Geologist talking about underground resources detection
- Sep 10, 2019-
I've been looking for these things over a few decades and along with other geologists doing this we have seen how we find things change somewhat. Many methods used a century ago are still in use, but with the addition of refinements. So looking at how large and small deposits were found will change over time. (Simple example of that would be that Romans and their contemporaries didn't use geophysics, but they did find major copper deposits in Spain.) Deposits are getting harder to find. It has been estimated that "most major outcrops in the world have been visited by a competent geologist".
But I must admit, I spend enough time in remote locations to question the statement.
Give prospectors credit for going out and banging on rocks. I know this sounds simplistic but prospectors did develop good intuition about where to look even though they did not apply the genetic models we like to work with today. Ultimately, getting out in the field and seeing what you could find was key. There were also a lot of part time prospectors who were primarily out to hunt or trap.
It takes several rounds (or companies) to usually find a deposit. They are hard to find, and typically you run out of investment and luck before that happens. There are various estimates on how many tries it takes on average, but looking at prospective areas where there have been several in there before you is not a bad idea.
A third thing that can help is revisiting an area that was previously abandoned for a reason other than geology. This could be a small mine that lost its workers to natural disasters, wars or other economic conditions. The previous work may have stopped because the exploration was in the "too hard" category. This is good areas to revisit - particularly in improvements in technology have opened new geochemical or geophysical methods that can tip the balance from too hard.
I throw these three things into "how to find deposits" because even though they are not specific technical methods, they are very much the kind of things exploration geologists think about when selecting areas to use their resources.