ORE DEPOSITS 



113 



HARRY SHAFT 



N 



EXPLANATION 



Rocks of the Franciscan 

 group 



Hilo. or narrow quartz- 

 dolomite vein, showing 

 dip 



Vertical hilo 



Intrusive contact, showing 

 dip 



Dashed where projected; scal- 

 loped on side of intrusive 

 rock 



Three compartment shaft 

 going above and below 

 level 



Geology and workings by U. S. Geological Survey 



KJf 



50 FEET 



DATUM IS MEAN SEA LEVEL 



FIGDEE 80. Map of a part of the 600 level of the Harry workings of the New Almaden mine showing an area of unmlnerallzed silica- 

 carbonate rock containing swarms of hilos adjacent to an intrusive contact. 



gin of the extensive serpentine sill shown by contours 

 in figure 81, (b) the ore bodies of the older part of 

 the Guadalupe mine (pis. 14, 15), and (c) the ore 

 bodies of the No. 3 vein in the Senator mine (pi. 14, 

 section B-B'). Many of these are localized by vari- 

 ous factors at particular places along the contact, 

 some chiefly by the intersection of swarms of hilos, a 

 few chiefly by the shape of the contact, and many 

 others apparently by a combination of the two. Ore 

 bodies localized by the intersection of hilos with steep 

 contacts are exemplified by the North and South Ran- 

 dol ore bodies of the New Almaden mine (pi. 4 and 

 fig. 93) and the ore bodies of the Senator mine (pis. 

 14, 15). Those controlled by the favorable shape of 

 the contact appear to develop largely where the con- 

 tact is relatively flat, for example, in the domal struc- 

 tures of the Velasco, Upper Pruyn, and Machine stopes 

 of the New Almaden mine (fig. 82). Ore bodies lo- 



calized along the crest of an inclined anticlinal arch 

 either with or without hilo fractures include the 

 Santa Eita, Santa Rita West, Victoria, Giant Powder 

 and Ponce, and the lower New World ore bodies (figs. 

 83, 84). The Harry ore body was localized along a 

 relatively flat terrace on an inclined contact, but its 

 geologic setting is further complicated by several over- 

 lying thin sills, which also are mineralized. 



Ore bodies with alta above and below 



A few of the ore bodies were localized in silica- 

 carbonate rock that replaced thin sill-like apophyses 

 of serpentine that diverged from larger masses. Where 

 such a body lay close to an ore body along the mar- 

 gin of the larger mass, the ore in both the apophysis 

 and the main mass was mined in a single stope. One 

 such composite body is the previously mentioned cen- 

 tral part of the Harry ore body in the New Almaden 

 mine. Where ore bodies were found in apophyses 



