Reviews 



Mineral Deposits of the Santa Rita and Patagonia Mountains, 



Arizona. By Frank C. Schrader, with contributions by 



James M. Hill. U.S. Geol. Survey, Bull. 582, 1915. Pp. 



373, pis. 25. 



This report covers an area of some 1,400 square miles extending 



north and east from the city of Nogales, Arizona, on the Mexican border. 



The mountain groups are short, irregular ranges bordered by broad, 



sloping plains of Quaternary gravels. Mesozoic granite, quartz diorite, 



and quartz monzonite, granite porphyry and - aplite, with Tertiary 



andesite, rhyolite, and bedded tuffs and agglomerates, constitute the 



two groups of igneous rocks which outcrop over about two-thirds of the 



mountainous area. The remaining third is occupied by a thick sequence 



of Cretaceous (?) shales unconformably underlain by Carboniferous 



and Devonian limestones and older shales and quartzites. 



The chief mineralization in this area accompanied or followed the 

 Mesozoic intrusions. Silver, copper, gold, and lead are the leading 

 metals. Fissure veins, contact-metamorphic deposits, replacement 

 deposits, and gold placers are all of notable importance. Copper is the 

 most important metal in the contact deposits, while silver and lead 

 dominate in the replacement type, which is here rather carefully dis- 

 tinguished from the contact deposits proper. The average depth of 

 ground- water level and of the oxide zone is about 250 feet. 



C. W. T. 



Some Mining Districts in Northeastern California and Northwestern 



Nevada. By James M. Hill. U.S. Geol. Survey, Bull. 594, 



1915. Pp. 196, pis. 12. 



This is a report on a reconnaissance of nineteen widely scattered 



mining districts below first rank in present-day importance, sixteen of 



them in Nevada and three in California The chief value of the work 



will be to those who are specially interested in the development of one or 



more of these districts, though a number of points of general interest 



in economic geology are brought out. 



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