70 Transact20?is. 



It is evident from these figures that this altered rock is a kaoUiiized 

 variety of the normal lode-formation. The bleaching and the total removal 

 of pyrite are probably due to the secondary processes of descending surface 

 waters, accompanied by the formation of kaolin. 



Present mine-workings have not yet shown what factors regulate the 

 occurrence of the quartz blocks. It is probable, however, that they are 

 connected with some local structural features. The No. 1 block, for instance, 

 occurred where the two reefs junction. 



A common occurrence of gold in this and other veins of the district is 

 as fine " paint " coating the clay selvages. This is probably due to pro- 

 cesses of secondary enrichment, the clay partings acting as a filter to the 

 gold-bearing solutions. In other words, this seems to be an instance of 

 adsorption- — the process recently studied by Kohler.* 



Microscopically the quartz occurs in coarse granules, with patches of 

 fine-grained quartz studded with pyrite crystals. Such patches evidently 

 indicate portions where replacement has occurred. 



Other Veins. — The Invincible, fifteen miles up the Rees Valley from 

 Glenorchy ; the extensive group of veins round Macetown ; some veins 

 near Arrowtown ; and the BuUendale or Phoenix vein, up Skipper's Creek, 

 as well as other smaller veins in the Shotover Basin, all belong to this type, 

 and have the same characteristics. 



(3.) Veins of the Carrick Range. 



The northern flank of the Carrick Range, overlooking the Bamiockburn 

 Flat, is intersected by a complicated system of small veins, striking in various 

 directions. The country rock is a mica-schist of varying type, striking 

 north and south, and dipping to the east. The eastern flank of the range 

 is bounded by a well-marked fault, which passes near the veins and drags 

 down the schist with it, the rock along the fault-hne standing almost verti- 

 cally. 



The veins, which are irregular and considerably disturbed, vary in width 

 from 18 in. to 3 ft., and the filling consists of mullock or highly crushed 

 schist, impregnated with pyrite, and traversed by stringers of gold-bearing- 

 quartz. Ulrich referred the irregularities of the veins to disturbances caused 

 by the intrusion of supposed dykes of " hornstone-porphyry."t As I have 

 shown elsewhere,! these dykes do not exist, and both Hutton and Uhich 

 made a peculiar mistake in failing to identify the horny sihcified gossan 

 of some of the vein-outcrops. 



The map of the Carrick Range veins shows the interesting system the 

 individual members of which have been described in detail in Bulletin No. 5, 

 N.Z. Geological Survey. They fall naturally into four groups — the Cale- 

 donian, Carricktown, Young Australia, and Antimony groups. 



1. The Caledonian Group. — The veins of this group, the most northerly 

 of all, occupy a radiating group of fissures, varying in strike from north 

 and south to north-west and south-east. They dip at high angles. 



2. Carricktown Group. — These veins, which occur near old Carricktown, 

 also form a similar radiating group, opening out, however, towards the 

 north and west, whereas those of the Caledonian group spread out to the 

 south and east. 



* E. Kohler, " Zeitschrift fur Pi-aktische Geologic," 1903, p. 49. 



t Hutton and Ulrich, " Geology of Otago," 1875, p. 162. 



I Finlayson, " Notes on the Otago Schists," Trans. N.Z. Inst., 1907, p. 72. 



