258 



University of California Publications. 



[Geology 



quite abundant, and with it is a considerable amount of micro- 

 cline. Some little micrographic intergrowth is also recognizable. 

 Biotite and muscovite are present in subordinate proportions. 

 A catalastic zircon was noted included in a muscovite plate. 

 Magnetite and zircon constitute the accessories. The structure 

 is allotriomorphic granular. 



A less unequivocal case of contact metamorphism was found 

 west of the ridge. Here the quartz porphyry, in which the 

 original dihexahedral character of the quartzes is better pre- 

 served than ordinarily, contains a small amount of common 

 garnet. The garnet is completely isotropic: it possesses a "sieve 

 structure" and contains inclusions of quartz. This specimen 

 was taken 100 feet from the contact. The various other sheared 

 porphyries failed to show any traces of garnet. 



THE RELATION OF THE MINERAL KING BELT TO THE GRANITE. 



The relatively greater uplift of the southern portion of the 

 Sierra Nevada has long been recognized, and LeConte has pointed 

 out that the intensification of the erosive activities produced 

 thereby, has effected an almost complete denudation of the 

 irruptive granites. In the High Sierras a few small detached 

 areas and narrow belts of schistified rocks are all that remain of 

 the extensive roof under which the plutonic magmas cooled. 

 Such isolated remnantal patches are known to occur at Mount 

 Tallae, Mount Dana, Mammoth, and Mineral King. 



At Mount Dana and neighboring parts of the mountain 

 crest the stratified rocks can be seen resting in irruptive discord- 

 ance upon the more or less uneven surface of the granite and in 

 part sunk into it.* At Mineral King, however, the relations are 

 rather different. Examination shows that the schists instead 

 of reposing upon a batholitic surface, are embedded beneath the 

 general surface of the granite. They occupy a trough-like depres- 

 sion the bottom of which is not revealed, in spite of the fact 

 that the hypsometric range within this limited area is more than 

 6,000 feet. This resemblance to a trough-like character is ac- 

 centuated by the deep strike valleys which selective erosion has 

 * Prof. A. C. Lawson, oral communication. 



