological remote sensing is to develop and improve different image processing algorithms and methods for mineral mapping and rock type discrimination. This paper investigates one of those sophisticated algorithms; the validity of Minimum Noise Fraction (MNF) components to improve the spectral separability of The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor image data of Terra satellite, and to develop a standard method of noise removal and image enhancement. Previous studies that used in image processing to eliminate MNF eigenvalues, eliminate values less than the unit. However, removing MNF eigenvalues more than this value and its effect on the data, has not been examined. Therefore, in this paper, we demonstrate that we can eliminate more than the unit up to 2 eigenvalue without a negative inherent effect on the origin data structure. A comparison study using different Image Quality Measures (IQMs) methods, has been accomplished on data distribution before and after MNF transformation of the original and atmospherically corrected data. Matched Filter (MF) classification was performed on data before and after MNF to map a chosen known alteration mineral (Kaolinite) by matching the image endmember spectra and its spectra from USGS library. By examining the spectral trends of specific mineral alteration type across these transformed channels, areas of interest that are unique by the related previous well-known uranium mineralization may become superficial apparent. This examination also showed how the use of MNF as a pre-processing technique could improve the capability to extract information from ASTER data of El-Missikat, El-Eridya and Kab Amiri areas in the Central Eastern desert as a case study district for uranium mineralization occurrences.

Mapping bedrock lithologies through in situ regolith using retained element ratios: a case study from the Agnew-Lawlers area, Western Australia

Large, high-quality multi-element geochemical datasets are becoming widely available in the exploration industry, and afford excellent opportunities to investigate geochemical processes. A dataset of over 2500 analyses of unweathered and variably weathered mafic and ultramafic rocks for over 50 elements has been collected by Gold Fields Ltd. in the auriferous Agnew-Lawlers area of the eastern Yilgarn Craton of Western Australia. This dataset is used to investigate changes in element abundances and inter-element ratios through varying degrees and styles of weathering in an area of thick regolith characterised by deep in situ weathering. Systematic interrogation of the data, using lithostratigraphic controls derived from regional mapping and geophysics, reveals that a suite of elements, including Ti, Al, Zr, Th, La, Sc and Nb, and to a lesser extent Cr and Ni, behave as essentially immobile components during saprolite formation. In some cases diagnostic element ratios persist into siliceous duricrust. Ratios of these elements are used as reliable discriminants of bedrock type, and delineate features such as cryptic layering within fractionated sills and subtle geochemical variants in a sequence of tholeiitic and komatiitic basalts. Mapping on the basis of discriminant element ratios greatly extends previous trace-element ratio-based schemes for rock type discrimination. The potential to determine several of these elements with adequate precision and accuracy using portable XRF technology opens a potentially useful technique for rapid geochemical bedrock mapping in residual terrains.

Discrimination of rock types and main rock-forming components in Bulgarian territories through spectral reflectance characteristics

Remote sensing studies on the spectral reflectance of natural formations – rocks, products of different physical and chemical processes in the Earth’s crust and its surface – are reported. Based on spectral reflectance characteristics (SRC) of selected representative rocks with different structure, mineral composition and colour characteristics – sedimentary (psephite-conglomerate) and metamorphic (kyanite schist) – and by applying statistical and deterministic methods the rock types and the main rock-forming components were discriminated. The spectral data were obtained in laboratory using a multichannel spectrometer developed in STIL-BAS, which delivers data in the spectral range 480–810 nm. The a priori mineralogical information about the specimens studied, the actual SRC data, affine and perspective transformations of the colour coordinates of SRC were all utilized to perform a primary classification of the main constituents of the specimens. Cluster analysis was applied and its results were used to design the necessary grouping variables as required for the implementation of linear discriminant analysis. The discriminant functions were constructed from the SRC values for a selected set of wavelengths and of transformed data. Classification of the main ingredients and the rock types were obtained. The proposed novel approach to the spectral discrimination of main rock-forming components is believed relevant for predictive classification of other specimens of rocks through discriminant functions.

