Abstract

Six hundred and two determinations, including 57 new determinations, of phosphorus in granitic rocks of North America have been investigated. The frequency distribution of phosphorus has been investigated for eight regions, the correlation between phosphorus and the major elements as well as between normative apatite and the other mineral norms for three regions, and the correlation between phosphorus and modal composition for one region.

In some cases the observed asymmetry of frequency distributions can be explained by correlation between concentration of phosphorus and variations in its distribution. In others the asymmetry can be explained by autometamorphic leaching of apatite. Examples of the former can be found in a belt which extends from Arizona via Oregon to northwestern North America. Examples that might be attributed to leaching can be found in a belt which extends from Texas to New England.

Phosphorus is a very important component of granites. Concentrations of phosphorus in granitic rocks can be correlated with mineralogic composition: the higher the quartz, the lower the phosphorus; the higher the percentage of mafic minerals, the higher the phosphorus. No correlations are observed between phosphorus and alkalies or feldspars, but a close correlation exists between phosphorus concentration and a whole set of major oxides.

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