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R. J. COLONY 



been similarly affected, with the production of acicular green horn- 

 blende. 



The action of end-stage emanation products on rocks which 

 igneous masses have invaded may be even more extensive and pro- 

 found. The extent and magnitude of these metamorphic changes 

 depend upon the character of the rocks intruded and upon the 

 quantity and quality of the emanation products themselves. 



Fig. 9 Fig. 10 



Fig. 9. — Photomicrograph of micropegmatite, Levak Siding, near Windy Lake, 

 Sudbury district, Ontario. Nicols crossed, magnification 20 diameters. Showing 

 coarsely micrographic intergrowths of end-stage crystallization. Actinolitic hornblende 

 in center, passing into chloritic aggregates. 



Fig. 10. — Photomicrograph of arkose, adjacent to the Palisades diabase, about 

 four miles south of Alpine. Nicols crossed, magnification 20 diameters. The 

 "detached," or slightly separated (not all of the grains are as distinctly separated as 

 here shown, however), and more or less reorganized and original clastic grains of 

 feldspar are shown set in a matrix of coarser unit grains of mosaic -like quartz. The 

 dark or black areas are quartz units in the position of extinction. 



All of the contact phenomena are directly related to the action 

 of magmatic end-stage emanations which produce a bewildering 

 series of silication, sericitization, chloritization, epidotization, 

 carbonatization, silicification, garnetization and metallic-mineraliza- 

 tion effects whose origin and significance were recognized long ago 

 by Lindgren, Kemp, Spurr, Berkey, and many others, and which 

 are beyond the scope of this paper to discuss. 



It has not been generally recognized, however, that such enor- 

 mous quantities of quartz and feldspar may be concentrated by the 



