The normative alterology, an efficient and helpful decision making tool for the multiform valorization of weathered rock materials of tropical countries
The evolution of lithospheric aluminosilicate-bearing rocks under the action of meteoric agents can be characterized, either by the means of the traditional and litho-dependent procedure, which uses mass balances done by reference to the supposedly homogeneous original rock with the help of invariant items, or while using the normative alterology, which is not litho-dependent, has no invariant item, exploits the chemical composition in major elements and determines alterological parameters, through interposed virtual mineralogical composition, namely those quantified
by reference to the hypothetical final evolution stage of aluminosilicates. These two looks, crossing on a same reality, are turned, the first one toward the origin and the second one toward the future of the examined materials. Statistical comparisons of real and virtual mineralogical compositions which the two characterization ways lean on, show a satisfactory convergence. The examination of eligible features in the choice of clayey materials, usable on the one hand in industries of
building, fine ceramics and refractory wares, and on the second hand to produce rubber, paper, paint and plastics, shows a qualitative gradation with regard to mineralogical composition. The normative alterology, applied on materials collected from regions between and around the tropics, appears then to be an appropriate and helpful tool for the selection decision.
Key words: Meteoric alteration - Weathering mass balance - Normative alterology - Convergence - Clay materials - Building materials - Fine ceramics - Refractory wares - Rubber - Paper - Paint - Plastic.
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