BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 10, pp. 253-262 April 17, 1899 



FORMATION OF DIKES AND VEINS 



BY N. S. SHALER 



{Presented before the Society December 30, 1898) 



CONTENTS 



Page 



Introduction 253 



Dike Assures 254 



Classes of dikes . . . . 254 



Modes of occurrence 254 



Effect of heat on walls 254 



Influence of stratification 255 



Influence of jointing 255 



Combination dikes 256 



Causes of diversity in dikes 256 



Efiect of rock structure 256 



Efi"ect of water. . . 257 



Variation in moisture of rock structures 258 



Condition of sills 258 



Vein fissures 259 



Dissimilarity between dikes and veins 259 



Untenability of theory of open fissures 259 



Illustration of vein-forming from geodes 260 



Condensing and deforming eflfects of vein and dike materials 262 



Introduction 



Although few writers appear to have concerned themselves, in any 

 careful way, with the question as to the conditions which determine the 

 formation of the fissures in which dikes and veins are deposited, they 

 commonly assume that these seats of the accumulations of igneous or 

 aqueous deposited materials existed before the intrusive matter which 

 ha3 entered the. rocks found its resting place. The aim of this paper is 

 to present certain facts and considerations which serve to make the steps 

 by which these structures were formed clearer than they now are. In 



XXXVII— Bull. Geol. Soc. Am., Vol. 10, 1898 (253) 



