Wednesday, April 11, 2012

All About Gold Mineralization (Part 5)

(Vein of sulphide gold ore extending across and into the "country rock.")


Most Likely Precious Metals Deposits

As I outlined in my previous post, we should focus our gold prospecting efforts on geological areas that were created in lower heat and pressure environments in most instances. Why? Once again, these are the geological locales that are most likely to contain precious metals deposits, including gold.

Placer Gold Locations

The host or “country rock” that contains lower temperature mineralization is often substantially altered by the metallic geochemical solutions it encloses. For example, a gold vein high in iron sulphides or oxides may “stain” the host rock a rusty reddish color or actually weaken its structure to the point where it crumbles or breaks away quite easily.

 Silver and Gold

The more recent the volcanic activity in a given geologic zone, the farther most mineralized elements will travel from their source. This is due to the fact that water-soluble, metallic elements are more easily transported in solution and as they are moved farther away from their source the more they cool. Additionally, they become less influenced by high pressure.

 (Cinnabar ore showing its typical reddish, reddish-pink color. Note the presence of sulphides in the lower half of this specimen.)

This is where minerals like cinnabar (mercury) and stibnite (antimony sulphide) get deposited close to the surface. Most importantly, this is also the type of environment where metallic elements like silver and gold get deposited.

"Enrichment"

These mineralized lodes, veins, or stringers (veinlets) then become affected by air and moisture near the surface of the ground where they are deposited. This, in turn, creates more geochemical reactions in those mineralized elements causing further geochemical changes as sulphides are transformed into sulfates.

(Sulfate-enriched gold ore specimen from a shallow deposit. This sample also contains argentite, or silver sulphide.)

As this happens, some of those sulfates will sink downward and are either removed entirely or become enhanced…take your pick. When they are enhanced, the result is often significant “enrichment” of the metallic elements that are already present.

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No, we’re not done yet my friends. There’s more to come, so stay tuned.

If you liked this post, you may want to read: "Weight Measurements for Gold Miners"

© Jim Rocha (J.R.) 2012

Questions? E-mail me at jr872vt90@yahoo.com




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