It is cvident from these figures that this altered rock is a kaolinized
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 counceted with some local structural fcatures. 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 hy kobler.*
Microscopically the quartz occurs in coarse granules, with patches of fine- quartz studded with pyrite crystals. Such patches evidently indicate portions where replacement has occurred.
Other l'eins. The Invincible, fifteen miles up the Rees Valley from Glenorehy; the extensive group of reins round Macetown: some veins near Arrowtown; and the Bullendale or Phoenix vein, up Skipper's Creek, as well as other smaller veins in the Shotover Basin, al belong to this type, and have the same cliaracteristics.
(3.) Veins of the Carrick Roge.
The northern flank of the Carriek Range, overlooking the Bannockburn Flat, is intersected by a complicated system of small vcins, striking in various directions. The country toek is a mica-sehist of varying type, striking north and south, and dipping to the cast. The castern Hank of the range is bounded by a well-marked fault, which passos near the veins and drags down the schist with it, the rock along the fault-line standing almost vertically.
The veins, which are irregular and considerably clisturbed, vary in width from 18 in. to 3 ft., and the filling consists of mullock or highly crushed xchist, impregnated with pyrite, traversed by stringers of gold-bearing quartz. Ulrich referred the irregularities of the veins to disturbances caused by the intrusion of supposed dykes of " horustone-porphyry."+ As I have show elsewhere, these dykes do not exist, and both İ’utton and Ulrich made a peculiar mistake in failing to identify the horny silicified gossan of some of the vein-outcrops.
The map of the Carriek Range veins shows the interesting system tlie individual members of which have been described in detail in Bulletin No.5, N.Z. Geological Survey. They fall naturally into four groups-the Caledonian, 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 worth and south to north-west and south-east. They dip at high angles.
2. Carricktown Group.—These veins, which occur near old Carricktowi, 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 Praktische Geologie," 1903. p. 49.
flutton and Ulrics, * Geology of Otago," 1875, p. 162. Finlayson, "Notes on the Otago Schists," Trans, W.Z. Inst., 1907, p. 79.
