During the late 1970s and throughout the 1980s, the “Arizona Strip” of northern Arizona – namely, the land immediately north and south of the Grand Canyon and west of the Navajo Indian Reservation -- was the site of the last US-based uranium exploration and mining boom.
The
basic supporting
reasons for this persistent uranium exploration and mining activity in
the US, during a period of gradually waning yellowcake price, were the
high grade and very compact nature of the collapse breccia pipes
located in the region.
This relatively unique uranium ore quality, permits breccia pipe uranium ore to be discovered, defined, mined, and milled for a total cost of about US 2007 $23/pound U3O8. Because average reserves for an individual mineralized pipe have been determined to be about 3,500,000 pounds U3O8, with an average ore grade of about 0.57 percent U3O8, at the current (3/07) US $91/UxC spot price level the average economically mineralized pipe has a before-tax, undiscounted in-ground value of about US $240,000,000. In the event that yellowcake price reaches the highest price level (2007 US $150/lb) of the last market boom, each average mineralized breccia pipe will reach a value of almost one half billion current US dollars.
Collapse breccia pipes are vertically-cylindrical bodies of broken sedimentary rock (the stationary breccia), rock down-dropped into deeper caverns formed in underlying massive limestone. See Figure 1 below. During mineralization, uraninite -- a reduced uranium ore mineral -- accumulated within the permeable column of broken/brecciated rock, in essence forming a cylindrical and vertical deposit rather than tabular, subhorizontal uranium roll front deposit that has migrated to its current site. Mineral and metal zoning show clearly that fluid flow direction of the mineralizing fluids was upward: As in roll front deposits, disseminated and massive sulfides are found on the downstream side of breccia pipe uranium accumulations; i.e., above the breccia pipe uranium ore. Contrary to what Figure 1 suggests, the brecciated rock column of breccia pipes rarely extends all of the way up to the present day surface.
The earliest Arizona breccia pipe to be mined for uranium was the Orphan, a mineralized pipe exposed on the southern wall of the Grand Canyon within Grand Canyon National Park.
During the late 70s, Denver’s Energy Fuels Nuclear, Inc., began a concerted effort to locate and then mine further examples of this previously neglected class of uranium deposit. With the exploration success of Energy Fuels and the ensuing development of the early Hack 1 and 2, Pigeon, and Kanab North mines, competing exploration and mining companies soon entered the northern Arizona region. At one time or another during the 1970s and 1980s, relatively large companies such as Gulf Resources, Pathfinder Mines Corporation, Rocky Mountain Energy Company, and Uranerz all competed with Energy Fuels for mineral rights in the predominantly public lands of the Arizona Strip. By 1989, at least 13 uranium-ore-bearing breccia pipes had been identified by the various companies. However, because of the low uranium price, nearly all northern Arizona uranium exploration had stopped by that year.
Figure
1. Colorado Plateau, northern Arizona, a uranium-mineralized collapse
breccia pipe in vertical cross-section. Kaibab Limestone makes up the
erosion surface in most cases, and most pipes do not stope up all the
way to the Kaibab surface.
Source: http://pubs.usgs.gov/bul/b2004/html/bull2004breccia_pipe_uranium_deposits.htm
Current Northern Arizona Uranium Exploration Activities
Since the 2004 rise in uranium price, various US and Canadian exploration companies have started to conduct uranium exploration work again in northern Arizona. The uranium price is today US $91.00/pound (www.uxc.com: 3/07), some 70 or so US dollars a pound more than the full exploration and production cost of average northern Arizona breccia pipe uranium ore.
Judging
from the
locations of economically-mineralized breccia pipes discovered to date,
approximately 2500 square miles of northern Arizona have the highest
potential for containing additional uranium-mineralized breccia pipes.
