FiNLAYSON. — Geology of the Rcejton Gold-vans. 97 



average width of from 2 ft. to 4 ft. It is probable that, as at Boatman's, 

 the values here have been improved by secondary enrichment. 



This is the most thriving portion of the district. The Big River mine is 

 undergoing vigorous development, and both mines promise to be good 

 dividend-payers for some time to come. 



Genesis of the Veins. 



The period of vein-formation probably followed closely on the intrusion 

 of the granite masses and the folding of the belt of slates. A zone of slate 

 was highly crushed and fractured (a shear-zone) along the axis of a synclinal 

 fold, and this gave access to thermal solutions, arising presumably as after- 

 effects of the granitic intrusions. 



The character and occurrence of the quartz, as well as the great loss of 

 material suffered by the altered rock, indicate that the quartz lenses which 

 comprise the workable portions of the veins are due largely to replacement 

 of rock and segregation of silica. Further, the manner in which the quartz 

 gradually peters out into the lode-formation also strongly suggests replace- 

 ment. 



McKay is inclined to believe that the period of vein-formation was prior 

 to the folding of the slates.* The evidence I have collected leads me, as 

 . I have stated, to the opposite conclusion. 



As regards the dip of the quartz blocks, this feature appears to have 

 originated as follows : When fissuring took place differential movement 

 between the w^alls of the fissures would be in a direction slightly inclined 

 to the vertical, if there was a combination of vertical gravitation forces 

 and more or less horizontal minor shearing-forces. Thus, where pressure 

 was greatest crusliing would presumably be concentrated along inclined 

 lines in the fissure-zone. Subsequently, wath the ascent of the mineralising 

 solutions, deposition and replacement w^ould naturally follow those lines 

 along which crushing and comminution of the rock had been most intense. 

 The fact that the dip of quartz blocks is practically the same throughout 

 the district, indicating a uniform direction of resultant movement, seems 

 to support this explanation, and it is also, I believe, applicable to explain 

 the similar dipping quartz shoots in the various groups of Otago veins 



History of Mining at Reefton. 



Quartz-mining at Reefton dates from 1870, when Anderson discovered 

 the Invincible line. Shiel the Ajax and Golden Fleece line, and Adam Smith 

 the appropriately named Wealth of Nations line. Boatman's and Rainy 

 Creek districts were prospected in 1872. and the Globe Mine was first opened 

 up in 1882. The poorest of these was the Rainy Creek, which has never 

 given good returns, although a good deal of desultory work has been done. 

 The various companies at Boatman's got high returns for some years, and 

 the best of them — the Welcome — has only just lately closed down. The 

 early workers had many difficulties to contend with, owing to the absence 

 of roads a)id tracks, but a good deal of work was done till about 1896. when 

 quartz-mining reached a low ebb. About this time Mr. David Ziman took 

 over a large number of claims on behalf of an English company, and formed 

 the Consolidated Goldfields of New Zealand (Limited), which held the 

 Wealth, Fleece, Welcome, Inkerman, and several others, as well as a large 



* A. McKay, " Geology of Reefton District," Reps. N.Z.G.S., 1882, p. 134. 

 4 — Trans. 



