BY H. I. JENSEN. 499 



Further a close scrutiny of Part iv. of Mr. Andrews' great 

 work and especially of Mr. J. C. H. Mingaye's analyses, accom- 

 panying this paper, reveals the fact that many of the New 

 England granites possess higher alkalinity than usual in this 

 rock-type. Mr. Card's petrological notes also prove many to be 

 rich in sphene, hence titanium-bearing. A comparison with the 

 Bathurst sphene granite shows that they are richer in alkali 

 (especially soda) and titanium, though more closely allied to it 

 than to the rocks of the alkaline areas. This feature is of impor 

 tance when read in conjunction with the fact that Mr. Andrews 

 finds evidence of very considerable assimilation of Palaeozoic 

 sediments. 



The following comparison of analyses brings out this fact : — 



i. Porphyritic microgranite, 2 m. E. of Tenterfield : alaskose.* 

 ii. Blue granite, 2 m. E. of Tenterfield : toscanose.* 



iii. Post-granitie dyke, near Hopetoun Battery, Hillgrove : toscanose.* 



iv. Bathurst sphene granite.* 



v. Jellore trachyte, near Mittagong : toscanose (?) (D. Mawson). 



vi. Timor trachyte, Warrumbungles : phlegrose (H. I. Jensen). 





i. 



n. 



in. 



iv. 



v. 



vi. 



Si0 2 



7368 



65-36 



70-74 



66-69 



66-68 



65 90 



Ti0 2 



•16 



•36 



•37 



tr. 



•20 



•25 



A1 2 3 



15-06 



16-37 



14-71 



17 03 



1463 



16 74 



Fe 2 3 



•68 



1-80 



•33 



3-15 



2-18 



1*72 



FeO 



•54 



2-68 



2-43 



•69 



2-31 



1-99 



MgO 



•26 



1-81 



•89 



2-50 



•30 



•06 



CaO 



•54 



3-82 



1-88 



1-82 



1-88 



•09 



Na„0 



3 36 



3-40 



3-29 



1-21 



6-12 



6-35 



K 2 



5 45 



3-75 



407 



626 



402 



5-77 



From the geology of New South Wales we may infer that 

 Barrell's statement as to periods of elevation and of subsidence is 

 in general correct, but yet these periods were not strictly coinci- 

 dent over large areas. J. Barrell's scheme fails in our part of the 

 world in this respect, that large areas of Australia were, in 

 Triassic and Trias-Jura times, undergoing gentle subsidence, sub- 

 mergence and sedimentation, processes which, in many parts, 



* N.S.W. Mines Department. 



