128 K B. Junner: 



the rocks. According to Spurr, there are transitions between the- 

 propylitic and sericitic facies. According to Kirk,i the chloritic 

 and sericitic phases 'of the alteration of the Butte Granite merge- 

 into each other very gradually. Stelzner and Bergeat^ and Schu- 

 maclier^ consider the propylitisation of the Tertiary andesites of 

 TraUvSylvania to be independent of the vein solutions and much 

 earlier, and Finlayson^ comes to similar conclusions with respect tO' 

 the alteration of the andesites of the Hauraki goldfield. 



The author's study of the auriferous diorites of the Wood's Point 

 gold belt, and also of the related rock from Queenstown, has con- 

 vinced him that the regional propylitic alteration undergone 1)y 

 these rocks is independent of the vein solutions and that the effects 

 of the latter are superimposed upon the propylitisation. The- 

 propylitic alteration is regional, and no relation appears to exist 

 between tlie amounts of chlorite, epidote and pyrrhotite, and the 

 proximity t(j a vein fissure. These minerals are just as abundant 

 20 feet away from the vein fissure as they are two feet away from 

 it. Certainly no transition occurs between the two types of altera- 

 tion such as (Spurr has described at Tonapah.'' Furtlier, the 

 minerals developed in the propylitic facies are generally charac- 

 teristic of high temperature deposits. Both clilorite (Pennine) and 

 epidote are common in the crystalline schists, and contact meta- 

 morphic ore deposits, which are formed under considerable pressure 

 and at relatively high temperatures. The vein solutions w^ere 

 undoubtedly moderately strong alkaline charbonate and sulphide 

 solutions, and both the above minerals appear to be unstable in 

 the presence of such. 



Significance of Pyrrhotite. — Pyrrhotite is usually regarded as a 

 high temperature mineral. Its occurrence as a primary mineral in 

 certain basic rcoks, and its association with such undoubted high 

 temperature minerals as garnet and magnetite in contact meta- 

 morphic ore deposits, clearly support this view. At Queenstown, 

 small quantities of pyrrhotite occur distributed through the propy- 

 litised diorite. It is closely associated with the ilmenite and 

 leucoxene, and in places occurs disseminated through these minerals. 

 In one section, narrow parallel bars of ilmenite traverse an irre- 



1 " Conditions of Mineralisation in the Copper Veins at Butte, Montana." Economic Geology, 

 vol. vii., 1912. 



■2 "DieErzlagerstatten." 1905-1906. 



;{ Zeitschr, f. prakt. Geol., pp. 1-8:"), 1912. 



4 " Problems in the Geology of the Hauraki Ctoldfielils. New Zealand." Economic Geology, vol 

 iv., No. 7, 1909, 



.S Op. Cit. p. 210. 



