252 Geology of 



CHAPTER IV. 



The G-keiss G-eanite Foemation. 



Peoceedeng now to give a short description of the several formations 

 according to their age, the first claiming our attention is the crys- 

 talline metamorphic formation, which, from the lowest visible rock, I 

 have named the " Gneiss -granite formation" — (No. 12 in the Geological 

 Map) . The greater portion of this formation is confined to "West- 

 land, and has been traced by me as far south as the Arawata river,* 

 without break, in a north-easterly direction to the eastern side o£ 

 Lake Brunner, where it enters the Nelson province. It consists of 

 gneiss-granite, always the lowest bed when visible, syenitic gneiss- 

 granite, laminated and protogene gneiss, mica schists in many varieties, 

 the latter often inter-stratified with gneissic schists. The mica schist 

 zone forms the central portion of the whole formation, where it often 

 assumes the character of graphite and talcose schists. It is followed 

 or overlaid by chlorite and hornblende schists, which may be said to 

 form the third zone, but here also mica schists are often inter-bedded. 

 The whole is capped by a quartzitic zone, divided into many beds by 

 the occasional occurrence of metamorphic schists, but they are not so 

 much altered, being merely micaceous, or chloritic schists. Of 

 accessory minerals, the gneissic schists often contain cyanite or 

 disthene ; the mica schists, chiastolite, actinolite and garnets; and the 

 chlorite schists, magnetic iron ore, often in large quantities. From 

 the latter, the black iron sands, found all along the coast and from 

 which so much gold has been extracted, are doubtless derived. 



* From information kindly furnished by Mr. G. Mueller, the Chief Surveyor of Westland, and 

 received sinee the Geological Map was printed, it appears that this belt, or at least a zone of igneoua 

 rock*, continues still further south, having been traced by Mr. Macfarlane, he Government Agent of 

 the special settlement of Jackson's Bay. It strikes in the direction of the McKerrow mountains. 





