F. H. lahee — Metamorphism and Geological Structure. 447 



Art. XXIV. — Relations of the Degree of Metamorphism to 

 Geological Structure and to Acid Igneous Intrusion in the 

 Narragansett Basin, Rhode Island; by Frederick H. 

 Lahee. 



(Concluded from p. 372.) 

 Part III. 



Contents. 



Petrology of the post-Carboniferous rocks. 

 Basic intrusives. 

 Description. 



Eelations of the minette to the Carboniferous sediments. 

 Summary. 

 Acid intrusives. 



Introductory remarks. 

 General and theoretical considerations. 

 The granite phase. 

 Description. 



Eelations to the Carboniferous sediments. 

 The pegmatite phase. 

 Description. 

 Relations between the pegmatite phase and the granite 



phase. 

 Relations of the pegmatite phase to the Carboniferous 

 sediments. 

 The quartz vein phase. 

 Description. 



Relations between the quartz vein phase and the pegma- 

 tite phase. 

 Relations of the quartz vein phase to the Carboniferous 

 sediments. 

 Summary. 



Relations of the intrusion of the acid intrusives to the folding, 

 metamorphism, and schistosity of the Carboniferous 

 sediments. 

 Conclusions to the study of the acid intrusives. 

 Relations between the minette dikes and the acid intrusives. 

 Summary and conclusions. 



Petrology of the Post-Carboniferous Rocks. 



Post-Carboniferous rocks, intrusive into the sediments of 

 the Narragansett Basin, may be classified from a relative stand- 

 point as basic or acid. To the former category belong a few 

 minette dikes ; and to the latter, an extensive series of acid 

 intrusives ranging from granites, through pegmatites, to quartz 

 veins.* These we shall consider in the order named. 



* Occasional aplite stringers, belonging to this series, cut the granites, and 

 one or two have been seen to intersect the pegmatite. 



