R. A. Daly — Secondary Origin of Certain Granites. 205 



logical changes. The metamorphism on the upper contact 

 extends outward for a distance of from 1000 to 1500 feet. 



There seems to be a decided lack of pneumatolytic action 

 (other than that due to water vapor) incident to the intrusion.* 



Coleman has concluded that the intrusion of the sheets 

 antedated the synclinal warping of the region to which the 

 present basin shape of the sheet is attributed. f 



The mineralogical compositions of the norite, intermediate 

 rock and micropegmatite-granite are summarized in Table I. 

 Their chemical compositions are entered in Table Y, taken 

 from Walker's paper, page 56. The corresponding specific 

 gravities also show the significant homologies existing between 

 these rocks and those of Pigeon Point and of the Moyie sill. 

 The value of a close study of these tables will appear in the 

 following general comparison of the rocks and of their rela- 

 tions to one another. 



Si0 2 



TiCX 



49-90$ 



1-47 



Al O „_ . 



16-32 



jL11 2 3 



Fe 2 3 



FeO 



MgO 



CaO 



13-54 



6*22 



6-58 



Na 2 



KO 



1-82 



2-25' 



h;o.._.. t . 



PO _ 



-76 



-17 



■*- 2 5 





Sp. gr 



99-03 

 3-026 



Table V. 









2 



3. 



4. 



5. 



51-52$ 



64-85$ 



69-27$ 



67-76$ 



1-39 







•78 



•46 



19-77 



11-44 



12-56 



14-00 



•47 



2-94 



2-89 







6-77 



6-02 



4-51 



5-18 



6-49 



1-60 



•91 



1-00 



8-16 



3-49 



1-44 



4-28 



2-66 



3-92 



3-12 



5-22 



•70 



3*02 



3-05 



1-19 



1-68 



•78 



•76 



1-01 



•10 



•24 



•06 



•19 



99-71 



98-30 



99-35 



100-29 



2-832 



2-788 



2-724 



2*709 



1 to 5 — "Specimens range from north to south" across the 

 Sudbury intrusive sheet, that is, from near lower contact (No. 1) 

 to near upper contact (No. 5). 



Synthetic Discussion. 



Magmatic Assimilation. — The secondary origin of granite 

 has long been maintained by N. H. Winchell, who has referred 

 to the Pigeon Point case as, among others, demonstrating the 

 fact.J Bayley came to the same belief for the granite and 

 granophyre of the point, but did not extend his argument in 

 detail to cover other occurrences among the Minnesota intru- 

 sives. On the other hand, the principle has not been accepted 



*A. E. Barlow, op. cit., p. 129. 



f 1903 report, p. 277. 



% Final Rep. Minn. Geol. Surv., vol. v, 1900, p. 62, etc. 



