Application of scanning electron microscopy to the study of deformed rocks

Lloyd, Geoffrey E.; Hall, M. G.

doi:10.1016/0040-1951(81)90037-8

Cited by 20 publications

(8 citation statements)

References 12 publications

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“…3) are typical of many geological materials in that they contain many phases. Backscattered Electrons have provided an excellent way of imaging phases of different composition Lloyd and Hall, 1981;Krinsley et al, 1983;White et al, 1984;Lloyd, 1985;1987) and the eclogite and granite provide good examples of this (Figs 2a,3a,c). However, normal-scanning OC images within one phase are often compromised by the presence of other phases.…”

Section: The Response Of Forescatter Detectors To Compositional and Cmentioning

confidence: 99%

Orientation contrast imaging of microstructures in rocks using forescatter detectors in the scanning electron microscope

et al. 1996

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We have developed a system using 'forescatter detectors' for backscattered imaging of specimen surfaces inclined at 50-80 ~ to the incident beam (inclined-scanning) in the SEM. These detectors comprise semiconductor chips placed below the tilted specimen. Forescatter detectors provide an orientation contrast (OC) image to complement quantitative crystallographic data from electron backscatter patterns (EBSP). Specimens were imaged using two detector geometries and these images were compared to those collected with the specimen surface normal to the incident beam (normal-scanning) using conventional backscattered electron detector geometries and also to an automated technique, orientation imaging microscopy (DIM). When normal-scanning, the component of the BSE signal relating to the mean atomic number (z) of the material is an order of magnitude greater than any OC component, making OC imaging in polyphase specimens almost impossible. Images formed in inclined-scanning, using forescatter detectors, have OC and z-contrast signals of similar magnitude, allowing OC imaging in polyphase specimens.OC imaging is purely qualitative, and by repeatedly imaging the same area using different specimen-beam geometries, we found that a single image picks out less than 60% of the total microstructural information and as many as 6 combined images are required to give the full data set. The DIM technique is limited by the EBSP resolution (1-2 ~ and subsequently misses a lot of microstructural information. The use of forescatter detectors is the most practical means of imaging OC in tilted specimens, but it is also a powerful tool in its own right for imaging microstructures in polyphase specimens, an essential asset for geological work.KEYWORDS: contrast images, scanning electron microscopy, backscattered electrons. Introductionpatterns (Alam et al., 1954;Venables and Harland, 1972;Dingley, 1981;; Dingley and Baba-Kishi, SELECTED area electron channelling patterns (Coates, 1990;Dingley and Randle, 1992;Randle, 1992; Day, 1967;Joy, 1974;Joy et al., 1982;Davidson, 1984; both provide quantitative data concerning Lloyd, 1985;1987;Schmidt and Olesen, 1989; Lloyd spatial variation of crystallographic orientations Lloyd, 1995) and electron backscatter minerals. In many problems relevant to geologists,

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Section: The Response Of Forescatter Detectors To Compositional and Cmentioning

confidence: 99%

Orientation contrast imaging of microstructures in rocks using forescatter detectors in the scanning electron microscope

et al. 1996

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“…This is not enough to calculate the seismic properties, which also depend on the a-and m-axes orientations, at least for the temperature range below the a-{3 quartz transition (about 573°C). The SEM was used to investigate quartz crystallographic orien tation using the channelling method and indexing Selected Area Electron Channelling Patterns (SAECP) (Lloyd and Hall, 1981;Lloyd et al, 1987). This powerful method allows measure ments of the complete crystallographic orienta tion of individual grains.…”

Section: S-wave Properties Of Monocrystalline Aggre Gatesmentioning

confidence: 99%

A quantitative evaluation of the contribution of crustal rocks to the shear-wave splitting of teleseismic SKS waves

Barruol

Mainprice

1993

Physics of the Earth and Planetary Interiors

192

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“…Electron microscopy has several advantages over conventional light microscopy, most notably better spatial resolution and greater depth of field (Lloyd and Hall 1981;Trimby and Prior 1999), and high-resolution topographic, structural, and compositional images from scanning electron microscopes are now widely used in the earth sciences. The principle of scanning electron microscopy is simple-electrons from a thermionic or field-emission cathode are accelerated to form a beam that is rastered across the sample surface.…”

Section: Introductionmentioning

confidence: 99%

Charge contrast imaging of geological materials in the environmental scanning electron microscope

Watt

Griffin

Kinny

2000

American Mineralogist

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The environmental scanning electron microscope (ESEM) allows high-resolution, high-magnification imaging of conductivity differences in uncoated geological samples. Under normal ESEM operating conditions, negative charge buildup at the sample surface (from bombardment by the electron beam) is prevented by the presence of a gas (usually water vapor) in the sample chamber. Backscattered and secondary electrons from the sample ionize this chamber gas, and the resultant positively charged gaseous ions migrate toward the negatively charged sample. When chamber gas pressures lower than approximately 250 Pa are used, however, charging of the sample can occur because insufficient charge balancing positively charged gaseous ions are produced. Charge implantation in the sample alters secondary electron emission, and, because intracrystalline conductivity contrasts occur in response to variations in defect density, secondary electron images reflect compositional variations and/or microstructural features. These secondary electron images are referred to as charge contrast images (CCI). To demonstrate potential geological applications of CCI, we present images of growth zones, microfractures, differential diffusion domains, pleochroic haloes, and relict fluid pathways from zircon (strongly luminescent), quartz (weakly luminescent), and biotite and cordierite (non-luminescent). CCI detect defects in a similar way to cathodoluminescence (CL), but have a higher resolution because the CCI signal is composed of secondary electrons that are generated from a much smaller interaction volume than photons utilized in CL. CCI imaging also can be applied to a wider variety of geological samples than CL, because electronic charge trapping is not restricted to wide-band gap electronic configurations. One of the most important potential applications of the CCI technique may lie in the direct imaging of relict fluid pathways in rocks that have experienced metasomatism or alteration.*

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Application of scanning electron microscopy to the study of deformed rocks

Cited by 20 publications

References 12 publications

Orientation contrast imaging of microstructures in rocks using forescatter detectors in the scanning electron microscope

Orientation contrast imaging of microstructures in rocks using forescatter detectors in the scanning electron microscope

A quantitative evaluation of the contribution of crustal rocks to the shear-wave splitting of teleseismic SKS waves

Charge contrast imaging of geological materials in the environmental scanning electron microscope

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