44 
Rex T. Prider. 
The most outstanding featiiros of this atialysis are the low CaO and the 
considerable Na.O content which indicate that the felspar prior to meta- 
morphism was moderately rich in the albite molecule and that the rock was 
approa.ching a spilitic type. It certainly differs consideral)ly from the later 
quartz-dolerites which contain a much higher proportion of lime (see Table 
IV.). An unusual feature is Uie excess of alumina and the appearance of 
corundum in the norm — this excess of alumina is no doubt contained in the 
chlorite and its i)r(^sence may be due to slight contamination of the epidiorite 
by the aluminous slates which is has intruded. 
Pignrc i5. 
The basic inlnisives. 
A. Uralitised ({uartz dolerite, sliowing subopliitic relation of uralite and turbid 
])lagioclase (dotted), plates of leucoxene after ilmenite and angular 
areas of cud piiase quartz with rods of apatite. 
B. Albite epidiorite, showing clear laths of albite in a ground of biotite, uralitic 
ainpliibole and tiirlnd epidotic material. 
The field relations of Ibis rock are sliown in figure 4. Consideration 
was given, on a pre\'ious page, to the contact metamorpliism effected by 
this sill on the (hirdup sediments, and, in the develoiunent of chloritoid, it 
was considei'ed that tiu' jiost Cardup earth movements took jilaee shortly 
after the intrusion of the chlorite-alhite epidiorite. This rock then is a low 
grade ('pidiorite showing a grade of metnmorphism com})aral)le with that 
of the associated sediments. The (|uartz-dol(*rite group (to be described 
presently) appi'ars to belong to a lnt(‘r perital of intnxsion, as a niicro- 
porphyritie epidiorite (desci'ibed under (iii) below) which is considered to be 
genetically related to the (piartz-dolerites is intrusive into tlu‘ chlorite-alhite 
epidiorite'. 
(ii) Uralilised qi((irtz-(loIentes. 
bocks ot this grou}) form the bulk of the post Cardu}) infrusions and 
all are v(*ry unitoriu in character. Variations in granularity dependent on 
the position in the dyke are* noticeable but the mineralogical composition 
remains eoiistnnt with the exception that the end phase quartz and micro- 
pegmatite are somewhat more abundant in the central ])arts of the dykes 
than on the edges. 
