606 GREAT SERPENTINE-BELT OF NEW SOUTH WALES^ V., 



base abuiKlantly charged with calcite, or a more coarsely granular 

 quartz-felspar mosaic, apparently greatly strained. It is, however, 

 just possible that the last two fragments are of altered sedimentary 

 rock. 



Rocks similar to these, but with rather smaller grainsize, form 

 the bulk of the Igneous Zone of the Middle Devonian, that sweeps 

 northwards to Moore Creek. They resemble the "Bowling Alley 

 breccias," of the earlier papers, with which they must assuredly be 

 correlated (16, p. 710-711). An example of these rocks, showing 

 a more diverse composition than usual, is illustrated in Plate liii., 

 fig. 6, which is from slide 1163, from a rock which accompanies 

 the porphjrritic spilites in Portion 48, Nemingha. It consists of 

 single crystals and rock-fragments. The former include quartz, 

 uralite, and acid felspar ; the latter range from spilites resembling 

 the base of the adjacent porphyritic spilite, to more crystalline 

 trachytic spilites, fine- and medium-grained keratophyres ; quartz- 

 keratophyre ; quartz-porphyrite ; and a soda-granophyre. In addi- 

 tion, there is a fragment of radiolarian mudstone. There is practi- 

 cally no groundmass. The metamorphic effect of the granites, 

 which are exposed within half a mile of here, is seen in the develop- 

 ment of abundant little flakes of secondary biotite in the fragments 

 of keratophyre. 



Other rocks in this zone differ from this in the presence of frag- 

 ments of dolerite, of more sedimentary rocks, and sometimes of 

 limestone, or in the presence of crystals of augite or magnetite In 

 others, again, more groundmass is present, generally finely divided 

 quartz, and felspar, with more or less chlorite. These are only differ- 

 ences of degree; no distinct varieties of pyroclastic rock can be 

 separated. In the most finely granular of these rocks, the frag- 

 ments are usually merely portions of single crystals, or of very 

 minutely crystalline keratophyre. They have often a more abun- 

 dant base of comminuted quartz and felspar, and, while they are 

 generally unstratified, bedding is at times very clearly marked. 

 Some of the pyroclastic rocks contain very well preserved radio- 

 laria(lO). The felspar is usually albite. In one instance only 

 has hypersthene been observed in these rocks. As a rule, the pre- 



