380 THOMAS L. WATSON 



and are sharply defined from the groundmass feldspar. No marked 

 or definite orientation has been observed among the phenocrysts in 

 any of the areas, but in some of the exposures a shght tendency 

 toward such was indicated. Flow structure in the groundmass is 

 entirely absent from all of the areas studied. 



The porphyritic feldspars almost entirely fail in places, reappearing 

 again within a short distance in their usual abundance and of conspic- 

 uous development. Over most of the areas the probable average 

 ratio of phenocrysts to groundmass is approximately one to one, 

 though extreme variations from this ratio in either direction occur. 

 In the transitional phases of the rock where gradation from the 

 porphyritic to the even-granular texture is observed, the phenocrysts 

 are so few and are so widely scattered that the rock could hardly be 

 termed porphyritic. On the other hand, in the porphyritic granite 

 area three miles southwest of Concord, in Cabarrus county, the 

 rock is composed almost entirely of the large feldspar individuals 

 with very scant groundmass. In all cases the phenocrysts display 

 good cleavage development and twinning on the Carlsbad law. 



In many of the areas where outcrops of the fresh or moderately 

 fresh granite are few, the rock can be traced almost as readily by its 

 residual decay. The loose phenocrysts are scattered over the sur- 

 face in places in a partially altered condition, often split into smaller 

 fragments along the cleavage directions. 



Relations between the porphyritic and the even-granular granite in 

 the Mooresville area. — Like the other areas studied, the porphyritic 

 and non-porphyritic granite of the Mooresville area differ from each 

 other only in texture. Without going into detail descriptions of the 

 two texturally unlike rocks, evidence is afforded at several places to 

 the south and the southwest of Mooresville for regarding the one as 

 intrusive in the other, and they do not represent separate facies of the 

 same granite mass. Were the latter true, the line between the two 

 rocks should mark a transitional zone from the porphyritic to the non- 

 porphyritic granite, and not indicate in the few exposures examined a 

 sharp contact. Furthermore, certain phenomena along this line 

 would be difficult of explanation on this supposition. On the other 

 hand, the evidence strongly suggests that the porphyritic rock is the 

 oldest, and that the even-granular granite is intrusive in it. The field 



