Topic
Petrography
About: Petrography is a research topic. Over the lifetime, 7449 publications have been published within this topic receiving 102018 citations.
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TL;DR: In this article, a petrographic study was made of sedimentary rocks of Permian, Triassic, and Jurassic age on the Colorado Plateau, and it was found that mean grain size can be translated as average grain size and is related to tectonic uplift, gradient, and energy level.
Abstract: A petrographic study was made of sedimentary rocks of Permian, Triassic, and Jurassic age on the Colorado Plateau. The source areas of the detrital sediments were positive areas of igneous, metamorphic, sedimentary, and volcanic terranes. Most of the sediments were deposited on a flat, slowly subsiding depositional plain; shallow-water embayments alternated with eolian or alluvial environments. It was found that mean grain size can be translated as average grain size and is related to tectonic uplift, gradient, and energy level. Standard deviation can be translated as average sorting and related to tectonic subsidence, rate of deposition, and amount of reworking. Skewness and kurtosis can be translated as measures of internal sorting contrasts and related to amount of reworking and accumulated energy. Differences in statistical measures of the grain-size distributions of samples from vertical sequences of sediments are interpreted in terms of minor and major tectonic changes in the source areas and areas ...
39 citations
TL;DR: In this article, a petrographic analysis using a thin section and a scanning electron microscope (SEM), combined with reservoir property data, was carried out to discuss the effects of primary mineral compositions on diagenetic processes and reservoir quality.
38 citations
TL;DR: In this article, a simple device is described which attaches to an ordinary petrographic microscope and permits luminescent observations as well as ordinary white or polarized light observations, which has the advantages of short pump down time (two min), large area of illumination by the electron beam (1×3 cm), and a minimum of charging and sparking problems.
Abstract: Thus far, all reported work on luminescence petrography has been accomplished by use of the microprobe, a very expensive instrument beyond the grasp of most petrographers. A simple device is described here which attaches to an ordinary petrographic microscope and permits luminescent observations as well as ordinary white or polarized light observations. The instrument has the advantages of short pump down time (two min), large area of illumination by the electron beam (1×3 cm), and a minimum of charging and sparking problems. In addition, ordinary uncoated rock or mineral thin sections may be used. The instrument has proven to be superior to the microprobe for luminescent observations of geological specimens. Other (nongeological) applications in fields such as ceramics and solid state physics are also likely.
38 citations
TL;DR: A hypothesized connection between clay diagenesis and magnetite authigenesis is supported by the results of paleomagnetic, rock magnetic, geochemical, and petrographic studies on Jurassic sedimentary rock of Skye, Scotland as mentioned in this paper.
Abstract: [1] A hypothesized connection between clay diagenesis and magnetite authigenesis is supported by the results of paleomagnetic, rock magnetic, geochemical, and petrographic studies on Jurassic sedimentary rock of Skye, Scotland. The results have implications for understanding remagnetization mechanisms and for the development of a paleomagnetic method to date clay diagenesis. Previous diagenetic studies indicate that rock in north Skye contains abundant detrital smectite, whereas the clays in the same age rock in south Skye have altered to illite because of Tertiary igneous activity. Geochemical (87Sr/86Sr, δ13C, δ18O) studies confirm that sedimentary rocks in south Skye are altered. The magnetization in the rocks in north Skye is weak and unstable. In contrast, the rocks in south Skye contain a multicomponent magnetization. At intermediate temperatures (225°–450°C) a magnetization with southerly declinations and negative inclinations or its antipodal equivalent is present. At higher temperatures (450°–580°C) a magnetization with northerly declinations and positive inclinations or its antipodal equivalent is removed. Both magnetizations have directions similar to Tertiary igneous rocks on Skye. Rock magnetic studies indicate the presence of pyrrhotite and magnetite. The intermediate-temperature component resides in pyrrhotite and/or magnetite and is interpreted as a thermoviscous remanent magnetization or a thermochemical remanent magnetization related to the heat and/or hydrothermal activity associated with the igneous activity. The high-temperature component resides in magnetite and is a chemical remanent magnetization (CRM). The presence-absence test and the timing of acquisition for this CRM suggest that magnetite authigenesis is related to the smectite-to-illite conversion and that clay diagenesis is a viable remagnetization mechanism.
38 citations
TL;DR: In this paper, the authors used petrographic studies and length change tests to identify Greywackes, argillites, phyllites, and some quartzites, schists and rhyolites as highly reactive.
38 citations