FUSION AND ABSORPTION. 735 



instances giving evidence of subcrustal fusion, the granite cuts the horn- 

 blendic schist in a most intricate fashion. However, in most cases the con- 

 tacts between the two rocks are knife-like in their sharpness, and this is true 

 whether the granite dikes and veins are large or small. At one place a few 

 feet square the granite and schist are so confused as to make it possible that 

 the hornblende-schists were locally softened. The granite near the contact 

 contains numerous fragments of the schist. The hornblendic schist gener- 

 ally retains its typical texture and structure directly to the contact with the 

 granite. The phenomena are clearly those of complex intrusion, with no 

 evidence whatever that the granite has crystallized from the fused horn- 

 blendic schist. Similar phenomena were found at other localities cited by 

 Lawson as evidence of subcrustal fusion. 



This case has been dwelt upon because it is the one in America where 

 it has been most strongly claimed that immense masses of igneous rocks 

 have been produced by the fusion of older solidified rocks. The relations 

 seem to me, however, to be clearly those which are characteristic of great 

 batholithic intrusions in the rocks of the zone of anamorphism. 



Another instance where in America it has been claimed that fusion meta- 

 morphism has taken place on a great scale is that described by Emerson. 

 It is well known that in eastern Massachusetts there are numerous great 

 batholiths of granite intrusive in the Paleozoic strata. Concerning these 

 batholiths Emerson makes substantially the following statements: 



The Quincy granites of eastern Massachusetts do not alter the Cambrian schists 

 and do not absorb any material from them. Several other granite bands extending 

 across Worcester County contrast with the Quincy band in the following particu- 

 lars: They are often coarsely porphyritic, while the Quincy granites are not. They 

 are microcline granites. The Quincy granites are orthoclase granites. They contain 

 biotite, or biotite and muscovite instead of biotite and hornblende or glaucophaue. 



These granite batholiths are also contrasted with the Quincy rock in having a 

 broad peripheral layer, which has all the peculiarities of pegmatite in some cases, and 

 grades into black albitic granites, or even quartz-diorites. 



These differences are largely due to the fact that in the Worcester district the 

 granites have fused much of the surrounding schist into their composition. This 

 was proved by finding characteristic inclusions of the schist in great numbers and of 

 every size in the granite, and also by tracing these inclusions into smaller and smaller 

 filaments, until they faded from sight, and finding with the microscope far beyond 

 this point in the fresh granite clear traces of the schists. Where the schist contains 

 pyrite, garnet, fibrolite, cordierite, or graphite, the granite becomes more ferruginous 

 and garnetiferous. The amber coarse fibrolite of the schist appears dissolved and 



