I70 R. J. COLONY 



plays an important part, and the now almost wholly consolidated 

 rock. These equilibrium adjustments, and the changes produced 

 by chemical attack, may be thought of as an extension of the 

 reaction effects described by Bowen. At this stage much of the 

 quartz and some of the alkalies, especially soda in such form as to 

 appear ultimately as albite, seem to be concentrated in the form of a 

 liquid consolidation-residuum, which, from such evidence as is 

 presented in the rocks themselves, must possess an extremely low 

 viscosity, great penetrating power, and considerable chemical 

 activity. 



During the consolidation of plutonic rocks especially, the 

 mineralizers operate to effect changes in some of the already formed 

 minerals, and in some cases cause profound changes in the rock 

 itself. When present to only a small extent their effects are usually 

 confined to the parent igneous rock. This is exhibited in various 

 ways. Frequently the end-phase products, quartz and albite, 

 penetrate the earlier feldspars, converting earlier orthoclase into a 

 sort of "injection perthite," beautifully exhibited in a granite near 

 Fort Ann, New York, and illustrated by Figure i . In this granite 

 each feldspar grain is surrounded by a narrow rim or border of 

 quartz and albite, which likewise penetrate the grains irregularly 

 and form also veinlets of microscopic dimensions in the rock. 

 Lying in and associated with such veinlets is a little graphite, which 

 apparently is of the same origin as the end-stage material itself. 

 The rock carries a little orthorhombic pyroxene as one of the 

 ferromagnesian components and this, wherever it appears, has 

 been converted to serpentine, which is here an end-stage reaction 

 product originating partly because of changes in equilibrium, and 

 partly because of hydration during the last stages of crystallization 

 of the rock. 



Sederholm'^^ describes as "deuteric effects" certain products 

 occurring as an intergrowth of two minerals at their contacts by 

 reason of the action of magmatic end-stage emanations; but the 

 structures thus described are very minute. The writer has extended 

 the term to cover all magmatic end-stage emanation phenomena, 



'J. J. Sederholm, "Synantetic Minerals and Related Phenomena," Bull, de la 

 Com. Geol. de Finlande, No. 48. 



