BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



VOL. 27, PP. 193-234 JUNE 1, 1916 



HYPEESTHENE SYENITE AND EELATED EOCKS OF^Pfl^nian j^ 

 BLUE EIDGE EEGION, VIEGINIA 1 /^ 



% AUG 30 i9' 



BT THOMAS L. WATSON AND JUSTUS H. CLINE I r " v ' 



(Presented before the Society December 29, 191k) ^sff'Ofla/ MuS^ 



CONTENTS 



Page 



Introduction .-. 194 



Previous geologic work 196 



Quartz-bearing hypersthene-andesine syenite 197 



Distribution • 197 



Megascopic character 198 



Microscopic character 199 



Chemical composition and classification 202 



Comparison with quartz monzonite 204 



Origin and application of name 204 



Chemical composition 205 



Comparison with akerite 206 



Comparison with syenite (andesine anorthosite) of Nelson County, 



Virginia ■ 209 



Comparison with pyroxene syenite of the Adirondacks 212 



Comparison with charnockite 218 



Unakite type 220 



Origin of name 220 



Distribution and characteristics of unakite 220 



Origin of the unakite 222 



Zirconif erous epidosite • 223 



Granite. 223 



Norite 225 



General discussion of characteristics and distribution 225 



Megascopic character 226 



Microscopic character 227 



Ilmenite-apatite gabbro 228 



Chemical composition and classification 229 



Pyroxenite 231 



Distribution 231 



Microscopic character 231 



Chemical composition and classification 232 



Age relations 233 



1 Manuscript received by the Secretary of the Society December 6, 1915. 



XV — Boll. Geol. Soc. Am., Vol. 27, 1915 (193) 



