8i 



above the critical temperature carrying ferric iron, alumina 

 and silica and consisting mainly of water gas strongly 

 ionized. Epidote and garnet, etc., were formed, and 

 the magnetite was probably formed contemporaneously 

 with them. When the formation of the above was well 

 advanced the character of the solutions changed somewhat 

 and chalcopyrite, pyrite and hematite were deposited 

 in and along the numerous minute fissures and cavities 

 in the lime-silicates. Calcite and quartz were the last 

 to deposit and completely filled the remaining minute spaces. 

 In the absence of any direct evidence, as there are no 

 large bodies of igneous plutonic rock in contact with or 

 adjacent to the zone of contact metamorphism at present, 

 it is suggested that these zones were overlain by more 

 or less irregular and thick sheets of granitic rock and that 

 these were the cause of the metamorphism of the limestone 

 and the source of the mineral bearing solutions. The 

 circulation would thus be descending and laterally and 

 would account for the ore bodies terminating abruptly 

 at comparatively shallow depths either against jasperoid 

 or crystalline limestone. The age of the deposit is referred 

 to post-Jurassic or the period immediately following the 

 intrusions of the granodiorite batholith of the Boundary 

 district. The ore bodies suffered from erosion in the 

 early Tertiary and are overlain unconformably by Oligocene 

 sediments. 



Method of Mining. — The ore bodies are mined along 

 their outcrops by large open quarries or "glory holes" and 

 underground by a system of tunnels and shafts. Stoping 

 by the pillar and room method is used entirely below the 

 level of the "glory holes". The development work is based 

 on the information gained by extensive prospecting with 

 diamond drills. 



ANNOTATED GUIDE (Phoenix to Midway.) 



Miles and 

 Kilometres. 



117 m. Greenwood — Alt. 2 464 ft. (751 m.). Green- 



188 km. wood is situated in the valley of Boundary 



creek about four miles (6 • 4 km.) west of Phoenix. 



The valley at this point is deeply eroded in 



granodiorite which underlies and surrounds 



36425—6 



