BY H. I. JENSEN. 



623 



better applied to hypabyssal rocks of similar composition (see 

 Harker's Petrology). 



1. Trachy-andesite W. 1, 

 Warrumbungle Mts. 



2. Keratophyre. 3. Rhombenporphyr. 



Blankenburg, Harz. Norway. 



58-54 

 17-28 

 8-61 

 1-81 

 3-04 

 7-181 

 3 24 J 



10-42 



The above table illustrates the close relationship between the 

 keratophyre of Rosenhusch, Brogger's rhombenporphyr, and the 

 Warrumbungle trachy-andesites. 



A comparison of chemical compositions also shows that the 

 monzonoses W. 1 and W.221ie between the arfvedsonite trachytes 

 (W.16, W.38) and the sapphire basalt. If any rock in the 

 district can be regarded as representing the parent magma, the 

 trachy-andesite is the one. 



The following table illustrates how the trachy-andesite may be 

 regarded as occupying a position intermediate between the 

 corundum basalt and the arfvedsonite trachyte. 



The orthoclase basalt, W.67, also approximates in composition 

 to a mixture of a dolerite, like the one from Dingo Creek in the 

 Nandewar Mountains (N.17), with the monzonose W.l, thus — 



