Gold Mining - Science topic

Of course...that is how scientific exploration works. Otherwise you have to keep re-inventing the wheel. The real question is not "type" but what you say about it. I attach a little "cartoon" I made regarding a major porphyry copper deposit in Chile. Having proposed a coherent geological mechanism involving a mine and a process...in this case copper bearing magmatism associated a proposed tectonic detachment feature, now I try to tie local deposits together. They may all be different types but they might fit into a larger process that you can use to predict or explain. You might find skarns here and dikes there or the remnants of a leakage pattern in a "fault" but they are part of a whole...assuming, of course the respective age dating allows it.

Magnetic surveys are principally used in mapping lithologies and structural zones of deformation. The latter are critical in providing pathways for hydrothermal fluids, particularly around dilation zones creating by reactivated or intersected faults. Magnetic surveys are therefore principally used to determine the structural deformation history of an area and pin point structural exploration targets. Additional geophysical techniques are then employed to determine the presence of sulphides which commonly are associated with gold. Of particular use are for example IP, ERT surveys and the in-phase component of EM Surveys.

Mercury pollution may be picked up by analyzing predatory fish at top of food chain. Mosquito fish (Ambrosia app.) have also been found to accumulate nitrogen. You might find added information from US National Mercury Lab. Wetlands in headwaters of black water streams have also been found to reduce mercury to toxic methyl mercury form.

As I thought...Anhydrite in Porphyry Au-Cu systems is really really good!

Take a look what we found by "accident" when we stopped relying on Google Earth Imagery for monitoring and paid money for some images. We found the strongly oxidized porphyry copper-gold porphyry at Milena Chile was being mined! Careful review of Google Earth image history files shows Google deleted the activity somehow. Sections of "orphaned" roadways are visible in Google Earth but pre-mining pixel arrays without ground disturbance were somehow spliced in.

Let that be a lesson.

As a result of acquiring independent imagery, significant economic gold was recognized as having been discovered and mined on what I have discussed above... a strongly oxidized Au-Cu porphyry. Based on its being mined...It is a fertile system....at least fertile enough to attract "illegal" placer gold miners.

So, in response to my original question..."... Anhydrite in Porphyry Coppers...just how good is anhydrite it really"? It is Great!

We can "chalk" this porphyry Au-Cu target up as a high gold copper porphyry on the basis of recent, apparently illegal, placer workings discovered by applying discoveries from drill hole work to surface work...and deducing anhydrite/gypsum washwater stains. We found it by simple remote sensing? Nobody told us we had an ongoing mine!

High resolution imagery of the porphyry system (below) shows someone got/removed/stole or otherwise high-graded enough placer gold off our concession to get shut down by local authorities apparently alerted by an environmental justice movement in our absence. That turns out to be a pretty good geological indicator....a good sign and a lesson for us to be there.

Attached is a blowup of work after Teck left the joint venture...that is...after they caused a significant political problem for us and not telling us at all. The image below shows what can only be placer wash plant heaps, obvious benches and work areas together with a "white" chalky smear from the wash plant. The full image attached below shows over a km of placer piles from mechanized operations and what appears to be an ore loading pad from surface scrapings. It also shows white stained runoff areas most likely wash-water full of anhydrite and gypsum that got away from their sedimentation retention pond area.

That means the Milena gold copper target has "economic" gold and probably lots of it. That's a bit of a surprise, Barrick missed it, Teck missed it...and sadly...so did I in my two days onsite.

The next question...can someone help me convert a good looking mining target to one that will focus not just on mineral production but on dedicating funds to provide water to the city of La Serena that would otherwise just dry up and evaporate in the hot sun?

The second image shows a comparison with mineralization at the other end of the Miocene belt...El Teniente. Smaller, older but same geometry, apparently the same latite and breccia pipe geology. Is Milena an mini El-Teniente?

The last image shows the full extent of mineralization. We need it to fund a snow-water storage and meltwater production facility to La Serena. That will be my next project...stay tuned.

I can only say that at least in our case, Anhydrite is a pathfinder to gold...follow the white stains to where the gold was and probably still is.

