THE BEHAVIOR OF INCLUSIONS IN IGNEOUS MAGMAS 561 



magmas that has led Daly to adopt basaltic magma as his solvent. 

 Thus all of Daly's syntectics are of basaltic magma with various 

 types of foreign matter. We have already seen, however, that the 

 saturated condition is no bar to a reaction between magma and 

 inclusions. This fact is as true of intermediate magmas as of any 

 others and the same principles apply to them. 



If the foreign material belongs to an earlier stage of the reaction 

 series the tendency is to make it over into those phases with which 

 the magma is saturated and to precipitate a further amount of these 

 phases from the magma itself. If the foreign material belongs to a 

 later stage of the reaction series it tends to become a part of the 

 liquid by precipitating phases with which the magma is saturated. 



Sediments do not belong in the reaction series at all and certain 

 types of sediments contain material belonging in both the above 

 classes and both effects may be obtained. Our chief purpose here is 

 to consider principles, and it seems unnecessary, therefore, to dis- 

 cuss individually the action of various intermediate magmas on 

 various foreign inclusions. 



It is perhaps desirable, however, to discuss the action of granitic 

 magma on sediments, its action on igneous inclusions having already 

 been described. For the reason mentioned above, only saturated 

 granitic magma will be considered. Quartzites and slaty rocks offer 

 no special problem. They are readily transformed into phases with 

 which the granite is saturated, an action that any magma will 

 accomplish in so far as the composition of the sediment permits. 

 The conversion of inclusions of such rocks by granitic magma into 

 masses of quartz, feldspars, and micas, in varying proportions, 

 should therefore be the result. A certain amount of mechanical dis- 

 integration might cause the strewing about of these products in such 

 a way as to make them an integral part of the mass but there should 

 be no solution. Intermediate steps might see the formation of such 

 minerals as sillimanite, garnet, and others characteristic of contact 

 rocks, but these should be temporary or should survive only because 

 of exhaustion of the liquid. 



The kind of effect that sillimanite produces by reaction with 

 basic magmas, namely, the precipitation of orthopyroxene and basic 

 plagioclase is not to be expected in granitic magma. Rather should 



