BY W. H. BRYAN. B.SC. 155 



primary biotite has considerably increased. The chlorite 

 resulting from the decomposition of this mineral also tends 

 to make the rock abnormally dark. 



A matter which is closely connected with the phen- 

 omena of contact metamorphism is the presence of 

 fragments of the country rock in the invading magma. 

 Such inclusions though very rare have been found on 

 the edge of the large Enoggera mass. They are much 

 more numerous in the Green Hill Area, a good develop- 

 ment occurring in the creek bed in the south-east 

 part of portion 310, parish of Indooroopilly. Here 

 the granite near the actual contact contains numerous 

 inclusions of schist, or rather of a gneissose rock similar 

 to the altered schist in the neighbourhood of the contact. 

 The largest of these fragments measures only about one 

 foot in length. The edges of these inclusions show a slightly 

 darker band from 1.5 to 2 millimetres in thickness, other- 

 wise they are entirely unaltered, preserving a very definite 

 outline strongly contrasted against the enclosing granite, 

 and internally in no way different from the adjacent country 

 rock. The inclusions seem limited to a narrow zone at the 

 edge of the granite, none having been found in the more 

 central portions of the mass. In this connection, it is 

 interesting to note that Daly's Zone of Apophyses^ — that 

 belt ' more remote from the intrusive bod}' " than the 

 Zone of Inclusions and consisting of " country rock inter- 

 sected by more or less numerous apophyses from the main 

 igneous mass " is quite wanting, the contact of granite and 

 schist even in the neighbourhood of the inclusions being 

 quite regular. 



In considering the various changes outlined above, 

 there is one fact of observation which is highly interesting. 

 It is that the phenomena of metamorphism resulting' from 

 the intrusion of the large mass seem to be more widely spread 

 but less intense in character than those of the smaller Green 

 Hill mass. The chief change caused by the larger intrusion 

 was the alteration in the strike of the intruded rocks and 

 their general hardening. The more pronounced meta- 



1. The Mechanics of Igneou.s Intrusion (Second paper) Amer. Jrnl. of 

 Sci., Auffvist. 190.J. 



