342 GREAT serI'p:ntike belt of new south Wales, \ ii., 



quartzose dolerite* with zoned andesine-felspar. Larger bands 

 of fine-grained dolerite and spilite cross the valley north of 

 Wallaby Mountain and the hills to the east. 



Lj neons Bocks in the Transitional Zone — More complex than 

 these are the features of a series of igneous rocks which lie along 

 the zone of passage between the Eastern Series, the zone else- 

 where represented by the Serpentine Line. The most northerly 

 of these masses are the group of dolerites and spilites by the 

 Loomberah Bridge in Portion 56, which occupy the greater part 

 of the small spur east of Sandy Creek. A very good exposure 

 of the spilite is seen in the road-cutting on the east of the hill, 

 in which typical pillow-structure is exposed {see Plate xxxiii.). 

 The pillows are about two feet in diameter, and have generally 

 a number of vesicles, often filled with calcite, arranged in con- 

 centric rows within the pillow. The rock itself is greatly altered, 

 as described below (p. 365). For this reason, the pillow-lavas 

 are more like the pillow-lavas seen by the writer in Cornwall f 

 than any others in the Great Serpentine Belt(5, p.l31 ). The 

 dolerite which occurs on the west side of the spur is also greatly 

 altered. The original ophitic structure has been preserved in 

 spite of the mineralogical changes. Magnetite is the only 

 original mineral; the augite has become platey chlorite, and the 

 felspar has been changed either to a mass of calcite with a small 

 amount of albite; or to much-strained quartz or chalcedonj' with 

 chlorite, spherulitic if in large patches, and sometimes associated 

 with a little carbonate. The dolerite itself is sometimes slightly 

 vesicular. These sills of spilite and dolerite are separated by 

 banded jasperised cherts or highly siliceous cherts which dip 

 W.4''N. at 60° on the east side of the hill, but dip E. at 60° on 

 the west side of the hill. 



Southwards of these, in the eastern end of Portions bh and 

 54, and again on the boundary of 53 and 52, are further intru- 

 sive masses. Spilite occurs on either side of the hill of chert 

 and jasper in Portion 54, but further to the east keratophyres 

 are found. 



" See footnote to p. 364 

 t For description of these lavas, see (17). 



