NO. 2005. MOUNT LYELL COPPER DISTRICT— GILBERT & POGUE. 611 



GEOLOGY. 



The geology of the Mount Lyell district is shown on the accom- 

 panying sketch map. A narrow belt of deeply dipping schistose 

 rocks is bordered on the east by an area of quartzitic conglomerates, 

 while to the west lies a sedimentary series of Silurian age, composed 

 of sandstones, quartzites, and clay slates with limestone intercala- 

 tions. The ore is confined to the schists, lying along their contact 

 with the conglomerate, which is marked by an important overthrust 

 fault. Igneous rocks, both acid and basic, are rather extensively 

 developed near the western coast of the island and approach in bulk 



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Sketch map of the Mount Lyell district. (Modified feom Geegoey. ) 



to within 1^ miles of the deposits; dikes of diabasic character come 

 nearer, though none are in contact with the ore. The region shows 

 signs of glaciation. 



The conglomerate is younger than the schists, containing inclusions 

 of the latter, and normally overlies them except near the mines, 

 where the relations are reversed by the overthrust fault. The for- 

 mation is predominantly reddish in color and is composed of rounded 

 to subangular pieces of quartz and quartzite, ranging from small 



