INCLUSIONS 325 



less than 20 miles across, was nowhere observed without inclusions. The 

 inclusions are all of one type, being composed of the same minerals as the 

 matrix but with a larger percentage of mica and hornblende. They are 

 somewhat finer grained than the including rock and they contain small 

 phenocrysts of white feldspar. Similar phenocrysts occur in the matrix, 

 but are less conspicuous because the general color of the rock is paler. 

 A further characteristic of the inclusions is their small size. Ordinarily 

 they range from two or three inches to about a foot in greatest diameter, 

 and the largest seen is only three feet across. In a general way they 

 constitute the tenth or twentieth part of the mass (plate 45, figure 1), 

 but there are many belts and limited tracts where they are much more 

 abundant, and in some places they form more than half the rock (plate 45, 

 figure 2). When closely aggregated they do not touch one another, but 

 are always separated by selvages or interstitial fillets of the matrix. In 

 form they range from oval to angular, the angular individuals having 

 rounded corners. Where they are closely assembled they indent one an- 

 other in such manner as to indicate plasticity. Their boundaries are 

 definite in the sense that there is not a gradual transition from inclusion 

 to matrix, but are not sharply drawn like those of a pebble in a conglom- 

 erate. The inclusions do not separate from the matrix in weathering. 

 While the inclusions are all of one type, they differ in size of grain and 

 also to some extent in shade. Where they are closely aggregated, indi- 

 viduals of different shade and texture may be seen side by side. The 

 assemblages may be only a few feet or a few yards across or may be sev- 

 eral hundred feet in extent. Often they constitute belts traversing the 

 ordinary granite, and sometimes the belts show evidence of flowage, ill 

 inclusions being elongated parallel to the general direction of the belt 

 (plate 46). In extreme cases this elongation is carried so far that the 

 individual inclusions become difficult to trace and the general appearance 

 is that of banding, but there is no development of schistosity. 



Somewhat similar inclusions observed a little farther south by Knopf 

 and Thelen* are regarded by them as concretions. A concretionary ex- 

 planation of the inclusions of the Kings Eiver region would account for 

 their omnipresence, for their uniformly small size, and for the frequent 

 recurrence of the oval outline. It seems to be opposed by the dominance 

 of subangular outlines and by the uniformity in texture of each individual 

 in all its parts. There is no suggestion of concentric structure. While I 

 gave some consideration in the field to the possibility of concretionary 

 origin, the hypothesis more prominently in mind was that of fragmental 



*A. Knopf and P. Thelen, Sketch of the geology of Mineral King, California : Univ. 

 Cal. Pubs., Geology, vol. 4, pp. 236-239. 