The United States Geological Survey (“USGS”) has
observed that the
average breccia pipe density in one area of northern Arizona with
particularly good rock exposure averages about one pipe per 3.5 square
miles. This USGS pipe frequency estimation suggests that about 700
breccia pipes likely exist in the 2500 square mile high potential
exploration area. Neglecting minor prospective ground lying within the
Kaibab Paiute, Hualapai, and Havasupai Indian Reservations, the DIR-075
JV’s structural analysis more tangibly shows that nearly nine
hundred
and fifty unclaimed pipe-type surface structural anomalies exist within
the area of highest exploration interest. For the foreseeable future,
the Kaibab Joint Venture will be operating only on US and Arizona state
public lands.
Granting that the majority of the identified pipe-type surface structural anomalies are actually pipe-related, it is critical to understand that the breccia pipe exploration work of the 1980s showed that not all of the collapse breccia pipes located by the initial structural analysis work of geologists contain uranium mineralization. Throughout all of northern Arizona, the USGS estimates that only about 1% of the Arizona breccia pipes contain significant uranium mineralization. Within the 2500 square mile highest potential exploration area, however, this percentage is already -- based on the results of the 1970s and 1980s uranium exploration period -- up to nearly 4%.
The
established
solution to the problem of uranium breccia pipe prospect generation has
three distinct steps that describe the first year of work that is being
carried out by DIR, the operator of the Kaibab Joint
Venture:
1. Locating, inspecting, and geochemically sampling a probable breccia pipe in the ground, and provisionally staking lode claim location monuments on the inspected target if surface geological indications at the site support remote structural analysis previously carried out in the office. Geochemical samples taken from each site are shipped out for analysis by contract analytical chemistry laboratories.
2. Determining the relative likelihood that any given target structure contains uranium mineralization in the subsurface by examining the lab results of geochemical samples taken from the surface rocks at each breccia pipe prospect.
3. If the step 2 determination is positive, then the final prospect-generating step is to complete lode claim staking and recording work with the pertinent Arizona counties and the Arizona office of the Bureau of Land Management in order to obtain mineral rights to the target ground.
The technical aspects of steps 1 and 2 are relatively simple, inexpensive, and rapid using reconnaissance geochemistry and DIR’s methods of landform analysis. Step 3 is more labor-intensive and costly, due to the labor and fees involved with claim-staking work.
Most access to the mineral prospects being examined by DIR geologists during the reconnaissance phase of the Kaibab JV uranium exploration program is gained by driving over roads in pickups and/or SUVs on already established on public lands administered by the Bureau of Land Management and/or the US National Forest Service. Minor distances are covered by walking cross-country to the sites of particular interest to the Kaibab Joint Venture.
The three DIR field geologists (Joe Cain IV, Zachary Harrison, and Larry Turner), usually working in the field on the Kaibab Joint Venture, operate out of a mobile field camp, staying in small tent trailers. Field season work is carried out on an approximate 14 days on, 7 days off schedule, during a field season that usually lasts 9 to 10 months of the year. Field operations are closed annually when snowfall and/or mud make it impossible to drive over BLM and/or Forest Service roads without getting stuck and/or without damaging the roadbed. Office work is primarily carried out in Colorado over 2 to 3 months of each year.
Once the breccia pipe prospects with the highest probability of being uranium-mineralized are staked in the first year of the Kaibab JV operations, ensuing years of joint venture work will be aimed at maintaining legal title to the claims, bringing individual projects into an increasingly improving technical form by conducting ground surveys on the surface of each prospect, and drilling the prospects. Surface geochemistry and geophysics surveys (magnetic and resistivity surveys), as well as vegetation and archeological drilling clearance studies, will help ready each prospect for exploration drilling and thereby add value to each mineral property.
Note that the Kaibab JV has a number of promising breccia pipe uranium prospects that have already been explored with surface work and preliminary exploration drilling by DIR (see map below): Some of these will be further drilled by the Kaibab JV early in the second year of the Kaibab JV operations.
Further detail regarding DIR and collapse breccia pipes can be obtained by reviewing DIR’s recent Arizona uranium exploration joint venture proposal: US High-Grade Uranium Exploration Joint Venture Proposal.