96 



University of California Publications. 



[Geology 



tact strikes nearly east and west and dips south at rather a high 

 angle. The actual contact is a very irregular surface, for the 

 schists are badly broken and invaded in all directions by apo- 

 physes of the plutonic rock. (See pi. 19a). The intrusions into 

 the schists are of three kinds and probably of three ages. The 

 oldest are the small finger-like portions of the main mass of the 

 granodiorite. These are commonly more basic than the normal 

 facies. Next come large dike-like intrusions of an acid phase of 

 the granitic magma, pinkish in color and almost free from dark 

 constituents. Lastly come the pegmatite dikes, that cut all other 

 rocks. After the intrusion of the last, much further squeezing 

 occurred, the whole complex being more or less plastic. The re- 

 sult of this is seen in the folding of the pegmatite dikes. 



In the Lakeview cut much absorption of the schist by the 

 crystalline rock is evident. A number of fragments of the older 

 rock of the general shape of huge eggs were taken out by the 

 writer, and exhibit well-marked zones of metamorphism from out- 

 side to center. Also, schist fragments occur many feet from the 

 actual contact. (See pi. 19b). Nor is this all. The presence of 

 basic inclusions in the granodiorite has been noted. Both at 

 Lakeview and north of Carson actual schist fragments can be 

 traced into inclusions identical to the unaided eye with the basic 

 inclusions far distant from undoubted schist areas. It would 

 be unwarrantable to assume without careful petrographic study 

 the derivations from schist of many basic inclusions in the 

 granite, but there can be no doubt that some have this mode of 

 genesis. It is to be noted further, however, that frequently the 

 basic inclusions have a form entirely compatible with this idea, 

 the cross-sections showing uniform width with usually much 

 greater length. Some show the roughly rhombic outline of the 

 jointed schist blocks. 



At Lakeview Hill the schists above the contact are character- 

 ized by a great amount of lime-garnet and epidote. The whole 

 mass of the rock is frequently entirely composed of one or both 

 of these minerals. The three important contact minerals are 

 garnet, epidote and hornblende. North of Carson similar results 

 are evident, but in the altered andesites epidote is the chief con- 

 tact mineral, developed along cracks and seams. These seams also 



