Petrology and Geochemistry of Ultramafic-Gabbroic Intrusions in the Abitibi Area, Ontario

Abstract

<p>A brief review of the general geology of the peridotite belt south of Lake Abitibi is presented. The petrography and geochemistry of each major intrusion is discussed in detail and mineral and element variation diagrams are drawn for a number of cross sections. The degree of differentiation of the initial magmas is discussed and illustrated by comparison with a hypothetical model. On the assumption that all ultramafic-gabbroic intrusions in the area are related, a model for the physical evolution of the assemblage is suggested. The criteria of classification of ultramafic rocks are examined with particular reference to the analysed rocks. In this relationship, a brief statement of the origin of basaltic magmas is presented.</p>