724 W. N. Benson — Origin of Serpentine. 



copper ores, stated: "Processes of hydration, which 

 appear to have been concentrated chiefly in the neighbor- 

 hood of the belt of sulphides, and to have acted with 

 diminishing intensity towards the other side of intrusion, 

 have resulted in the serpentinization of the olivine rocks 

 with the exception of the residual mass which composes 

 the summit of Dun Mountain. Subsequent alterations, 

 due to dynamic agencies, have resulted in the develop- 

 ment of uralite, saussurite, and antigorite. ' ' Speaking 

 generally of the serpentines throughout New Zealand he 

 said : "It is noteworthy that the most highly serpentin- 

 ized occurrences are associated closely with evidences of 

 considerable solfataric action. Thus the sulphide zone at 

 Dun Mountain is perfectly serpentinized, and the serpen- 

 tines of the Hokitika area are likewise associated with 

 solfataric effects. Where such action has been wanting, as 

 around the dunite of Nelson and at Milford Sound, ser- 

 pentinization is absent, although the rocks have been 

 much crushed by pressure and movement. The study of 

 the processes of serpentinization strongly suggests that 

 hydrothermal action, during and following the intru- 

 sions, has been a potent factor of serpentinization. ' ' At 

 the same time it must be noted that this assumes the mag- 

 matic origin of the cupriferous solutions, which brings 

 in once more the vexed question of the relative importance 

 of magmatic solutions as compared with lateral secre- 

 tion in the production of ore bodies. While the magmatic 

 solutions are perhaps most generally credited with the 

 predominant role, there are strong opponents of this ; e. g. 

 Van Hise (1904, pp. 1043-1081 and numerous citations), 

 who, however, refers to a matter of particular interest 

 in this connection, namely the occurrence of high-grade 

 copper sulphide ores in the serpentinized peridotites of 

 Tuscany and Liguria, described by Lotti (1899), and held 

 by Vogt to be of indubitably magmatic origin (Vogt 

 1902). They were later described by Delkeskamp (1907). 

 Other occurrences of copper ores in serpentine are 

 noted by Weed and Beck. ( See under Lotti 1899. ) 



V. The Formation of Nephrite. 



The close association of nephrite with serpentine is 

 very often observed, and without doubt there is a genetic 

 connection. Though the writer has not studied in detail 

 the extensive literature on the formation of nephrite, a 