Rock-type discrimination by field, TM and SPOT data, Tarn Flat, Antarctica

A lithologic investigation has been performed on the Tarn Flat area, Antarctica, based on Landsat-TM and SPOT-XS processed images and on radiometric field data acquired by an EXOTECH radiometer. Results from the field survey, performed during the austral summer 1994-95 expedition, were used to verify the ability of satellite images to discriminate between the main rock. Principal Component transformation allowed to enhance the spectral information of rocks, despite the high band correlation of TM data, while high-pass filtering and TM-SPOT merging allowed a fairly accurate detection of morphologic features. A supervised classification has been carried out on the processed satellite images as a further demonstration of the utility of remote observation to investigate extreme environments.

Potential of LANDSAT Thematic Mapper image for crystalline rock type discrimination: Gregory Rift, Kenya

Abstract In order to test the full potential of the computer‐enhanced image of original Landsat Thematic Mapper data the semi‐arid area of the Gregory Rift Valley (Kenya) was selected. The aim is to estimate the capability of false partially colour composite in bands 1, 3 and 4 to discriminate among metamorphic and various volcanic rock types. Furthermore signal reflectance differences among rocks of various ages but equal chemical characteristics were evaluated. Field surveys of the authors and published geological data made it possible to gather a great amount of ground truth. Comparison of satellite image interpretation and field geological data has demonstrated the validity of this T.M. image enhancement in lithotype discrimination but also has led to better definition of the spatial distribution of the various rock types in the area.

Statistical analysis of thematic mapper simulator data for the geobotanical discrimination of rock types in southwest oregon

An evaluation of Thematic Mapper Simulator (TMS) data for the geobotanical discrimination of rock types based on vegetative cover characteristics is addressed in this research. A methodology for accomplishing this evaluation utilizing univariate and multivariate techniques is presented. TMS data acquired with a Daedalus DEI-1260 multispectral scanner were integrated with vegetation and geologic information for subsequent statistical analyses, which included a chi-square test, an analysis of variance, stepwise discriminant analysis, and Duncan's multiple range test. Results indicate that ultramafic rock types are spectrally separable from nonultramafics based on vegetative cover through the use of statistical analyses.

New Techniques for Clay Mineral Identification by Remote Sensing: ABSTRACT

In the past three years there have been major advancements in our ability to identify clay minerals by remote sensing. Two different technologies have been used--imaging broad-band multispectral scanners and non-imaging narrow-band radiometers and spectrometers. Multispectral scanners, including NASA's Thematic Mapper Simulator (analog for Landsat-D Thematic Mapper) have had several broad-band channels in the wavelength region of 1.0 to 2.5 µm. In particular, the wavelength region 2.0 to 2.5 µm contains diagnostic spectral-absorption features for most layered silicates. Computer processing of image data obtained with these scanners has allowed the identification of the presence of clay minerals, without, however, being able to identify specific mineralogies. Studies of areas with known hydrocarbon deposits and porphyry copper deposits have demonstrated the value of this information for rock-type discrimination and recognition of hydrothermal alteration zones. Non-imaging, narrow-band radiometers and spectrometers have been used in the field, from aircraft, and from space to identify individual mineralogical constituents. This can be done because of diagnostic spectral absorption features in the 2.0 to 2.5 µm region characteristic of different clay types. The Shuttle Multispectral Infrared Radiometer (SMIRR), flown on the second flight of the space shuttle Columbia in 1981, had 10 narrow-band channels specifically chosen to evaluate the ability to identify directly clay minerals and carbonates. Preliminary analysis of SMIRR data over Egypt showed that kaolinite, carbonate rocks, and possibly montmorillonite, could be identified directly. Plans are currently under way for development of narrow-band imaging systems which will be capable of producing maps showing the surface distribution of individual clay types. This will represent a major step in remote sensing, by allowing unique identification of minerals rather than the current ability only to discriminate among materials. Applications of this technology will provide geologists with a powerful new tool for resource exploration and general geologic mapping problems. The research described in this abstract was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. End_of_Article - Last_Page 410------------

