﻿244 



DR. A. HOLMES ON THE TERTIARY 



[vol. lxxii, 





A. 



B. 



C. 



D. 



E. 



SiO, 



48-82 



47-20 



46-36 



50-22 



49-43 



Al.,0, 



15-93 



15-29 



16-70 



16-20 



12-73 



Fe,0, 



7-18 



9-57 



7-53 



3-13 



5-06 



FeO 



6-63 



6-13 



6-23 



8-07 



8-47 



MgO 



6-02 



5-90 



5-84 



7-54 



6-96 



CaO 



8-67 



8-93 



9-77 



8-57 



8-59 



Na.,0 



3-29 



3-61 



3-22 



3-36 



3-50 



K,0 .... .« 



1-41 



0-85 



1-12 



1-38 



1-21 



H"0 



1-52 



1-12 



0-35 



0-22 



1-84 



CO, 











0'28 



TiO, 



0-83 



1-14 



1-88 



1-95 



2-26 



MnO 



0-32 









U'Uo 







0-46 



0-58 





0-49 



Totals 



100-62 



100-20 



99-58 



100-64 



100-90 



























A. Basalt, Sanhuti River, Mozambique (an. Holmes). 



B. Basalt, Philippi Lake, Kerguelen Island, South Indian Ocean. 



C. Basalt, Mount Drygalski, Heard Island, South Indian Ocean. 



D. Basalt, Glass, Cockburn Is., Louis-Philippe Land, Antarctica (an. Prior). 



E. Basalt, Yandina, Queensland (an. Jensen). 



The composition of the basalt is in no way abnormal, and can be 

 closely matched by that of other basalts from many other localities. 

 Some of these are cited above for comparison with the Sanhuti 

 example. The closest resemblance is found in the case of basalts 

 from the islands of the South Indian Ocean. 



XIII. Picrite-Basalt. (PL XX, fig. 5.) 



Overlying the phonolite, described above, is a nearly black 

 vesicular rock. Most of the vesicles are empty, but a few are 

 occupied by a powdery form of phillipsite. The refractive 

 index of the mineral is" T53, its double refraction is very, low, and 

 the cleavage is good. 



In thin section the minerals present and their relative proportions, 

 determined by the Eosiwal method, are as follows : — 



Minerals. Percentage by volume. 



„. f Titaniferous augite 21 



Phenocrysts| olivine u 



f Labradorite 

 ] Titaniferous 

 5 | Magnetite ai 

 ^Isotropic base 



', Titaniferous augite 



Ground - mass 1 Magnetite and ilmenite P° 



Total 100 



The rock is conspiciiously porphyritic, though augite alone is 

 represented in two generations. Olivine, in clear colourless 

 crystals, which have suffered some resorption but practically no 

 serpentinization, is present only as phenocrysts. Labradorite, 



