Uranium Deposits Under Central/Southern U.S.?
60-65 MILLION YEARS AGO
C ataclysmic volcanic activity that occurred approximately 60-65 million years ago resulted in what our geologists believe may be a significant uranium system underlying portions of western Kentucky, Tennessee and southeastern Missouri. The volcanism resulted in airborne ash containing minute amounts of uranium or it could have been river-borne ash from the Great Plains, fed by the ancestral Mississippi and Missouri rivers. In either case, the final resting area for the uranium-carrying ash coincides with the horseshoe-shaped pattern (see map below) comprising the geologic region called the Northern Mississippi Embayment.
Image: USGS, Northern Mississippi Embayment
TODAY
Gustavson Uranium Systems is in the process of examining historic mineral data from this area and drilling of test wells in varying locations and depths. Both uranium mining leases and options have been secured in areas favoring drilling targets. Appr oximately four areas form the core of the current exploration activity. Our initial work has focused on testing and understanding the various stacked sandstone and clay systems in the subsurface. The results provide us with a water quality baseline as well as with information about pathfinder elements for uranium such as selenium and molybdenum. We have also detected structural deformation (faulting), which may present traps for uranium mineralization. Sampling and analyses of the clay formation remaining from the original ash has revealed residual uranium content identical to the well-known Texas uranium systems. Therefore, our current plans call for $4 million in additional exploration work to test the most favorable targets and to identify areas with the highest probability for uranium.
Image: USGS
AN EXPLORATION APPROACH BROUGHT OVER FROM OIL & GAS EXPLORATION
This project is different from the conventional uranium mining venture in that the project follows the exploration approach frequently applied by oil companies in frontier regions. We provide here a description of the project with terms well known from the oil industry and which provides full disclosure about the project.
This project diverges in its early stages from the conventional uranium exploration venture (normally described on basis of an actual uranium discovery) in that:
1. a uranium discovery has not yet been made in this entire region although radioactivity and trace elements have been detected,
2. this project follows the exploration approach applied by oil companies by locating a source for the resource followed by search for traps , and
3. actual mining, if a commercial uranium deposit is delineated, will be conducted by In-Situ Recovery[1], only.
2 The Systems Approach
The similarity is evident after first considering a systematic oil or gas exploration project. There, the company geologists may identify
1) a source rock, which may undergo….
2) maturation (a chemical change), followed by….
3) migration of the liberated hydrocarbons, until entering….
4) a suitable trap, which may accumulate the hydrocarbons in....
5) a favorable reservoir rock.
These components, when all in evidence, are referred to as a complete petroleum system. Oil companies typically explore in virgin territories in those places, where as many as possible of the components are already recognized. The exploration then focuses on discovering the remaining components. Sometimes these are found, but sometimes they are lacking. That is the risk of exploration. Recently, the oil companies have seen great success in focusing on so-called resource plays in which the development is aimed at the source rock for resources of shale gas and shale oil.
This present uranium project is a true parallel, since Gustavson Uranium Systems is focusing on finding resources in areas where enormous amounts of potential uranium source rock are found. The source rock is the 60-65 million year old Porter's Creek clay in the Mississippi Embayment.
In this project there are also the necessary components, which together may comprise a uranium system[2]. There is 1) a source rock of 100-foot thickness. In the Missouri-Kentucky-Tennessee project area, the source rock was the mineral precursor to the present Porter's Creek clay, which is ubiquitous in the project area. The precursor mineral was a felsic (silica-rich), volcanic ash (also known as a tuff), which likely contained about 10 ppm of uranium, originally trapped in the glassy shards of the airborne tuff.
The ash was originally spewed into the air by volcanoes active in the 60-65 million year interval with locations still not determined. Some evidence suggest local sources associated with the ancient rift system deeply buried under the Mississippi Embayment; other evidence points to the volcanism experienced across the Great Plains as far west as the Yellowstone area with the fresh ashes being washed into to Embayment by precursors of the Missouri river systems. In any case the glassy material was slowly buried over the millions of years by sedimentation in the alternating coastal plain and shallow seas reaching far north from the Gulf of Mexico. This glassy source material was sandwiched between overlying and underlying sandstone formations.
In geologic time, 2) a chemical change or maturation took place, and the glassy dust decomposed into the present, thick clay formation. The Porter’s Creek clay is a well-known formation, fully mapped and described in geological literature[3], although its origin and its original uranium content have been generally glossed over until now. Our project has specifically studied and added that component to the geological knowledge of the overall uranium system. The Porter’s Creek clay became a source of uranium, most of which has been released.
The following section view [4] , looking north, shows the Porter's Creek clay underlie the horse shoe-shaped embayment. Together with other sedimentary beds the formation dips gently toward the axis of the Embayment and toward the South. The combination plunge is about 1/2 degree. That may seem small, but it is sufficient to create artesian wells in many of the water bearing sediments, where trapped by interfingering clay and shale.