Dear Paula, please have a look at the attached papers and references therein. Kind regards, Daniel

Based on my general understanding and opinion only, artisanal and small scale gold mining stake holders are exposed to both noise and mercury pollution at the same time. However, the impact of both kinds of pollution on their bodies depends directly on the techniques being used. For example, a low noise, low mercury way of mining gold would impact less than a high noise, high mercury technique. Note that the impacts are different, as the chemical effects of mercury poisoning are very different to the more physical and potentially psycological effects of noise pollution. Unfortunately, I do not know any literature that explores this coincidence explicitly.

Please take a look at this useful RG link for insights.

Dear Anouar,

Thank you for your interest in my project.

In my project I have just considered Truck-Shovel and IPCC systems. Bucket wheel excavators are not included in the scope of my proejct. Nevertheless, it would be interesting if you can do such a comparison in your work.

Actually, this project is my Ph.D. thesis and I have to develop it alone. But still we can work in other frames e.g. papers for conferences, articles etc.

Best regards,

Hossein

Can I please ask you which type of markers can be used to be assure about the strain and spp.

Yes

Introducing policies that will help children; financially and also raising awareness

Hi Nursyasya,

In terms of the species I won't be much help, but if you look into the literature on phytomining, I'm sure someone will have an example of a tropical plant that is a good bioaccumulator of gold. 

With regard to the analysis you have plenty of options, particularly with the low detection limits of ICP-MS. Firstly the soil - this depends on whether a significant proportion of your gold is associated with silicates, if not then it's relatively simple. Make sure your sample is dry, then digest the soil sample in aqua regia (3 parts conc HCl, 1 part conc HNO3) with a solid to liquid ratio of no more than 0.1. Due to the hazard involved in this stage, do this in small batches, generally a few grams in 50 mL depending on the expected content in the sample. Then filter and dilute the sample for analysis. Where you have silicate-associated gold, you may need to grind the sample significantly finer to release it. This is because silica phases will not dissolve to a significant extent in aqua regia.

The plant samples are most likely best dealt with by burning the plant matter and treating the ash as with the soil above. The issue here is trying to make the procedure reproducible so that you're experiments can be compared to each other. Therefore, you'll need the same part of the plant, with similar moisture contents, etc. The moisture is best removed by freeze drying to minimise potential plant decomposition during conventional drying. 

I'll add a caveat here that I'm by no means a biologist and so am happy to be corrected about my suggestion for the plant treatment.

If you need more detail or advice just ask. Good luck!

Cheers,

Laurence

Dear Mr. Maqadze,

you explicitly declined to know the classification of gold deposits but want to know how you can classify gold ore.

You can make a desctinction which is intergranular between between hard rock ore (gold ore minerals are intergrown with the gangue minerals) and soft rock ore (gold ore minerals are part of a loose modern placer mineral association or heavy mineral suite with no joint surface of minerals). The other one is intragranular. Visible gold can be spotted as a distinct mineral , whereas invisible gold is accommodated in the structure of certain host minerals such as pyrite or arsenopyrit, as inclusion or part of the lattice).

Best regards

H.G.Dill

The difference is probably in the formation of second phases while conducting heat treatments to the steel. For example for Mn-alloyed steel, usually, second phase will not be detected while in Mo based metal different second phases might appear.

The formation of second phases might have a significant effect on the mechanical properties and they can significantly reduce the steel's ductility.

Hi Hannelore,

Do you need information about the current situation of women as miners, or are you also looking for older literature of earlier times?

Are you looking solely for written records, or are you also interested in original photo documents? I have some interesting fotos in my mining postcard collection.

I can recommend a German book that deals specifically with women's mining work in Bolivia (see attached the scans from the front cover, the ISBN number and the back cover).

Best regards,

Guenter

My research focuses on the recent history of the (small-scale) gold mining sector in Tanzania. There is a little section on this in "Just picking up stones: Gender and technology in a small-scale gold mining site."

Dear Pouria,

here is a link that reviews the techniques for exploring gold placers

and also two doc. that overview different methods for placer exploration in general

Hope these informations will be useful for you

Kind Regards, Anicet

Dear colleagues--

Many thanks for your interest in my mining book project and your many helpful suggestions and offers of help.  I don't know if Research Gate has a protocol for one-to-one communication, but I should be able to find most of you with a simple Web search.  (My own personal contact information is easily found by searching for Robert Healy, Duke University.

