204 ABNOLD AND STRONG — CRYSTALLINE ROCKS OF S^N GABRIEL 



The granites described are of the biotite variety and are found in the 

 central part of the chain. The granodiorites consist of two facies, a fine 

 grained hornblende-bearing variety from the Sierra Madre or southern 

 border range and a somewhat coarser grained variety, containing por- 

 phyritic orthoclase, from the central mass. These granodiorites differ 

 from those found in the Sierra Nevada of central California by being, on 

 the average, finer grained and having less quartz, titanite, and zircon. 

 Hornblendite, consisting mostly of hornblende, but also containing a 

 little plagioclase, is found throughout the whole area. Aplite is found 

 over the whole region, while micropegmatite was found only in the 

 vicinity of Pine flats. Quartz-hornblende-porphyrite and diabase por- 

 phyry occur in dikes in the southern range. Of the metamorphic rocks 

 hornblende-diorite-gneiss is by far the commonest. Together with some 

 biotite-granite-gneiss, it is associated with the granodiorites and quartz- 

 monzonites of the Sierra Madre. Hornblende-schist and garnetiferous 

 schist, found by the writers only in the southern range, complete the list 

 of crystalline rocks described. 



