124 REGINALD A. DALY 
to ordinary weathering or to the action of seepage waters. Possibly 
much of the alteration is due to magmatic water. Similarly the 
segregation of the Kiruna magnetite in a liquid phase was perhaps 
possible because that phase temporarily carried appreciable amounts 
of oxygen, water, or other gases. 
Whatever values these surmises may have, neither the field 
relations nor the microscopical petrography of a dunite or of the 
Kiruna magnetite seem to be compatible with the idea that either 
rock type is a “‘raft”’ of accumulated crystals. The writer believes, 
therefore, that it is wise to keep the hypothesis of liquid unmixing 
as still one of the competing explanations in these two cases also. 
Failure of sufficient allowance for magmatic assimilation —The 
difficulty of excluding syntexis as a significant general process may 
be illustrated from a field where Bowen himself has worked. In 
1910 he concluded that the granophyre at the roofs of several | 
diabasic sills in the Gowganda district, Ontario, is to be referred 
to the solution of the invaded sediments.t Later he wrote: 
This opinion was arrived at principally because of the difficulty of picturing 
any process of pure differentiation whereby a quartzose rock could be formed 
from basaltic magma. With this difficulty removed the writer has no hesita- 
tion in concluding that the granophyre and the micropegmatite interstices of 
the diabase were formed after the manner detailed in the present paper [frac- 
tional crystallization of pure basalt] and that interchange of material between 
the granophyre and the adinolized sediment was a subsidiary process contribut- 
ing to the soda-rich nature of the border phases.? 
Since rg10 Collins has studied the sills of the same district in 
detail, proving that granophyric (micropegmatitic or myrmekitic) 
material has resulted from the interaction of the diabasic magma 
and the invaded quartzite, etc. Though Collins is conservative in 
theorizing about the origin of the main granophyric bodies, his 
evidence agrees with the findings of Bayley, Lawson, and the writer 
at Pigeon Point, and with the first field impression of Bowen in 
Collins’ field. In view of the close analogy between granophyre 
and granite the agreement is significant. 
tN. L. Bowen, Jour. Geol., XVIII (10910), 658. 
2 Ibid., Suppl., XXIII (1915), 40. 
3 W. H. Collins, op. cit., pp. 60, 90. See especially the remarkable photograph 
mm PVA: 
