OLIVINE-BEARING QUARTZ-MONZONITE FROM KIANDRA. Dd) 
the St. David’s Head quartz-dolerites,’ there was a repulsion 
between the crystallizing pyroxene and felspar on the one 
hand, and the small minerals of early crystallization on the 
other, whereby these latter, which would ordinarily have 
become inclusions, were pushed outwards away from the 
other minerals, 
It is quite probable, however, that in the conditions 
existing during crystallization, possibly on account of the 
presence of mineralizers, the apatite and iron ore remained 
soluble until a fairly late stage in the consolidation. This 
late crystallization of apatite has been noticed not merely 
in the quartz-bearing basic rocks such as those described 
by Elsden, but in others in which water must have been 
present, such as the analcite-dolerite from Ourrabubula,’ 
and the so-called essexite from Prospect,? in both of which 
rocks a good deal of the apatite is found enclosed in the 
primary analcite. In this connection it is perhaps signifi- 
cant that the pegmatitic facies of basic intrusions, where 
such exist, may sometimes be rich in apatite and iron ore. 
Conclusion. 
The crystallization of this quartz-monzonite, then, 
epitomizes the course of crystallization of a large body of 
magma, and its differentiation into a series of rocks rang- 
ing from basic to acid, as pictured by Bowen in the paper 
already referred to, and as sometimes found in the field. 
In these cases the removal of the olivine has been accom- 
plished largely by sinking under gravity in the still liquid 
magma, whereas in the present instance the same result 
has been achieved through the enclosure of the olivine by 
pyroxene. 


1 Q.J.G.S., Vol. 64, 1908, p. 289. 
7 Proc. Linn. Soc. N.S.W., Vol. 45, 1920, p. 421. 
* This Journal, Vol. 45, 1911. 
