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Der chemische Verwitterungsgrad von Gesteinen als Maß für ihre ingenieurgeologische Verwendbarkeit

  • W. Smykatz-Kloss
  • J. Goebelbecker
Conference paper

Summary

Chemical weathering of rocks is mainly due to hydrolysis. That is, the weathering cycle includes processes of dissolution of primary rock constituents (e.g. see fig. 1) and of precipitation from weathering solutions. These precipitation products (see figs. 2 and 3) include (OH) — ions or water or both. Thermal methods of analysis are well suited to characterize the influence of hydrolysis on rocks, e.g. by determining the amount of newly formed weathering products (sheet Silicates, hydroxi des). In the present paper a differential thermal analytical method is briefly described which allows the determination of the degree of chemical weathering (= the amount of neoformations, that is the formation of new minerals, expressed as a percentage of the weight of the whole rock) of granitic and basaltic rocks. The method uses the fact that all observed neoformations include (OH). Therefore, a weathering index can be calculated from the determination of all dehydroxylation effects as seen in Standard DTA curves (see fig. 4). For this, the sum of the peak areas multiplied by the sum of the values of the peak heights (= △T) of all dehydroxylation effects is used (figs. 4 – 6). A scaled relationship of clay minerals (e.g. kaolinite in granitic and nontronite in basaltic rocks) to the weathering index is a suitable measure of the degree of chemical weathering of siliceous rocks (such as granite, basalt, gabbro, gneiss) which are poor in primary OH-bearing minerals. The method offers a quick and reliable tool for engineering geologists to estimate the applicability of siliceous rocks.

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Literatur

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Copyright information

© Springer-Verlag Berlin Heidelberg 1985

Authors and Affiliations

  • W. Smykatz-Kloss
    • 1
  • J. Goebelbecker
    • 1
  1. 1.Mineralogisches InstitutUniversität KarlsruheKarlsruheGermany

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