COPPER. 



581 



era belt, it is at poiuts more or less broken by the north-south Texian cross- 

 trend that the ores are mainly apparent. The section (Fig. 63) gives a fair idea 

 of the general situation, although it is impossible to indicate all the compli- 

 cations of structure which are similar to those outlined in the figure, but 

 with less of localization of special features. 



Copper BUR NET/IN 



Fig. 63. 



Section from C to D on map (Plate XXI), crossing the Mason Copper Field transversely to 



the Burnetian Axis. 



In this belt there are three lines along which the indications of copper are 

 sufficient to justify further exploration. The carbonate ores show at surface 

 chiefly where the north-south Texian uplift is evident, and this restricts the 

 developments largely to the eastern half of Mason County, because in the 

 other areas the earlier or later strata exert the greater influence. In Llano 

 County the Pernandian and Burnetian systems cover the greater portion of 

 the middle belt, with comparatively few evidences of serious disturbance or 

 igneous irruption which can be assigned to the Texian Period. West of the 

 valley of Comanche Creek, in Mason County, this belt is covered deeply by 

 the Paleozoic rocks for the most part, and this feature even more effectually 

 obscures the Texian effects which may presumably have once been evident 

 in that region. Thus erosion, or possibly lack of deposition, in the east, and 

 subsequent sedimentation without adequate erosion in the west, have left a 

 more restricted area in which copper can be reasonably sought in the Mason 

 belt than in the case of the Llano-San Saba belt. 



The Northern Outcrops. — The exposures in the Mason belt lying in the 

 45— geol. 



