CONTENTS. XVII 



Page. 

 Deacriptivo geology of Leaclville and vicinity — Continued. 



Fryer Hill 2.55 



Prospect Mountain 257 



Crest of the ridge 257 



Southern slope 258 



Little Evans anticline 259 



Yankee Hill anticline — Little Stray Horse syncliue — Big Evans anticline 260 



Area west of Carbonate and Fryer Hills 2()1 



General structure 2G1 



Easteru rim of basin 262 



VVestern rim 263 



Explanation of transverse sections 263 



Chapter VL 



Discussion of geological phenomena 276 



Sedimentary rocks 276 



Archean 276 



Paleozoic 277 



Dolomitic sediments 278 



Serpentine 281 



Origin of the serpentine 282 



Structural features 284 



Folds and faults • 284 



Hade of faults 287 



The one-sided orSshaped fold 290 



Eruptive rocks 292 



Age 293 



Manner of occurrence — Intrusive sheets 295 



Dikes 296 



Relation of form to composition 297 



Amount of intrusive force 298 



Source of intrusive force 299 



Why intrusive and not surface flows ? 300 



Internal structure 302 



Orthoelastic aud plagioclastic rocks 304 



Distribution of intrusive rocks in the Rocky Mountains 305 



Contact metamorphism 307 



Non-absorption of sedimentary rocks by eruptive masses - 308 



Appendix A, by Whitman Cross. 



PETROGRAPHY. 



Introduction 319 



Discussion of classification in general 319 



C'lassiPcation of Mosquito Range eruptives 322 



Older eruptives .' 323 



Quartz-Porphyry 323 



Mount Zion Porphyry 323 



White or Leadville Porphyry 324 



Pyritiferous Porphyry 326 



Mosquito Porphyry 327 



Lincoln Porphyry 328 



Gray Porphyry 330 



MON XII II 