Radar Image Processing for Rock-Type Discrimination

Radar images have unique radiometric and geometric characteristics which present unique problems and opportunities for geological application. This paper reviews preprocessing and analytical techniques found useful or promising for applications of radar images to geologic problems such as rock-type discrimination. The use of coherent monochromatic illumination in radar images results in image speckle noise which interferes with characterization of the imaged surface. Median value filtering of the radar images removes speckle with minimal edge effects and resolution degradation. Variations in radar scene illumination due to uncompensated sensor platform motions or antenna pattern effects can be somewhat corrected for by mean and variance equalization in a direction perpendicular to the resulting image gradient. Registration of radar images to a map base and compensation of terrain induced image distortion can be accomplished by registration to digital elevation models and knowledge of imaging geometry. Analysis of SEASAT images with coregistered LANDSAT images indicates that the radar data can make a significant contribution to rock-type discrimination, especially if textural measures are incorporated. The sensitivity of radar backscatter to local slopes makes radar images an excellent medium from which to extract textural measures. Three techniques for extraction of the textural data inherent in the radar images are presented. Computation of image tone variance over various areas can numerically encode image texture. Hue-saturation-intensity split spectrum processing displays low-frequency variations in color while preserving high-frequency detail.

Clay Mineral Identification by Remote Sensing: ABSTRACT

In the past three years there have been major advancements in our ability to identify clay minerals by remote sensing. Two different technologies have been used--imaging broad-band multispectral scanners and non-imaging narrow-band radiometers and spectrometers. Multispectral scanners, including NASA's Thematic Mapper Simulator (analog for Landsat-D Thematic Mapper) have had several broad-band channels in the wavelength region of 1.0 to 2.5 µm. In particular, the wavelength region 2.0 to 2.5 µm contains diagnostic spectral-absorption features for most layered silicates. Computer processing of image data obtained with these scanners has allowed the identification of the presence of clay minerals, without, however, being able to identify specific mineralogies. Studies of areas with known hydrocarbon deposits and porphyry copper deposits have demonstrated the value of this information for rock-type discrimination and recognition of hydrothermal alteration zones. Non-imaging, narrow-band radiometers and spectrometers have been used in the field, from aircraft, and from space to identify individual mineralogical constituents. This can be done because of diagnostic spectral absorption features in the 2.0 to 2.5 µm region characteristic of different clay types. The Shuttle Multispectral Infrared Radiometer (SMIRR), flown on the second flight of the space shuttle Columbia in 1981, had 10 narrow-band channels specifically chosen to evaluate the ability to identify directly clay minerals and carbonates. Preliminary analysis of SMIRR data over Egypt showed that kaolinite, carbonate rocks, and possibly montmorillonite, could be identified directly. Plans are currently under way for development of narrow-band imaging systems which will be capable of producing maps showing the surface distribution of individual clay types. This will represent a major step in remote sensing, by allowing unique identification of minerals rather than the current ability only to discriminate among materials. Applications of this technology will provide geologists with a powerful new tool for resource exploration and general geologic mapping problems. The research described in this abstract was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. End_of_Article - Last_Page 1442------------

Rock-Type Discrimination from Ratioed Infrared Scanner Images of Pisgah Crater, California

The radiances in two thermal infrared channels of an airborne scanner system were ratioed to produce images that recorded compositionally diagnostic emittance variations for several silicate rock types near Pisgah Crater, California.

Spectral reflectance and photometric properties of selected rocks

Studies of the spectral reflectance and photometric properties of selected rocks at the USGS Mill Creek, Oklahoma, remote sensing test site demonstrate that discrimination of rock types is possible through reflection measurements, but that the discrimination is complicated by surface conditions, such as weathering and lichen growth. Comparisons between fresh-broken, weathered, and lichen-covered granite show that whereas both degree of weathering and amount of lichen cover change the reflectance quality of the granite, lichen cover also considerably changes the photometric properties of the granite. Measurements of the spectral reflectance normal to the surface of both limestone and dolomite show limestone to be more reflective than dolomite in the wavelength range from 380 to 1550 nanometers. The reflectance difference decreases at view angles greater than 40° owing to the difference in the photometric properties of dolomite and limestone.