I think, however, that it may also be worthwhile to share some of my reactions to comments with the group as a whole.  So here are some initial thoughts:

(1) I'm delighted to find some people with knowledge of Laurion/Lavrion.  It is one of two sites I have not yet visited.  The Laurion story is remarkable.  It provided the silver to build the Parthenon, and (as mentioned) the Athenian fleet.  Also, it is said that during the Peloponnesian War, 10,000 slaves escaped from the mine!

(2) I find that I can access a copy of Dr. Ghorbani's very interesting book on Iran.  My book is limited by its case study/tourism approach so that I can't cover some extremely important mining locations (China and Egypt, for example).  But the narrative that links the case will deal with general history and I am well aware that many of the early mining techniques came from the Near East and Middle East before spreading to Western Europe.

(3) Of course I will deal with the Spanish mines in the New World, indeed important for Europe as well as the Americas.  Potosi is one of my case sites, and I will also discuss the silver mines of Mexico.  The mercury amalgamation process for freeing silver from its ore (based on the mercury at Almaden) was perfected at Real de Montes in Mexico.  And there is a very interesting 19th century connection between Cornwall and Mexico.  I probably won't say much about Brazil, but I'm very interested in the tourism aspect of Ouro Preto.

(4) Many thanks for the offer of photos.  I intend to use many illustrations in the book, though it is early to do more than make a file of key things that I find.

(5) Yes, the history of mining, especially for silver (and much later for uranium) in the Czech Republic is very important.  My conception of the Erzgebirge includes Joachimsthal/Jacymov.  Among other things, I MUST include Agricola (and also Johannes Mathesius,author of mining sermons and mining songs.)

(6) As you can perhaps infer from what I've written, my book will be for a general audience and will not be a work of original scholarship.  I find that there are tens of thousands of books on specific mines, minerals and countries, but virtually none that give the big picture over the long sweep of history.   I hope to correspond with several of you individually.  And I will post some of the material I've already written in case you wish to comment, or simply enjoy the amazing story of man's quest for metals over the millennia.

The method depends on quantity of clay in your ore and mode of it's occurrence.

First of all you may try attrition scrubbing the ore prior to milling, washing it in a perforated drum to remove clay from coarse crushed material. it will give you improvement in milling and flotation and increase flotation feed rate.

You may also use long cone cycloning on ground product if you have no gold/pyrite in fines. It will take most of the slimes out of the circuit.

To depress the clays in flotation you may try sodium silicate, sodium polyacrylate, starch, dextrin or other cellulose compounds using them before addition of collector and frother. NaSiO3 is probably the cheapest.

You can send us some samples to give you the most concrete solution.

#'Seun Sanuade: Thanks baba!

#Daniel: I appreciate.

#Raymond and Sagar: Thanks much.

#Andrzej: Thanks so much.

According to National Environmental Board, Pollution control Department, Thiland and Environmental Protection Agency-EPA (2012), the acceptable limit of cyanide level in the agricultural soil is about 40 mg CN- equivalent/Kg soil, 11 mg.kg CN- for inhabitant sites and 55.00 mg.Kg-1 for other industrial purposes. The maximum allowable CN-concentrations in uncontaminated soils used as fill material at regulated fill operations was fixed to 40 mg CN equivalent/Kg soil according EPA, 2012.

The following links are useful to know the concentration of total cyanide in various sites  

Oberthür, T. (1994)Editor Metallogenesis of Selected Gold Deposits in Africa. – Geol. Jb., Reihe D 100, 679 pp

Dear Mr. Jurkovic,

Our study of rare metals, including indium and thallium content in tailings of Bolivian lead-zinc-silver and gold deposits revealed the following range:

Thallium - 0 to 35 ppm (mean - 10 ppm)

Indium - 0 to 230 ppm (mean - 100 ppm)

Please compare the paper of Morteani, G., and Fuganti, A. (1988) The gold deposits of Bolivia - A genetic classification and economic consideration. Geological Society of Australia, Abstract Series, Vol. 23-1, 403-405.

The tailings consisted mainly of pyrite, quartz, and carbonates.

To find out to which mineral phases high thallium and indium contents are linked, the following sample groups were analyzed:

1) vein (lode) ore

2) run-of-mine ore

3) mineral concentrates

4) waste pile, tailings

In addition, the mineral concentrates were embedded in resin and polished cross sections were analyzed by electron microprobe (Cu, Fe, Pb, Sn, Zn, S, Ag, Au, Bi, Cd, Ga, Ge, In, Tl, Se, Te) ,

In the investigation of gold deposits should be noted:

Each of the hundreds of thousands of gold deposits is different!

