Kruszywo naturalne i skały węglanowe w Polsce na tle ich zmienności

Stefan Kozłowski, Jadwiga Pawłowska




The coefficient of variation has been calculated for deposits recognized in categories C2 and Cl. Data have been grouped into frequency classes, and for various populations the arithmetic mean (x), dispersion of random variables – variation of mean, sometimes of the weighted mean S2 and mean deviation have been computed. General coefficient of grid variation Vo and the minimum spacing of the exploratory grid have been found for square d1 and d2. The necessary number of observations for the coefficient of variation found can be read from Fig. 1.
Fig. 2 gives the spacing of development work (square grid) as a function of the coefficient of variation applied.
Studies have been completed for the main genetic groups of deposits: moraine, fluvioglacial, stream terraces, and stream terraces in mountain areas (the Carpathian and Sudetes mountains).
As to the rock flour content the greatest variability is noted in fluvioglacial deposits (Fig. 3). Histograms of the sand-size fraction content are demonstrated in Fig. 4, and of the pebble-cobble fraction content in Fig. 5. The greatest variability has been noted in deposits of stream terraces (Fig. 6) while the moraine deposits show the less variable features.
Sizeable deposits classified into group I (Tabs. 4 and 5) are related solely to the Leszno, North Mazovia, and Mazovia-Podlasie phases. Spacing between observations established on the basis of the coefficient of variation is close to that assumed for group 1. As to the required spacing between observations, other deposits fall into group I. Only in the development work in broken stone deposits of the stream terraces in the southern part of the country the lower spacing limit (in meters) should be adopted. For the most variable deposits the introduction of group III is postulated.
The statistical analysis has been completed for 8 groups of limestones (Tab. 6).
The analysis of variability of limestones is based on four principal chemical components expressed in percentages by weight: CaO, MgO, H2O3, and SiO2.
Mean values for the chemical parameters of limestones are listed in Tab. 7. The highest coefficients of variation are shown by MgO and SiO2. The maximum coeficients of variation have been found for the Carboniferous and Devonian deposits confirming the earlier information on siliceous and dolomitic admixtures in these limestones. The CaO parameter shows an exceptionally low variability, which in this case is a favourable feature. However, this parameter should not be regarded as the only one by which the variability of limestones is expressed.
Obviously in this case the detrimental admixtures are much more critical. The SiO2 parameter seems to be the most characteristic factor. The necessary number of observations and spacing in a square grid, as computed from formulas 1–3 discussed previously, is given in Tab. 9.
It results that spacing closer than that used so far should be adopted for evaluation of limestone deposits. The above applies even to group III which has been reserved for magnesites only. All that points to the necessity of a revision of methods used so far for evaluating the carbonate deposits. Particularly a new division into groups and requirements for spacing between observations for each group should be set up.

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