340 



GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



Analyses of shoshonites and transitional rocks. 



Constituent. 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 - 



11 



SiO-2 



50.06 



51.75 



53.49 



52.86 



52.49 



54.86 



56.05 



54.97 



50.99 



52.11 



53.71 



TiO-. 



.51 



.86 



.71 



1.04 



.81 



.69 



.98 



.97 



.67 



.53 



.74 



A1,0 3 .... 



17.00 



17.48 



17.19 



17.51 



17.89 



17.28 



19.70 



18.38 



15.62 



16.58 



18.00 



FejOs .... 



2.96 



6.42 



4.73 



5.18 



5.76 



4.08 



3.74 



3.06 



8.47 



3.66 



3.99 



FeO 



5.42 



1.46 



3.25 



3.31 



2.08 



2.28 



2.32 



4.22 



1.43 



4.99 



4.05 



MnO 



.11 



Trace. 



.14 



Trace. 



.09 



.19 



Trace. 



Trace. 



Trace. 



.23 



.24 





















.07 







BaO 







.06 

 4.42 



4.18 



.30 

 3.49 



.37 

 4.19 













MgO 



3.61 



4.05 



2.51 



2.38 



5.23 



6.87 



5.19 



CaO 



8.14 



8.20 



6.34 



6.51 



7.01 



5.42 



4.34 



5.43 



6.53 



6.43 



6.88 



LiiO 









.04 









.03 









Na^O 



3.53 



3.33 



3.23 



3.22 



3.18 



3.94 



3.29 



3.45 



3.39 



3.25 



3.50 



K 2 



3.40 



3.72 



3.86 



3.41 



3.73 



3.96 



4.44 



3 37 



3.05 



3.20 



3.10 



P^Oe 



.66 



.67 



.43 



.53 



.55 



.48 



.66 



.42 



.53 



.63 



.38 



CI 





Trace. 

 .17 





.16 

 .22 









Trace. 



.03 



2.92 



.82 









S0 3 

















COi 

















H 2 .. 



4.85 



2.26 



2.17 



1.76 



2.63 



2.16 



1.86 



3.87 



1.99 



.55 



100. 28 



100. 37 



100. 02 



99.93 



100. 01 



99. 90 



100. 14 



100. 45 



99.85 



100. 47 



100. 33 



1. Shoshonite, lava sheet, Lamar River, south of Bisoii Peak. Analyst, L. G. Eakius. (1131.) 



2. Shoshonite, lava flow, northeast hase of Sepulchre Mountain. Analyst, J. E. Whitfield. (379.) 



3. Shoshonite, lava sheet, southeast fork of Beaverdaiu Creek. Analyst, L. G. Eakins. (1647.) 



4. Shoshonite, lava sheet, southeast fork of Beaverdam Creek. Analyst, J. E. Whitfield. (1651.) 



5. Leucite-shoshonite, lava sheet, mountain east of Pyramid Peak. Analyst, L. G. Eakius. (1476.) 



6. Oliviue-free shoshonite, dike northeast of Indian Peak. Analyst, L. G. Eakins. (1316.) 



7. Shoshonite, lava sheet, Two Ocean Pass. Analyst, J. E. Whitfield. (1715.) 



8. Shoshonite, summit of Baldy Mountain, Bear Gulch, Montana. Analyst, J. E. Whitfield. 



9. (?) Hornblende-basalt, dike near head of Stinkingwater Canyon. (1462.) 



10. Orthoclase-bearing basalt, dike, ridge south of Hurricane Mesa. (1325.) 



11. Orthoclase-beariug gabbro, core, Hurricane Mesa, Crandall Basin. (1430.) 



The rock whose chemical composition is shown by the first analysis is 

 exposed as a snrficial lava flow at the base of Bison Peak on Lamar River 

 (1131). It is dark gray, with a waxy luster, and carries abundant pheno- 

 crysts of labradorite, augite, and olivine, and some small amygdules of 

 zeolite and calcite. In thin section it is holocrystalline, the groundmass 

 consisting of lath-shaped lime-soda feldspar and considerable orthoclase in 

 zones surrounding the plagioclase microlites and also in twinned prisms, 

 besides augite, magnetite, and a little serpentine. The phenocrysts of 

 labradorite are twinned, with very narrow lamella?. Those of augite and 



