Contribution toward the chemical compostition of the crystalline rocks of south-east Missouri

Abstract

The study of the chemical composition of the crystalline rocks of South-East Missouri was undertaken a few years ago by Prof. J.A. Gibson. Prof. Gibson, assisted by Mr. W.J. Bray, collected several samples of granites near Fredericktown, in Madison County. These samples were taken from a single series or one outcropping of granite. A complete description of the rocks used in this series of analyses, the topography of the region where they were collected, and the methods of collecting and preparing the samples is given in the first nine pages of Mr. Bray's unpublished paper (a copy of this paper can be found in the University Library). Sample one is a coarse grained granite and the grain of each sample grows finer to number five which Dr. Erasmus Haworth calls porphyry. The purpose of the present work is to determine completely the chemical composition of his samples one, two, three, four, and five, and whether there is any difference in the chemical composition of these samples corresponding to the change in texture. Mr. Bray determined the major constituents of samples one, four, and five. The present paper, therefore, will deal with both the major and the minor constituents of samples one, two, three, four, and five. I have accepted from Mr. Bray's paper the determinations of silica, alumina, lime, magnesia, the alkalis, water, and the oxides of iron, after making the necessary corrections for the minor constituents. A complete analysis of an igneous rook is necessary for its exact chemical classification.