WARREN. ALKALI-GRANITES AND PORPHYRIES. 



303 



iOuf 



E3 Gr^nUt 

 l*--^! Oranite-Porph^ru, 

 H Ci>'^tad Phast ./ Ptrpht,ry 

 m A^orhijoUlc. 

 Bail Eni 1^ 



RatlUsrifike Hiil., 



itu.te '/x' - "Set '^oo(l■ 



Section through Rattlesnake and Wampatuck Hills, Blue Hills. 



This section, drawn approximately to scale, is taken through the eastern 

 and lower end of Wampatuck Hill and the central portion of Rattlesnake Hill 

 and is intended to illustrate the writer's conception of the relations existing 

 between the aporhyolite, contact-porphyry, granite-porphyry etc. The 

 actual width of the chilled contact zone immediately against the aporhyolite 

 is exaggerated in order to show it on this scale diagram. 



AC 





Ui 1 1 ++ -^ ^ +/^tv^v^2^^V4-^ + + :?: + + + + 



+ ^--4-+ + 



"V-^ I GyaniCe 



\'€^~\ Contact P/i&se jf Por/>^ y rif. 



00.. XenoZilAs. 



Section through the Aporhyolite-porphyry Contact East of Pine hill, 



West Quincy. 



This section, drawn approximately to scale, illustrates the relation, as woi'ked 

 out by the writer, existing between the aporhyolite, granite-porphyry etc. 

 along those portions of the contact between these rocks found at relatively 

 deeper levels than that shown in the Rattlesnake Hill section. Here the very 

 dense immediate contact rock is succeeded by a nari'ow zone of coarsely and 

 profusely porphyritic rock which in turn passes gradually, but rapidly, 

 through granite-porphyry into the porphyritic phase of the coarse granite. 

 Flow structures are strongly developed near the contact, and dark colored 

 xenoliths are found in the coarsely porphyritic phase and also in the granite- 

 porphyry and granite somewhat more distant fi-om the contact. 



