All About Gold Mineralization (Part 3)
(Metamorphic quartzitic gold ore showing heavy iron (Fe) staining.)
Alteration is the Key
I mentioned some of the large-scale geological drivers that influence mineralization in my previous post on this topic. I also touched on the fact that both geophysical and geochemical factors influence precious metals mineralization to a great degree, and that similar elements tend to be found in close association in many instances.
The next key point to remember about gold mineralization is that its occurrence is much more likely if the original mineral deposits that preceded it were altered significantly over time. That alteration can be the result of geochemical changes (the addition or subtraction of certain chemical "building blocks") or significant geological agents such as high pressure and intense heat.
Change is Good
One rock classification that is very common in geology is metamorphic rock. This term (of and by itself) implies change or alteration and it's no wonder that many metamorphics here in the Western and Southwestern U.S have been big-time silver, gold, and copper producers.
(Old gold mine dug into metamorphic rock...in this case amphibolite is the host or "country" rock. Note the presence of iron "staining" in the soil and rock nearby.)
What you need to take away from this from a gold prospecting standpoint is simply this: when it comes to gold mineralization, change is good. So as a general rule, the greater the geochemical or geophysical changes over time, the better the chance for the formation of primary (lode or vein) gold deposits. Once again, that's why metamorphics can be good (but NOT the only) gold producers.
The Changes Never Stop
The sorts of geochemical and geophysical changes responsible for mineralization in general and for gold formation in particular are ongoing, 24-7, 365 days a year. So those changes and alterations I just discussed never stop.
(The presence of iron and other sulphides in this wall of metamorphic rock is a visual clue that literally screams mineralization.)
Does this mean that new primary gold deposits will eventually be formed here on earth? Perhaps...but that process of geological alteration of basic minerals into significant deposits of precious metals takes a very long time (millions of years in most instances) and we won't be around to witness it.
Where to Find Gold
That's it for now. I'll be back with more next time.
Best of luck to you.
If you liked this post, you may want to read: "Gold Mining Questions and Answers: Part 19"
(c) Jim Rocha (J.R.) 2012
Questions? E-mail me at firstname.lastname@example.org