CoLF — Contact-Thcnomcna af J}(ncfion of Liafi a))f/ Dolcvite, 61 



Various Kalksilicathornfclso," produced by contact-raotaraorph- 

 ism, have been described from time to time;^ and an interchange of 

 material with the adjacent igneous rock has been usually accepted to 

 account for the variety of minerals formed. The carbon dioxide seems 

 generally driven off and lost. 



More appropriate still is a comparison with the Cambrian lime- 

 stones of Skye, described by Harker,^ which have been invaded by 

 Cainozoic gabbro and granite. In one place in the gabbro area, and 

 at another in the granite area, a white bed of minutely granular 

 diopside has replaced a zone of the Cambrian marble. "Where chert 

 existed in the latter, as in connexion with sponge-remains, meta- 

 morphic silicates are now specially abundant. The crusts of sponges 

 have been replaced by tremolite, while diopside occurs within 

 them, in a granular aggregate of carbonates in which dolomite is 

 predominant. 



Fig. 2. 



Section of junction of fluidal olivine-basalt (darker mass) and Liassie 

 shale (lighter mass), small quarry, Portrush, showing the fusion 

 and intermingling that have gone on in places. The light- 

 coloured hand often seen along the actual contact-surface is formed 

 of minute granules of pyroxene, which also abound throughout 

 the altered shale. The basalt contains olivine and rods of felspar, 

 hut is very fine-grained, fluidal, and compact, x 15. 



At Portrush, where the basaltic magma has penetrated along the 

 bedding-planes of the calcareous shales in thin sheets, a centimetre 



^ E.g., Fr. Slavik, " Ueber einen Granathomfels von Predazzo," Centralhlatt 

 fiir Min., &c., 1904, p. 661. 



Tertiary Igneous Rocks of Skye," Mem. Geol. Survey of United Kingdom 

 (1904), pp. 146-7. 



