BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 VOL. 33, PP. 231-254 MARCH 31, 1922 



AFTEK-KFFKCTS OF [GNEOUS INTRUSION J 



PRESIDENTIAL ADDRESS BY JAMES P. KEMP 



(Read before the Society December 2H, 1921) 



CONTENTS 



Page 



Development of microscopic petrography in the last fifty years 231 



After-effects of igneous intrusion 2:;2 



Frequency of the unexpected discovery of igneous rooks 2.'>.", 



Mineralizers remaining in crystallized igneous rocks 2:u 



Eviction of mineralizers from a crystallizing magma 235 



After-effects in crystallized igneous rocks 2.*;<; 



Reaction rims and related phenomena — deuterics 236 



Xenoliths, more or less digested 2.'57 



Orbicular granites 2.'i7 



Actual analyses of escaping gases at volcanic vents 238 



Kilauea, by Day and Shepherd 238 



Katmai, by Allen and Zies 239 



Compilations by F. C. Lincoln 239 



Comparison of effusive emissions with those of intrusive rocks 240 



Interpretation of Precambrian impregnated strata 241 



Contact zones, especially from limestones 24.*', 



Mineral veins 245 



Igneous after-effects 245 



Exaggerated estimates of meteoric ground-waters 240 



Magmatic emissions as producers of veins 247 



Water in solid solution in pitchstones 24S 



Conclusion 249 



References 250 



Development of microscopic Petrography ix the last fifty Years 



A backward look over the course of geologic thought and interest in 

 North America during the life of our Society, and perhaps for ten or 

 fifteen years earlier, brings into the foreground some striking features. 

 A span of years of this duration is not beyond the personal recollections 



1 Manuscript received by the Secretary of the Society January IT, 1922. 



(231) 



