SANDSTONE DIKES OF UTE PASS. 137 



of the sand ; that the facts do show that the fissures of 

 this dike complex were filled b}' fine quicksand injected 

 from a source containing a large amount of homogeneous 

 material ; that such a system of fissures, large or small, 

 with their many intersections, could not remain open to 

 be filled by any slow process ; that the uniformity and 

 purity of the material filling fissures, varying from mere 

 films on cleavage planes of orthoclase grains in the granite 

 to dikes several hundred yards in width, could not have 

 resulted from infiltration ; and, finally, that none of the 

 sedimentary formations of the region can be regarded as 

 prol^able sources of the material. 



My study enables me to accept all of these gejieraliza- 

 tions, except the last one. The main purpose of the pre- 

 ceding detailed descriptions of the dikes which have come 

 under my special notice is to set forth the facts which 

 the true theory of the dikes must explain. The most im- 

 portant of these are : first, their very evident close rela- 

 tionship to an important zone of displacement; second, 

 the homogeneity of the materials and the general absence 

 of stratification in the dikes; third, the great maximum 

 and average widths of the dikes. 



The relations of the dikes to the great Ute fault are 

 indisputable. Not only is the fault at most points closely 

 accompanied by one or more dikes ; but nowhere have 

 I been able to find any trace of the dikes more than a few 

 hundred feet (500 to 1000 feet) distant from the princi- 

 pal line of displacement. Of course it can not be pos- 

 itively asserted now, in the absence of sedimentary 

 deposits in those districts, that the dikes of the Turkey 

 Creek and Nipple Mountain areas accompany lines or 

 zones of displacement ; bnt it is certainly a fair presump- 

 tion that they do, in view of the fact that they are, 

 apparently, in every other respect, identical in character 



