Exploring Iron Oxide Copper Gold Deposits
November 2017 by Chris Ralph
The excitement over IOCG deposits began with the discovery of a monster deposit at Olympic Dam in Australia in 1976. The discovery was accidental as the operator was searching for strata-bound copper deposits.
There were some exceptional times in the far-flung history of the West. Rich finds of minerals that set men’s souls ablaze. From the rich gold fields of California, men who arrived too late to find riches went searching in every direction. The trail that we will follow leads east, past the shining silver district of the Comstock Lode.
We have to remember that the earliest miners were not geologists, but came from a variety of backgrounds. Their survival depended on finding enough gold so they worked hard and adapted to whatever challenges these new areas presented.
While both zinc and lead deposits also are enriched by the surface weathering process, in part two we will look at the enrichment process for copper and also gold deposits, and at the interpretation of leached outcrops to figure how rich the concentrated deposits below them may be.
The actions of the hot, ore-bearing solutions are not limited only to the deposition of material within the walls of the fissures.
Most gold-bearing veins in this region are controlled by fractures associated with the Melones Fault, a late Cretaceous structure that is 108 to 127 million years old.
The specific gravity of chalcedony is 2.58 to 2.64. This is slightly lower than coarsely crystalline quartz because of slight porosity in chalcedony. Being so light, it will easily wash out of a gold pan.
There is reason to believe these stream valleys are still rich with gold, silver and copper.
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