Abstract

Frequency distributions of the major/minor oxides SiO2, Al2O3, Fe2O3, MgO, MnO, CaO, SrO, BaO, TiO2, Na2O, K2O and the trace elements Ni, V, Cu, Be, Y, Zr, La, Sc and Cr for 119 samples of Rensselaer Graywacke were tested against both normal and log normal distribution models. Based on chi square and moments, the distribution of SiO2, Al2O3, SrO, BaO, Na2O. and Sc were compared against the normal distribution model, whereas Fe2O3, MgO, MnO, CaO, TiO2, K2O, Ni, V, Cu, Be, Y, Zr, La, and Cr were converted to natural logarithms and their distributions tested against the expected log normal model. Most distributions fail to strictly follow either of the proposed hypothetical distributions; however, SiO2, BaO, and Na2O closely approximate the normal distribution, whereas Fe2O3, MgO, K2O, Y, Zr, and La are similar to the log normal model. If we accept the “Prior Knowledge Concept,” that is, based on previous information, state that the frequency distributions of elements approximately follow either the normal or log normal law, we may attribute discrepancies from the theorized distribution model to nonrandom sampling of a stratified population or to sampling of more than one population. Alternatively the samples may represent random samples from a non-normal parent population.

The Rensselaer, Franciscan (Bailey and others, 1964) and “average” graywacke of Pettijohn (1963) when compared against the “average” arkose, lithic arenite, and quartzite of Pettijohn (1963), are enriched in A12O3, total iron, and Na2O and have Na2O/K2O ratios of greater than unity, whereas the other sedimentary rock types have ratios less than 1.0. The present investigation agrees with earlier findings that graywackes have Na2O/K2O ratios of greater than unity; this appears to be a peculiarity of high-rank graywackes.

The concentrations of trace elements Ni, V, Cu, and Cr in the Rensselaer are lower than the crustal abundance, whereas Y, Zr, La, and Sc are higher in concentration. Concentrations greater or less than ten times the crustal abundance, are not apparent. The Graywacke is enriched in La and Sc 60 and 26 times respectively over Pettijohn's element range for sandstones (1963); all remaining trace elements are in favorable agreement. Hence, in chemistry the Rensselaer Gray-wacke appears to represent closely the composition of the “average” earth's crust.

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