UNIVERSITY OF CALIFORNIA PUBLICATIONS 



BULLETIN OF THE DEPARTMENT OF 



GEOLOGY 



Vol. 8, No. 17, pp. 309-318, pis. 30-31 Issued December 5, 1914 



NOTES ON THE COPPER ORBS AT 

 ELY, NEVADA 



BY 



ALFEED E. WHITMAN 



CONTENTS 



PAGE 



Introduction 309 



The Ore-Porphyry 310 



Ore-Porphyry Intruded by a Later Monzonite-Porphyry 310 



Inclusions in Ore-Porphyry 311 



Alteration of Ore-Porphyry 311 



Deposition of Secondary Sulfids 312 



Loci of Greatest Alteration and Enrichment Coincident 313 



Precipitation of Sulfids above Water Table 315 



Quartz Blout 316 



Pyroclastic Dykes 317 



Conclusion 318 



INTEODUCTION 



In the summer of 1913 the writer spent several weeks studying 

 the geology of the porphyry-copper belt near Ely, Nevada. At that 

 time the most complete study of the geology available was the paper 

 by Professor A. C. Lawson, 1 for which the observations were made in 

 1904. The mining operations that have been carried on since then 

 have made it possible to observe several new points of interest. The 

 writer's attention being directed to the genetic relations of the ores, 

 the general geology of the district did not receive special attention. 

 The main features may, however, be briefly summarized. 



The oldest rocks are limestones and shales, probably of Devonian 

 age. Upon these rests a series of Carboniferous limestones. After 

 the deposition of these sediments, the region was subjected to com- 

 pression, which resulted in the production of gentle folds of a north- 



i Univ. Calif. Publ. Bull. Dept. Geo!., vol. 4, no. 14, pp. 287-357, May, 1906. 



