CHEMICAL ANALYSES OF ANDESITES. 



263 



Analyses of andesites from Sepulchre Mountain, 



Constituent. 



421 



471 



407 



386 



| SiO 



55. 83 

 1.05 



17.11 



4.07 



3.75 



None. 



7.40 



55.92 



.94 



17.70 



3.16 



4.48 



Trace. 



5.90 



56.61 

 .79 



13.62 



5.89 



2.60 



.35 



6.61 



.14 



5.48 



Trace. 



57. 17 

 1.03 



17. 25 



2.48 



4.31 



None. 



6.61 



TiO, 





FeO 



MnO 



GaO 



BaO 



MgO 



SrO . 



5.05 



4.34 



4.83 



Li,0 



None. 



2.94 



1.71 



.21 



Trace. 



None. 



.09 



4.08 



2.28 



.18 



Trace. 



None. 



Trace . 



3.44 



2.03 



.05 



Trace. 



Trace. 





3.13 



2.71 



.06 



(?) 



K„0 



p.,o, 



SO:, 



CI 



CO, 



None. 

 2.27 



H,0 



1.28 



1.42 



1.20 





100. 40 



100. 45 



100. 26 



100. 40 





These analyses are higher in magnesia and lime and a little lower in 

 alumina and alkalies. The rocks from which they were made are pyroxene- 

 andesite and hornblende-pyroxene-andesite, without mica or olivine. Their 

 coarsely crystalline equivalents at Electric Peak are pyroxene-andesite- 

 porphyry and ' pyroxene-mica-diorite. The rocks from which analyses 

 7 and 8 were made are orthoclase-gabbro-diorite. They consist of plagio- 

 clase with some orthoclase and a little quartz, much biotite, augite, hyper- 

 sthene, and magnetite, and a little hornblende, but no olivine. When 

 compared with the corresponding gTanular rocks at Electric Peak, they are 

 found to differ from them in having less hornblende and more augite and 

 hypersthene, with less quartz and considerable orthoclase. 



The next three analyses in the table (9, 10, 11) are slightly more 

 siliceous, and are all from intrusive bodies. They are similar to the pre- 

 vious analyses, but the ninth shows more alumina and less magnesia. This 

 rock is very coarse grained and feldspathic, and is a diorite facies of the 

 gabbro. The tenth is the fine-grained monzonite with the poikilitic ortho- 

 clase and little biotite, besides much augite, hypersthene, and magnetite, and 