No gold deposit coincides with another!

Best regards,

Guenter Grundmann

Depth prediction is tough.  The best we have accomplished to date is to understand the 'architecture' of a porphyry system based on mineralogy and rock type for each of its phases (i.e. hypogene, supergene etc.). Depending on the development of the system (temporal and spatial) each zone will be dimensionally different.  

Hi Mike:

I would be happy to carry on this discussion outside of the researchgate forum. If you go to my website: www.syngeneticgold.com, you will find several relevant links. In the Noranda-Malartic-Val d’Or corridor, there are many deposits that are clearly synvolcanic. The work of Dick Hutchinson and students addresses some of these and volcanic-hosted gold deposits in general. The Bousquet deposit is generally accepted as synvolcanic. The websites for Virginia Mines (Akasaba deposit); Alto (Destiny Project); Agnico-Eagle (Lapa Deposit) all contain good grade thickness plots from which you can deduct vent geometry. The Val d’Or-Cadillac-Larder Lake Break is a complex stratigraphic interval and not everywhere a fault with displacement and there are several different types of deposits within it. The talc schist in your Figure 2 looks like an altered komatiite and does not present a compelling case that the Pontiac group is faulted against the Piche Group (Legault & Rabeau). One of the most important papers for exploring for syngenetic mineralization is by Phil Thurston, John Ayer et al (2008) in Ec. Geol. They deal with correlative conformities and stratigraphic correlations between authochthonous panels that separate seven discrete volcanic stratigraphic episodes on the basis of groupings of numerous U-Pb zircon ages. Syngenetic concepts have been virtually expunged from the gold deposit literature by articulate epigeneticists. The arguments have been ongoing for 100 years or more, but as we learn more about modern sea-floor hydrothermal systems, we can better understand the Archean equivalents. Also a major breakthrough has come from understanding the role of “lamprophyres”, which is what has compelled me to persist with research on gold deposits. So, I hope syngenetic ideas will be revived again or at least seriously considered instead of continuing to being arbitrarily dismissed or ignored.

Thank you very much for your help, Sajjad.

we have frogs (genera Bombina, Bufo and Rana) calling in ponds heavily polluted with compounds used processing of Aluminium, but up to the present it was impossible to establish if the specimens exposed to the various substances used by the aluminium-factory are reproducing or not (respectively, if they are influenced or not by the substances)...

As Jan said,   X-rays of energy 50keV have a 1/e penetration depth into Au of 71 microns.

That is, mu for Au at 50 keV is 7.26 cm^2/gr.  For Other sources, see  the tables of Elam, Ravel, and Seiber:  http://dx.doi.org/10.1016/S0969-806X(01)00227-4, and available  from either https://github.com/XraySpectroscopy/XrayDB  or   https://github.com/xraypy/xraylarch   or https://github.com/bruceravel/demeter) or see https://github.com/tschoonj/xraylib/wiki.

With a density of 19.37 gr/cm^3,  that gives a mu = 7.26 * 19.37 cm^-1, and so a 1/mu depth of 0.0071 cm = 71 microns.

However, the escape depth for the Au Lalpha1 line (at 9.7 keV) would only be 4 microns, and for Au Lbeta1 line (at 11.4 keV) would only be 6 microns.  

 

 

 

 

 

 

 

First, gold has to be there; with separatable concentrations, with certain chemical mode of occurrence. The efficiency of cyanide to separate gold is influenced by the presence of other minerals like chalcocite (CuS), for example.

I have noticed a relationship of higher silver with the presence of organic matter in the host rocks or the basement (coal, black shale, bitumen, etc. reductants). Agree with Ulrich that it may be a function of oxygen fugacity and availability of a sulfur. Worth asking the question.

The minimum quantity of gold present in a mineral, for mining process to be economical depends on various factors, for example:

- If the mineral is located in deep underground or at opencast

- Gold content in the reservoir

- Reservoir size and volume

- Distance between the reservoir and the mineral processing plant

- Mineral beneficiation technology

Afterward you make a feasibility study and considers the previous examples in this study and other factors. Then, it is when you determine whether or not it is feasible its exploitation