Jackson generated a video on the title subject in 2018. This is the PDF version of the video (here).
"I’ll start with a general discussion of uranium its uses, production, resources and the main uranium ore minerals. Then I want to focus the bulk of the course on the types of Uranium Ore deposits, discussing as I go along how those deposit types are formed and how we go about exploring for them. Then I’ll course briefly about how Uranium deposits are mined and how the ore is treated to produce a final saleable product. As usual I’ll end up with a short list of critical take away points.
So let’s starts off with some background to Uranium and the Uranium mining industry. What makes Uranium a particularly economic importance is its radioactivity. Uranium decays through a series of reactions to form a number of new elements:
- Thorium
- Radium
- Radon
- Polonium
- Lead
At each of these steps it spins off alpha particles from the nucleus and produces energy. Uranium is not a rare element, it’s found in most rocks although it is more common in felsic rocks like granite than in mafic rocks like gabor. Granite in general contains about five parts of a million of uranium. This grade will be more than enough to form an economic deposit, if we dealing with gold but uranium need a lot of natural enrichment to reach economic grades.
Uranium’s average crustal abundance is 2.7 parts of a million which makes it twice as common as molybdenum or tin 40 times more abundant than silver and 500 times more abundant than gold but the lowest grade primary uranium deposits being mined today have about 100 times of this crustal abundance.
The highest grade deposits have about 5 million times this concentration. Uranium grades are usually expressed in terms of percent U3O8. The usual saleable end product is U3O8 or yellow cake as it’s commonly called. This contains approximately 85% of uranium by weight but uranium is an emotive product with its mental associations with past nuclear disasters, nuclear weapons and the fear of the invisible.
The ghost of Three Mile Island, Chernobyl and Fukushima loom large in public’s mind. Much of the future demand for uranium depends on this emotive factor. The war of words waged between those strongly in favor of nuclear power versus those passionately against it, however in the long run population pressure and the rising standards of living of Third World countries will force governments to rely heavily on nuclear energy to power their nations, in spite of Fukushima incident the number of new reactors being constructed is increasing.
Whereas there have been virtually no new nuclear reactors built in the US or Canada in the last 30 years, in fact four nuclear power stations were closed down in the first half of 2013 as of July 2013, the US has three in construction and another nine being planned. China by comparison has 28 under construction 43 more in the planning stage and 118 proposed, for Russia the same figures are 10 under construction 24 in planning and 20 proposed for India 7, 18 and 29. So these are large numbers of reactors and they are going to need uranium to power them so where are they going to get it all from.
Let’s look first at where the current suppliers are coming from. The top producers globally in order of the size of production are Kazakhstan, by far and away the biggest producer, Canada, Australia, Niger, Namibia, Russia, Uzbekistan, USA, China, Malawi and Ukraine. Looking ahead the list of defined world uranium resources is somewhat different. Canada stands head and shoulders above the rest of the world thanks largely to the Athabasca basin; it’s followed by Brazil, Uzbekistan, China, Kazakhstan, Ukraine and Niger.
Interestingly the Uranium that was used in the world’s first two atomic bombs was mined in the Congo DRC a country which doesn’t even feature on the current list of either producers or holders of resources. Uranium metal is the most unimpressive looking material, it’s a dull silver gray material it’s heavy with specific gravity of 18.7 almost the same as gold but unlike gold uranium metal never occurs in the elemental form in nature it’s always combined with other elements and these are some of the more common uranium minerals; Uraninite, including pitchblende is one of the most common ore minerals it has a black lustrous color and is an oxide of uranium, Brannerite another more complex oxide is also black although it may have a slightly yellowish tinge sometimes, Carnotite it’s complex but more common in uranium or mineral and is usually bright yellow or orange and is most common in secondary uranium deposits. Those where the uranium that are deposited by groundwater. Uranophane are hydrated calcium uranium silicate it’s yellow green in color but it will fluorescent bright green if you put it under a UV blacklight and finally Autunite a calcium uranium phosphate is also yellowish green in color.
Now let’s move on to the various deposit types that uranium occurs in. There are at least 14 different deposit types as you will probably have noticed some geologists are splitters but only six of these are really economically significant in global terms. These can be broadly grouped into two; primary deposits where the uranium is introduced with the original magma and secondary deposits where the uranium is dissolved by groundwater and then re-deposited on solution.
Most of the primary uranium deposits are associated with either IOCG – Iron oxide, copper, gold deposits or with mesothermal veins and pegmatite in other words deposited directly from magmas or by hydrothermal fluids derived from felsic rocks at intermediate depths. The first of these primary deposit types are IOCG’s virtually the only economic uranium deposit of this kind and type is BHP giant Olympic Dam deposit in South Australia. Although it is the only significant IOCG uranium mine, it produces almost 4000 tons of U3O8 per annum making it the second-largest producer in the world after MacArthur River which provides about 6% of global uranium production.
Olympic Dam has an incredibly low uranium grade of just 0.034% U3O8 and the only reason it can produce at this grade is that it’s primarily a copper producer and the uranium is just a fortunate by product. The resources of the Olympic Dam are a stunning 9.5 billion tons, there were plans to double the annual production but environmental and antinuclear protest have put these plans on the back burner for the time being. It is pretty old but I don’t think the model has changed much since 1995 when it was published. The genetic model calls for a mixing of cool, shallow saline oxidizing groundwater from within the basaltic volcanics, which are yellow in the section with hot deep more reduced magmatic water; blue in the section, the uranium is postulated to have been brought in with a shallow saline water and precipitated in the mixing zone due to reduction, as you will see this precipitation of the uranium from unoxidized fluid as a result of the reduction is a common theme in uranium deposits.
The top of the Olympic Dam mineralization is at a depth of 350 m below surface buried under transported cover and baring post mineral sediments. The mine is being operated as an underground mine since its inception. The new expansional core for the development of a super pit.
The mineralized rocks are quite impressive being full of red hematite, various green uranium minerals, blue bornite and black magnetite-pitchblende and brannerite. So if the Olympic Dam is hidden under 350 m of overburden and post mineral sediments; how do the explorations discover it and the other IOCG’s that are similarly buried? Geochemistry won’t work unless the deposit is at or close to the surface instead geophysics plays a dominant role, because IOCG deposits have several features that geophysical techniques can detect. If the deposit outcrops radio-metrics may work, however this is not the case in the Olympic Dam area but magnetics can detect the abundant magnetite that is often associated with IOCG’s.
Read on ................
Also see Uranium in Alberta, Canada (here).
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