 As a result of the chemical change (2) above, the uranium became mobile and was ready to migrate into the surrounding sands.
Migration, the third component, took place whenever the liberated uranium could enter any adjacent water passage as long as the water therein was rich in oxygen. It is a chemical fact that uranium is soluble in oxygen-rich water. In our case, numerous rivers and streams carrying oxygen-rich groundwater surrounded and penetrated the Porter’s Creek clay during the lengthy decomposition process. Some of these deep sands and ancient aquifers have been mapped within the project area, but their morphology during the historic migration remains to be mapped in detail upon high-density well drilling.
These ancient and deep-lying aquifers are generally sands with excellent characteristics as potential reservoir rocks, upon the grains of which uranium minerals may form a coating, when trapped.
The entrapment may be created by a barrier of chemical nature, because uranium will be precipitated out of the watery solution as the water becomes anoxic (oxygen-poor). It is a chemical fact that uranium is insoluble in oxygen-poor water. Consequently, uranium traps exist in those places, where oxygen in the water has been removed. The oxygen may have been used up by admix of reducing agents such as pyrite or buried organic material or from methane gas and hydrogen sulfide gas leaking up along faults from even deeper-lying shales.
When reaching such anoxic conditions in the ancient groundwater environment, the uranium would precipitate out and form so-called roll front deposits. These are shaped as winding elongate rolls, which can snake along many hundreds of feet in length.
The general components of the uranium system are well known from South Texas, which has given the name to this type of sedimentary uranium deposit. The Texas deposits have been commercially mined, and are being mined again today. Mining is now focused on the In-Situ Recovery method, reminiscent of the water-flooding of oil fields.
A rich literature base is available about the South Texas uranium systems and about how the individual components can be determined.
Our new work therefore commenced in November 2007 with a regional study along the entire Gulf Coast Geological Province to identify new locations, which appeared to be similar to the South Texas uranium districts. We found a number of candidates including the project area in Southeastern Missouri, Western Kentucky and Tennessee. In the age of Paleocene volcanic eruptions this area was located along the Mississippi Embayment trough, which with changing sea levels brought the Gulf of Mexico coastal plain this far north [5]. Varying sea levels caused a frequently changing environment of fluvial to shallow marine upon which the Porter's Creek clay was deposited.
Our original exploration locations were filtered against the five criteria for South Texas-type of uranium systems. The current project area appears to meet all criteria for 1) a source, 2) chemical release, 3) migration, 4) entrapment in suitable reservoir rock.
In our project we have relied upon the findings by the early 1980’s U.S. Government NURE water-sampling program, which identified uranium and pathfinder elements in groundwater in some wells in the project area. We have built upon those historic findings, we have conducted our own water well sampling over the last two years and we have mapped the structural nature of the area. We have identified possible traps from seismicity data available from studies of the New Madrid Seismic Zone. We have studied the possibility of the existence of the complete uranium system at greater depth. Our work has resulted in 1) the identification of the source rock, 2) the proof of decomposition into clays with the release of the uranium into the ancient groundwater cycle and 3) the location of possibly trapping faults.
In addition, our work has identified two specific old sands with 4) reservoir qualities in the project area, namely the underlying McNairy formation and the overlying Lower Wilcox formation. These two sands must now be studied in much detail in order to map 3) the possible migration paths.
Our work has also identified a number of local faults, which may have served the double purpose of bringing reducing gases into the old aquifers and possibly formed 5) traps while also having leaked uranium and pathfinder elements all the way up into the shallow groundwater wells in the project area.
This detection of uranium and other pathfinder elements (such as molybdenum) in the shallow groundwater wells has thus become a telltale of leakage paths from deep-seated faults with possibility for uranium deposits. Very recent work by our scientists has also established the tectonic movements and structural deformation, which created these ancient faults in the first place.
[1] The subsurface is characterized by young, sedimentary rocks, wherefore the Company in its leases has limited itself to the environmentally more acceptable method of ISR. This mining method for uranium shows strong resemblance with waterflood recovery of oil deposits, which can be fully isolated from overlying groundwater aquifers.
[2] Mickle, D. G., and Mathews, G. W., eds., 1978, Geologic characteristics of environments favorable for uranium deposits: U.S. Department of Energy Open-File Report GJBX-67(78), 250 p.
[3]Sims, John D., 1972, Petrographic evidence for volcanic origin of part of the Porters Creek clay, Jackson Purchase Region, Western Kentucky: in U.S. Geol. Survey Prof. Paper 800-C.
[4] Davis, R. W., Hansen, A. J., and Lambert, T. W., 1973, Subsurface geology and ground water resources of the Jackson Purchase region, Kentucky: U.S. Geological Survey Water-Supply Paper #1978.)
[5]Van Arsdale, R.B. and Randel T. Cox, 2007, The Mississippi’s Curious Origins, Scientific American, January 2007.
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