ADDITIONAL COMMENTS ON THE GEOLOGY OF THE JUAN FERNANDEZ ISLANDS 83 



Table I. 

 Analyses of the rocks from the Juan Fernandez Islands. 



SiO, .... 

 TiO, . . . . 

 A 1,03 . . . . 

 Fe.O, ... 

 FeO .... 

 MnO . . . . 

 CaO . . . . 



BaO 



Mg-O . . . . 

 Na^O . . . . 



KjO 



PA .... 

 Cr,03 . . . , 



F 



CI 



S 



Masatierra (I — IV) 



Masafucra (V— VIII; 



I 



II 



III 



IV 



V 



VI 



VII 



46.08 

 348 



15.98 

 2.75 

 8.83 



0.23 

 10.54 



6.53 



3.61 



1.36 



0.32 



0.34 



0.05 



46.10 



3.80 



16.54 



5.48 



7.25 



0.24 

 10.64 



4.58 



2.94 

 0.88 

 0.30 



0.96 



0.37 



46,50 

 3-04 



13-34 

 5-34 

 6.71 



O.II 



10.04 



8.89 

 2.32 

 0.63 

 0.29 



1.63 

 1.39 



47.62 

 3-42 



16.24 

 474 

 7-14 

 0.18 



10.60 



4.41 

 2.60 

 0.68 

 0.36 



1.24 

 1.61 



46.51 



3-25 

 16.68 



4-30 

 8.17 

 0.18 

 8.85 



O.OI 



6.40 



2.80 

 0.36 

 0.46 



0.15 



0.08 



1.09 

 1.06 



43-37 

 1.03 

 8.48 

 2.91 



1 1. 00 

 0.13 

 5-03 



25-93 

 1-33 

 0.58 

 0.19 



0.08 

 trace 



0.19 



43-47 

 2.68 



17.30 

 6.87 

 7.09 

 0.07 

 6.09 



8.60 



2-53 

 0.74 

 0.27 

 0.13 



0.18 

 0.12 



3-36 



VIII 



63-43 

 0.28 



18.64 

 2.78 

 1.02 

 0.09 

 1.68 



1-38 

 6.77 

 3.82 

 0.18 



0.04 



O.OI 



0.24 

 100.35 



100.08 



100.23 



99.84 1 100.35 1 100.25 



99-48 



I. Olivine basalt (^dolerite). Masatierra, Bahia Cumberland. Raoult anal. 

 II. Olivine basalt. Masatierra, Bahia Cumberland. Raoult anal. 



III. Olivine basalt. Masatierra, Bahia (Cumberland. Raoult anal. 



IV. Aphyric basalt. Masatierra, Bahia Cumberland. Raoult anal. 



V. Feldspar phyric basalt. Elevation I 420 m. Masafuera. A.-M. Bystrom anal. 

 \'I. Picrite basalt (^Masafuerite, Oceanite^i dike rock. Masafuera. N. Sahlbom anal. 

 VII. Iddingsite-basalt. Elevation i 000 m. Masafuera. N. Sahlbom anal. 

 VIII. Soda trachyte. Elevation i 200 m. Masafuera. N. Sahlbom anal. 



Analyses I — IV have been made for A. Lacroix from specimens collec ed at Bahia Cumberland 

 by members of Dumont d'Urville's e.xpedition in 1854. These analyse:, were first published in 

 Lacroix' paper: Constitution lithologique des iles volcaniques de la Polyne'sie Australe in 1927. 



Analysis No. V is new, representing a sample of the abundant light grey feldspar basalts at 

 higher elevations on Masafuera. 



Analyses VI— VIII are produced from my earlier paper on the geology of the Juan Fernandez 

 Islands (No. 12). 



