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 click to enlarge (pdf 3.5 Mb)   | |  Project Overview The 27 square mile, wholly-owned Lisbon Valley Project is located in the Lisbon Valley Mining District, San Juan County, Utah, approximately 35 miles south of the town of Moab. The Lisbon Valley area is a world-class uranium mining district with past production of over 100 million pounds of U3O8. None of the major mines in the district were exposed at the surface; all were discovered by wildcat exploration drilling. Principal Target Mesa Uranium is pursuing the concept that 1/2 of the district has remained buried and undiscovered on the down-faulted, eastern flank of the Lisbon Valley anticline. Historic uranium production of 65 million pounds of U3O8 came from 15 mines along a narrow horizon skirting the western flank of the anticline. Geologists and miners observed this trend and postulated that uranium mines should exist along a similar horizon on the eastern side of the Lisbon Valley fault. Wildcat drilling in 1968 validated the concept with the discovery of the district's largest mine, the Lisbon Mine, which produced 20 million pounds of U3O8 at a grade of 0.3% U3O8 (6 pounds per ton). The decline of uranium prices in the late 20th century brought a halt to further mining and exploration in the district. Recent drilling by Mesa (see news release dated 9/10/2007) encountered significant U3O8 mineralization 8,000 feet east of the Lisbon Mine. Highlights from drill hole L-15 are: • 3.5 feet of 0.28% U3O8 (5.6 pounds/ton) • 1.0 foot of 0.16% U3O8 (3.2 pounds/ton) • 1.5 feet of 0.13% U3O8 (2.6 pounds/ton) Strong mineralization between these three higher-grade intercepts resulted in an overall mineralized interval of 17.5 feet grading 0.11% U3O8 (2.2 pounds/ton).
Geology The dominant geologic feature of the Lisbon Valley is the Lisbon Valley anticline, a salt anticline typical of the Paradox Basin. Subsequent to doming the anticline was faulted by the Lisbon Valley fault, a northwest trending normal fault along the longitudinal axis of the anticline. Uranium deposits are known to occur in three formations located in the Lisbon Valley. (1) The Moss Back member of the Chinle Formation is the most significant in terms of past production and future targets on the east side of the Lisbon Valley Fault. (2) Morrison Formation (Salt Wash member), and (3) the Cutler Formation. All three formations underlie the Projects primary target areas. History Uranium exploration in the Lisbon Valley is entering its third era of activity. The previous 2 periods of exploration resulted in a series of mines stretching for 16 miles forming an actuate belt of deposits around the Lisbon Valley anticline known as the Lisbon Valley Mining District. The earliest reported uranium-vanadium ore discovery was made in 1913, at the south end of Lisbon Valley anticline in outcrops of basal Chinle sandstone. Later in 1948 low-grade uranium was discovered and mined in the upper Cutler sandstone in the center of the west flank of the anticline. Prompted by the high demand for uranium and incentive rewards from the United States Atomic Energy Commission (now the Department of Energy), exploration activity in the Lisbon Valley area increased rapidly. In 1952 geologist Charlie Steen drilled into 13 feet of U3O8 ore (uraninite) in the basal Chinle formation, discovering the famous Mi Vida Mine. The discovery led to a major regional exploration boom, historically known as the 'uranium boom'. Following Steen's discovery 16 major U3O8 mines were discovered and developed in the Lisbon Valley Mining District. | | |
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