Faulting at Ballarat East. 347 



Effect of the crosscourses and other faults on the position of rich ore. 



Tlie change of value or dimensions of ore on crossing a fault 

 are in many cases directly due to the fact that the ore, where 

 first recovered, is not the part severed from tliat portion of the 

 lode at which the fault was met. At Ballarat East, however, the 

 actual veins lost are usually recoverable at no great difference of 

 level on the other side of a crosscourse. The difficulty in ascer- 

 taining the throw is often due to the large number of veins of 

 not very different character, and the fact that in working they 

 are soon removed. The correct correlation of rich and poor 

 portions in neighbouring fault blocks can only be made by taking 

 account of the actual movement. 



The indicator belt as at present known terminates abruptly at 

 Crosscourse No. 1, Black Hill. It seems unlikely that any rich 

 continuation on the surface could have so long escaped detection. 

 It may be that the faulting has brought up to the surface level a 

 poor portion of the indicator. [Some of the veins crossing the 

 indicator run from a slide on which may be a " main lode." 

 Such series of veins form oblique bands, and, if the slide is too far 

 from the indicator, may not reach it at all, though they may be 

 worked on other slates. Some of the unworked portions of the 

 indicator are due to this arrangement, and some very rich 

 specimens recently found at the North Woah Hawp Co. were 

 found where one of the.se slides crossed the indicator]. Another 

 explanation of its absence may be that strike faults, being 

 reversed faults, leave a gap in the indicator between certain levels. 

 If the fault and strata have almost the some strike a particular 

 bed or series of beds may be absent at the surface for a long 

 distance. 



Geometrical constrjictions to ascertain the trtie movement on the 

 fault., or to recover a lost lode, or other deposit, displaced by a fault. 

 In Figs. 1 to 4, supposed drawn on a horizontal plane : 

 Let ROF be the line of strike of the fault ; 



DO the line of strike of the lode on the side where already 



known ; 



RE the position of the lode on the other side of the fault ; 



01, RJ the projections on the horizontal plane of the lines 



of intersection of the two parts of the lode with the fault. 



[For convenience, the word "lode" will be used for the faulted 



deposit, except where some special case is referred to. The 



