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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)

Abstract


Journal of Sedimentary Petrology
Vol. 48 (1978)No. 2. (June), Pages 642-650

Estimating Pore and Cement Volumes in Thin Section: METHOD PAPER

Robert B. Halley

ABSTRACT

Previous HitPointNext Hit count estimates of pore, grain and cement volumes from thin sections are inaccurate, often by more than 100 percent, even though they may be surprisingly precise (reproducibility ± 3 percent). Errors are produced by: 1) inclusion of submicroscopic pore space within solid volume and 2) edge Previous HiteffectsNext Hit caused by grain curvature within a 30-micron thick thin section. Submicroscopic porosity may be measured by various physical tests or may be visually estimated from scanning electron micrographs. Edge error takes the form of an envelope around grains and increases with decreasing grain size and sorting, increasing grain irregularity and tighter grain packing. Cements are greatly involved in edge error because of their position at grain peripheries and their generally small grain size. Edge error is minimized by methods which reduce the thickness of the sample viewed during Previous HitpointNext Hit counting. Methods which effectively reduce thickness include use of ultra-thin thin sections or acetate peels, Previous HitpointTop counting in reflected light, or carefully focusing and counting on the upper surface of the thin section.


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