Geology of Kennecott
simplified version
You definitely need to click this map to make sense of it.
What is important here is that we have an underlying level of unknown depth of Nicolai greenstone which is essentially barren of minerals. Above it is the Chitistone limestone. That is a dolomite which is the host rock for the copper veins which are mostly of chalcocite, chalcopyrite, malachite and azurite, with the chalcocite being the dominant mineral. The plane where the two join is known as the contact zone and it is very obvious because of a distinct change in color. The mine adits were all located at the base of this contact zone as you can see from the map. The plane inclines at a roughly thirty-degree angle, which is what determined the angle of the various incline tunnels. Jumbo was 33 degrees. Bonanza was 30 degrees and Mother Lode was 26 degrees.
The large porphyry formation to the south is significant to the occurrences of such rich copper veins to the northwest, but is itself largely barren.
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