DISTRIBUTION OF ASSOCIATIONS OF PETROCHEMICAL PROPERTIES OF GRANITES IN GROUPS OF ROCKS WITH DIFFERENT SIO2 CONTENTS

Abstract

Igneous rocks are currently classified into specific types associated by a common mode of evolution and similar composition. An important aspect of this approach is the identification of groups of igneous rocks with similar chemical compositions, making use of the statistical distributions of petrochemical properties. In the case of granites, which are essentially quartz-feldspathic rocks, it is best to consider three parameters. The first of these parameters (AS) is an indicator of the total alkalinity of silicic rocks; the second (K/Na) indicates the type of alkalinity, and the third (KAl) indicates the degree of alumina saturation of the rocks as a fraction of that in feldspathic minals. This investigation involved statistical analysis of the average chemical compositions of granitic extrusive bodies that developed under various geological and structural conditions. The study was confined to granites containing at least 57 percent of SiO2 and a maximum total alkalinity of 12 percent.