A CONTRIBUTION TO THE GEOLOGY OF SOUTHERN MAINE 531 



THE PERSALANES. 



Grano-Lassenose. I. 4. 2. 4. (Granite.) Occurrence. — This 

 type was found in the form of dikes on Damariscove Island. 

 There were many of the dikes, some running with the strike, 

 some cutting across it at various angles. There was considerable 

 variation in coarseness of grain, and the borders of the dikes 

 were often pegmatitic. The schist was much contorted near the 

 contact and was full of quartz lenses. In fact the whole island 

 was thoroughly injected. Time did not allow of detailed map- 

 ping of these dikes. Specimens were collected of all that were 

 found and slides were studied. All of the dikes appeared to be 

 of essentially the same type, so one analysis only was made 

 of them. 



Table IV. 



Chemical Composition and Classification of Damariscove Lassenose. 







Molecular 



Norm. 









Proportions. 







Si0 2 



67-59 



1. 126 



Qu 



19.56 



Al 2 O s 



17.41 



.171 



Or 



15-59 



Fe 2 3 



•15 



.009 



Ab 



41.39 



FeO 



2.98 



.040 



An 



14.18 



MgO 



1.40 



■°3S 



Cor 



i-33 



CaO 



3-°5 



•054 



Hyp 



6.27 



Na 2 



4.89 



.079 



Mag 



2.09 



K 2 



2-59 



.028 



11m 



1.52 



H 2 + 



.18 





Ap 



•34 



H,0- 



.04 







- 



co 2 



none 









Ti0 2 



•83 



.010 







P 2 O s 



.19 



.OOI 







Total 



101.30 





On consulting Washington's tables ' it becomes evident that 

 lassenose is one of the commonest of rock types, hence a com- 

 parison with other regions would be futile. 



, Microscopic characters. — Microscopically the dikes are found 

 to be essentially alike, differing mainly in coarseness of grain. 

 They contain biotite, brown hornblende, a very little augite, 



iProf. Paper, 14., U. S. G. S. 



