A factor analysis study of the major element geochemistry of granitic rocks

A Varimax-rotated R-mode factor analysis was performed on a collection of 195 whole-rock major element chemical analyses of granitic rocks, mainly Finnish. Factor loadings with corresponding eigenvalues and communalities were computed separately for 3 to 6 factors. The rapakivis, the non-rapakivis and the combined group of all the granitic rocks were each studied individually. The results show that, in contrast to the other granites, the rapakivis form a fairly homogeneous group with pronouncedly high mutual correlations between the components. A factor analysis, therefore, reveals one single factor with a very high eigenvalue. This factor is designated the femic factor on the basis of the most important participating components. In other granitic rocks three main factors emerge; these are termed the femic, the one-alkali and the biotite factor, respectively. The existence of the one-alkali factor reflects the even stronger negative correlation of Na20 and K 2 0 in the nonrapakivis compared with the rapakivis.