Help Oroblanco

Non LDM treaure hunting and Old West history.
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RONN
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Help Oroblanco

Post by RONN »

Oroblanco - Sorry to be a pest, but a couple weeks or so ago you posted an excellent post on the various rocks and how they were formed found in the Superstitions, like Epithermal etc. I meant to make a copy of your post but.......well, could I please ask you to post that explanation of rocks again. It would be most appreciated. Many thanks.
Ronn
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Oroblanco
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Re: Help Oroblanco

Post by Oroblanco »

Hola amigo Ronn,
Muchas gracias for the very kind words, and no you are not pestering! In fact it is wise to learn some geology if a fellow wants to hunt for a lost mine even if only from an armchair as some of us do. I am not sure which post you are referring to as I get carried away very easily on the subject, but a real geologist wrote up an excellent article on the geology of the Superstitions that explains it far better than I could. <I am just a prospector, a student of geology not an expert> Here is a link to that article, written by Tom Kollenborn,; Tom has a degree in geology and knows the Superstition range very intimately.

http://www.superstitionmountain.info/ch ... 20_08.html

That whole argument over epithermal, mesothermal etc really was splitting hairs as all of those types of gold deposits are "hydrothermal" that is the gold was deposited in the host rock by extremely hot water solutions which carried the gold in a dissolved form there. Hydrothermal gold veins are the type prospectors usually look for, and are basically the gold-in-quartz we are all familiar with but there are other types not so easily recognized and which may have very low amounts of gold per ton, yet still be economically viable to mine profitably by modern methods like heap-leaching; some of the most productive gold mines operating today are of this type. Wiki has an explanation on this part of the puzzle, not the best but there are many resources online:

Lode gold deposits are generally high-grade, thin, vein and fault hosted. They are primarily made up of quartz veins also known as lodes or reefs, which contain either native gold or gold sulfides and tellurides. Lode gold deposits are usually hosted in basalt or in sediments known as turbidite, although when in faults, they may occupy intrusive igneous rocks such as granite.

Lode-gold deposits are intimately associated with orogeny and other plate collision events within geologic history. Most lode gold deposits sourced from metamorphic rocks because it is thought that the majority are formed by dehydration of basalt during metamorphism. The gold is transported up faults by hydrothermal waters and deposited when the water cools too much to retain gold in solution.

Intrusive related gold (Lang & Baker, 2001) is generally hosted in granites, porphyry or rarely dikes. Intrusive related gold usually also contains copper, and is often associated with tin and tungsten, and rarely molybdenum, antimony and uranium. Intrusive-related gold deposits rely on gold existing in the fluids associated with the magma (White, 2001), and the inevitable discharge of these hydrothermal fluids into the wall-rocks (Lowenstern, 2001). Skarn deposits are another manifestation of intrusive-related deposits.


Some types of "lode gold" deposits are really very ancient placers, which have solidified under pressure of overlying layers of rock into a solid rock, not different from conglomerate rocks and sandstones. Sometimes these ancient placers are very, very rich in gold though most often they do not have enough gold to make it worth trying to extract it. The famous Lost Cement mine was of this type, the ore looked like a reddish cement, shot through with loads of gold; similar type deposits were also found in the Black Hills around the famous Homestake mine and had ore that was even richer than the Lost Dutchman, so these ancient placers are well worth looking for.

I hope that helps a bit, there are some very knowledgeable folks among your fellow LDGM members here who can likely explain all of this more clearly, so you have a large 'pool' of knowledge and experience you can draw on. Our little disagreements on whether some ore is epithermal or hypothermal etc are just technicalities really and even the experts are often divided on how to classify any specific ore, so don't be surprised if we can't agree on that issue. I would be happy to try to answer any question you may have, and am sure many other members will likewise.
your friend,
Roy ~ 'Oroblanco'

<Just to make this post a bit more attractive>
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"We must find a way, or we will make one." --Hannibal Barca
RONN
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Re: Help Oroblanco

Post by RONN »

Roy - Oroblanco
Thank you so very much for answering my post re your article on geology. It was very much appreciated and I also clicked on the link and found a wealth of more information from Tom Kollenborn. Thanks again, and please know that I find your posts most interesting.
Ronn
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Oroblanco
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Re: Help Oroblanco

Post by Oroblanco »

Thank you for the very kind words amigo, and I very much enjoy your posts as well! I hope we can meet around the campfire some day, perhaps at a Dutch-hunters rendezvous.
your friend,
Oroblanco
"We must find a way, or we will make one." --Hannibal Barca
Joe Ribaudo
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Re: Help Oroblanco

Post by Joe Ribaudo »

Ronn & Roy,

The most reliable source for the history of the LDM and the Superstition Mountains is Tom Kollenborn. There are many posers in the LDM game, but Tom is not one of them. He has been there and done that. In addition to Tom's experiences, he has his father's history to draw on. It just don't get any better than that.

Take care,

Joe
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Re: Help Oroblanco

Post by Oroblanco »

Joe - now you may be shocked and insulted by this, but I have to agree with your post 100%!
:mrgreen: :D
"We must find a way, or we will make one." --Hannibal Barca
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