708 W. N. Benson — Origin of Serpentine. 



this opinion. Other regions yield less definite evidence. 

 Thus the great continental block of Western Australia 

 is invaded near its center by the thoroughly serpentin- 

 ized rocks of Kalgoorli (Thomson 1913), Meetkathara 

 (Clarke 1916) and elsewhere, which were not very likely 

 to have been covered by more than a temporary extension 

 of later Paleozoic or Cretaceous seas, and there is no 

 proof that even these extended so far. The ultrabasic 

 rocks of New Caledonia (Card 1900, Glasser 1903, 1904), 

 New Zealand, and the Pyrenees (Bonney 1877, Lacroix 

 1890) though in geosynclinal regions, where intruded 

 during the late Mesozoic or early Tertiary orogenic 

 movement and have not certainly been flooded over by 

 the sea in subsequent periods. They are, as a rule, only 

 partly serpentinized. The peridotites of the Red Sea 

 Hills in S. E. Egypt are largely serpentinized, and it is 

 possible, though by no means certain, that they may have 

 been covered for a short time by the Cretaceous Sea 

 (Ball 1912). The ultrabasic rocks in the great conti- 

 nental block of South Africa, namely those associated 

 with the great norite dike of Rhodesia (Mennell 1910, 

 Zeally 1915), or the Bushveld Complex (Henderson 

 1898) have never been under the sea so far as can be 

 ascertained and are only partly hydrous. The peri- 

 dotites of Skye, which have probably not been covered 

 by sea-water, are almost anhydrous, though their intru- 

 sion has been followed by that of a series of magmas, 

 gabbro, and granite, which however, do not elsewhere 

 show much evidence of being greatly charged with mag- 

 matic water (Harker 1905). 



Steinmann (1905) suggested that "The problematical 

 process of serpentinization may be the result of the rapid 

 cooling of an extremely peridotitic magma in the 

 strongly cooled region below the sea, with the simulta- 

 neous introduction of sea-water under high pressure,' ' 

 an hypothesis suggested by the frequent association of 

 serpentines with deep-sea marine sediments, but which 

 can have no great bearing upon the development of ser- 

 pentine that occurs among the gneisses. 



If, however, we accept Holland's general statement of 

 the mode of occurrence as sufficiently accurate, it seems 

 possible that it has another significance from that which 

 he has ascribed to it. It may, perhaps, be stated as 

 follows : In those regions in which the intrusive masses 

 of peridotite have extended into the upper parts of the 



