92 ECONOMIC GEOLOGY 



synclinal folds with many faults that have the same general 

 direction as the axes of the fold. They do not coincide exactly 

 with them but pass into folds at their extremities. The folds are 

 nearly vertical on their western slope and less inclined on the east. 

 It is along the higher and steeper slope that the greatest amount 

 of fracturing has taken place. (Fig. 67.) 



Faults: The displacement in general has been toward the 

 east. The maximum upthrow in any one fault is recorded in the 



FIG. 66. View from the top of Carbonate Hill, Leadville, Colorado, 

 looking toward Iron Hill. The valley in center ground marks position of 

 the Iron fault. Shaft house is that of the Tucson shaft, and ridge in distance 

 fault scarp of Mosquito Range. (By permission of the Macmillan Company, 

 from Ries' Economic Geology.) 



Mosquito fault, measuring about 5000 ft. The mineral veins 

 themselves have been folded and faulted with the enclosing 

 sedimentary and eruptive rocks. This fact alone would prove 

 that the mineral deposition took place prior to the dynamic 

 movements that formed the Mosquito Range itself. (See Fig. 

 68.) 



Mode of Occurrence: The typical form of the Leadville de- 

 posits seem to be a contact sheet whose upper surface is the Lead- 



