Sort of like how we quest for oil now at remote parts of the earth but if we no longer needed fossil fuels we would lose over time our geoknowledge of deep sea oil fields if records were lost - and in the bronze age most records were orally remembered and passed down from captain to captain. In time they remained as only legends in the memory.
The need for rare tin during the bronze age made discoveries even of the Americas possibble by bronze age mariners - but when the iron age came about the dicoveries were lost as the need for tin was reduced.Hey, I think you're onto something, although I think it was the other way around -- as deposits were mined out, or access otherwise lost (for example, due to the climate cycle, or the fall of Carthage, or rising prices/barter rates) to the mines, or, as the energy costs fell (due to changes in the type or supply of fuel), iron superceded bronze (over a long period).
The ancient and extensive copper mining activity in the Great Lakes area is indicative of European/Middle Eastern activity as the copper trinkets that have been found at Indian sites are far too sparse to account for the thousands of tons of copper that was removed from those mines.