334 
(5) They are of secondary origin, and represent the 
albitization of original microcline dyke-rocks, this 
albitization being accomplished by magmatic soda- 
rich solutions. 
(c) They represent the ‘‘end product" and final differ- 
entiate of the residual magma, and are therefore 
directly related to the potassic-aplites. 
a) Am immiscible phase of the liquid residual magma.— 
Daly,@) Grout,(22) and others have resorted to liquid immis- 
cibility to explain certain types of differentiation. 
mechanism is untenable, for homoge ock masses aboun 
in which all minerals herein concerned, viz., quartz, micro- 
cline, and albite, are associated in a wide ran f mixtures 
ed in a e 
t is to be noted here, however, that the objection raised by 
Bowen (233) that the formation of a monomineralic rock is 
generally impossible by liquid immiscibility, owing to the fact 
that this would necessitate its crystallization at its true melt- 
ing point——Á.e., far above the temperature of the magma, Sa 
for albite, 1100? C.—ienores the possibility, theoretically, 
of albite and a volatile mineralizer (e.g., water) separating 
as a liquid phase, in which case the reductio ad absurdum 
argument fails. ico 
(b) Albitization of original potassic rocks.—This ber 
immediately admits the albitites to beof secondary origin an 
the process of albitization to have been produced by magmatic 
. 
soda-rich solutions. 
suggest such a replacement. Both occurrence and texture are 
strongly against their derivation from original potassic-aplites. 
(c) The albitites represent the final differentiate or end 
product of the residual magma.—The writer is of the opinion 
that the albitites represent the final differentiate of the residual 
magma. 
. The intimate relationship of the potassic-aplites and the 
_ albite-pegmatites is indicated by the presence, in each, of the 
Ge . @)R. A. Daly: Igneous Rocks and their Origin, p. 226. 
-. @)¥. F. Grout: Econ. Geol, 1918, p. 185. 
uc Bowen: Journ. Geol, Dec., 1915 (Supplement), 
