552 W. N. BENSON. 



Essexite, it may be here noted, occurs in sills at Jellore, 

 intruding Permo-Carboniferous and Triassic rocks, and 

 associated with picrite, corresponding apparently to the 

 gabbro poor in felspar of tliis paper. 1 Bssexitic rocks also 

 occur in the igneous series at the Nandewar Mountains. 2 

 The dolerite inclusions in the basalt might easily have con- 

 solidated in dykes from such a magma as now forms the 

 basalt. Further, the various types of alteration which 

 have modified the rocks of the plutonic inclusions seem all 

 such as might have taken place while the rocks were in 

 their present position. Pressure has played an almost 

 negligible part in their metamorphism, hydration, carbon- 

 ation and silicification, a very important one. Flaser-and- 

 saussurite-gabbros or schistose serpentines, such as one 

 might expect on the margin of ancient basic batholiths 

 have not been found in the volcanic necks and dykes. The 

 trachytic and hyalopilitic basalts may be fragments from 

 Hows which are extensions of the Oambewarra volcanic 

 series, which is an earlier expression of the magma that 

 has given rise to the Sydney basalts/ 1 



It therefore seems most satisfactory to regard the in- 

 clusions of igneous rocks in the volcanic necks as homoeo- 

 genous. They seem in every way fragments of rock masses 

 not mere segregations. They, therefore, are to be classed 

 in the allomorphous group. The plutonic members of the 

 series of inclusions probably were part of a differentiated 

 crust to the magma reservoir from which the basalt has 

 arisen. In mineralogical composition the gabbros and 

 norites are homologous with the basalt, the peridotites 

 antilogous. As the anorthosites ami pyroxenites may be 

 considered as derived from the gabbros by splitting, they 

 may be classed as antilogous. The doleritic and basaltic 

 inclusions are distinctly homologous. 



' Taylor and Mawson, Proc. Koy. Soc X.S.W, 1903, p. 324. 

 * H. I. Jensen. 1'r..,-, Linn. >,..-. X.S.W., l'J07. p. 883. 



