A Técnica de Difração de Elétrons Retro-Espalhados (EBSD) em Microscópio Eletrônico de Varredura (MEV) e sua Aplicação no Estudo de Rochas Deformadas

The electron backscattered diffraction technique in the scanning electron microscope (EBSD/SEM) is based on the diffraction of a high-energy electron beam by the crystalline structure of a given material, in all possible directions within the sample. Some of the diffracted electrons escape from the specimen with virtually the same initial energy, interact with a phosphorescent screen and the generated EBSP pattern can be picked up with a low-luminosity charge couple device (CCD) camera. These patterns can be indexed using pre-determined patterns for a large variety of minerals, which allows the determination of complete orientation of each single mineral within an aggregate. In this paper we briefly discuss the physical aspects related to the diffraction of an electron beam by crystalline matter and how the EBSP patterns are generated. We also present a short introduction of the necessary instruments to acquire EBSD data, as well as the calibration procedures, acquisition and indexing software of EBSPs. The pitfalls of the technique and possible error sources are also discussed with examples. Considering the scarce availability of literature on geological sample preparation, the polishing method of silicate-rich rocks for EBSP is described in detail in the last part of this paper.The electron backscattered diffraction technique in the scanning electron microscope (EBSD/SEM) is based on the diffraction of a high-energy electron beam by the crystalline structure of a given material, in all possible directions within the sample. Some of the diffracted electrons escape from the specimen with virtually the same initial energy, interact with a phosphorescent screen and the generated EBSP pattern can be picked up with a low-luminosity charge couple device (CCD) camera. These patterns can be indexed using pre-determined patterns for a large variety of minerals, which allows the determination of complete orientation of each single mineral within an aggregate. In this paper we briefly discuss the physical aspects related to the diffraction of an electron beam by crystalline matter and how the EBSP patterns are generated. We also present a short introduction of the necessary instruments to acquire EBSD data, as well as the calibration procedures, acquisition and indexing software of EBSPs. The pitfalls of the technique and possible error sources are also discussed with examples. Considering the scarce availability of literature on geological sample preparation, the polishing method of silicate-rich rocks for EBSP is described in detail in the last part of this paper

A Análise de Lineamentos Estruturais, Sob a Óptica da Geometria Fractal, no Maciço Alcalino de Poços de Caldas (MG)

This work presents the evolution of geological history of the Alkalic Mass of Poços de Caldas, based on a lineament study. The lineaments are correlated to ruptil fractures on the ground. For this purpose, the fractal geometry of lineaments was used to explain the results.The lineaments were obtained from Landsat-TM and Radar images. Graphics were generated such as the cumulative frequency of direction, histograms of structural lineaments direction per cumulative length and a plot of direction by lineament length. A map of fractal dimension of these lineaments was generated too.The correspondence between the plans of processed data, the structural context and the location of mineralizations allowed to conclude: (1) the uranium mineralizations are associated to fractures oriented preferentially NW and NE and (2) the zirconium mineralizations are oriented preferentially NS and EW.This work presents the evolution of geological history of the Alkalic Mass of Poços de Caldas, based on a lineament study. The lineaments are correlated to ruptil fractures on the ground. For this purpose, the fractal geometry of lineaments was used to explain the results.The lineaments were obtained from Landsat-TM and Radar images. Graphics were generated such as the cumulative frequency of direction, histograms of structural lineaments direction per cumulative length and a plot of direction by lineament length. A map of fractal dimension of these lineaments was generated too.The correspondence between the plans of processed data, the structural context and the location of mineralizations allowed to conclude: (1) the uranium mineralizations are associated to fractures oriented preferentially NW and NE and (2) the zirconium mineralizations are oriented preferentially NS and EW

The structural lineaments analysis on fractal geometry view of alkalic mass of Poços de Caldas, MG, Brazil

This work presents the evolution of geological history of the Alkalic Mass of Poços de Caldas, based on a lineament study. The lineaments are correlated to ruptil fractures on the ground. For this purpose, the fractal geometry of lineaments was used to explain the results.The lineaments were obtained from Landsat-TM and Radar images. Graphics were generated such as the cumulative frequency of direction, histograms of structural lineaments direction per cumulative length and a plot of direction by lineament length. A map of fractal dimension of these lineaments was generated too.The correspondence between the plans of processed data, the structural context and the location of mineralizations allowed to conclude: (1) the uranium mineralizations are associated to fractures oriented preferentially NW and NE and (2) the zirconium mineralizations are oriented preferentially NS and EW.This work presents the evolution of geological history of the Alkalic Mass of Poços de Caldas, based on a lineament study. The lineaments are correlated to ruptil fractures on the ground. For this purpose, the fractal geometry of lineaments was used to explain the results.The lineaments were obtained from Landsat-TM and Radar images. Graphics were generated such as the cumulative frequency of direction, histograms of structural lineaments direction per cumulative length and a plot of direction by lineament length. A map of fractal dimension of these lineaments was generated too.The correspondence between the plans of processed data, the structural context and the location of mineralizations allowed to conclude: (1) the uranium mineralizations are associated to fractures oriented preferentially NW and NE and (2) the zirconium mineralizations are oriented preferentially NS and EW