FENNER, THE WATCHUNG BASALT 105 



found in minute quantities at most in the normal basalt. These could 

 not have been formed by a simple rearrangement of the ingredients of the 

 primary minerals in contact with the circulating waters. • 



If the conditions under which the lava consolidated have been correctly 

 interpreted, it is not difficult to account for the relative concentration of 

 these latter ingredients. The elements which are in excess are those 

 which have often been observed as sublimates deposited in crevices in lava 

 flows. They differ from aqueous vapors in that the temperature of subli- 

 mation is high, and a relatively slight cooling causes deposition in the 

 solid form, often near the point of derivation. 



The elimination of vapors of B0O3 from consolidating lavas and their 

 deposition in crevices appear to be normal phenomena of volcanic activity. 

 Deville and Leblanc in their observations at Vulcano^^ found that gas 

 from one of the craters,, issuing at a temperature above the melting point 

 of lead and emitting flames, deposited boric acid. At the "soffionis" of 

 Tuscany, jets of steam carrying boric acid emerge from the ground. The 

 condensible vapors from the fumaroles oi Monte Cerboli contain boric 

 acid, together with ammonia and hydrogen sulphide. Borates are also 

 found in hot springs in numerous volcanic regions, — Northern Cali- 

 fornia, the Yellowstone Park, the Cordilleras of Coquimbo, Argentina,. 

 Tibet, on the sea of Azov and in other localities. Borates appear, indeed, 

 to be among the commonest volcanic sublimates.^^ 



A. von Groddeck^'' has reviewed the geological occurrence of boron 

 minerals and expresses the conviction that the borosilicates (tourmaline, 

 axinite, datolite, danburite) and water-free borates (rhodizite, jeremeje- 

 vite etc.,) with the exception of boracite, appear exclusively as autogenic 

 forms in eruptive, archean and metamorphic rocks ; and that in the whole 

 series of fossil-bearing strata, borosilicates which have been formed with- 

 out doubt in situ are wanting. By the latter, however, he doubtless did 

 not intend to exclude the effects of contact metamorphism by means of 

 vapors given off by an intruded eruptive, by which tourmaline is fre- 

 quently formed. He emphasizes the fact that axinite, danburite and 

 datolite are only crevice and druse minerals, and he considers that the 

 chief field of distribution of axinite and datolite is notably in basic erup- 

 tive rocks, hornblende schists, chlorite schists and green schists, in which 

 tourmaline almost not at all or only seldom appears. 



It is interesting to note, however, that at the contact of the diabase sill 

 which forms the Palisades along the Hudson, the arkose Newark shales' 



" F. W. Clarke : "Data o£ Geo-Chemistry," Bull. 330, U. S. Geol. Surv., p. 214, 1908. 

 18 A. Geikie: "Textbook of Geology," London, p. 269. 1903. 

 i» Zeitschr. deutsch. geol. Gesell., vol. 39, p. 253, 1887. 



