The Antwerp and Fowter Belt—Crosby. 241 
dioritic rocks - the Sudbury district, in those containing free 
quartz: 
In view ofall these considerations, it appears to me most 
probable that the chloritic rock or greenstone is a highly al- 
tered, basic eruptive; although I recognize that some facts 
point to its derivation from the granite, and especially that the 
disséminated granular quartz would find thus its readiest ex- 
planation. Again, a basic dike six miles or more in length ap- 
pears far more probable than a sharply defined and apparently 
persistent zone of granite showing such a radical and unusual 
transformation as the alternative hypothesis calls for, especially 
as such a zone of alteration, while unique, and on chemical 
lines, at least, highly improbable for the granite, is entirely 
normal for the dike. In other words, if the basic dike be 
granted, the development of the sulphides in it by magmatic 
segregation, the chloritization of the silicates while still at a 
great depth, and the subsequent development of the iron ore 
by the differential oxidation of the REET appear as entirely 
normal incidents of its history. 
I may add to this that some of my specimens from the Sterl- 
ing mine show sulphides, still unoxidized, disseminated in the 
slickensided chloritic rock precisely as in the dioryte of the 
Sudbury and Gap mines; and in this connection it is interest- 
ing to note, further, that according to Brooks* and several of 
the sections given by Emmons, tle normal position of the iron 
ore is, more or less distinctly, peripheral with reference to the 
chloritic rock, thus parallelling another important feature of 
the deposits having their origin in magmatic segregation. 
Since writing this paper, I have had an opportunity to 
study some of the auriferous veins of the new Michipicoten 
district of Ontario; and I was specially interested in an occur- 
rence on the southeast side of lake Wawa, where, during the 
alteration of a basic dike, the resulting chloritic matter has 
impregnated and saturated the bordering acid granite to such 
a degree that the latter rock is completely disguised, the gran- 
ite falling under the hammer into thin, angular fragments 
which are completely coated with the shining, black, chloritic 
glaze and being easily mistaken for a chloritized trap. Closer 
* Am. Jour, Sci., 3rd series, vol. iv, pp. 22-26. 
